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Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
Chapter 6
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies Bert Droste-Franke EA European Academy of Technology and Innovation Assessment GmbH, Bad Neuenahr-Ahrweiler, Germany
Chapter Outline 6.1 6.2 6.3 6.4
Introductory Remarks Selected Studies with German Focus Selected Studies with European Focus Discussion of Study Results 6.4.1 Required Electric and Storage Power 6.4.1.1 Reserve Energy 6.4.1.2 Load Leveling and Long-Term Storage 6.4.2 Energy Capacity Need 6.4.3 Transferability of the Results to Other Regions 6.4.3.1 Weather Conditions
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The aim of this chapter is to give an overview of studies dealing with the assessment of the requirement for storage in a quantitative way and to provide an impression of the amount of storage that will prospectively be needed depending on the share of renewable energies used for electricity production in future. The number of studies exclusively concentrating on the discussion of the storage demand is small. Furthermore, these concentrate on a variety of aspects. Thus, most of the selected studies discussed here have a different main focus, such as presenting the options for an overall energy system in 2050. Energy storage is in that case only one aspect of the overall system. However, for the purpose of demonstrating that the overall system provides a certain level of secure energy supply, energy system studies show increasing engagement in modeling as one aspect of the need for balancing fluctuations in the provision of electricity from renewable sources and discussing the use of storage facilities. Arising from the governmental project of an energy transition (‘Energiewende’) in Germany many studies have been carried out analyzing options for future energy systems with the focus on Germany in the European context. A first impression
6.4.3.2 6.4.3.3 6.4.3.4 6.4.3.5
Topological and Geological Conditions Political Conditions Electricity Grid Competing TechnologiesdBiomass, CSP, Backup Capacities, Curtailment, and Demand Side Measures
6.5 Conclusions Abbreviations References
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84 84 85 85
about the quantity of available studies dealing with the subject can be seen in the (incomplete) list of studies provided by the German Energy Agency [1]. It has about 80 entries considering publications from 2008 to 2012. As, additionally, electricity supply is typically a task for a region of continental rather than global size, the review concentrates on studies carried out for the German and European perspective of storage needs with some discussions on the transferability of the results.
6.1 INTRODUCTORY REMARKS As a result of the derived scenarios, increasing the share of renewable sources used for the production of electricity and heat leads in most areas to an extension of the direct use of sources with variable availability like wind speed and solar irradiation. Variable production is a large challenge for the provision of electricity because the transport of electricity via alternating current with constant quality over the grid requires that input and output of electricity are equal at any time. Differences that could lead to the violation of defined safety ranges must be balanced as soon as possible in order
Electrochemical Energy Storage for Renewable Sources and Grid Balancing. http://dx.doi.org/10.1016/B978-0-444-62616-5.00006-1 Copyright Ó 2015 Elsevier B.V. All rights reserved.
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to avoid damage to electronic equipment as well as to human beings and to prevent the shutdown of energy supply triggered by safety mechanisms. In practice, a large number of tasks arise with the need of a continuous electricity supply with a high share of variable sources used. Besides matching the supply and demand side, electricity storage can be used to support network management in transmission and distribution grids, optimize network usage, realize power supply in emergency cases, manage the demand charge, manage the quality of electricity, and realize further tasks (see, for example, [2]). Key characteristics of the individual tasks are the specific requirements of charging and discharging power as well as energy capacity. Additionally, it is important how long the technology needs from launch to reach full operation mode. Thus, for a well-designed integration of renewable energies, the fluctuations to be balanced have to be distinguished with respect to different timescales. A more detailed consideration of the variations in the availability of wind and solar irradiation gives more insight into the challenges. While fluctuations can occur in very short timescales down to seconds, e.g., because of rapid cutoff of wind turbines due to storm conditions or fast-changing cloud coverage above photovoltaic plants, the weather conditions and the electricity supply show changes also from minute to minute or hour to hour. A particular gap in production occurs, of course, during night for all technologies using solar irradiation. Longer gaps of electricity production could occur during periods with only small wind speed for several days. The variety of such gaps can be seen in Figure 6.1 showing the load and wind power together with the power prognosis over several days for the Eastern control area in Germany. Besides very sharp peaks in the difference between prognosis and real power production, a gap of about
FIGURE 6.1 Load curve, wind prognosis and wind power in the German Eastern control area during a Period in 2008. Ref. [3], p. 6, based on Ref. [4], p. 13.
10 days was observed. Leveling out the gap to a mean value for the provision of electricity would require a power of several GW over 10 days and, thus, some hundred gigawatt-hour of energy capacity from the balancing technology. Having in mind that currently only 7 GW of pumped hydro is installed in Germany with 40 GWh storage capacity, represented by the area of the vertical bar in Figure 6.1, it becomes obvious that the task can by far not be fulfilled by using the currently installed storage capacity. Finally, seasonal variations of electricity provision and variations between the years also have to be considered for the design of the system. The example makes clear that the higher the share of electricity produced from wind and solar power is, the larger become the gaps. At the same time, situations in which the electricity production exceeds the load will occur and their number will increase. Therefore, options will be required to provide positive and, ideally, also negative control power on the different relevant timescales. Numerous competing technologies exist to fit these tasks: conventional power plants (as used for the provision of balancing power today), the management of loads, further extension of the installed power of renewable energies in other regions together with respective network extensions, and several options for energy storages, electrochemical storages being some of them. Thus, the storage capacity required highly depends on the remaining energy system installed and the available electricity grid. In the following, various studies are presented and discussed, which provide insights into the required storage capacity on the basis of different scenarios for the future energy systems in Germany and Europe. First, the individual studies and study results are described and characterized and subdivided into studies with German and with European focus. Then key results with respect to storage needs are summarized and discussed with respect to selected tasks.
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Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
6.2 SELECTED STUDIES WITH GERMAN FOCUS In the study of the German Environment Agency on the ‘Energy Target 2050’ (Table 6.1) scenarios for 100% electricity from renewable sources are developed. The most interesting one is ‘Regionenverbund’ (network of regions). For this scenario it is supposed that all regions in Germany use their potentials extensively and exchange electricity between each other. The import from outside Germany is assumed to be small. Thus, the scenario should show how 100% electricity production from renewable sources is possible without relying too much on imports from other countries. This scenario is analyzed via a dynamic simulation in more detail. The calculations show a temporal resolution of 1 h and a spatial resolution of 14 14 km2.
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Four years of weather data were applied for the calculations (2006e2009). Thus, influences of weather changes and extreme weather conditions on the electricity production could be investigated in detail. The share of variable electricity production from wind and photovoltaic systems is assumed to be 87% in terms of power and 84% in terms of electricity production. The modeling process starts with the estimation of the base consumption (401 TWh), which includes all types of consumption already observed today. In a next step the base consumption is complemented by additional ‘must-run’ consumption that will occur with the application of new technologies like electric vehicles and heat production. After considering the production of electricity from some renewable sources (wind, photovoltaic, water, geothermal power) as ‘must-run’ facilities for the calculation of the residual load,
TABLE 6.1 Energy Target 2050: 100% Electricity from Renewable Sources, Germany Study CharacteristicseStudy Data Sheet Study title
Energieziel 2050: 100% Strom aus erneuerbaren Quellen (energy target 2050: 100% electricity from renewable sources)
Year of publication
2010
Author(s)
T. Klaus, C. Vollmer, K. Werner, H. Lehmann, K. Mu¨schen
Institution(s)
Umweltbundesamt (German Environment Agency)
Support/occasion
Umweltbundesamt (German Environment Agency)
Aim of study
Vision of a electricity supply in Germany in 2050, realized with renewable energy only
Relevant chapter(s)
Simulation des Szenarios ‘Regionenverbund’ (Simulation of the scenario ‘network of regions’)
Author(s)
C. Pape, M. Sterner, N. Gerhardt, Y. M. Saint-Drenan, M. Jentsch, A. von Oehsen
Institution(s)
Fraunhofer-institut fu¨r Windenergie und Energiesystemtechnik (IWES), Kassel
Analysis of Energy Storage NeeddSimulation of the Scenario ‘Network of Regions’ Approach and models used
SimEE: hourly simulation of load, electricity production renewables, demand-side management (DSM), storage with a fixed merit order
Spatial horizon/resolution
Germany, small import/c. 14 14 km2
Temporal horizon/resolution
Year around 2050/hourly, 4 years of weather data (2006e2009)
Technologies/technical resolution
Conversion: 100% renewable energy (details in the text) Grid: Copper plate in Germany, losses considered Demand: base consumption þ DSM via heat pumps, e-mobility, air conditioner Residual load: 1. DSM, 2. Pumped hydro, 3. Biogas-CHP (combined heat and power) plant, 4. Import renewable energy (RE), 5. turbines with H2/CH4, 6. Biogas turbines (reserve energy)
Quantitative Assumptions and Results Input data/assumptions
Scenario: usage of renewable potentials in Germany, small international exchange
Individual results Dispatchable electricity required in Germany with ambitious targets
Required electric power: 8.6 GW pumped hydro (including 4 GW for reserve energy), 30.4 GW H2-CC (combined cycle)/28 GW CH4-CC þ2.5 GW biogas-CHP, 6.9/9.3 GW imports, 17.5 biogas turbine Required energy capacity: About 50 GWh pumped hydro, >75 TWh H2 or >65 TWh CH4 Required storage power: 7.9 GW For pumping water, 44 GW for electrolyzers
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adaptable consumption (air conditioning, heat pumps, e-vehicles) is used for smoothing the load (load in total around 500 TWh (average consumption over the 4 years)). For further balancing, pumped hydro power is applied before hydrogen (H2) and methane (CH4) are produced to provide negative control power or biogas combined heat and power (CHP), imports, H2/CH4 in combined cycle gas turbines and biogas turbines are used in order to provide positive control power. In this way 99% of the produced electricity is finally used. Excess energy that could not be used in the described steps has to be curtailed. Providing additional electrolyzers to be able to use also the last percentage of the electricity produced would not be reasonable with respect to the energy benefit achieved. With respect to energy storage it is assumed that today’s pumped hydro plants are extended by a small amount to reach 8.6 GW (turbines, 7.9 GW pumps) in total. Four gigawatt turbines and pumps are used for the provision of reserve power and can therefore not be applied for hourly balancing. With an average capacity of 5.5 h, these provide about 50 GWh of storage capacity. For hydrogen (H2) and methane (CH4) production the calculations show that 30.4 and 28 GW of turbine power is required to fill the gaps in power production, respectively. The maximum storage use per event is about 45 TWh for H2 storage and 40 TWh for CH4 storage, which is possible to be realized with the potential of the system envisaged. However, as the storage cannot be recharged fast enough before the next event occurs in winter, the dimension of storage has to be a minimum of about 75 TWh for H2 and 65 TWh for CH4. In order to have enough excess capacity, the storage size should be increased. As already indicated above, the power of the electrolyzer is chosen so that 99% of the energy can be used over the 4 years. The power required for this assumption is 44 GW. For balancing the residual load, however, further technologies (see above) are also included. Thus, the total power required to balance the residual load is higher. The maximum hourly residual load over the 4 years is 57.3 GW. In addition to the estimates based on hourly simulations, values for the required reserve power based on the statistical concept of secured power are derived. The numbers show a range from 7 GW (hourly simulation) to about 15 GW (concept of secured power) if secured power import of up to 7 GW is assumed. Several technologies, like biomass power plants, pumped hydro, and demand side management can contribute to the reserve market. The study of long-term scenarios and strategies for the extension of renewable energies in Germany (Table 6.2) is the latest in a series of studies (‘Leitstudien’ (lead studies)) that have been carried out since 2007 aiming at proving that an energy supply relying to a large extent on renewable energy sources is possible. The scenarios, called ‘Leitszenarien’ (lead scenarios), are the basis of many further
studies in the area. For instance, most of the studies discussed here with respect to the analysis of German conditions rely on these scenarios. The study discussed here in more detail represents the latest study of the series published in March 2012. While the earlier study published in 2010 also included an analysis of the residual load via a dynamic simulation, using, among other things, the SimEE-model already discussed in the context of the first study ([5], p. 92ff), in this study a model of the Fraunhofer IWES ‘Virtuelles Stromversorgungssystem’ (virtual system of electricity supply) (VSVS) is used together with a version of the REMix model developed by the German Aerospace Center. While the REMix model is used to assess the surrounding electricity production with high geographical resolution and exchange within the area of Europe and North Africa, the VSVS model is used to derive the optimized load management and power plant operation on a more detailed level for Germany. The assessed storage need for a scenario with a share of renewable energy of about 80% in terms of power (including imports of about 5%) is about 9 GW for load leveling with short-term storage, 7e8 GW short-term storage for reserve power, and 3.3 GW for long-term storage. Additionally, about 39e49 GW of power is produced with thermal plants (10 GW from biogas, 3.3 GW from hydrogen, the remaining from fossil fuels). Furthermore, 7e11 GW is imported and up to 20 GW potential for demand-side management is assumed with a high share of electric vehicles, contributing up to 10 GW. Besides the 80% scenarios also a 100% scenario was calculated for 2060. In that case the use of long-term storage for electricity is increasing from 7 TWh per year to 69 TWh per year. The installed turbine power is 28 GW in that case. This is supplemented by 1.8 GW from fossil/ solid sources in thermal power plants, 44 GW of imports, and 10.4 GW from biomass. Estimations of power required for covering the residual load, not considering imports, for Germany result in 12.6 GW turbine power required from pumped hydro. However, the residual load is mainly covered by thermal power plants fueled with fossil fuels as well as biogas and hydrogen (3.3 GW). Overall 46e55 GW of secured power is required resulting in 54e64 GW installed power (including 5% security margin) in this purely national scenario. The study of ways to reach 100% power supply from renewable sources in Germany carried out by the German Advisory Council on the Environment (SRU) (see Table 6.3) compares four different situations of energy political situations with each other. The first is 100% selfproduction of electricity in each hour by each country separately. The second is a regional combination of the energy systems of Germany, Denmark, and Norway in which each country can import and export energy, but,
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TABLE 6.2 Long-Term Scenarios and Strategies for the Extension of Renewable Energies in Germany Study CharacteristicseStudy Data Sheet Study title
Langfristszenarien und Strategien fu¨r den Ausbau der erneuerbaren Energien in Deutschland bei Beru¨cksichtigung der Entwicklung in Europa und global (Long-term scenarios and strategies for the extension of renewable energies in Germany, considering the developments in Europe and globally)
Year of publication
2012
Author(s)
J. Nitsch, T. Pregger, T. Naegler, D. Heide, D. L. de Tena, F. Trieb, Y. Scholz, K. Nienhaus, N. Gerhardt, M. Sterner, T. Trost, A. von Oehsen, R. Schwinn, C. Pape, H. Hahn, M. Wickert, B. Wenzel
Institution(s)
German Aerospace Center (DLR), Fraunhofer IWES, IFNE
Support/occasion
German Ministry of Environment (BMU)
Aim of study
Elaborating strategies that show how the long-term climate protection targets and transition to renewable energy sources in Germany can be reached
Relevant chapter(s)
Dynamic simulation of the system for electricity supply; security aspects of the conversion of the energy supply
Analysis of Energy Storage NeeddChapters on Dynamic Simulation and Energy Security Approach and models used
REMix: Cost-minimum optimization Virtuelles Stromversorgungssystem (VSVS): Cost minimizing power plant resource planning with rolling horizon of 48 h and hourly resolution (day ahead-, intraday-market) (mixed integer linear optimization) the models are coupled via technology inventory and imported/exported load
Spatial horizon/ resolution
REMix: Europe with parts of North Africa, 10 10 km2 VSVS: Germany, high resolution for renewable energy (RE) potentials
Temporal horizon/ resolution
REMix: Hourly (Germany), 5 h (rest), 1 weather year (2006) VSVS: Hourly, 48 prognosis horizon
Technologies/ technical resolution
REMix: Individual technologies, conventional power production per block, storage: short-term storage, H2/CH4 production for electricity and transport, grid: international grid connections as result of first optimization step VSVS: Production from renewable energies, demand, demand-side management, short-term storage (CAES, pumped hydro), long-term storage (H2, CH4), conventional power fleet, grid: grid regions model in Germany
Quantitative Assumptions and Results Input data/ assumptions
Scenarios: 80% and 100% renewable energy in Germany in 2050 and 2060, respectively
Individual results Dispatchable electricity required in Germany with ambitious targets
Required electric power (80%/100%): Short-term storage: 9 GW (Load leveling) þ 7e8 GW (power reserve), 3.3/ 28 GW long-term storage, 10 GW biomass, 26e36/1.8 GW fossil and solid fuels Required energy capacity (80%/100%): Up to 7/69 TWh H2 (annual production), pumped hydro (assuming 5.5 h): About 90 GWh Required storage power: 12.6 GW Pumped hydro without international exchange in 80% scenario
aggregated over a year, has to provide 100% of its demand by itself. In the third variant, 15% of import is allowed in the annual balance. In the fourth variant 15% import of energy is allowed in the annual balance and the area in which electricity is exchanged is enlarged to the whole of Europe plus all Mediterranean countries and North Africa. All scenarios are calculated for electricity demands of 509 TWh and 700 TWh in Germany. As 509 TWh is the core scenario and the assumptions in the remaining studies are closer to this value, the further discussion focuses on these scenarios. A look on the scenario with an electricity demand of 700 TWh shows that most of the numbers
assessed increase slightly while the need for compressed air energy storage (CAES) in Germany decreases significantly considering international exchange. For the assessment the energy system model REMix was chosen, which was applied to set up a cost-efficient energy system on an hourly basis using data with a geographical resolution of about 10 10 km2. From the results it can be seen that much less balancing demand exists if storage outside Germany can be used. This can particularly be seen in less storage capacity required in the whole area and less biomass required particularly in Germany.
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TABLE 6.3 SRU Special Report: Ways to a 100% Renewable Electricity Supply Study CharacteristicsdStudy Data Sheet Study title
Wege zur 100% erneuerbaren Stromversorgung, Sondergutachten (Ways to a 100% renewable power supply, special report)
Year of publication
2010
Author(s)
German Advisory Council on the Environment (SRU)
Institution(s)
German Advisory Council on the Environment (SRU)
Support/occasion
German Advisory Council on the Environment (SRU)
Aim of study
Support decisions with respect to a 100% energy supply in Germany by analyzing important questions like security of supply, costs, intermediate technologies, measures, and instruments needed
Relevant Chapter(s)
Substudy analyzing the potentials and limits of the integration of various energy sources to a 100% renewable electricity supply of Germany
Author(s)
Yvonne Scholz
Institution(s)
German Aerospace center (DLR)
Analysis of Energy Storage NeeddSubstudy on Potentials and Limits Approach and models used
Dimensioning power supply including the HVDC grid via linear cost optimization in an energy system model
Spatial horizon/ resolution
Europe with parts of North Africa and the Mediterranean region, 10 10 km2
Temporal horizon/ resolution
Hourly (Germany), 5 h (rest), 1 weather year (2006)
Technologies/ technical resolution
Conventional power production as gas power plant storage: pumped hydro (current installation þ70 TWh in Norway, capacity for 8 h), adiabatic CAES, hydrogen storage grid: HVDC power lines, nationally, regionally: no restriction
Quantitative Assumptions and Results Input data/ assumptions
Maximal installable power, hourly potentials, biomass potentials, costs, lifetime, hourly load, 509 TWh scenarios
Individual results Dispatchable electricity required in Germany with ambitious targets
Required electric power (De/EUNA): 509 TWh electricity demand: 31.6/30.6 GW CAES, 0.5/0.8 GW pumped hydro, 33.4/4.9 GW biomass 700 TWh electricity demand: 37.0/13.5 GW CAES, 0.6/0.6 GW pumped hydro, 38/5.2 GW biomass Required energy capacity (De/EUNA): 509 TWh electricity demand: 0.75/0.19 TWh CAES, 0.05 TWh pumped hydro 700 TWh electricity demand: 1.03/0.05 TWh CAES, 0.05 TWh pumped hydro Required storage power: not provided
The resulting storage capacities used are small for Germany in the case of the first scenario, because the potential for pumped hydro in Germany is restricted and biomass is used instead. The capacities installed in Germany add up to 32.1 GW of power and 0.8 TWh of energy capacity. In the second scenario it can be seen that Germany obviously switches from biomass usage to the use of pumped hydro storage installed outside Germany. In total the need for 16 TWh of storage capacity is assessed for the whole scenario.
In addition to the results of the German scenarios, the results for the scenario including Europe, the Mediterranean countries, and North Africa will be used in the discussion as well. While the storage power used increases to 509 GW (102 GW pumped hydro and 407 GW CAES), the energy capacity installed remains at about the same value (17 TWh). The study ‘Model Germany’ (Table 6.4) carried out for the World Wildlife Fund in 2009 provides a picture of a possible energy system in 2050 in Germany by modeling the demand of heat and electricity including households
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TABLE 6.4 Model Germany, Climate Protection Until 2050 Study CharacteristicsdStudy Data Sheet Study title
Modell Deutschland, Klimaschutz bis 2050 (Model Germany, climate protection until 2050)
Year of publication
2009
Author(s)
A. Kirchner, M. Schlesinger, B. Weinmann, P. Hofer, V. Rits, M. Wu¨nsch, M. Koepp, L. Kemper, U. Zweers, S. Strabburg, F. C. Matthes, J. Busche, V. Graichen, W. Zimmer, H. Hermann, G. Penninger, L. Mohr, H.-J. Ziesing
Institution(s)
¨ ko-Institut e.V. Prognos AG, O
Support/Occasion
World Wildlife Fund (WWF)
Aim of study
Elaboration of a target of reducing greenhouse gas emissions in Germany by 95% by 2050, requirements on temporal development of the energy system, technologies, economic structure, and way of life
Analysis of Energy Storage Need Approach and models used
Detailed model of conventional power plants, partly with carbon capture and storage, assessing the coverage of the residual load per hour following a merit order fixed for 1 year
Spatial horizon/resolution
EU 27 countries in power plant model, focus Germany, renewable energies based on lead study 2008, no defined spatial resolution
Temporal horizon/resolution
Individual years from 2005 to 2050/hourly calculations
Technologies/technical resolution
Conventional power plants, renewable energies, storage technologies aggregated
Quantitative Assumptions and Results Input data/assumptions
Maximal power and weather data, energy resource prices, CO2 prices, maximum full load hours of renewables, extension of renewables, and CHP
Individual results Dispatchable electricity required in Germany with ambitious targets
Electric power: Storage: 20.4 GW, biomass: 6.7 GW (At 97% RE) or storage: 12.9 GW, biomass 6.7 GW (at 76% RE) Required storage energy over 1 year (76/97% RE): 36.5/54.7 TWh Storage power: n.a.
and services, industry, and transport, as well as the energy supply considering conventional technologies and the use of renewable energies. Particular focus was laid on the analysis of an energy system with and without using carbon capture and storage (CCS). For the modeling of the power plant fleet a European power plant model is used, considering conventional power plants (>30 MW) in the 27 countries of the European Commission. The basic principle is the coverage of the load for each hour throughout the year. Within the calculations, first the load is assessed before it is reduced by renewable power generation, based on the available power, which varies with the weather conditions on an hourly basis. The resulting residual load is then covered by conventional power plants following a fixed merit order. The extension of the renewable power and CHP plants is taken from scenarios of the lead study 2008. The required additional conventional power is assessed on the basis of the maximally awaited load in the current year. Technologies are
chosen with regard to the awaited economic revenues considering estimates on secured power from renewables and CHP plants increasing over time. Sources cannot yet be clearly assigned for the residually occurring requirements on import of electricity. Concerning biomass, with 41.3 TWh, a more conservative annual potential than assumed in the lead study 2008 (53.8 TWh) is used ([6]). From the results it can be seen that the storage demand will rise in all scenarios with ‘innovative technologies,’ with and without CCS technology, while in the reference scenario with CCS balancing is taken over by gas power plants. In the reference without CCS the installed power of short-term storage slightly increases from 5.4 GW in 2005 to 6.4 GW in 2050 while the electricity produced increases from 7.1 to 18.3 TWh. Biomass power increases from 2.2 to 7.2 GW, producing 44.7 TWh in 2050. In the innovation scenario with CCS (76% electricity from renewable sources) the increase in power production from renewable
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sources is lower than in the scenario without CCS. Nonetheless, installed short-term energy storage increases in terms of power by a factor of 2.4 from 5.4 to 12.9 GW and in terms of energy produced from 7.1 TWh to 36.5 TWh. In the innovation scenario without CCS (97% electricity from renewable sources), the energy storage required in 2050 is 20.4 GW of power and 54.7 TWh of energy. The study on 100% renewable energies for electricity and heat in Germany (Table 6.5) is designed to set up a cost-optimal energy system for a future year, for which 2050 was assumed. Input data are technology data including house restoration data as one option together with time series of wind (onshore/offshore) and photovoltaic power production. The cost-optimal system is developed over time from a large number of potential technological combinations. The pumped hydro potential was defined as 10 GW with 60 GWh (6 h) of storage capacity. Batteries are assumed to have a storage capacity around 50 GWh.
Long-term storage is performed via a power-to-gas process involving the production of methane. In the system with the lowest costs a power-to-gas process with 88 and 94 GW for the production of electricity from gas is installed. The methane storage requires an energy capacity of 86 TWh. Additionally, the timing of a lack in wind power of 4 weeks was varied, resulting in the largest effect on the required storage size if it occurred in February. The maximum estimate for storage capacity results in a need for 140 TWh (see [7]) according to these estimations. The study of the relevance of electricity storage at high share of renewable energy used in Germany (Table 6.6) assesses the storage capacity required for two different shares of renewable energies in the electricity system in 2050, 80% and 100% of electricity consumption. For sensitivity analysis four scenarios are defined varying the recharging process of electric vehicles (16 million, electric and plug-in hybrids) and assuming a decrease in annual production from renewable sources.
TABLE 6.5 Hundred Percent Renewable Energies for Electricity and Heat in Germany Study CharacteristicsdStudy Data Sheet Study title
100% Erneuerbare Energien fu¨r Strom und Wa¨rme in Deutschland (100% renewable energies for electricity and heat in Germany)
Year of publication
2012
Author(s)
H.-M. Henning, A. Palzer
Institution(s)
Fraunhofer ISE
Support/Occasion
Fraunhofer ISE
Aim of study
Development of an energy system for a future year, e.g., 2050, with 100% energy from renewable sources
Analysis of Energy Storage Need Approach and models used
Cost optimization of an energy system based on a large number of balanced annual energy demand/supply combinations
Spatial horizon/resolution
Germany/none (based on hourly supply curves from 2011)
Temporal horizon/resolution
One year around 2050/hourly
Technologies/technical resolution
Conversion: Electricity: Wind onshore, wind offshore, photovoltaic, biomass (CC plants, large and small CHP), water power, heat: Solarthermal, biomass, heat pumps (electricity, gas), heating networks, restoration measures Storage: Pumped hydro, batteries, heat storages with water, power-to-gas plants (with CC gas plants, large and small CHP) Electricity grid: (only low-temperature heat, no transport, no industry)
Quantitative Assumptions and Results Input data/assumptions
Supply curves of wind and photovoltaic from 2011, technology data
Individual results Dispatchable electricity required in Germany with ambitious targets
Electric power: Pumped hydro: Fixed to 10 GW, batteries: n.a., power-to-gas: 88 GW gas production/81 GW CC þ 13 GW CHP (þ107 GW gas heat pump) Storage capacity: batteries: 52 GWh, pumped hydro (maximum): 60 GWh, power-to-gas: 86 TWh (methane)
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TABLE 6.6 Relevance of Electricity Storage at High Share of Renewable Energy Used in Germany Study CharacteristicsdStudy Data Sheet Study title
Bedeutung der Stromspeicher bei hohen Anteilen erneuerbarer Energien in Deutschland (Relevance of electricity storage at high shares of renewable energies in Germany)
Year of publication
2011
Author(s)
N. Hartmann, R. Barth
Institution(s)
Institute for energy economics and the Rational use of energy (IER), University of Stuttgart
Support/occasion
Paper for Conference ‘Optimising in energy economics,’ Verein Deutscher Ingenieure (The Association of German Engineers), VDI
Aim of study
Analysis of relevance of electricity storage at shares of 80% and 100% of electricity consumption
Analysis of Energy Storage Need Approach and models used
Cost minimizing power plant resource planning with rolling horizon (day ahead-, intradaymarket, reserve energy)
Spatial horizon/resolution
Germany without exchange/resolution not defined
Temporal horizon/resolution
Individual year 2050/hourly calculations
Technologies/technical resolution
Conventional power plants, renewable energies, storage technologies (CAES, pumped hydro, batteries in e-vehicles)
Quantitative Assumptions and Results Input data/assumptions
Energy resource costs, CO2 certificate costs, investment and operation costs (including maintenance, etc.), consumption: 534 TWh
Individual results Dispatchable electricity required in Germany with ambitious targets
Electric power: n.a. Storage capacity (80%/100%): 2.3 (0.5 pumped hydro, 0.9 diabatic CAES, 0.9 adiabatic CAES, 0.04 batteries)/24 TWh Storage power: n.a.
The method applied is cost-minimizing power plant resource planning with a rolling horizon considering dayahead, intraday, and reserve market with an hourly resolution. Although the recharging control of electric vehicles in the study allows feeding in of electricity, the batteries are predominantly being charged in the calculations. The reason is the high costs assumed for battery charging. Over all, storage with energy capacity of 2.3 TWh is required in the 80% scenario and of 24 TWh in the 100% scenario. In the 80% scenario with controlled recharge of vehicles annually about 8.6 TWh electricity is provided by pumped hydro, (0.0003 TWh by batteries) 19.4 TWh by adiabatic CAES, and 3.3 TWh by diabatic CAES. Thus, over the year about 31 TWh electricity was provided by storage plants. The study that focuses on optimizing power plant and energy storage extension with an iterative hybrid model (Table 6.7) carries out a cost optimization using three different models: a model for investment planning of power plants, a model for power plants and storage dispatch as well as storage investment and a model for probabilistic estimation of the secured supply. In order to be able to
calculate the whole time period from today to 2050 on an hourly basis, the resolution of the data and calculation steps used as well as the number of feedback-loops were minimized with respect to the specific subtasks. The scenario analyzed is a power supply with a share of 80% renewable energy used in 2050. As results the optimal energy capacity in 2050 as well as the optimal power of storage plants was estimated. The 4.8 TWh of optimal storage size is provided mainly by hydrogen storage, whereas, most of the required power of 12 GW is provided by adiabatic compressed air storage (about 7 GW). The study balancing renewable electricitydenergy storage, demand-side management, and network-extension from an interdisciplinary perspective (Table 6.8)ddiscusses options for balancing the demand and supply of electricity with high shares of renewable energies in the system from an interdisciplinary perspective. Besides technical analyses, energy economic, broader economic, legal, political, and environmental/resource aspects are discussed. As a basis for the discussions one part deals with the assessment of storage requirement in the case that a system with a high
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
TABLE 6.7 Optimizing Power Plant and Energy Storage Extension with an Iterative Hybrid Model Study CharacteristicsdStudy Data Sheet Study title
Optimierung des Kraftwerks- und Speicherausbaus mit einem iterativen und hybriden Modell (Optimizing power plant and energy storage extension with an iterative hybrid model)
Year of publication
2011
Author(s)
Ph. Kuhn, M. Ku¨hne
Institution(s)
TU Mu¨nchen
Support/occasion
Paper for Conference on optimizing in energy economics, VDI
Aim of study
Quantification of an efficient potential of storage
Analysis of Energy Storage Need Approach and models used
Cost-optimization using a combination of investment model, dispatch model, secured power estimation, in detail adapted in the optimization procedures to the specific task
Spatial horizon/resolution
Germany/Germany
Temporal horizon/resolution
Today to 2050/optimized for individual tasks, up to hourly
Technologies/technical resolution
Existing power plants; extension: OC-, CC-gas turbines, conventional and new hard coal and lignite power; pumped hydro, adiabatic CAES, hydrogen storage
Quantitative Assumptions and Results Input data/assumptions
Power plant inventory, parameters of new technologies, electricity from renewables, cost developments, restrictions, electricity demand, political framework conditions
Individual results Dispatchable electricity required in Germany with ambitious targets
Energy capacity: 4.8 TWh, hydrogen storage >90% Electric power (additional): 12 GW (About 2 GW H2, 7 GW AA-CAES, 3 GW pumped hydro)
share of renewable energies in the electricity supply is realized. Besides the results derived from existing energy system studies, which are discussed below, an alternative new methodology to assess the storage demand in Europe was developed. The first reliable results of the European model, which was developed at the RWTH Aachen in parallel, were published by [10] (see the discussion of European studies below). The basis for the analysis of storage requirements was scenario III of the energy concept 2030 ([9]) and the lead study 2009 ([8]). Besides an estimation of secured power on the basis of typical days, an analysis of extreme situations on the basis of 43,800 h of offshore wind data (2002e2006) was carried out. The larger problems with covering the load are still awaited for the lead scenario. Therefore, only this scenario was investigated in more detail. The results show that storage power of 18 GW is required for 2030 and 35 GW for 2050 in case of the lead scenario. Wind calms with a limit power of 5% and 87 h of duration are determining the maximum capacity required for 2030, which is about 0.6 TWh for one calm. In 2050 calms with a limit of 20% and 218 h duration lead to the
maximum energy required of 1.7 TWh. The analysis shows that different types of calms, varying in length and depth, have similar effects on the energy capacity required. Within the study of the Association for Electrical, Electronic & Information Technologies (VDE) on storage demand and impacts on the grid structure (Table 6.9), the assessment of storage need for different shares of renewable energies in the electricity sector in Germany is a central focus. Therefore, different variants were analyzed. The most important ones are electricity systems without storage and with short-term and long-term storage for 40%, 80%, and 100% of electricity produced from renewable sources. The basis for the analyses is detailed data on the renewable energies with a high spatial resolution derived by using the lead study 2010, an operation simulation model for power plants and storage facilities with hourly resolution and a storage model. The results show that in the case of 40% electricity produced from renewable sources, curtailment of renewable electricity production and the application of conventional power plants for balancing is economically more efficient than using storage. Furthermore, in that situation,
Chapter | 6
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
71
TABLE 6.8 Balancing Renewable ElectricitydEnergy Storage, Demand-Side Management, and Network Extension from an Interdisciplinary Perspective Study CharacteristicsdStudy Data Sheet Study title
Balancing Renewable Electricity, Energy Storage, Demand-Side Management, and NetworkExtension from an Interdisciplinary Perspective
Year of publication
2012
Author(s)
B. Droste-franke, B. P. Paal, C. Rehtanz, D. U. Sauer, J.-P. Schneider, M. Schreurs, T. Ziesemer
Institution(s)
Europa¨ische Akademie GmbH, University of Freiburg, TU Dortmund, RWTH Aachen, FU Berlin, Maastricht University
Support/Occasion
German Aerospace Center (DLR)
Aim of study
Exploring and analyzing alternative strategies and technologies that can balance gaps between supply and demand at unsuitable weather conditions
Relevant Chapter(s)
Assessing the balancing demand and storage employment based on scenarios for Germany (Chapter 4.1)
Author(s)
Leading: C. Rehtanz with T. Noll
Institution(s)
Leading: TU Dortmund
Analysis of Energy Storage Need Approach and models used
Rough analysis of power required to cover the maximum residual load based on generalized statistical values and analysis of individual long wind calms with offshore wind data
Spatial horizon/resolution
Germany without exchange/nonedbased on lead scenario 2009 ([8]) and Scenario III of study to an energy concept 2030 ([9])
Temporal horizon/resolution
Individual year around 2050/assessment based on residual load of typical days (288 hourly data) and hourly calculation for extreme weather conditions (basis: Data from the years 2002e2006)
Technologies/technical resolution
Estimation of power requirements: technologies as assumed in the used studies without international exchange Estimation of energy capacity: wind offshore
Quantitative Assumptions and Results Input data/assumptions
Load and feed-in profiles for typical days (288 h), synthetic off-shore wind feed-in data (43,800 h, 2002e2006)
Individual results Dispatchable electricity required in Germany with ambitious targets
Electric power: 18 GW In 2030 (lead scenario), 35 GW around 2050 Energy capacity (for one wind calm): 0.6 TWh in 2030 (lead scenario), 1.7 TWh around 2050
only a small amount of excess energy is observed, while large amounts of residual load occur so that the usage of storage does not seem to be appropriate. For the case of 80% electricity from renewable sources, a small curtailment of production leads to a large decrease in the required power (14 instead of 26 GW short-term storage, 18 instead of 29 GW long-term storage). The analysis of the full production from renewable energies (100%) results in much higher amounts of storage required (data are provided in Table 6.9). The difference in costs between the 80% and the 100% scenario is found to be higher than to go from 17% renewable energies in 2010 to 80% in 2050.
6.3 SELECTED STUDIES WITH EUROPEAN FOCUS The Roadmap 2050 (Table 6.10) generated by the European Climate Foundation (ECF) shows how an ambitious energy system can be built up in Europe. The analysis uses the back-casting approach starting with the target scenario to assess how it could be reached from today. The analysis of backup capacities is carried out with a generation dispatch model. Additional storage facilities were not applied for the system. Fossil power plants used are based on CCS technology.
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
TABLE 6.9 Energy Storage for Energy Transition, Storage Need, and Impacts on the Transmission Grid for Scenarios Until 2050 Study CharacteristicsdStudy Data Sheet Study title
Energiespeicher fu¨r die Energiewende, Speicherungsbedarf und Auswirkungen auf das ¨ bertragungsnetz fu¨r Szenarien bis 2050 U (Energy storage facilities for the energy transition, storage need, and impacts on the transmission grid for scenarios until 2050)
Year of publication
2012
Author(s)
F. Adamek, T. Aundrup, W. Glaunsinger, M. Kleimaier, H. Landinger, M. Leuthold, B. Lunz, A. Moser, C. Pape, H. Pluntke, N. Rotering, D. U. Sauer, M. Sterner, W. Wellbow (ETG-Task Force Energiespeicherung)
Institution(s)
RWTH Aachen, Fraunhofer IWES, TU Kaiserslautern, Ludwig-Bo¨lkow-Systemtechnik GmbH, Hochschule Regensburg
Support/Occasion
The power Engineering Society (ETG) in the German Association for electrical, electronic & Information technologies (VDE)
Aim of study
Analyzing the storage need and impact on electricity grids for different shares of renewable energy in the electricity system
Relevant Chapter(s)
Assessment to energy storage need
Analysis of Energy Storage Need Approach and models used
Annual operation simulation model of power plants and electricity storage (RWTH Aachen), electricity production of renewable sources on basis of lead scenario 2010 (IWES), storage model (RWTH Aachen)
Spatial horizon/ resolution
Germany without international exchange/14 14 km2 as for the lead study 2010 (SimEE)
Temporal horizon/ resolution
2050, 1 year between 2020 and 2025, 1 weather year (2007)/hourly
Technologies/ technical resolution
Conventional power plants, renewable power plants, short-term storage (mix: DSM, pumped hydro, CAES, batteries), long-term storage (H2/CH4), grid: no restrictions (‘copper plate’)
Quantitative Assumptions and Results Input data/ assumptions
Energy system from lead study 2010, weather data, grid optimally extended, no imports/exports, only electricity system, 100% scaled from 80%
Individual results Dispatchable electricity required in Germany with ambitious targets
40%: Curtailment and conventional power plants efficient for balancing 80%/100% scenario
Short-term storage
Long-term storage
Electric power (GW)
14e26/35
18e29/42
Storage cap (TWh)
0.07e0.14/0.18
7e8/26
Storage power (GW)
14e28/36
18e36/68
In addition to the generation capacities, required backup capacities are indicated in the results. The numbers can be found in the table. The needed backup capacities can be reduced by reserve sharing between the regions at about 35e40%. Furthermore, demand response of 20% was assumed. Required backup capacities as well as required transmission capacities would increase strongly without demand response. The EU-project assessed the ‘required share of stable supply’ in the EU-27 for different shares of renewables in
the system (Table 6.11). It uses hourly data from the IRENE-40 scenarios that are close to the ECF Roadmap 2050 scenarios. Based on these data balancing need and, by assuming costs for several options for balancing, cost estimates were derived. The net need for balancing, defined as the difference between peak and off-peak electricity demand minus stable supply, is assessed to be only from a share of 28% variable renewables of the electricity supply onward. At the maximum of 75% fluctuating generation, the net balancing
Chapter | 6
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
73
TABLE 6.10 Roadmap 2050, a Practical Guide to a Prosperous, Low-Carbon Europe Study CharacteristicsdStudy Data Sheet Study title
Roadmap 2050, a practical guide to a prosperous, low-carbon Europe
Year of publication
2010
Author(s)
European climate foundation (ECF)
Institution(s)
European climate foundation (ECF)
Support/Occasion
European climate foundation (ECF)
Aim of study
‘Outlining plausible ways to achieve an 80% reduction target from a broad European perspective’
Relevant Chapter(s)
Especially, Decarbonizing power: Technical results
Analysis of Energy Storage Need Approach and models used
Generation dispatch model (from Imperial College London) optimizing transmission requirements, backup plants and balancing actions on a daily basis
Spatial horizon/ resolution
EU-27/regions in Europe
Temporal horizon/ technical resolution
2050/hourly
Technologies/ resolution
Fossil fuels, solar photovoltaic, wind onshore, wind offshore, other (nuclear, hydro, biomass, geothermal, solar CSP), backup plants, demand response
Quantitative Assumptions and Results Input data/ assumptions
Economic growth from ‘reputable sources,’ shares of energy, power, and demand from PRIMES model, demand and emissions via extrapolation, energy efficiency, etc.
Individual results Dispatchable electricity required in Europe with ambitious targets
Electricity production by backup plants (baseline: 120 GW) Demand response 20% (0%)
40% RE
60% RE
80% RE
Power (GW)
190 (270)
240 (325)
270 (375)
Energy (TWh)
17e83
21e105
24e118
Renewable Energy Systems (RES) curtailment (%)
2 (2)
1 (2)
2 (3)
a
a
Rough estimates assuming load factor of 1e5%.
need of 930 GW will, following the results, most likely be covered by 20% demand response, 20% interconnections, 25% storage, 27% backup capacity, 5% RES curtailment, and 3% outages. This would result in about 230 GW of storage power required for 100% renewables in the system. In a closer look at the roadmap for 2050 (Table 6.12) an optimization of the power generation system and the transmission system was carried out for Europe from today to 2050 in steps of five years considering options for electricity storage. The dispatch is calculated for four typical days per year (one for each season) for the individual countries on an hourly basis. The storage usage is a result of the optimization process. The installed power results in 140 GW for the whole region. In total 58 TWh electricity is produced by storage. These estimates result for an optimal grid (lower estimate in the table). Higher estimates are assessed for a ‘moderate extension of European interconnectors’dlimiting the
extension to projects that ‘have already entered the planning or permission phase today’ ([11], p.2). However, the optimal grid leads to building of additional open cycle gas plants as backup close to the consumption areas because of the large geographical distances between supply and consumption. Additionally, a switch from biomass and concentrated solar power (CSP) to wind is observed with a better grid. A grid vs storage in a 100% renewable Europe study (Table 6.13) is focused on an optimization of an energy system consisting of wind and photovoltaic power facilities, varying the amount of backup capacities, a grid as ‘copper plate’ with varying radius, and varying storage capacity on an hourly basis for 8 weather years. Wind and photovoltaic power production is installed in a fixed (optimal) relation to each other of 65%/35% of electricity consumption with respect to the whole of Europe (see also [12]). The scheduling is optimized in such a way that the backup capacity required is minimized. The different radii
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
TABLE 6.11 Assessment of the Required Share for a Stable Electricity Supply Until 2050 Study CharacteristicsdStudy Data Sheet Study title
Assessment of the required share for a stable EU electricity supply until 2050
Year of publication
2011
Author(s)
W. Lise, J. van der Laan, K. Rademaekers, F. Nieuwenhout, C. Kirchsteiger
Institution(s)
ECORYS Nederland BV, energy research Centre of the Netherlands (ECN), DG energy
Support/occasion
European Commission
Aim of study
‘To assess the required share for a stable EU electricity supply until 2050 (and the midterm 2030)’
Analysis of Energy Storage Need Approach and models used
Statistical analysis of hourly data with respect to the maximum residual load/balance need (and costs)
Spatial horizon/ resolution
EU27 þ Norway, Switzerland/nine European regions
Temporal horizon/ resolution
The year 2050/hourly
Technologies/ technical resolution
Nuclear, solar, wind, hydro, other renewable, solids-fired, gas-fired, oil-fired, biomass waste-fired fuel cell, geothermal heat, other fuels
Quantitative Assumptions and Results Input data/ assumptions
Scenarios from Infrastructure Roadmap for Energy Networks in Europe, IRENE-40 RES, close to ECF 80% RES used (See http://www. irene-40.eu/)
Individual results Dispatchable electricity required in Europe with ambitious targets
Net balancing need Share of variable renewable electricity
[GW]
<28%
0
40%
280
50%
430
60%
600
70%
820
75%
930
of the grid lead to local regions with 100% renewable energies with diverging ratios of wind to photovoltaic for which the supply was scaled to fit the demand in each case. The study proposes that 10% of consumption is the maximum possible contribution of biomass in Europe. Starting from this value, fixing the backup capacity to 10% of consumption, and making the often-made assumption that the national grid is well established, but international exchange is weak or zero, would suggest about 100e500 km of radius for the copper plate. In this case storage capacity of a bit less than a week of average demand is necessary for the smaller size and a few days (around 2 days) for the larger size. With a well-established grid without restriction in Europe a storage capacity of only about 4 h is needed to cover the average demand. Storage size expressed in percentages of total consumption results as follows: only distribution grid without restriction: 2%, regional/small country grid without restrictions: 1.5%, national grids without restrictions: 0.5% and European grid without restrictions: 0.05%. Installing larger capacities of renewable energies (e.g., by 130%) would be another alternative to storage implementation, but turns out to be too costly. Assuming instead a scenario without extra backup capacity the storage need increases strongly. For good national situations a storage capacity of 30e90 days would be sufficient while for a good international grid 7e30 days would be needed. More results are shown in Table 6.13. A study of storage- and grid-expansion needs with 100% renewable electricity (Table 6.14) involves an optimization of a system consisting of photovoltaic and wind power for power production, short-term and long-term storage, and a high-voltage direct current (HVDC) grid for international connection to satisfy the annual demand. The genetic optimization process starts with a random sample of technologies installed and calculates the costs for the weather years 2000e2007 in an hourly simulation as indicator for its fitness to the task. Via the genetic algorithm new generations of the overall system are derived until the costs to satisfy the load in each hour converge to a minimum. With the assumed annual demand of about 4000 TWh a maximum load of about 670 GW is reached in the EUMENA region (Europe, Mediterranean region, and North Africa). About 1800 GW wind power is installed with additionally about 1100 GW photovoltaic power. The capacity of the built HVDC grid is 1100 GW * 1000 km. The short-term storage installed by the optimization process has a capacity of only 2 TWh while it shows an electric power of 230 GW and a storage power of 480 GW. The long-term storage, however, shows a higher storage capacity with about 320 TWh and electrical power of 710 GW compared to storage power of 570 GW. The study of storage needs in an electricity supply with (100%) renewable energy (Table 6.15) assesses the storage
Chapter | 6
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
75
TABLE 6.12 Roadmap 2050da Closer Look Study CharacteristicsdStudy Data Sheet Study title
Roadmap 2050da closer look. Cost-efficient RES-E penetration and the role of grid extensions
Year of publication
2011
Author(s)
M. Fu¨rsch, S. Hagspiel, C. Ja¨gemann, S. Nagl, D. Lindenberger, L. Glotzbach, E. Tro¨ster, T. Ackermann
Institution(s)
Institute of energy economics at the University of Cologne (EWI), energynautics
Support/ Occasion
Gesellschaft zur Fo¨rderung des Energiewirtschaftlichen Instituts an der Universita¨t zu Ko¨ln gGmbH
Aim of study
Integrated optimization ‘of the overall European electricity system development until 2050, while comprising fossil, nuclear, and renewable generation, storage as well as transmission of electricity’
Analysis of Energy Storage Need Approach and models used
Analysis of typical days in an hourly resolution/dispatch, European electricity market model, grid model (European extra high-voltage grid)
Spatial horizon/ resolution
EU27 (without Cyprus, Malta) þNorway, Switzerland, North Africa as satellite region/subcountry level (different regions for wind, solar)
Temporal horizon/ resolution
Until 2050, dispatch: 4 typical days per year/5 year steps, dispatch: Hourly
Technologies/ technical resolution
Vintage classes of conventional plants (hard coal, lignite, natural gas), nuclear power plants, storage technologies (pumped hydro, hydro storage, CAES), renewable technologies (photovoltaics (roof, ground), wind (onshore, offshore), biomass (solid, gas), biomass CHP (solid, gas), geothermal, hydro (storage, run-of-river), solar thermal plants (CSP), grid: European extra high-voltage grid
Quantitative Assumptions and Results Input data/ assumptions
Electricity demand, technology parameters (plants, transmission), RES-potentials and feed-in profiles, political restrictions
Individual results Dispatchable electricity required in Europe with ambitious targets
Storage use in 2050 Whole region
Germany
Electric power (GW)
92e141
7.89
Electric energy (TWh)
58e113
9.1e10.2
need for different variations of wind and solar technologies used for power production primarily for Europe. Further variations include the availability of a perfect grid, the height of production reserves and wind power technologies (20% and 50% degree of usage). For the assessment a simulation in time steps of 3 h is chosen. The results of the simulation show that a storage power of 160% of the average consumption is sufficient for the scenarios. The results for the storage capacity needed are presented in terms of the time period over which an average consumption has to be provided by energy storage or by other options to fill gaps in the power production of
varying renewable production. For a production reserve of 30%, used to balance storage losses and to bridge years with low irradiation and wind speed, the minimum storage demand assessed was 6 days (50% degree of wind power usage, no grid restrictions), the maximum 30 days (20% degree of wind power usage, no international grid connections). Assuming a demand of 4900 TWh (see ECF: Roadmap 2050) and 1500 GW installed capacity in Europe, which is about the height assumed for other European studies, this would result in storage power required of 895 GW (160%) and a storage capacity required of 80e400 TWh (6e30 days).
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
TABLE 6.13 Grid vs Storage in a 100% Renewable Europe Study CharacteristicsdStudy Data Sheet Study title
Grid vs storage in a 100% renewable Europe
Year of publication
2012
Author(s)
F. Steinke, Ph. Wolfrum, C. Hoffmann
Institution(s)
Siemens Corporate technology, Siemens Infrastructure & Cities
Support/Occasion
Paper in ‘renewable energy’
Aim of study
Assessing an order of magnitude for the dependence of backup system requirements from grid extension and storage capacities
Analysis of Energy Storage Need Approach and models used
Optimal scheduling of assumed supply technologies to fit the load with General Algebraic Modeling System (GAMS)/CPLEX optimization package with parameter variation of grid (copper plate size), storage, and backup capacities
Spatial horizon/ resolution
Europe/control areas, 50 50 km2 grid
Temporal horizon/ resolution
One year/hourly
Technologies/ technical resolution
Wind (65% of consumption), photovoltaic (35% of consumption), backup capacities, grid: different sizes of a ‘copper plate’
Quantitative Assumptions and Results Input data/ assumptions
2007 demand with European Network of Transmission System Operators for Electricity (ENTSO-E) curves, 65% (of consumption) wind, 35% photovoltaics, grid: Copper plate within circular regions of varying radius R (local 100% scenarios), hourly weather data for 8 years
Individual results Dispatchable electricity required in Europe with ambitious targets
Storage capacity needed assuming demand of 4900 TWh per year (s. ECF: Roadmap 2050 if 10% (490 TWh) and 0% backup capacity is realized Radius of grid without restrictiona
Storage capacity required (TWh)b 10% Backup
0% Backup
25 km (Distribution grid)
94 (7d)
1200 (around 90d)
100 km (Regional grid)
81 (6d)
400e1200 (30e90d)
500 km (National grid)
27 (2d)
400e1200 (30e90d)
3000 km (European grid)
2.2 (4h)
94e400 (7e30d)
a
averaged over 16 center points over Europe. roughly estimated from the figures.
b
A study of the prospects for large-scale energy storage in decarbonized power grids, Table 6.16, has the aim to analyze the role of long-term storage in a future electricity system with a high share of renewable energy used. The basis consists of data for the generation mix and the daily and annual load curves. Photovoltaics and wind are simulated on the basis of typical technical behavior. Simulating the smoothing effect of randomly varying power from wind turbines reveals that variation ratios between 10% and 30% can be expected if the fluctuations are independent of each other. While most of the variations can be balanced with
existing natural gas combined cycle plants, particularly in 2010, by 2050 large power variations will prospectively exceed the power at full load, which can be provided by the middle load operation. Therefore, other solutions are required and these are proposed to be storage plants. The typical daily load curves show surpluses and, thus, storage requirements of 40e100 GW. Considering the already existing 33 GW storage power installed in Western Europe, further 7e67 GW of balancing capacities have to be installed to be able to deal with prospective wind power fluctuations in 2050.
Chapter | 6
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
77
TABLE 6.14 Storage- and Grid-Expansion Needs with 100% Renewable Electricity Study CharacteristicsdStudy Data Sheet Study title
Speicher- und Netzausbaubedarf in einem europa¨ischen Elektrizita¨ts-versorgungssystem mit 100% EE-Versorgung (Storage- and grid-expansion needs in a European electricity supply system with 100% renewable energy)
Year of publication
2012
Author(s)
T. Thien, M. Leuthold, F. Steinke, D. U. Sauer
Institution(s)
ISEA RWTH Aachen, E.ON ERC RWTH Aachen, JARA energy, Siemens AG
Support/Occasion
Paper for VDE conference ‘Smart grid,’ 5./6.11.2012
Aim of study
Estimation of storage and grid requirements for a scenario of 100% wind and photovoltaic
Analysis of Energy Storage Need Approach and models used
Deriving a cost-minimized energy supply system via a genetic algorithm
Spatial horizon/resolution
Europe, Mediterranean region and North Africa (EUMENA)/country groups
Temporal horizon/ resolution
One year/hourly
Technologies/technical resolution
Wind power, photovoltaic, short-term storage (total efficiency: 81%), long-term storage (total efficiency: 35%), HVDC grid
Quantitative Assumptions and Results Input data/assumptions Individual results Dispatchable electricity required in Europe with ambitious targets
Hourly weather data (2000e2007), load curves, cost data, technical parameters Short-term storage
Long-term storage
Storage capacity (TWh)
2
320
Electric power (GW)
230
710
Storage power (GW)
480
570
The study mainly shows a framework of how the task of estimating power can be tackled. For established estimates, a detailed analysis of smoothing effects in real situations has to be carried out. In a last step the assessment is applied for other regions of the world. The different storage needs assessed particularly depend on the load curves and the shares of photovoltaic and wind implemented in the energy system. For the whole world it is assessed that a storage capacity of 189e305 GW is needed (15e30% net variation). This value is assessed here only for short-term variations and requires supplement assessments of storage needs for other timescales.
6.4 DISCUSSION OF STUDY RESULTS The collection of studies above shows that various types of approaches are followed to estimate the future demand for energy storage. Besides the derivation of complete energy scenarios for which storage technologies are among the
issues to be taken into account, other studies specifically concentrate on the derivation of storage usage and storage demand. The studies show that the assessment of storage need does not include only one aspect. A bundle of technological parameters will, in the end, be decisive in the selection of technologies for specific tasks and thus will determine the need for specific technologies to supplement the variable electricity supply from renewable sources (mainly from wind and solar irradiation). In order to carry out a detailed discussion, both the studies on country and continent level, and the studies looking at individual tasks in smaller regions, at the local area, and at different selected case studies have to be investigated. The study review here starts by concentrating on work analyzing the national (German) and continental (European) levels. The national and international scenario analyses, can provide assessments of the overall installed power and
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
TABLE 6.15 Storage Needs in an Electricity Supply with (100%) Renewable Energy Study CharacteristicsdStudy Data Sheet Study title
Speicherbedarf bei einer Stromversorgung mit erneuerbaren Energien (Storage needs in an electricity supply with renewable energy)
Year of publication
2010
Author(s)
M. Popp
Institution(s)
TU Braunschweig
Support/Occasion
Dissertation
Aim of study
Estimation of storage need for covering the electricity demand to 100% with renewable sources
Analysis of Energy Storage Need Approach and models used
Simulation of storage need per time step, including variations between full (copper plate) and no grid, of different shares of existing production reserves, of different mixtures with respect to wind and solar power and of different wind power technologies
Spatial horizon/ resolution
Europe/wind data: 50 grid Elements, solar data: urban centers
Temporal horizon/ resolution
Multiple years/3-hourly
Technologies/ technical resolution
Wind power, solar technology proportional to global irradiation, production reserve, storages (80% efficiency)
Quantitative Assumptions and Results Input data/ assumptions
Up to hourly weather data (2000e2007), load curves, cost data, technical parameters, installed variable electricity power is proportional to the share of electricity consumption of the country within Europe
Individual results Dispatchable electricity required in Europe with ambitious targets
Length of full-load provision assuming 30% production reserve: No international connections
Unlimited grid connections
Optimal mix 20% degree of usage of wind power
30 days
14 days
Optimal mix 50% degree of usage of wind power
16 days
6 days
Storage power required: 1.6 times The average consumption at maximum
energy capacity required, bearing in mind specific tasks, such as l
l
l
long-term storage, bridging gaps of several days to weeks or even seasonal variations, short-term storage, smoothing the load levels on an hourly basis, and very short-term storage, required to serve the demands covered today by the reserve market, which starts from variations of the scale of seconds to variations of some minutes.
From the studies reviewed here it can be seen that not all of the results are presented according to these categories. Furthermore, the assumptions about the underlying scenarios are very different and often implicitly include competing technologies that already deal with the balancing task to a certain extent: l
demand-side management/demand response (sometimes already including the use of batteries, e.g., in cars),
l l
l
l
l
extended overseas networks and wind/solar power, conventional power plants (gas, oil, coal, lignite, nuclear) able to serve mid and peak load, other dispatchable nonconventional power plants (geothermal, biomass, CSP plants with thermal storage (typically storing about six full-load hours)) or undefined import of energy from other, uncharacterized sources and curtailment of power from renewable sources.
The differences between the assumptions behind the analyses, which also include further major parameters, make it difficult to use the various analyses to get an impression about the key needs for balancing. As far as possible in this discussion, the study results were analyzed with respect to the question to assess l l
power capacity required and energy capacity required
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Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
79
TABLE 6.16 Prospects for Large-Scale Energy Storage in Decarbonized Power Grids Study CharacteristicsdStudy Data Sheet Study title
Prospects for Large-Scale Energy Storage in De-carbonised Power Grids
Year of publication
2009
Author(s)
S.-I. Inage
Institution(s)
International energy agency (IEA)
Support/Occasion
International energy agency (IEA)
Aim of study
Analyzing the role that large-scale energy storage systems can play in future power systems
Relevant Chapter(s)
Prospects of energy storage growth
Analysis of Energy Storage Need Approach and models used
Simulating the energy supply via assumptions for the different technologies: photovoltaics: Three weather patterns, wind: randomized assuming Weibull distribution with smoothing effect
Spatial horizon/resolution
Western Europe/Western Europe
Temporal horizon/resolution
One year around 2050/typical daily (6 min resolution)/annual load and synthetic production curves
Technologies/technical resolution
Base load (nuclear, coal, hydro), photovoltaics, wind, natural gas combined cycle plants for middle load
Quantitative Assumptions and Results Input data/assumptions
Generation mix and daily/annual load curve (from BLUE Map scenario, ETP 2008), base load: 37.5%, middle load: 32.5%, wind: 4.6%, photovoltaics: 25.4% Of total production
Individual results Dispatchable electricity required in Europe with ambitious targets
Electric power: 40 (10% variation ratio) to 100 GW (30% variation ratio)
for both, electricity storage and feed-in, considering the three different tasks discussed above. Furthermore, it is discussed how far the results of the studies can be applied to other regions.
even represent the cost-efficient solution. Most of the studies give only values of the required electrical power so that the following summarizing discussion is limited to this aspect.
6.4.1.1 Reserve Energy
6.4.1 Required Electric and Storage Power The task to balance the variable electricity production from renewables can be further subdivided into the storage task and the power provision task, i.e., the provision of positive and negative power. The provision of power relates to the central task to fill occurring gaps due to (unpredicted) variations. This is of course an essential task to ensure a continuous power supply at a high share of renewable energy in the system. The provision of negative power and, thus, extra load, which in case of storage can later be fed in as electricity once more, is connected to the task of using excess amounts of energy produced. This function for which enough storage power has to be installed, is not as crucial as the provision of positive control power, as alternatively plants can be curtailed. Such an option can
Depending on the timescale/task analyzed, different methodologies are applied in the studies. Most studies concentrate on assessing load leveling and long-term balancing. The timescale below 1 h is investigated only within a few studies. Estimates of power demand for this area for Germany are derived by Klaus et al. [13]: 4 GW and Nitsch et al. [14]: about 7 GW for secondary and minutes reserve. Klaus et al [13] come up with a range of numbers starting from about 7 GW and going up to about 15 GW, depending on the approach used (hourly simulation or the concept of secured power) when assuming a maximum of 7 GW import of secured power. They point out that the power can be provided by a mixture of technologies, e.g., biomass power plants, pumped hydro plants, and demand-side management.
Electrochemical Energy Storage for Renewable Sources and Grid Balancing
These values are assessed to be slightly higher than the requirements today as can be seen in Nitsch et al. [14], p. 189, rising from about 5 GW to about 7 GW. However, additional power for the reserve market is provided in the study by remaining conventional or biomass power plants.
6.4.1.2 Load Leveling and Long-Term Storage In order to assess the required power, analyses either with 1 h resolution or on the basis of statistical estimates for secured power are followed. Klaus et al. [13] provide a comparison of both methodologies. It shows that the statistical methodology systematically leads to higher values because of its various characteristics as follows (Klaus et al. [13], p. 109f): l
l
l l
It is often assumed that a secure energy supply has to be provided with only national sources (no import assumed). More extreme situations are generally considered with the statistical methodology. Analyzing real weather data, situations in which all power plants show their worst performance usually do not occur. The potential of load management may be underestimated. Potential systematic correlation between load and supply is not considered.
Values are mainly assessed on the basis of data for a time period with an hourly resolution or for an extreme situation like an evening in winter assuming no wind power but a high load. Looking at results of the national scenarios shows a wide variation in the assessed storage requirement. The results of Adamek et al. [15] suggest that in the case of 40% electricity produced from renewable sources storage is not yet needed for balancing. For the 80% scenarios the estimates for German energy supply in 2050 range from 12 (þ7 (reserve energy)) GW [14] to more than 32 and 35 GW [3,15]. The estimates for the 100% variants are between 31 and 44 GW for [13,14,16] with extreme values of 20 GW from Kirchner et al. [17] and 77 GW from Adamek et al. [15]. Henning and Palzer [18] even install 88 GW of storage power and 94 GW of electric power for the long-term storage option of power-to-gas with additional pumped hydro plants and batteries. A closer look into the studies shows that a more detailed analysis of balancing need is difficult for the German scenarios because imports are not fully specified, neither with respect to the source nor with respect to the application, but play an important role in some scenarios like, for example, in the SRU study [19]. The role of imports is less important for the European scenarios. Only imports from North Africa are considered differently. Assessing the required power for balancing per total production power (installed production power in EU
countries plus CSP, not including power of storage facilities) and plotting it against the share of varying electricity production from renewable energies with respect to total production power, results in the picture presented in Figure 6.2. To show the ECORYS results, the power data from the ECF Roadmap 2050 scenarios are taken, which are comparable to the IRENE-40 scenarios used in the analysis. The ratio of balancing power per total electricity production installed for the studies of SRU [19] and Thien et al. [10] are much lower than would have been expected from the other results. The reason is that they consider a much larger region, covering, not only Europe, but also the complete Mediterranean region and parts of North Africa. Obviously, a higher amount of variable renewable energy integrated in the system over such a large area requires relatively less balancing power. To make the results of the two studies comparable to the others, the value of the total power installed is scaled down to about the power installed in other European scenarios (1500 GW), which can be interpreted as the assumption that besides CSP only wind and photovoltaic power are additionally installed in the non-European Mediterranean and Northern African areas and the amount of balancing technologies remains the same. The results are printed in Figure 6.2 in the data points without filling. It shows that these roughly adapted values would fit into a correlation curve very well. A more elaborate correlation would require a further analysis of the results from the different models and a more sophisticated adaption of the results. Figure 6.2 shows that the amount of installed power to serve the balancing need divided by the total power installed for electricity production increases with the share of varying renewable sources in terms of power. Starting with no balancing power needed at up to 28% of variable renewable generation, the required balancing power strongly increases to about 50% with around 70% of varying renewables and, considering also the adapted 70 Power of balancing technologies/ total producƟon power (%)
80
60 ECORYS
50
EWI
40
SRU 30
Thien et al.
20
Popp (1500 GW)
10
SRU (1500 GW) Thien et al. (1500 GW)
0 0 20 40 60 80 100 Share of wind and photovoltaic power (%)
FIGURE 6.2 Results for power of balancing technologies divided by the total production power installed at different shares of variable renewable power. Source: Own calculations based on data from Refs. [10,11,19e21].
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Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
results from SRU [19] and Thien et al. [10]; it increases to more than 60% with 100% varying renewables installed. Although the results seem to be consistent with respect to the amount of balancing technologies applied and balancing need assessed if the adaptions are considered, a large difference exists between the studies in the types of technologies used to provide the power. While the scenario of ECORYS [20] assesses balancing need directly, the EWI [11] scenario uses thermal power plants fueled with fossil gas and biomass in addition to storage facilities and the SRU scenario uses biomass plants and CSP plants with thermal storage in addition to storage facilities. Thien et al. [10] and Popp [21] assess storage demand for a scenario including only wind and solar photovoltaic. Accordingly, the amount of storage assessed varies strongly between the studies. Starting roughly from low share to high share of renewables the storage demand derived is l
l
ECORYS study [20] (with 20%/without demand response): l 40% electricity from renewables: 190/270 GW l 60% electricity from renewables: 240/325 GW l 80% electricity from renewables: 270/375 GW EWI study [11] (about 80% of electricity from renewables): 92 GW
Then, all for 100% electricity from renewables l
l
l
l
SRU study [19]: 102 GW pumped hydro, 407 GW compressed air storage Thien et al. [10]: 233 GW short-term storage, 711 GW long-term storage Popp [21]: 895 GW storage (160% of average consumption assuming an annual consumption of 4900 TWh has proved to be sufficient) International Energy Agency study [22]: 40e100 GW has to be covered by fast plants or storages
A distinction between different types of storage technologies is only made in SRU [19] and Thien et al. [10] resulting in ratios of 1/5 to 1/4 for short-term storage to long-term storage.
6.4.2 Energy Capacity Need The overall energy capacity required in an energy system is predominantly determined by the type of gaps in energy provision occurring over the year, which may last from several days to weeks. Important gaps show different characteristics and could reduce the power from variable renewables down to 20% or below. An analysis of wind data in Droste-Franke et al. [3] shows that, depending on the share of renewable energies, various gaps differing in depths and lengths can determine the maximum amount of energy required.
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As storage has to be recharged until the next incident occurs, not only the characteristics of single gaps, but also the frequency and timing of such gaps determines the storage capacity needed. The additional, seasonal, variation influences the storage size required as shown in the derived annual loading curve of the long-term storage technologies in Klaus et al. [13]. About 40e45 TWh is required in the scenario per event, but seasonal variation and the sequence of gaps require a total storage capacity of from 65 (methane) to 75 (hydrogen) TWh. Henning and Palzer [18] produced similar results with 86 TWh of storage size required in the cost-minimal system and, with disadvantageous timing of an individual lack of 4 weeks in wind production, a maximum of 140 TWh is derived for a medium cost scenario. Difficulties arise from the analysis of the studies, because, particularly in scenario analyses, the total energy provided per year is shown rather than the storage size required. More promising in this regard are studies concentrating on the analysis of storage demand, which often assess the required storage capacity alone. The results for an energy supply with about 80% electricity produced from renewables in Germany range from 1.7 (for one incident) through 2.3e4.8 TWh and 7e8 TWh (considering long-term storage explicitly) as derived by Droste-Franke et al. [3], Hartmann and Barth [23], Kuhn and Ku¨hne [24] and Adamek et al. [15], respectively, with results that are all in the same order of magnitude. With the share of renewables increased to 100% in Germany, a larger amount of storage capacity is required. For this case the SRU [19] results indicate only 0.14 TWh storage capacity required, which represents mostly shortterm storage. However, a high amount of biomass is assumed, which can be used to tackle most balancing tasks. Electricity production from biomass in Germany is 37 TWh higher than in the scenario combining Denmark, Norway, and Germany in which a storage capacity of 31 TWh, mainly in pumped hydro storage, is assumed. As about 16 TWh was the need of Norway and Denmark in the scenario without international exchange and it is to be expected that the effects of synergy occur with the combination, presumably more than 15 TWh of storage capacity is used for balancing the German electricity production. Hartmann and Barth [23] and Adamek et al. [15] come up with almost the same numbers for energy capacity needed: 24 TWh compared to 26 TWh. Furthermore, Steinke et al. [25] assess a needed capacity of about 27 TWh if a good national electricity grid is installed. The study of Klaus et al. [13]; as already mentioned above, results in higher amounts of 40e45 TWh per case and about 65 (methane) to 75 (hydrogen) TWh as total storage size, assuming only a small amount of electricity production of 11 TWh from biomass. Henning and Palzer [18] apply gas storage of 86 TWh in the cost-optimal scenario. Furthermore, they
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
carry out a sensitivity analysis with different timings of wind gaps lasting about a month with similar data that result in a maximum of 140 TWh storage size required if the gap occurs in February. These numbers compare to the amounts of electricity from storage aggregated over 1 year in other scenarios of 54.7 TWh [17] and 69 TWh [14]. For the European scale many studies provide numbers for aggregated energy produced with energy storage, but only four of the analyzed studies give numbers for energy capacity required. Steinke et al. [25] assess 2 days to 4 h with increasingly better grid extension from good national to good European grid that are used additionally for 10% backup capacity. This results in 27e2.2 TWh with about 490 TWh of backup capacity if 4900 TWh of electricity production is assumed [26]. Thien et al. [10] come up with numbers of 320 TWh energy capacity representing 450 h (19 days) of full load required and additionally about 2 TWh (9 h) for short-term storage for Europe plus the Mediterranean region and North Africa. Results from Ref. [21] indicate 6e30 days of electricity production as the range of storage size developing with different assumptions on the available grid connections and the wind technology applied and assuming a production reserve of 30%. This lies in about the same range as the estimates from the studies discussed above. For the SRU study Scholz [19] comes up with a value of 17 TWh energy capacity required for the same regions, including 16 TWh from pumped hydro storage and 1 TWh from compressed air storage. This study additionally assumes a large amount of electricity from biomass per year of 360 TWh together with 1080 TWh of annual electricity production from CSP plants in the system while allowing for 15% of import with respect to the annual balance in all countries. All in all one can see that the amount of energy storage capacity required strongly depends on the assumptions made in the studies. With a higher amount of biomass and a larger share of import assumed, less storage is needed.
6.4.3 Transferability of the Results to Other Regions The changes in results depending on the different assumptions for the energy system and the different regions considered in Europe show that a simple transfer of the findings to other regions is not possible. However, some influences and dependencies that can be identified from the analyzed studies are discussed in the following.
6.4.3.1 Weather Conditions The weather conditions have the highest influence on storage power and energy capacity required. Thus, results for regions with similar weather conditions to those in Europe could be similar, but for a good transferability of
results, beside the general conditions, additionally specific weather phenomena in the region that may lead to stable weather conditions over several days and even weeks have to be considered. Such extremely stable conditions determine especially the requirements for energy capacity. As an example from the studies, it can be seen that enlarging the region of Europe by adding also the Mediterranean region and North Africa leads to less variable electricity production from solar irradiation and wind and, thus, to more reliable production (s., e.g., [10,19]). The reason is that in the additional regions, in general, less frequent changes between low and high pressures occur than in Europe and, thus, more stable weather conditions are experienced in general. Figure 6.3 gives an overview of the general wind and weather systems. While Europe lies to a large part within the West wind drift zone, Northern Africa lies in the subtropical high-pressure belt. The regions with overall similar weather conditions to those in Europe are particularly those between about 30 and 60 latitude all over the world. In order to have comparable situations, the regions in focus should also be of comparable spatial extension to the regions analyzed. A more detailed correlation of storage demand with specific weather events and an analysis of historical weather data with respect to their occurrence, together with projections on how the extreme weather events and their influence on wind and solar irradiation will prospectively develop within the next decades, could help to get a better understanding and more robust estimates for the future energy supply, also for other regions.
6.4.3.2 Topological and Geological Conditions The topological and geological conditions of the regions analyzed strongly influence the technological and economical storage potential with respect to pumped hydro, compressed air, and hydrogen/methane storage underground. Europe has great potential for pumped hydro particularly in Scandinavia, in the Alps and some highlands spread over Europe. Furthermore, some regions like Germany show good conditions for building salt caverns that can be used for the storage of air or other gases. Topological conditions also have influence on the optimal distribution of wind power plants over the region. Slightly increasing altitude from the coasts with some highlands and higher mountain areas as existing in Germany is generally a good situation for efficient wind power installations spread over the whole country. In contrast, with high coasts or completely flat land or only slightly increasing altitude without additional highlands the best potential for wind power is mainly at the coast. Having high coasts, as found in Norway, pumped water is, furthermore, a good option for the storage of electricity close to the converters.
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Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
Polar high Circum-polar East winds Subpolar lows Polar front West wind dri zone
Arc fall winds
Sub tropical high pressure belt
Descending air in highs
83
Rising air in lows Ferrel-circulaon
Northern Hadley cell Nord-East trade wind
Inner-tropical convergence zone
Rising air in convecon cells
Equator
South-East trade wind
Southern Hadley cell
Sub tropical high pressure belt
Descending air in highs
West wind dri zone Polar front Subpolar lows Circum-polar East winds Polar high
Ferrel-circulaon Rising air in lows Arc fall winds
FIGURE 6.3 General global wind and weather patterns (source, Ref. [27]), “H” means a high-pressure area (high) and “T” means low-pressure area (low).
6.4.3.3 Political Conditions Politically installed funding schemes and (legal) framework conditions in the countries influence the future development of energy systems. Furthermore, exchange between countries and between regions within a country depends on the level of collaboration in setting up an energy system. Therefore, the right political conditions and adjusted political strategies are crucial elements for the realization of technological or economical optimal solutions. Differing political situations could lead to differences in all areas in the energy system including among other things the energy demand, installed power technologies, grid installation, and usage of technologies.
6.4.3.4 Electricity Grid The electricity grid is the technical precondition for electricity exchange between countries and within countries. The studies show that grids can only help with balancing demand if excess and demand occur in different regions at the same time. Temporal shift between production and demand cannot be tackled by grids alone. Even with an optimal grid covering large regions there still exists need for balancing, which can be covered by energy storage or alternative balancing technologies (s., e.g., [25]). Grid extensions are particularly needed if the structure of the
electricity system is strongly changing. Especially low potential for renewable energy or little usage of existing potential in a country or in parts of the country leads to an increasing need for spatial exchange between countries or within a country. It can be seen from the studies that storage demand decreases with decreasing net restrictions. The dependence of the results for storage demand on the realization of the electricity grid can be seen in the work of Steinke et al. [25] who vary the size of regions with good grid connection, assuming no external exchange. The storage demand is clearly decreasing with an increasing size of the areas with good grid connections. Another example is shown in the SRU study (s., e.g., [19]). Here, three scenarios of the three countries Germany, Denmark, and Norway are compared to each other differing in the amount of electricity exchange allowed. Relying on exchange of electricity, strongly changes the electricity production mix and the usage of energy storage. Exchange here leads to an even larger use of storage capacities because of opening the potential for storing electricity produced in Germany in storage facilities in Scandinavia instead of extending other domestic alternatives like, e.g., electricity production from biomass in Germany. However, balancing the need-per-total-power installed in the region is decreasing and this can be even better observed in the case of the extension of the area to Europe plus Mediterranean countries and North Africa.
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
6.4.3.5 Competing TechnologiesdBiomass, CSP, Backup Capacities, Curtailment, and Demand Side Measures Biomass, CSP (with thermal storage) and other existing backup capacities (including CCS technologies) can take over the tasks of balancing to a large amount if the usage of excess electricity production from renewable sources is not an issue. Particularly, competing technologies using renewable sources are in direct competition with the installation of photovoltaic and wind power together with storage. Further options are, of course, curtailment to cut peaks of wind and solar electricity production and demandside measures that can temporally reduce or increase the load. Having all the alternative options in mind, it becomes clear that storage facilities are only one of several options to balance variable electricity production and the storage need is therefore very dependent on the design of the remaining electricity system. Thus, in general, it is much easier to discuss or transfer results on balancing need than results on storage demand.
6.5 CONCLUSIONS The discussion of studies shows that the large number of influencing parameters and differences in the studies make it difficult to give precise estimates for the storage capacity required dependent on the share of renewable energies in the system. In order to get at least an idea about the storage need, three major tasks and specific requirements were distinguished: very short-term balancing (reserve energy, time-scale: below 1 h) and short-term balancing (load leveling, timescale: 1 h to several hours), which determine the requirements for storage power as well as long-term balancing (daily to weekly or even seasonal timescale), which determines the required storage size with respect to energy capacity. Furthermore, because the potentials for wind, photovoltaic, and biomass are varying geographically, the region in focus (Germany, Europe) has to be considered so that values can only be derived for certain specific framework conditions. Many studies concentrate on the assessment of total power required for balancing, which is determined by steep gradients in the wind and photovoltaic electricity supply. With respect to the reserve market in Germany it can be said that the requirements may slightly increase. In Ref. [14] the installed capacity is rising from 5 to 7 GW. The reserve energy is used to level out very short-term effects with a timescale of less than an hour, which are occurring anyway, at least in part, because of unforeseen variations in the load. These variations are prospectively similar to those in other regions so that a slight increase in the need for reserve capacity could be expected also for
other regions in the world. By varying the estimation methodologies and discussing technological options Ref. [13] shows the potential range assessed, which starts from about 7 GW (hourly calculation) to about 15 GW (concept of secured power) for the balancing need, when additionally 7% imports are considered. Besides assessments for the typical reserve requirements, which aim at a timescale below 1 h, an additional analysis with hourly resolution can cope with the further power required to react on an hourly scale for load leveling. This is the resolution chosen in most of the selected studies. The studies concentrating on hourly load leveling in Germany result in a controllable power installed (plus energy storage) of about 60e70 GW for an 80% share of renewables in the electricity supply. Adding also the potential imports, the power increases to about 70e90 GW. Although consistently assessed studies result in a higher amount of dispatchable power with a higher share of renewables in the electricity supply, some studies give lower estimates than others. Including imports, which are very important in some of the studies, the estimated values for approximately 100% power production from renewable sources lie between about 50 and 130 GW. Thus, in total, it can be concluded that the control power needed for Germany with a share of renewable energies of about 80% and more of the electricity supply in order to cope with hourly variations is assessed to be in the range of about 50e130 GW. Depending on the scenario composition, the installed storage power is in the order of 20e35 GW for 80% and 20e80 GW for 100% renewables used. One study concludes that electricity storage is not needed at all for balancing up to 40% of electricity from renewable sources. Looking in detail into the studies for Europe shows that a relationship between the share of variable renewables and the balancing need in terms of power is likely from the results of the four applicable studies. However, the derivation of a sound correlation would require a more detailed analysis. The results indicate that, below about 28% of varying renewables, extra balancing need does not exist in the European electricity system. From this percentage onward the need could increase up to approximately 50% for the ratio of dispatchable power to total production power if power production from variable renewable sources reaches 70%. With higher shares of variable renewables the balancing need would prospectively increase further. Scholz [19] and Thien et al. [10] show that the share of variable renewables can be increased without any higher relative balancing demand by increasing the region considered to Europe plus Mediterranean countries and North Africa. Assuming that the balancing demand in these studies solely results from the installations in Europe indicates that with further investigations a correlation between the share of variable renewables and balancing demand could potentially be established. The ratio of
Chapter | 6
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
power installed for balancing need to total power installed in Europe could then increase to more than 60%. While a correlation for balancing need seems to be assessable with more detailed analyses, the required amount of electrical power from storage facilities strongly varies between the different scenarios. Of course, in the 100% variable renewable sources scenario only storage is used, but in other scenarios, the controllable power consists, e.g., of CSP and biomass or with lower shares of renewables of gas/oil plants and demand-side measures. The lowest estimate of storage size was derived by Fu¨rsch et al. [11] with 92 GW (70% of renewables, 44% variable renewables). The highest value was assessed by Thien et al. [10] with 940 GW (100% variable renewables). These two results already show the large range that could be expected. In order to assess the energy capacity required, the size and the timing of long gaps in wind power production are analyzed in the studies to obtain insight into the need for long-term or even seasonal balancing. Studies concentrating on Germany come up with values of about 2e8 TWh of storage size needed for a share of 80% renewable energies used in the electricity production and, thus, all are in the same order of magnitude. With 100% of electricity produced from renewable energies, the required storage size increases. However, the variations in the results of the SRU study [19] show that biomass can be used instead of storages. Estimated storage sizes range from about 15 TWh through about 25 TWh to 75 or even 86 TWh. In the case of the 75 TWh storage the single gaps in power are much smaller with about 40e45 TWh. The importance of the timing of gaps is shown with a variation carried out by Henning and Palzer [7] resulting in a maximum of 140 TWh and, thus, nearly a doubling of size is required if bad timing occurs. Studies looking at a larger region like Europe show that a smoothing effect can be observed by exchanging electricity from variable renewables internationally. Furthermore, more sources of dispatchable or more reliable production of electricity from renewables can be developed such as from CSP, photovoltaics, and wind in the Mediterranean region and in North Africa. This is impressively shown in Ref. [25], which assesses that 27 TWh (2 days) of storage size is needed if a region with a good national grid and without international exchange is assumed and 10% backup capacity exists. With no backup capacity the estimate for a good national grid and no international exchange is that 30e90 days of storage capacity is required while, with a good European grid, 7e30 days of storage capacity would be sufficient. This compares well with the results of Ref. [10], which comes up with about 3 weeks (320 TWh) of full load hours of long-term storage required and Ref. [21], which shows a range of 6e30 days of storage capacity required, depending on the grid performance and the wind power technologies used. The discussion in
85
Ref. [25] emphasizes that the storage demand has to be discussed with respect to different grid conditions. With bad grid connections between regions and no backup capacity installed, which would be a worst case situation, the (average) storage demand for the regions increases to about 90 days. The review of the studies on need for energy storage capacity showed that a transfer of the results to other regions outside Europe is difficult and can only be done considering the specific circumstances in the scenarios to be analyzed. This holds particularly for long-term storage demand, which highly depends on extreme weather conditions varying strongly over different regions. The findings for very short-term balancing (reserve capacity) and load leveling could be comparable in other regions, particularly in regions also situated in the west wind drift zone (between about 30 and 60 of Northern and Southern latitude), because the wind systems and general weather conditions are similar to those in Central Europe/Northern Africa and at least part of the reserve is required to manage load variations.
ABBREVIATIONS CAES Compressed air energy storage CC Combine cycle CCS Carbon capture and storage CHP Combined heat and power CSP Concentrated solar power DSM Demand-side management HVDC High-voltage direct current RE Renewable energy
REFERENCES [1] dena. Studienlotse. Analysen zur Umgestaltung des Energiesystems. Deutsche Energie-Agentur (dena), http://www.effiziente-energie systeme.de/nc/studien-statistiken/studienlotse.html, 2012. [2] J. Eyer, G. Corey, Energy Storage for the Electricity Grid: Benefits and Market Potential Assessment Guide. A Study for the DOE Energy Storage Systems Program, Sandia Report, SAND20100815, Sandia National Laboratories, Albuquerque, 2010. [3] B. Droste-Franke, B.P. Paal, C. Rehtanz, D.U. Sauer, J.-P. Schneider, M. Schreurs, T. Ziesemer, Balancing Renewable Electricity. Interdisciplinary Perspectives on Energy Storage, Smart Grids, E-mobility and Network Extension, in: Ethics of Science and Technology Assessment, vol. 40, Springer, Berlin, 2012. [4] U. Bu¨nger, F. Crotogino, S. Donadei, C. Gatzen, W. Glaunsinger, M. Kleinmaier, M. Ko¨nemund, H. Landinger, T.J. Lebioda, W. Leonhard, D. Sauer, H. Weber, A. Wenzel, E. Wolf, W. Woyke, S. Zunft, Energiespeicher in Stromversorgungssystemen mit hohem Anteil erneuerbarer Energietra¨ger, ETG Task Force Energiespeicher, Energietechnische Gesellschaft im VDE (ETG), VDE, Frankfurt, 2009. [5] J. Nitsch, T. Pregger, Y. Scholz, T. Naegler, M. Sterner, N. Gerhardt, A. von Oehsen, C. Pape, Y.-M. Saint-Drenan, B. Wenzel, Langfristszenarien und Strategien fu¨r den Ausbau der erneuerbaren
86
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
Electrochemical Energy Storage for Renewable Sources and Grid Balancing
Energien in Deutschland bei Beru¨cksichtigung der Entwicklung in Europa und global, 2010. Leitstudie 2010‘. Deutsches Zentrum fu¨r Luft- und Raumfahrt (DLR), Fraunhofer Institut fu¨r Windenergie und Energiesystemtechnik (IWES), Ingenieurbu¨ro fu¨r neue Energien (IFNE), BMU - FKZ 03MAP146, German Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), Bonn. J. Nitsch, ‘Leitstudie 2008’eWeiterentwicklung der ‘Ausbaustrategie Erneuerbare Energien’ vor dem Hintergrund der aktuellen Klimaschutzziele Deutschlands und Europas, 2008. Ivestigations in collaboration with the German Aerospace Center (DLR), German Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), Bonn. H.-M. Henning, A. Palzer, 100% Renewables for Electricity and Heatea Holistic Model for a Future German Energy System, in: 7th International Renewable Energy Storage Conference (IRES 2012), November 12e14, 2012, Fraunhofer Institute for Solar Energy Systems ISE, Berlin, 2012b. J. Nitsch, B. Wenzel, Langfristszenarien und Strategien fu¨r den Ausbau erneuerbarer Energien in Deutschland unter Beru¨cksichtigung der europa¨ischen und globalen Entwicklung, Leitszenario 2009, Investigations on behalf of the German Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), Bonn, 2009. D. Lindenberger, M. Bartels, F. Borggrefe, D. Bothe, R. Wissen, B. Hillebrand, H.G. Buttermann, M. Bleul, Energiewirtschaftliches Gesamtkonzept 2030, Institute of Energy Economics at the University of Cologne (EWI), Energy Environment Forecast Analysis GmbH (EEFA), Bundesverband der Energie- und Wasserwirtschaft (BDEW), Berlin, 2008. T. Thien, M. Leuthold, F. Steinke, D.U. Sauer, Speicher- und Netzausbaubedarf in einem europa¨ischen Elektrizita¨tsversorgungssystem mit 100% EE-Versorgung, in: Paper for the VDE Conference ‘Smart Grid’, November, 5e6, 2012, Stuttgart, 2012. M. Fu¨rsch, S. Hagspiel, C. Ja¨gemann, S. Nagl, D. Lindenberger, L. Glotzbach, E. Tro¨ster, T. Ackermann, Roadmap 2050ea Closer Look. Cost-efficient RES-e Penetration and the Role of Grid Extensions, Final Report, Institute of Energy Economics at the University of Cologne (EWI), energynautics, Ko¨ln, 2011. D. Heide, L. von Bremen, M. Greiner, C. Hoffmann, M. Speckmann, S. Bofinger, Seasonal optimal mix of wind and solar power in a future highly renewable Europe, Renewable Energy 35 (2010) (2010) 2483e2489. T. Klaus, C. Vollmer, K. Werner, H. Lehmann, K. Mu¨schen, Energieziel 2050: 100% Strom aus erneuerbaren Quellen, Umweltbundesamt, Dessau-Roßlau, 2010. J. Nitsch, T. Pregger, T. Naegler, D. Heide, D.L. de Tena, F. Trieb, Y. Scholz, K. Nienhaus, N. Gerhardt, M. Sterner, T. Trost, A. von Oehsen, R. Schwinn, C. Pape, H. Hahn, M. Wickert, B. Wenzel, Langfristszenarien und Strategien fu¨r den Ausbau der erneuerbaren Energien in Deutschland bei Beru¨cksichtigung der Entwicklung in Europa und global, 2012. German Aerospace Center (DLR), Fraunhofer IWES, IFNE, Schlussbericht, BMU - FKZ 03MAP146, German Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), Bonn.
[15] F. Adamek, T. Aundrup, W. Glaunsinger, M. Kleimaier, H. Landinger, M. Leuthold, B. Lunz, A. Moser, C. Pape, H. Pluntke, N. Rotering, D.U. Sauer, M. Sterner, W. Wellßow, Energiespeicher fu¨r die Energiewende Speicherungsbedarf und Auswirkungen auf ¨ bertragungsnetz fu¨r Szenarien bis 2050, ETG-Task Force das U Energiespeicherung, VDE, Frankfurt am Main, 2012. [16] SRU, Wege zur 100% erneuerbaren Stromversorgung, Sondergutachten, Sachversta¨ndigenrat fu¨r Umweltfragen (SRU), Berlin, 2011. [17] A. Kirchner, M. Schlesinger, B. Weinmann, P. Hofer, V. Rits, M. Wu¨nsch, M. Koepp, L. Kemper, U. Zweers, S. Straßburg, F.C. Matthes, J. Busche, V. Graichen, W. Zimmer, H. Hermann, G. Penninger, L. Mohr, H.-J. Ziesing, Modell Deutschland, Klimaschutz bis 2050: Vom Ziel her denken, Prognos AG, ¨ ko-Institut e.V, World Wildlife Fund (WWF), Basel/Berlin, O 2009. [18] H.-M. Henning, A. Palzer, 100% Erneuerbare Energien fu¨r Strom und Wa¨rme in Deutschland, Fraunhofer Institute for Solar Energy Systems ISE, Freiburg, 2012a. [19] Scholz, Mo¨glichkeiten und Grenzen der Integration verschiedener regenerativer Energiequellen zu einer 100% regenerativen Stromversorgung der Bundesrepublik Deutschland bis zum Jahr 2050, Endbericht, Deutsches Zentrum fu¨r Luft- und Raumfahrt, Materialien zur Umweltforschung, SRU, Berlin, 2010. [20] W. Lise, J. van der Laan, K. Rademaekers, F. Nieuwenhout, C. Kirchsteiger, Assessment of the Required Share for a Stable EU Electricity Supply until 2050, 2011 final report, ECORYS Nederland BV, Energy research Centre of the Netherlands (ECN), DG Energy, European Commission, Contract No TREN/R1/350-2008 Lot 2, EUR 24996, Brussels. [21] M. Popp, Speicherbedarf bei einer Stromversorgung mit erneuerbaren Energien, Springer, Berlin, 2010. [22] S.-I. Inage, Prospects for Large-scale Energy Storage in Decarbonised Power Grids, Working Paper, International Energy Agency (IEA), Paris, 2009. [23] N. Hartmann, R. Barth, Bedeutung der Stromspeicher bei hohen Anteilen erneuerbarer Energien in Deutschland, Institut fu¨r Energiewirtschaft und Rationelle Energieanwendung (IER), Universita¨t Stuttgart, 2011. VDI-Berichte Nr. 2157, 285e 303. [24] Ph Kuhn, M. Ku¨hne, Optimierung des Kraftwerks- und Speicherausbaus mit einem iterativen und hybriden Modell, TU Mu¨nchen, 2011. VDI-Berichte Nr. 2157, 305e 317. [25] F. Steinke, P. Wolfrum, C. Hoffmann, Grid vs storage in a 100% renewable Europe, Renewable Energy 50 (2013) (2012) 826e832. [26] ECF, Roadmap 2050, a Practical Guide to a Prosperous, Lowcarbon Europe, European Climate Foundation (ECF), Den Haag, 2010. [27] W. Roedel, Physik Unserer Umwelt. Die Atmospha¨re, SpringerVerlag, Berlin, 1992. [28] N. Hartmann, Data for Scenarios Used in Hartmann and Barth (2011), Personal Communication, Institut fu¨r Energiewirtschaft und Rationelle Energieanwendung (IER), Universita¨t Stuttgart, Stuttgart, 2012.
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies Bert Droste-Franke EA European Academy of Technology and Innovation Assessment GmbH, Bad Neuenahr-Ahrweiler, Germany
Chapter Outline 6.1 6.2 6.3 6.4
Introductory Remarks Selected Studies with German Focus Selected Studies with European Focus Discussion of Study Results 6.4.1 Required Electric and Storage Power 6.4.1.1 Reserve Energy 6.4.1.2 Load Leveling and Long-Term Storage 6.4.2 Energy Capacity Need 6.4.3 Transferability of the Results to Other Regions 6.4.3.1 Weather Conditions
61 63 71 77 79 79 80 81 82 82
The aim of this chapter is to give an overview of studies dealing with the assessment of the requirement for storage in a quantitative way and to provide an impression of the amount of storage that will prospectively be needed depending on the share of renewable energies used for electricity production in future. The number of studies exclusively concentrating on the discussion of the storage demand is small. Furthermore, these concentrate on a variety of aspects. Thus, most of the selected studies discussed here have a different main focus, such as presenting the options for an overall energy system in 2050. Energy storage is in that case only one aspect of the overall system. However, for the purpose of demonstrating that the overall system provides a certain level of secure energy supply, energy system studies show increasing engagement in modeling as one aspect of the need for balancing fluctuations in the provision of electricity from renewable sources and discussing the use of storage facilities. Arising from the governmental project of an energy transition (‘Energiewende’) in Germany many studies have been carried out analyzing options for future energy systems with the focus on Germany in the European context. A first impression
6.4.3.2 6.4.3.3 6.4.3.4 6.4.3.5
Topological and Geological Conditions Political Conditions Electricity Grid Competing TechnologiesdBiomass, CSP, Backup Capacities, Curtailment, and Demand Side Measures
6.5 Conclusions Abbreviations References
82 83 83
84 84 85 85
about the quantity of available studies dealing with the subject can be seen in the (incomplete) list of studies provided by the German Energy Agency [1]. It has about 80 entries considering publications from 2008 to 2012. As, additionally, electricity supply is typically a task for a region of continental rather than global size, the review concentrates on studies carried out for the German and European perspective of storage needs with some discussions on the transferability of the results.
6.1 INTRODUCTORY REMARKS As a result of the derived scenarios, increasing the share of renewable sources used for the production of electricity and heat leads in most areas to an extension of the direct use of sources with variable availability like wind speed and solar irradiation. Variable production is a large challenge for the provision of electricity because the transport of electricity via alternating current with constant quality over the grid requires that input and output of electricity are equal at any time. Differences that could lead to the violation of defined safety ranges must be balanced as soon as possible in order
Electrochemical Energy Storage for Renewable Sources and Grid Balancing. http://dx.doi.org/10.1016/B978-0-444-62616-5.00006-1 Copyright Ó 2015 Elsevier B.V. All rights reserved.
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
to avoid damage to electronic equipment as well as to human beings and to prevent the shutdown of energy supply triggered by safety mechanisms. In practice, a large number of tasks arise with the need of a continuous electricity supply with a high share of variable sources used. Besides matching the supply and demand side, electricity storage can be used to support network management in transmission and distribution grids, optimize network usage, realize power supply in emergency cases, manage the demand charge, manage the quality of electricity, and realize further tasks (see, for example, [2]). Key characteristics of the individual tasks are the specific requirements of charging and discharging power as well as energy capacity. Additionally, it is important how long the technology needs from launch to reach full operation mode. Thus, for a well-designed integration of renewable energies, the fluctuations to be balanced have to be distinguished with respect to different timescales. A more detailed consideration of the variations in the availability of wind and solar irradiation gives more insight into the challenges. While fluctuations can occur in very short timescales down to seconds, e.g., because of rapid cutoff of wind turbines due to storm conditions or fast-changing cloud coverage above photovoltaic plants, the weather conditions and the electricity supply show changes also from minute to minute or hour to hour. A particular gap in production occurs, of course, during night for all technologies using solar irradiation. Longer gaps of electricity production could occur during periods with only small wind speed for several days. The variety of such gaps can be seen in Figure 6.1 showing the load and wind power together with the power prognosis over several days for the Eastern control area in Germany. Besides very sharp peaks in the difference between prognosis and real power production, a gap of about
FIGURE 6.1 Load curve, wind prognosis and wind power in the German Eastern control area during a Period in 2008. Ref. [3], p. 6, based on Ref. [4], p. 13.
10 days was observed. Leveling out the gap to a mean value for the provision of electricity would require a power of several GW over 10 days and, thus, some hundred gigawatt-hour of energy capacity from the balancing technology. Having in mind that currently only 7 GW of pumped hydro is installed in Germany with 40 GWh storage capacity, represented by the area of the vertical bar in Figure 6.1, it becomes obvious that the task can by far not be fulfilled by using the currently installed storage capacity. Finally, seasonal variations of electricity provision and variations between the years also have to be considered for the design of the system. The example makes clear that the higher the share of electricity produced from wind and solar power is, the larger become the gaps. At the same time, situations in which the electricity production exceeds the load will occur and their number will increase. Therefore, options will be required to provide positive and, ideally, also negative control power on the different relevant timescales. Numerous competing technologies exist to fit these tasks: conventional power plants (as used for the provision of balancing power today), the management of loads, further extension of the installed power of renewable energies in other regions together with respective network extensions, and several options for energy storages, electrochemical storages being some of them. Thus, the storage capacity required highly depends on the remaining energy system installed and the available electricity grid. In the following, various studies are presented and discussed, which provide insights into the required storage capacity on the basis of different scenarios for the future energy systems in Germany and Europe. First, the individual studies and study results are described and characterized and subdivided into studies with German and with European focus. Then key results with respect to storage needs are summarized and discussed with respect to selected tasks.
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Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
6.2 SELECTED STUDIES WITH GERMAN FOCUS In the study of the German Environment Agency on the ‘Energy Target 2050’ (Table 6.1) scenarios for 100% electricity from renewable sources are developed. The most interesting one is ‘Regionenverbund’ (network of regions). For this scenario it is supposed that all regions in Germany use their potentials extensively and exchange electricity between each other. The import from outside Germany is assumed to be small. Thus, the scenario should show how 100% electricity production from renewable sources is possible without relying too much on imports from other countries. This scenario is analyzed via a dynamic simulation in more detail. The calculations show a temporal resolution of 1 h and a spatial resolution of 14 14 km2.
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Four years of weather data were applied for the calculations (2006e2009). Thus, influences of weather changes and extreme weather conditions on the electricity production could be investigated in detail. The share of variable electricity production from wind and photovoltaic systems is assumed to be 87% in terms of power and 84% in terms of electricity production. The modeling process starts with the estimation of the base consumption (401 TWh), which includes all types of consumption already observed today. In a next step the base consumption is complemented by additional ‘must-run’ consumption that will occur with the application of new technologies like electric vehicles and heat production. After considering the production of electricity from some renewable sources (wind, photovoltaic, water, geothermal power) as ‘must-run’ facilities for the calculation of the residual load,
TABLE 6.1 Energy Target 2050: 100% Electricity from Renewable Sources, Germany Study CharacteristicseStudy Data Sheet Study title
Energieziel 2050: 100% Strom aus erneuerbaren Quellen (energy target 2050: 100% electricity from renewable sources)
Year of publication
2010
Author(s)
T. Klaus, C. Vollmer, K. Werner, H. Lehmann, K. Mu¨schen
Institution(s)
Umweltbundesamt (German Environment Agency)
Support/occasion
Umweltbundesamt (German Environment Agency)
Aim of study
Vision of a electricity supply in Germany in 2050, realized with renewable energy only
Relevant chapter(s)
Simulation des Szenarios ‘Regionenverbund’ (Simulation of the scenario ‘network of regions’)
Author(s)
C. Pape, M. Sterner, N. Gerhardt, Y. M. Saint-Drenan, M. Jentsch, A. von Oehsen
Institution(s)
Fraunhofer-institut fu¨r Windenergie und Energiesystemtechnik (IWES), Kassel
Analysis of Energy Storage NeeddSimulation of the Scenario ‘Network of Regions’ Approach and models used
SimEE: hourly simulation of load, electricity production renewables, demand-side management (DSM), storage with a fixed merit order
Spatial horizon/resolution
Germany, small import/c. 14 14 km2
Temporal horizon/resolution
Year around 2050/hourly, 4 years of weather data (2006e2009)
Technologies/technical resolution
Conversion: 100% renewable energy (details in the text) Grid: Copper plate in Germany, losses considered Demand: base consumption þ DSM via heat pumps, e-mobility, air conditioner Residual load: 1. DSM, 2. Pumped hydro, 3. Biogas-CHP (combined heat and power) plant, 4. Import renewable energy (RE), 5. turbines with H2/CH4, 6. Biogas turbines (reserve energy)
Quantitative Assumptions and Results Input data/assumptions
Scenario: usage of renewable potentials in Germany, small international exchange
Individual results Dispatchable electricity required in Germany with ambitious targets
Required electric power: 8.6 GW pumped hydro (including 4 GW for reserve energy), 30.4 GW H2-CC (combined cycle)/28 GW CH4-CC þ2.5 GW biogas-CHP, 6.9/9.3 GW imports, 17.5 biogas turbine Required energy capacity: About 50 GWh pumped hydro, >75 TWh H2 or >65 TWh CH4 Required storage power: 7.9 GW For pumping water, 44 GW for electrolyzers
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
adaptable consumption (air conditioning, heat pumps, e-vehicles) is used for smoothing the load (load in total around 500 TWh (average consumption over the 4 years)). For further balancing, pumped hydro power is applied before hydrogen (H2) and methane (CH4) are produced to provide negative control power or biogas combined heat and power (CHP), imports, H2/CH4 in combined cycle gas turbines and biogas turbines are used in order to provide positive control power. In this way 99% of the produced electricity is finally used. Excess energy that could not be used in the described steps has to be curtailed. Providing additional electrolyzers to be able to use also the last percentage of the electricity produced would not be reasonable with respect to the energy benefit achieved. With respect to energy storage it is assumed that today’s pumped hydro plants are extended by a small amount to reach 8.6 GW (turbines, 7.9 GW pumps) in total. Four gigawatt turbines and pumps are used for the provision of reserve power and can therefore not be applied for hourly balancing. With an average capacity of 5.5 h, these provide about 50 GWh of storage capacity. For hydrogen (H2) and methane (CH4) production the calculations show that 30.4 and 28 GW of turbine power is required to fill the gaps in power production, respectively. The maximum storage use per event is about 45 TWh for H2 storage and 40 TWh for CH4 storage, which is possible to be realized with the potential of the system envisaged. However, as the storage cannot be recharged fast enough before the next event occurs in winter, the dimension of storage has to be a minimum of about 75 TWh for H2 and 65 TWh for CH4. In order to have enough excess capacity, the storage size should be increased. As already indicated above, the power of the electrolyzer is chosen so that 99% of the energy can be used over the 4 years. The power required for this assumption is 44 GW. For balancing the residual load, however, further technologies (see above) are also included. Thus, the total power required to balance the residual load is higher. The maximum hourly residual load over the 4 years is 57.3 GW. In addition to the estimates based on hourly simulations, values for the required reserve power based on the statistical concept of secured power are derived. The numbers show a range from 7 GW (hourly simulation) to about 15 GW (concept of secured power) if secured power import of up to 7 GW is assumed. Several technologies, like biomass power plants, pumped hydro, and demand side management can contribute to the reserve market. The study of long-term scenarios and strategies for the extension of renewable energies in Germany (Table 6.2) is the latest in a series of studies (‘Leitstudien’ (lead studies)) that have been carried out since 2007 aiming at proving that an energy supply relying to a large extent on renewable energy sources is possible. The scenarios, called ‘Leitszenarien’ (lead scenarios), are the basis of many further
studies in the area. For instance, most of the studies discussed here with respect to the analysis of German conditions rely on these scenarios. The study discussed here in more detail represents the latest study of the series published in March 2012. While the earlier study published in 2010 also included an analysis of the residual load via a dynamic simulation, using, among other things, the SimEE-model already discussed in the context of the first study ([5], p. 92ff), in this study a model of the Fraunhofer IWES ‘Virtuelles Stromversorgungssystem’ (virtual system of electricity supply) (VSVS) is used together with a version of the REMix model developed by the German Aerospace Center. While the REMix model is used to assess the surrounding electricity production with high geographical resolution and exchange within the area of Europe and North Africa, the VSVS model is used to derive the optimized load management and power plant operation on a more detailed level for Germany. The assessed storage need for a scenario with a share of renewable energy of about 80% in terms of power (including imports of about 5%) is about 9 GW for load leveling with short-term storage, 7e8 GW short-term storage for reserve power, and 3.3 GW for long-term storage. Additionally, about 39e49 GW of power is produced with thermal plants (10 GW from biogas, 3.3 GW from hydrogen, the remaining from fossil fuels). Furthermore, 7e11 GW is imported and up to 20 GW potential for demand-side management is assumed with a high share of electric vehicles, contributing up to 10 GW. Besides the 80% scenarios also a 100% scenario was calculated for 2060. In that case the use of long-term storage for electricity is increasing from 7 TWh per year to 69 TWh per year. The installed turbine power is 28 GW in that case. This is supplemented by 1.8 GW from fossil/ solid sources in thermal power plants, 44 GW of imports, and 10.4 GW from biomass. Estimations of power required for covering the residual load, not considering imports, for Germany result in 12.6 GW turbine power required from pumped hydro. However, the residual load is mainly covered by thermal power plants fueled with fossil fuels as well as biogas and hydrogen (3.3 GW). Overall 46e55 GW of secured power is required resulting in 54e64 GW installed power (including 5% security margin) in this purely national scenario. The study of ways to reach 100% power supply from renewable sources in Germany carried out by the German Advisory Council on the Environment (SRU) (see Table 6.3) compares four different situations of energy political situations with each other. The first is 100% selfproduction of electricity in each hour by each country separately. The second is a regional combination of the energy systems of Germany, Denmark, and Norway in which each country can import and export energy, but,
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65
TABLE 6.2 Long-Term Scenarios and Strategies for the Extension of Renewable Energies in Germany Study CharacteristicseStudy Data Sheet Study title
Langfristszenarien und Strategien fu¨r den Ausbau der erneuerbaren Energien in Deutschland bei Beru¨cksichtigung der Entwicklung in Europa und global (Long-term scenarios and strategies for the extension of renewable energies in Germany, considering the developments in Europe and globally)
Year of publication
2012
Author(s)
J. Nitsch, T. Pregger, T. Naegler, D. Heide, D. L. de Tena, F. Trieb, Y. Scholz, K. Nienhaus, N. Gerhardt, M. Sterner, T. Trost, A. von Oehsen, R. Schwinn, C. Pape, H. Hahn, M. Wickert, B. Wenzel
Institution(s)
German Aerospace Center (DLR), Fraunhofer IWES, IFNE
Support/occasion
German Ministry of Environment (BMU)
Aim of study
Elaborating strategies that show how the long-term climate protection targets and transition to renewable energy sources in Germany can be reached
Relevant chapter(s)
Dynamic simulation of the system for electricity supply; security aspects of the conversion of the energy supply
Analysis of Energy Storage NeeddChapters on Dynamic Simulation and Energy Security Approach and models used
REMix: Cost-minimum optimization Virtuelles Stromversorgungssystem (VSVS): Cost minimizing power plant resource planning with rolling horizon of 48 h and hourly resolution (day ahead-, intraday-market) (mixed integer linear optimization) the models are coupled via technology inventory and imported/exported load
Spatial horizon/ resolution
REMix: Europe with parts of North Africa, 10 10 km2 VSVS: Germany, high resolution for renewable energy (RE) potentials
Temporal horizon/ resolution
REMix: Hourly (Germany), 5 h (rest), 1 weather year (2006) VSVS: Hourly, 48 prognosis horizon
Technologies/ technical resolution
REMix: Individual technologies, conventional power production per block, storage: short-term storage, H2/CH4 production for electricity and transport, grid: international grid connections as result of first optimization step VSVS: Production from renewable energies, demand, demand-side management, short-term storage (CAES, pumped hydro), long-term storage (H2, CH4), conventional power fleet, grid: grid regions model in Germany
Quantitative Assumptions and Results Input data/ assumptions
Scenarios: 80% and 100% renewable energy in Germany in 2050 and 2060, respectively
Individual results Dispatchable electricity required in Germany with ambitious targets
Required electric power (80%/100%): Short-term storage: 9 GW (Load leveling) þ 7e8 GW (power reserve), 3.3/ 28 GW long-term storage, 10 GW biomass, 26e36/1.8 GW fossil and solid fuels Required energy capacity (80%/100%): Up to 7/69 TWh H2 (annual production), pumped hydro (assuming 5.5 h): About 90 GWh Required storage power: 12.6 GW Pumped hydro without international exchange in 80% scenario
aggregated over a year, has to provide 100% of its demand by itself. In the third variant, 15% of import is allowed in the annual balance. In the fourth variant 15% import of energy is allowed in the annual balance and the area in which electricity is exchanged is enlarged to the whole of Europe plus all Mediterranean countries and North Africa. All scenarios are calculated for electricity demands of 509 TWh and 700 TWh in Germany. As 509 TWh is the core scenario and the assumptions in the remaining studies are closer to this value, the further discussion focuses on these scenarios. A look on the scenario with an electricity demand of 700 TWh shows that most of the numbers
assessed increase slightly while the need for compressed air energy storage (CAES) in Germany decreases significantly considering international exchange. For the assessment the energy system model REMix was chosen, which was applied to set up a cost-efficient energy system on an hourly basis using data with a geographical resolution of about 10 10 km2. From the results it can be seen that much less balancing demand exists if storage outside Germany can be used. This can particularly be seen in less storage capacity required in the whole area and less biomass required particularly in Germany.
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
TABLE 6.3 SRU Special Report: Ways to a 100% Renewable Electricity Supply Study CharacteristicsdStudy Data Sheet Study title
Wege zur 100% erneuerbaren Stromversorgung, Sondergutachten (Ways to a 100% renewable power supply, special report)
Year of publication
2010
Author(s)
German Advisory Council on the Environment (SRU)
Institution(s)
German Advisory Council on the Environment (SRU)
Support/occasion
German Advisory Council on the Environment (SRU)
Aim of study
Support decisions with respect to a 100% energy supply in Germany by analyzing important questions like security of supply, costs, intermediate technologies, measures, and instruments needed
Relevant Chapter(s)
Substudy analyzing the potentials and limits of the integration of various energy sources to a 100% renewable electricity supply of Germany
Author(s)
Yvonne Scholz
Institution(s)
German Aerospace center (DLR)
Analysis of Energy Storage NeeddSubstudy on Potentials and Limits Approach and models used
Dimensioning power supply including the HVDC grid via linear cost optimization in an energy system model
Spatial horizon/ resolution
Europe with parts of North Africa and the Mediterranean region, 10 10 km2
Temporal horizon/ resolution
Hourly (Germany), 5 h (rest), 1 weather year (2006)
Technologies/ technical resolution
Conventional power production as gas power plant storage: pumped hydro (current installation þ70 TWh in Norway, capacity for 8 h), adiabatic CAES, hydrogen storage grid: HVDC power lines, nationally, regionally: no restriction
Quantitative Assumptions and Results Input data/ assumptions
Maximal installable power, hourly potentials, biomass potentials, costs, lifetime, hourly load, 509 TWh scenarios
Individual results Dispatchable electricity required in Germany with ambitious targets
Required electric power (De/EUNA): 509 TWh electricity demand: 31.6/30.6 GW CAES, 0.5/0.8 GW pumped hydro, 33.4/4.9 GW biomass 700 TWh electricity demand: 37.0/13.5 GW CAES, 0.6/0.6 GW pumped hydro, 38/5.2 GW biomass Required energy capacity (De/EUNA): 509 TWh electricity demand: 0.75/0.19 TWh CAES, 0.05 TWh pumped hydro 700 TWh electricity demand: 1.03/0.05 TWh CAES, 0.05 TWh pumped hydro Required storage power: not provided
The resulting storage capacities used are small for Germany in the case of the first scenario, because the potential for pumped hydro in Germany is restricted and biomass is used instead. The capacities installed in Germany add up to 32.1 GW of power and 0.8 TWh of energy capacity. In the second scenario it can be seen that Germany obviously switches from biomass usage to the use of pumped hydro storage installed outside Germany. In total the need for 16 TWh of storage capacity is assessed for the whole scenario.
In addition to the results of the German scenarios, the results for the scenario including Europe, the Mediterranean countries, and North Africa will be used in the discussion as well. While the storage power used increases to 509 GW (102 GW pumped hydro and 407 GW CAES), the energy capacity installed remains at about the same value (17 TWh). The study ‘Model Germany’ (Table 6.4) carried out for the World Wildlife Fund in 2009 provides a picture of a possible energy system in 2050 in Germany by modeling the demand of heat and electricity including households
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67
TABLE 6.4 Model Germany, Climate Protection Until 2050 Study CharacteristicsdStudy Data Sheet Study title
Modell Deutschland, Klimaschutz bis 2050 (Model Germany, climate protection until 2050)
Year of publication
2009
Author(s)
A. Kirchner, M. Schlesinger, B. Weinmann, P. Hofer, V. Rits, M. Wu¨nsch, M. Koepp, L. Kemper, U. Zweers, S. Strabburg, F. C. Matthes, J. Busche, V. Graichen, W. Zimmer, H. Hermann, G. Penninger, L. Mohr, H.-J. Ziesing
Institution(s)
¨ ko-Institut e.V. Prognos AG, O
Support/Occasion
World Wildlife Fund (WWF)
Aim of study
Elaboration of a target of reducing greenhouse gas emissions in Germany by 95% by 2050, requirements on temporal development of the energy system, technologies, economic structure, and way of life
Analysis of Energy Storage Need Approach and models used
Detailed model of conventional power plants, partly with carbon capture and storage, assessing the coverage of the residual load per hour following a merit order fixed for 1 year
Spatial horizon/resolution
EU 27 countries in power plant model, focus Germany, renewable energies based on lead study 2008, no defined spatial resolution
Temporal horizon/resolution
Individual years from 2005 to 2050/hourly calculations
Technologies/technical resolution
Conventional power plants, renewable energies, storage technologies aggregated
Quantitative Assumptions and Results Input data/assumptions
Maximal power and weather data, energy resource prices, CO2 prices, maximum full load hours of renewables, extension of renewables, and CHP
Individual results Dispatchable electricity required in Germany with ambitious targets
Electric power: Storage: 20.4 GW, biomass: 6.7 GW (At 97% RE) or storage: 12.9 GW, biomass 6.7 GW (at 76% RE) Required storage energy over 1 year (76/97% RE): 36.5/54.7 TWh Storage power: n.a.
and services, industry, and transport, as well as the energy supply considering conventional technologies and the use of renewable energies. Particular focus was laid on the analysis of an energy system with and without using carbon capture and storage (CCS). For the modeling of the power plant fleet a European power plant model is used, considering conventional power plants (>30 MW) in the 27 countries of the European Commission. The basic principle is the coverage of the load for each hour throughout the year. Within the calculations, first the load is assessed before it is reduced by renewable power generation, based on the available power, which varies with the weather conditions on an hourly basis. The resulting residual load is then covered by conventional power plants following a fixed merit order. The extension of the renewable power and CHP plants is taken from scenarios of the lead study 2008. The required additional conventional power is assessed on the basis of the maximally awaited load in the current year. Technologies are
chosen with regard to the awaited economic revenues considering estimates on secured power from renewables and CHP plants increasing over time. Sources cannot yet be clearly assigned for the residually occurring requirements on import of electricity. Concerning biomass, with 41.3 TWh, a more conservative annual potential than assumed in the lead study 2008 (53.8 TWh) is used ([6]). From the results it can be seen that the storage demand will rise in all scenarios with ‘innovative technologies,’ with and without CCS technology, while in the reference scenario with CCS balancing is taken over by gas power plants. In the reference without CCS the installed power of short-term storage slightly increases from 5.4 GW in 2005 to 6.4 GW in 2050 while the electricity produced increases from 7.1 to 18.3 TWh. Biomass power increases from 2.2 to 7.2 GW, producing 44.7 TWh in 2050. In the innovation scenario with CCS (76% electricity from renewable sources) the increase in power production from renewable
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
sources is lower than in the scenario without CCS. Nonetheless, installed short-term energy storage increases in terms of power by a factor of 2.4 from 5.4 to 12.9 GW and in terms of energy produced from 7.1 TWh to 36.5 TWh. In the innovation scenario without CCS (97% electricity from renewable sources), the energy storage required in 2050 is 20.4 GW of power and 54.7 TWh of energy. The study on 100% renewable energies for electricity and heat in Germany (Table 6.5) is designed to set up a cost-optimal energy system for a future year, for which 2050 was assumed. Input data are technology data including house restoration data as one option together with time series of wind (onshore/offshore) and photovoltaic power production. The cost-optimal system is developed over time from a large number of potential technological combinations. The pumped hydro potential was defined as 10 GW with 60 GWh (6 h) of storage capacity. Batteries are assumed to have a storage capacity around 50 GWh.
Long-term storage is performed via a power-to-gas process involving the production of methane. In the system with the lowest costs a power-to-gas process with 88 and 94 GW for the production of electricity from gas is installed. The methane storage requires an energy capacity of 86 TWh. Additionally, the timing of a lack in wind power of 4 weeks was varied, resulting in the largest effect on the required storage size if it occurred in February. The maximum estimate for storage capacity results in a need for 140 TWh (see [7]) according to these estimations. The study of the relevance of electricity storage at high share of renewable energy used in Germany (Table 6.6) assesses the storage capacity required for two different shares of renewable energies in the electricity system in 2050, 80% and 100% of electricity consumption. For sensitivity analysis four scenarios are defined varying the recharging process of electric vehicles (16 million, electric and plug-in hybrids) and assuming a decrease in annual production from renewable sources.
TABLE 6.5 Hundred Percent Renewable Energies for Electricity and Heat in Germany Study CharacteristicsdStudy Data Sheet Study title
100% Erneuerbare Energien fu¨r Strom und Wa¨rme in Deutschland (100% renewable energies for electricity and heat in Germany)
Year of publication
2012
Author(s)
H.-M. Henning, A. Palzer
Institution(s)
Fraunhofer ISE
Support/Occasion
Fraunhofer ISE
Aim of study
Development of an energy system for a future year, e.g., 2050, with 100% energy from renewable sources
Analysis of Energy Storage Need Approach and models used
Cost optimization of an energy system based on a large number of balanced annual energy demand/supply combinations
Spatial horizon/resolution
Germany/none (based on hourly supply curves from 2011)
Temporal horizon/resolution
One year around 2050/hourly
Technologies/technical resolution
Conversion: Electricity: Wind onshore, wind offshore, photovoltaic, biomass (CC plants, large and small CHP), water power, heat: Solarthermal, biomass, heat pumps (electricity, gas), heating networks, restoration measures Storage: Pumped hydro, batteries, heat storages with water, power-to-gas plants (with CC gas plants, large and small CHP) Electricity grid: (only low-temperature heat, no transport, no industry)
Quantitative Assumptions and Results Input data/assumptions
Supply curves of wind and photovoltaic from 2011, technology data
Individual results Dispatchable electricity required in Germany with ambitious targets
Electric power: Pumped hydro: Fixed to 10 GW, batteries: n.a., power-to-gas: 88 GW gas production/81 GW CC þ 13 GW CHP (þ107 GW gas heat pump) Storage capacity: batteries: 52 GWh, pumped hydro (maximum): 60 GWh, power-to-gas: 86 TWh (methane)
Chapter | 6
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
69
TABLE 6.6 Relevance of Electricity Storage at High Share of Renewable Energy Used in Germany Study CharacteristicsdStudy Data Sheet Study title
Bedeutung der Stromspeicher bei hohen Anteilen erneuerbarer Energien in Deutschland (Relevance of electricity storage at high shares of renewable energies in Germany)
Year of publication
2011
Author(s)
N. Hartmann, R. Barth
Institution(s)
Institute for energy economics and the Rational use of energy (IER), University of Stuttgart
Support/occasion
Paper for Conference ‘Optimising in energy economics,’ Verein Deutscher Ingenieure (The Association of German Engineers), VDI
Aim of study
Analysis of relevance of electricity storage at shares of 80% and 100% of electricity consumption
Analysis of Energy Storage Need Approach and models used
Cost minimizing power plant resource planning with rolling horizon (day ahead-, intradaymarket, reserve energy)
Spatial horizon/resolution
Germany without exchange/resolution not defined
Temporal horizon/resolution
Individual year 2050/hourly calculations
Technologies/technical resolution
Conventional power plants, renewable energies, storage technologies (CAES, pumped hydro, batteries in e-vehicles)
Quantitative Assumptions and Results Input data/assumptions
Energy resource costs, CO2 certificate costs, investment and operation costs (including maintenance, etc.), consumption: 534 TWh
Individual results Dispatchable electricity required in Germany with ambitious targets
Electric power: n.a. Storage capacity (80%/100%): 2.3 (0.5 pumped hydro, 0.9 diabatic CAES, 0.9 adiabatic CAES, 0.04 batteries)/24 TWh Storage power: n.a.
The method applied is cost-minimizing power plant resource planning with a rolling horizon considering dayahead, intraday, and reserve market with an hourly resolution. Although the recharging control of electric vehicles in the study allows feeding in of electricity, the batteries are predominantly being charged in the calculations. The reason is the high costs assumed for battery charging. Over all, storage with energy capacity of 2.3 TWh is required in the 80% scenario and of 24 TWh in the 100% scenario. In the 80% scenario with controlled recharge of vehicles annually about 8.6 TWh electricity is provided by pumped hydro, (0.0003 TWh by batteries) 19.4 TWh by adiabatic CAES, and 3.3 TWh by diabatic CAES. Thus, over the year about 31 TWh electricity was provided by storage plants. The study that focuses on optimizing power plant and energy storage extension with an iterative hybrid model (Table 6.7) carries out a cost optimization using three different models: a model for investment planning of power plants, a model for power plants and storage dispatch as well as storage investment and a model for probabilistic estimation of the secured supply. In order to be able to
calculate the whole time period from today to 2050 on an hourly basis, the resolution of the data and calculation steps used as well as the number of feedback-loops were minimized with respect to the specific subtasks. The scenario analyzed is a power supply with a share of 80% renewable energy used in 2050. As results the optimal energy capacity in 2050 as well as the optimal power of storage plants was estimated. The 4.8 TWh of optimal storage size is provided mainly by hydrogen storage, whereas, most of the required power of 12 GW is provided by adiabatic compressed air storage (about 7 GW). The study balancing renewable electricitydenergy storage, demand-side management, and network-extension from an interdisciplinary perspective (Table 6.8)ddiscusses options for balancing the demand and supply of electricity with high shares of renewable energies in the system from an interdisciplinary perspective. Besides technical analyses, energy economic, broader economic, legal, political, and environmental/resource aspects are discussed. As a basis for the discussions one part deals with the assessment of storage requirement in the case that a system with a high
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
TABLE 6.7 Optimizing Power Plant and Energy Storage Extension with an Iterative Hybrid Model Study CharacteristicsdStudy Data Sheet Study title
Optimierung des Kraftwerks- und Speicherausbaus mit einem iterativen und hybriden Modell (Optimizing power plant and energy storage extension with an iterative hybrid model)
Year of publication
2011
Author(s)
Ph. Kuhn, M. Ku¨hne
Institution(s)
TU Mu¨nchen
Support/occasion
Paper for Conference on optimizing in energy economics, VDI
Aim of study
Quantification of an efficient potential of storage
Analysis of Energy Storage Need Approach and models used
Cost-optimization using a combination of investment model, dispatch model, secured power estimation, in detail adapted in the optimization procedures to the specific task
Spatial horizon/resolution
Germany/Germany
Temporal horizon/resolution
Today to 2050/optimized for individual tasks, up to hourly
Technologies/technical resolution
Existing power plants; extension: OC-, CC-gas turbines, conventional and new hard coal and lignite power; pumped hydro, adiabatic CAES, hydrogen storage
Quantitative Assumptions and Results Input data/assumptions
Power plant inventory, parameters of new technologies, electricity from renewables, cost developments, restrictions, electricity demand, political framework conditions
Individual results Dispatchable electricity required in Germany with ambitious targets
Energy capacity: 4.8 TWh, hydrogen storage >90% Electric power (additional): 12 GW (About 2 GW H2, 7 GW AA-CAES, 3 GW pumped hydro)
share of renewable energies in the electricity supply is realized. Besides the results derived from existing energy system studies, which are discussed below, an alternative new methodology to assess the storage demand in Europe was developed. The first reliable results of the European model, which was developed at the RWTH Aachen in parallel, were published by [10] (see the discussion of European studies below). The basis for the analysis of storage requirements was scenario III of the energy concept 2030 ([9]) and the lead study 2009 ([8]). Besides an estimation of secured power on the basis of typical days, an analysis of extreme situations on the basis of 43,800 h of offshore wind data (2002e2006) was carried out. The larger problems with covering the load are still awaited for the lead scenario. Therefore, only this scenario was investigated in more detail. The results show that storage power of 18 GW is required for 2030 and 35 GW for 2050 in case of the lead scenario. Wind calms with a limit power of 5% and 87 h of duration are determining the maximum capacity required for 2030, which is about 0.6 TWh for one calm. In 2050 calms with a limit of 20% and 218 h duration lead to the
maximum energy required of 1.7 TWh. The analysis shows that different types of calms, varying in length and depth, have similar effects on the energy capacity required. Within the study of the Association for Electrical, Electronic & Information Technologies (VDE) on storage demand and impacts on the grid structure (Table 6.9), the assessment of storage need for different shares of renewable energies in the electricity sector in Germany is a central focus. Therefore, different variants were analyzed. The most important ones are electricity systems without storage and with short-term and long-term storage for 40%, 80%, and 100% of electricity produced from renewable sources. The basis for the analyses is detailed data on the renewable energies with a high spatial resolution derived by using the lead study 2010, an operation simulation model for power plants and storage facilities with hourly resolution and a storage model. The results show that in the case of 40% electricity produced from renewable sources, curtailment of renewable electricity production and the application of conventional power plants for balancing is economically more efficient than using storage. Furthermore, in that situation,
Chapter | 6
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
71
TABLE 6.8 Balancing Renewable ElectricitydEnergy Storage, Demand-Side Management, and Network Extension from an Interdisciplinary Perspective Study CharacteristicsdStudy Data Sheet Study title
Balancing Renewable Electricity, Energy Storage, Demand-Side Management, and NetworkExtension from an Interdisciplinary Perspective
Year of publication
2012
Author(s)
B. Droste-franke, B. P. Paal, C. Rehtanz, D. U. Sauer, J.-P. Schneider, M. Schreurs, T. Ziesemer
Institution(s)
Europa¨ische Akademie GmbH, University of Freiburg, TU Dortmund, RWTH Aachen, FU Berlin, Maastricht University
Support/Occasion
German Aerospace Center (DLR)
Aim of study
Exploring and analyzing alternative strategies and technologies that can balance gaps between supply and demand at unsuitable weather conditions
Relevant Chapter(s)
Assessing the balancing demand and storage employment based on scenarios for Germany (Chapter 4.1)
Author(s)
Leading: C. Rehtanz with T. Noll
Institution(s)
Leading: TU Dortmund
Analysis of Energy Storage Need Approach and models used
Rough analysis of power required to cover the maximum residual load based on generalized statistical values and analysis of individual long wind calms with offshore wind data
Spatial horizon/resolution
Germany without exchange/nonedbased on lead scenario 2009 ([8]) and Scenario III of study to an energy concept 2030 ([9])
Temporal horizon/resolution
Individual year around 2050/assessment based on residual load of typical days (288 hourly data) and hourly calculation for extreme weather conditions (basis: Data from the years 2002e2006)
Technologies/technical resolution
Estimation of power requirements: technologies as assumed in the used studies without international exchange Estimation of energy capacity: wind offshore
Quantitative Assumptions and Results Input data/assumptions
Load and feed-in profiles for typical days (288 h), synthetic off-shore wind feed-in data (43,800 h, 2002e2006)
Individual results Dispatchable electricity required in Germany with ambitious targets
Electric power: 18 GW In 2030 (lead scenario), 35 GW around 2050 Energy capacity (for one wind calm): 0.6 TWh in 2030 (lead scenario), 1.7 TWh around 2050
only a small amount of excess energy is observed, while large amounts of residual load occur so that the usage of storage does not seem to be appropriate. For the case of 80% electricity from renewable sources, a small curtailment of production leads to a large decrease in the required power (14 instead of 26 GW short-term storage, 18 instead of 29 GW long-term storage). The analysis of the full production from renewable energies (100%) results in much higher amounts of storage required (data are provided in Table 6.9). The difference in costs between the 80% and the 100% scenario is found to be higher than to go from 17% renewable energies in 2010 to 80% in 2050.
6.3 SELECTED STUDIES WITH EUROPEAN FOCUS The Roadmap 2050 (Table 6.10) generated by the European Climate Foundation (ECF) shows how an ambitious energy system can be built up in Europe. The analysis uses the back-casting approach starting with the target scenario to assess how it could be reached from today. The analysis of backup capacities is carried out with a generation dispatch model. Additional storage facilities were not applied for the system. Fossil power plants used are based on CCS technology.
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
TABLE 6.9 Energy Storage for Energy Transition, Storage Need, and Impacts on the Transmission Grid for Scenarios Until 2050 Study CharacteristicsdStudy Data Sheet Study title
Energiespeicher fu¨r die Energiewende, Speicherungsbedarf und Auswirkungen auf das ¨ bertragungsnetz fu¨r Szenarien bis 2050 U (Energy storage facilities for the energy transition, storage need, and impacts on the transmission grid for scenarios until 2050)
Year of publication
2012
Author(s)
F. Adamek, T. Aundrup, W. Glaunsinger, M. Kleimaier, H. Landinger, M. Leuthold, B. Lunz, A. Moser, C. Pape, H. Pluntke, N. Rotering, D. U. Sauer, M. Sterner, W. Wellbow (ETG-Task Force Energiespeicherung)
Institution(s)
RWTH Aachen, Fraunhofer IWES, TU Kaiserslautern, Ludwig-Bo¨lkow-Systemtechnik GmbH, Hochschule Regensburg
Support/Occasion
The power Engineering Society (ETG) in the German Association for electrical, electronic & Information technologies (VDE)
Aim of study
Analyzing the storage need and impact on electricity grids for different shares of renewable energy in the electricity system
Relevant Chapter(s)
Assessment to energy storage need
Analysis of Energy Storage Need Approach and models used
Annual operation simulation model of power plants and electricity storage (RWTH Aachen), electricity production of renewable sources on basis of lead scenario 2010 (IWES), storage model (RWTH Aachen)
Spatial horizon/ resolution
Germany without international exchange/14 14 km2 as for the lead study 2010 (SimEE)
Temporal horizon/ resolution
2050, 1 year between 2020 and 2025, 1 weather year (2007)/hourly
Technologies/ technical resolution
Conventional power plants, renewable power plants, short-term storage (mix: DSM, pumped hydro, CAES, batteries), long-term storage (H2/CH4), grid: no restrictions (‘copper plate’)
Quantitative Assumptions and Results Input data/ assumptions
Energy system from lead study 2010, weather data, grid optimally extended, no imports/exports, only electricity system, 100% scaled from 80%
Individual results Dispatchable electricity required in Germany with ambitious targets
40%: Curtailment and conventional power plants efficient for balancing 80%/100% scenario
Short-term storage
Long-term storage
Electric power (GW)
14e26/35
18e29/42
Storage cap (TWh)
0.07e0.14/0.18
7e8/26
Storage power (GW)
14e28/36
18e36/68
In addition to the generation capacities, required backup capacities are indicated in the results. The numbers can be found in the table. The needed backup capacities can be reduced by reserve sharing between the regions at about 35e40%. Furthermore, demand response of 20% was assumed. Required backup capacities as well as required transmission capacities would increase strongly without demand response. The EU-project assessed the ‘required share of stable supply’ in the EU-27 for different shares of renewables in
the system (Table 6.11). It uses hourly data from the IRENE-40 scenarios that are close to the ECF Roadmap 2050 scenarios. Based on these data balancing need and, by assuming costs for several options for balancing, cost estimates were derived. The net need for balancing, defined as the difference between peak and off-peak electricity demand minus stable supply, is assessed to be only from a share of 28% variable renewables of the electricity supply onward. At the maximum of 75% fluctuating generation, the net balancing
Chapter | 6
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
73
TABLE 6.10 Roadmap 2050, a Practical Guide to a Prosperous, Low-Carbon Europe Study CharacteristicsdStudy Data Sheet Study title
Roadmap 2050, a practical guide to a prosperous, low-carbon Europe
Year of publication
2010
Author(s)
European climate foundation (ECF)
Institution(s)
European climate foundation (ECF)
Support/Occasion
European climate foundation (ECF)
Aim of study
‘Outlining plausible ways to achieve an 80% reduction target from a broad European perspective’
Relevant Chapter(s)
Especially, Decarbonizing power: Technical results
Analysis of Energy Storage Need Approach and models used
Generation dispatch model (from Imperial College London) optimizing transmission requirements, backup plants and balancing actions on a daily basis
Spatial horizon/ resolution
EU-27/regions in Europe
Temporal horizon/ technical resolution
2050/hourly
Technologies/ resolution
Fossil fuels, solar photovoltaic, wind onshore, wind offshore, other (nuclear, hydro, biomass, geothermal, solar CSP), backup plants, demand response
Quantitative Assumptions and Results Input data/ assumptions
Economic growth from ‘reputable sources,’ shares of energy, power, and demand from PRIMES model, demand and emissions via extrapolation, energy efficiency, etc.
Individual results Dispatchable electricity required in Europe with ambitious targets
Electricity production by backup plants (baseline: 120 GW) Demand response 20% (0%)
40% RE
60% RE
80% RE
Power (GW)
190 (270)
240 (325)
270 (375)
Energy (TWh)
17e83
21e105
24e118
Renewable Energy Systems (RES) curtailment (%)
2 (2)
1 (2)
2 (3)
a
a
Rough estimates assuming load factor of 1e5%.
need of 930 GW will, following the results, most likely be covered by 20% demand response, 20% interconnections, 25% storage, 27% backup capacity, 5% RES curtailment, and 3% outages. This would result in about 230 GW of storage power required for 100% renewables in the system. In a closer look at the roadmap for 2050 (Table 6.12) an optimization of the power generation system and the transmission system was carried out for Europe from today to 2050 in steps of five years considering options for electricity storage. The dispatch is calculated for four typical days per year (one for each season) for the individual countries on an hourly basis. The storage usage is a result of the optimization process. The installed power results in 140 GW for the whole region. In total 58 TWh electricity is produced by storage. These estimates result for an optimal grid (lower estimate in the table). Higher estimates are assessed for a ‘moderate extension of European interconnectors’dlimiting the
extension to projects that ‘have already entered the planning or permission phase today’ ([11], p.2). However, the optimal grid leads to building of additional open cycle gas plants as backup close to the consumption areas because of the large geographical distances between supply and consumption. Additionally, a switch from biomass and concentrated solar power (CSP) to wind is observed with a better grid. A grid vs storage in a 100% renewable Europe study (Table 6.13) is focused on an optimization of an energy system consisting of wind and photovoltaic power facilities, varying the amount of backup capacities, a grid as ‘copper plate’ with varying radius, and varying storage capacity on an hourly basis for 8 weather years. Wind and photovoltaic power production is installed in a fixed (optimal) relation to each other of 65%/35% of electricity consumption with respect to the whole of Europe (see also [12]). The scheduling is optimized in such a way that the backup capacity required is minimized. The different radii
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
TABLE 6.11 Assessment of the Required Share for a Stable Electricity Supply Until 2050 Study CharacteristicsdStudy Data Sheet Study title
Assessment of the required share for a stable EU electricity supply until 2050
Year of publication
2011
Author(s)
W. Lise, J. van der Laan, K. Rademaekers, F. Nieuwenhout, C. Kirchsteiger
Institution(s)
ECORYS Nederland BV, energy research Centre of the Netherlands (ECN), DG energy
Support/occasion
European Commission
Aim of study
‘To assess the required share for a stable EU electricity supply until 2050 (and the midterm 2030)’
Analysis of Energy Storage Need Approach and models used
Statistical analysis of hourly data with respect to the maximum residual load/balance need (and costs)
Spatial horizon/ resolution
EU27 þ Norway, Switzerland/nine European regions
Temporal horizon/ resolution
The year 2050/hourly
Technologies/ technical resolution
Nuclear, solar, wind, hydro, other renewable, solids-fired, gas-fired, oil-fired, biomass waste-fired fuel cell, geothermal heat, other fuels
Quantitative Assumptions and Results Input data/ assumptions
Scenarios from Infrastructure Roadmap for Energy Networks in Europe, IRENE-40 RES, close to ECF 80% RES used (See http://www. irene-40.eu/)
Individual results Dispatchable electricity required in Europe with ambitious targets
Net balancing need Share of variable renewable electricity
[GW]
<28%
0
40%
280
50%
430
60%
600
70%
820
75%
930
of the grid lead to local regions with 100% renewable energies with diverging ratios of wind to photovoltaic for which the supply was scaled to fit the demand in each case. The study proposes that 10% of consumption is the maximum possible contribution of biomass in Europe. Starting from this value, fixing the backup capacity to 10% of consumption, and making the often-made assumption that the national grid is well established, but international exchange is weak or zero, would suggest about 100e500 km of radius for the copper plate. In this case storage capacity of a bit less than a week of average demand is necessary for the smaller size and a few days (around 2 days) for the larger size. With a well-established grid without restriction in Europe a storage capacity of only about 4 h is needed to cover the average demand. Storage size expressed in percentages of total consumption results as follows: only distribution grid without restriction: 2%, regional/small country grid without restrictions: 1.5%, national grids without restrictions: 0.5% and European grid without restrictions: 0.05%. Installing larger capacities of renewable energies (e.g., by 130%) would be another alternative to storage implementation, but turns out to be too costly. Assuming instead a scenario without extra backup capacity the storage need increases strongly. For good national situations a storage capacity of 30e90 days would be sufficient while for a good international grid 7e30 days would be needed. More results are shown in Table 6.13. A study of storage- and grid-expansion needs with 100% renewable electricity (Table 6.14) involves an optimization of a system consisting of photovoltaic and wind power for power production, short-term and long-term storage, and a high-voltage direct current (HVDC) grid for international connection to satisfy the annual demand. The genetic optimization process starts with a random sample of technologies installed and calculates the costs for the weather years 2000e2007 in an hourly simulation as indicator for its fitness to the task. Via the genetic algorithm new generations of the overall system are derived until the costs to satisfy the load in each hour converge to a minimum. With the assumed annual demand of about 4000 TWh a maximum load of about 670 GW is reached in the EUMENA region (Europe, Mediterranean region, and North Africa). About 1800 GW wind power is installed with additionally about 1100 GW photovoltaic power. The capacity of the built HVDC grid is 1100 GW * 1000 km. The short-term storage installed by the optimization process has a capacity of only 2 TWh while it shows an electric power of 230 GW and a storage power of 480 GW. The long-term storage, however, shows a higher storage capacity with about 320 TWh and electrical power of 710 GW compared to storage power of 570 GW. The study of storage needs in an electricity supply with (100%) renewable energy (Table 6.15) assesses the storage
Chapter | 6
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
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TABLE 6.12 Roadmap 2050da Closer Look Study CharacteristicsdStudy Data Sheet Study title
Roadmap 2050da closer look. Cost-efficient RES-E penetration and the role of grid extensions
Year of publication
2011
Author(s)
M. Fu¨rsch, S. Hagspiel, C. Ja¨gemann, S. Nagl, D. Lindenberger, L. Glotzbach, E. Tro¨ster, T. Ackermann
Institution(s)
Institute of energy economics at the University of Cologne (EWI), energynautics
Support/ Occasion
Gesellschaft zur Fo¨rderung des Energiewirtschaftlichen Instituts an der Universita¨t zu Ko¨ln gGmbH
Aim of study
Integrated optimization ‘of the overall European electricity system development until 2050, while comprising fossil, nuclear, and renewable generation, storage as well as transmission of electricity’
Analysis of Energy Storage Need Approach and models used
Analysis of typical days in an hourly resolution/dispatch, European electricity market model, grid model (European extra high-voltage grid)
Spatial horizon/ resolution
EU27 (without Cyprus, Malta) þNorway, Switzerland, North Africa as satellite region/subcountry level (different regions for wind, solar)
Temporal horizon/ resolution
Until 2050, dispatch: 4 typical days per year/5 year steps, dispatch: Hourly
Technologies/ technical resolution
Vintage classes of conventional plants (hard coal, lignite, natural gas), nuclear power plants, storage technologies (pumped hydro, hydro storage, CAES), renewable technologies (photovoltaics (roof, ground), wind (onshore, offshore), biomass (solid, gas), biomass CHP (solid, gas), geothermal, hydro (storage, run-of-river), solar thermal plants (CSP), grid: European extra high-voltage grid
Quantitative Assumptions and Results Input data/ assumptions
Electricity demand, technology parameters (plants, transmission), RES-potentials and feed-in profiles, political restrictions
Individual results Dispatchable electricity required in Europe with ambitious targets
Storage use in 2050 Whole region
Germany
Electric power (GW)
92e141
7.89
Electric energy (TWh)
58e113
9.1e10.2
need for different variations of wind and solar technologies used for power production primarily for Europe. Further variations include the availability of a perfect grid, the height of production reserves and wind power technologies (20% and 50% degree of usage). For the assessment a simulation in time steps of 3 h is chosen. The results of the simulation show that a storage power of 160% of the average consumption is sufficient for the scenarios. The results for the storage capacity needed are presented in terms of the time period over which an average consumption has to be provided by energy storage or by other options to fill gaps in the power production of
varying renewable production. For a production reserve of 30%, used to balance storage losses and to bridge years with low irradiation and wind speed, the minimum storage demand assessed was 6 days (50% degree of wind power usage, no grid restrictions), the maximum 30 days (20% degree of wind power usage, no international grid connections). Assuming a demand of 4900 TWh (see ECF: Roadmap 2050) and 1500 GW installed capacity in Europe, which is about the height assumed for other European studies, this would result in storage power required of 895 GW (160%) and a storage capacity required of 80e400 TWh (6e30 days).
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
TABLE 6.13 Grid vs Storage in a 100% Renewable Europe Study CharacteristicsdStudy Data Sheet Study title
Grid vs storage in a 100% renewable Europe
Year of publication
2012
Author(s)
F. Steinke, Ph. Wolfrum, C. Hoffmann
Institution(s)
Siemens Corporate technology, Siemens Infrastructure & Cities
Support/Occasion
Paper in ‘renewable energy’
Aim of study
Assessing an order of magnitude for the dependence of backup system requirements from grid extension and storage capacities
Analysis of Energy Storage Need Approach and models used
Optimal scheduling of assumed supply technologies to fit the load with General Algebraic Modeling System (GAMS)/CPLEX optimization package with parameter variation of grid (copper plate size), storage, and backup capacities
Spatial horizon/ resolution
Europe/control areas, 50 50 km2 grid
Temporal horizon/ resolution
One year/hourly
Technologies/ technical resolution
Wind (65% of consumption), photovoltaic (35% of consumption), backup capacities, grid: different sizes of a ‘copper plate’
Quantitative Assumptions and Results Input data/ assumptions
2007 demand with European Network of Transmission System Operators for Electricity (ENTSO-E) curves, 65% (of consumption) wind, 35% photovoltaics, grid: Copper plate within circular regions of varying radius R (local 100% scenarios), hourly weather data for 8 years
Individual results Dispatchable electricity required in Europe with ambitious targets
Storage capacity needed assuming demand of 4900 TWh per year (s. ECF: Roadmap 2050 if 10% (490 TWh) and 0% backup capacity is realized Radius of grid without restrictiona
Storage capacity required (TWh)b 10% Backup
0% Backup
25 km (Distribution grid)
94 (7d)
1200 (around 90d)
100 km (Regional grid)
81 (6d)
400e1200 (30e90d)
500 km (National grid)
27 (2d)
400e1200 (30e90d)
3000 km (European grid)
2.2 (4h)
94e400 (7e30d)
a
averaged over 16 center points over Europe. roughly estimated from the figures.
b
A study of the prospects for large-scale energy storage in decarbonized power grids, Table 6.16, has the aim to analyze the role of long-term storage in a future electricity system with a high share of renewable energy used. The basis consists of data for the generation mix and the daily and annual load curves. Photovoltaics and wind are simulated on the basis of typical technical behavior. Simulating the smoothing effect of randomly varying power from wind turbines reveals that variation ratios between 10% and 30% can be expected if the fluctuations are independent of each other. While most of the variations can be balanced with
existing natural gas combined cycle plants, particularly in 2010, by 2050 large power variations will prospectively exceed the power at full load, which can be provided by the middle load operation. Therefore, other solutions are required and these are proposed to be storage plants. The typical daily load curves show surpluses and, thus, storage requirements of 40e100 GW. Considering the already existing 33 GW storage power installed in Western Europe, further 7e67 GW of balancing capacities have to be installed to be able to deal with prospective wind power fluctuations in 2050.
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Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
77
TABLE 6.14 Storage- and Grid-Expansion Needs with 100% Renewable Electricity Study CharacteristicsdStudy Data Sheet Study title
Speicher- und Netzausbaubedarf in einem europa¨ischen Elektrizita¨ts-versorgungssystem mit 100% EE-Versorgung (Storage- and grid-expansion needs in a European electricity supply system with 100% renewable energy)
Year of publication
2012
Author(s)
T. Thien, M. Leuthold, F. Steinke, D. U. Sauer
Institution(s)
ISEA RWTH Aachen, E.ON ERC RWTH Aachen, JARA energy, Siemens AG
Support/Occasion
Paper for VDE conference ‘Smart grid,’ 5./6.11.2012
Aim of study
Estimation of storage and grid requirements for a scenario of 100% wind and photovoltaic
Analysis of Energy Storage Need Approach and models used
Deriving a cost-minimized energy supply system via a genetic algorithm
Spatial horizon/resolution
Europe, Mediterranean region and North Africa (EUMENA)/country groups
Temporal horizon/ resolution
One year/hourly
Technologies/technical resolution
Wind power, photovoltaic, short-term storage (total efficiency: 81%), long-term storage (total efficiency: 35%), HVDC grid
Quantitative Assumptions and Results Input data/assumptions Individual results Dispatchable electricity required in Europe with ambitious targets
Hourly weather data (2000e2007), load curves, cost data, technical parameters Short-term storage
Long-term storage
Storage capacity (TWh)
2
320
Electric power (GW)
230
710
Storage power (GW)
480
570
The study mainly shows a framework of how the task of estimating power can be tackled. For established estimates, a detailed analysis of smoothing effects in real situations has to be carried out. In a last step the assessment is applied for other regions of the world. The different storage needs assessed particularly depend on the load curves and the shares of photovoltaic and wind implemented in the energy system. For the whole world it is assessed that a storage capacity of 189e305 GW is needed (15e30% net variation). This value is assessed here only for short-term variations and requires supplement assessments of storage needs for other timescales.
6.4 DISCUSSION OF STUDY RESULTS The collection of studies above shows that various types of approaches are followed to estimate the future demand for energy storage. Besides the derivation of complete energy scenarios for which storage technologies are among the
issues to be taken into account, other studies specifically concentrate on the derivation of storage usage and storage demand. The studies show that the assessment of storage need does not include only one aspect. A bundle of technological parameters will, in the end, be decisive in the selection of technologies for specific tasks and thus will determine the need for specific technologies to supplement the variable electricity supply from renewable sources (mainly from wind and solar irradiation). In order to carry out a detailed discussion, both the studies on country and continent level, and the studies looking at individual tasks in smaller regions, at the local area, and at different selected case studies have to be investigated. The study review here starts by concentrating on work analyzing the national (German) and continental (European) levels. The national and international scenario analyses, can provide assessments of the overall installed power and
78
Electrochemical Energy Storage for Renewable Sources and Grid Balancing
TABLE 6.15 Storage Needs in an Electricity Supply with (100%) Renewable Energy Study CharacteristicsdStudy Data Sheet Study title
Speicherbedarf bei einer Stromversorgung mit erneuerbaren Energien (Storage needs in an electricity supply with renewable energy)
Year of publication
2010
Author(s)
M. Popp
Institution(s)
TU Braunschweig
Support/Occasion
Dissertation
Aim of study
Estimation of storage need for covering the electricity demand to 100% with renewable sources
Analysis of Energy Storage Need Approach and models used
Simulation of storage need per time step, including variations between full (copper plate) and no grid, of different shares of existing production reserves, of different mixtures with respect to wind and solar power and of different wind power technologies
Spatial horizon/ resolution
Europe/wind data: 50 grid Elements, solar data: urban centers
Temporal horizon/ resolution
Multiple years/3-hourly
Technologies/ technical resolution
Wind power, solar technology proportional to global irradiation, production reserve, storages (80% efficiency)
Quantitative Assumptions and Results Input data/ assumptions
Up to hourly weather data (2000e2007), load curves, cost data, technical parameters, installed variable electricity power is proportional to the share of electricity consumption of the country within Europe
Individual results Dispatchable electricity required in Europe with ambitious targets
Length of full-load provision assuming 30% production reserve: No international connections
Unlimited grid connections
Optimal mix 20% degree of usage of wind power
30 days
14 days
Optimal mix 50% degree of usage of wind power
16 days
6 days
Storage power required: 1.6 times The average consumption at maximum
energy capacity required, bearing in mind specific tasks, such as l
l
l
long-term storage, bridging gaps of several days to weeks or even seasonal variations, short-term storage, smoothing the load levels on an hourly basis, and very short-term storage, required to serve the demands covered today by the reserve market, which starts from variations of the scale of seconds to variations of some minutes.
From the studies reviewed here it can be seen that not all of the results are presented according to these categories. Furthermore, the assumptions about the underlying scenarios are very different and often implicitly include competing technologies that already deal with the balancing task to a certain extent: l
demand-side management/demand response (sometimes already including the use of batteries, e.g., in cars),
l l
l
l
l
extended overseas networks and wind/solar power, conventional power plants (gas, oil, coal, lignite, nuclear) able to serve mid and peak load, other dispatchable nonconventional power plants (geothermal, biomass, CSP plants with thermal storage (typically storing about six full-load hours)) or undefined import of energy from other, uncharacterized sources and curtailment of power from renewable sources.
The differences between the assumptions behind the analyses, which also include further major parameters, make it difficult to use the various analyses to get an impression about the key needs for balancing. As far as possible in this discussion, the study results were analyzed with respect to the question to assess l l
power capacity required and energy capacity required
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Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
79
TABLE 6.16 Prospects for Large-Scale Energy Storage in Decarbonized Power Grids Study CharacteristicsdStudy Data Sheet Study title
Prospects for Large-Scale Energy Storage in De-carbonised Power Grids
Year of publication
2009
Author(s)
S.-I. Inage
Institution(s)
International energy agency (IEA)
Support/Occasion
International energy agency (IEA)
Aim of study
Analyzing the role that large-scale energy storage systems can play in future power systems
Relevant Chapter(s)
Prospects of energy storage growth
Analysis of Energy Storage Need Approach and models used
Simulating the energy supply via assumptions for the different technologies: photovoltaics: Three weather patterns, wind: randomized assuming Weibull distribution with smoothing effect
Spatial horizon/resolution
Western Europe/Western Europe
Temporal horizon/resolution
One year around 2050/typical daily (6 min resolution)/annual load and synthetic production curves
Technologies/technical resolution
Base load (nuclear, coal, hydro), photovoltaics, wind, natural gas combined cycle plants for middle load
Quantitative Assumptions and Results Input data/assumptions
Generation mix and daily/annual load curve (from BLUE Map scenario, ETP 2008), base load: 37.5%, middle load: 32.5%, wind: 4.6%, photovoltaics: 25.4% Of total production
Individual results Dispatchable electricity required in Europe with ambitious targets
Electric power: 40 (10% variation ratio) to 100 GW (30% variation ratio)
for both, electricity storage and feed-in, considering the three different tasks discussed above. Furthermore, it is discussed how far the results of the studies can be applied to other regions.
even represent the cost-efficient solution. Most of the studies give only values of the required electrical power so that the following summarizing discussion is limited to this aspect.
6.4.1.1 Reserve Energy
6.4.1 Required Electric and Storage Power The task to balance the variable electricity production from renewables can be further subdivided into the storage task and the power provision task, i.e., the provision of positive and negative power. The provision of power relates to the central task to fill occurring gaps due to (unpredicted) variations. This is of course an essential task to ensure a continuous power supply at a high share of renewable energy in the system. The provision of negative power and, thus, extra load, which in case of storage can later be fed in as electricity once more, is connected to the task of using excess amounts of energy produced. This function for which enough storage power has to be installed, is not as crucial as the provision of positive control power, as alternatively plants can be curtailed. Such an option can
Depending on the timescale/task analyzed, different methodologies are applied in the studies. Most studies concentrate on assessing load leveling and long-term balancing. The timescale below 1 h is investigated only within a few studies. Estimates of power demand for this area for Germany are derived by Klaus et al. [13]: 4 GW and Nitsch et al. [14]: about 7 GW for secondary and minutes reserve. Klaus et al [13] come up with a range of numbers starting from about 7 GW and going up to about 15 GW, depending on the approach used (hourly simulation or the concept of secured power) when assuming a maximum of 7 GW import of secured power. They point out that the power can be provided by a mixture of technologies, e.g., biomass power plants, pumped hydro plants, and demand-side management.
Electrochemical Energy Storage for Renewable Sources and Grid Balancing
These values are assessed to be slightly higher than the requirements today as can be seen in Nitsch et al. [14], p. 189, rising from about 5 GW to about 7 GW. However, additional power for the reserve market is provided in the study by remaining conventional or biomass power plants.
6.4.1.2 Load Leveling and Long-Term Storage In order to assess the required power, analyses either with 1 h resolution or on the basis of statistical estimates for secured power are followed. Klaus et al. [13] provide a comparison of both methodologies. It shows that the statistical methodology systematically leads to higher values because of its various characteristics as follows (Klaus et al. [13], p. 109f): l
l
l l
It is often assumed that a secure energy supply has to be provided with only national sources (no import assumed). More extreme situations are generally considered with the statistical methodology. Analyzing real weather data, situations in which all power plants show their worst performance usually do not occur. The potential of load management may be underestimated. Potential systematic correlation between load and supply is not considered.
Values are mainly assessed on the basis of data for a time period with an hourly resolution or for an extreme situation like an evening in winter assuming no wind power but a high load. Looking at results of the national scenarios shows a wide variation in the assessed storage requirement. The results of Adamek et al. [15] suggest that in the case of 40% electricity produced from renewable sources storage is not yet needed for balancing. For the 80% scenarios the estimates for German energy supply in 2050 range from 12 (þ7 (reserve energy)) GW [14] to more than 32 and 35 GW [3,15]. The estimates for the 100% variants are between 31 and 44 GW for [13,14,16] with extreme values of 20 GW from Kirchner et al. [17] and 77 GW from Adamek et al. [15]. Henning and Palzer [18] even install 88 GW of storage power and 94 GW of electric power for the long-term storage option of power-to-gas with additional pumped hydro plants and batteries. A closer look into the studies shows that a more detailed analysis of balancing need is difficult for the German scenarios because imports are not fully specified, neither with respect to the source nor with respect to the application, but play an important role in some scenarios like, for example, in the SRU study [19]. The role of imports is less important for the European scenarios. Only imports from North Africa are considered differently. Assessing the required power for balancing per total production power (installed production power in EU
countries plus CSP, not including power of storage facilities) and plotting it against the share of varying electricity production from renewable energies with respect to total production power, results in the picture presented in Figure 6.2. To show the ECORYS results, the power data from the ECF Roadmap 2050 scenarios are taken, which are comparable to the IRENE-40 scenarios used in the analysis. The ratio of balancing power per total electricity production installed for the studies of SRU [19] and Thien et al. [10] are much lower than would have been expected from the other results. The reason is that they consider a much larger region, covering, not only Europe, but also the complete Mediterranean region and parts of North Africa. Obviously, a higher amount of variable renewable energy integrated in the system over such a large area requires relatively less balancing power. To make the results of the two studies comparable to the others, the value of the total power installed is scaled down to about the power installed in other European scenarios (1500 GW), which can be interpreted as the assumption that besides CSP only wind and photovoltaic power are additionally installed in the non-European Mediterranean and Northern African areas and the amount of balancing technologies remains the same. The results are printed in Figure 6.2 in the data points without filling. It shows that these roughly adapted values would fit into a correlation curve very well. A more elaborate correlation would require a further analysis of the results from the different models and a more sophisticated adaption of the results. Figure 6.2 shows that the amount of installed power to serve the balancing need divided by the total power installed for electricity production increases with the share of varying renewable sources in terms of power. Starting with no balancing power needed at up to 28% of variable renewable generation, the required balancing power strongly increases to about 50% with around 70% of varying renewables and, considering also the adapted 70 Power of balancing technologies/ total producƟon power (%)
80
60 ECORYS
50
EWI
40
SRU 30
Thien et al.
20
Popp (1500 GW)
10
SRU (1500 GW) Thien et al. (1500 GW)
0 0 20 40 60 80 100 Share of wind and photovoltaic power (%)
FIGURE 6.2 Results for power of balancing technologies divided by the total production power installed at different shares of variable renewable power. Source: Own calculations based on data from Refs. [10,11,19e21].
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Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
results from SRU [19] and Thien et al. [10]; it increases to more than 60% with 100% varying renewables installed. Although the results seem to be consistent with respect to the amount of balancing technologies applied and balancing need assessed if the adaptions are considered, a large difference exists between the studies in the types of technologies used to provide the power. While the scenario of ECORYS [20] assesses balancing need directly, the EWI [11] scenario uses thermal power plants fueled with fossil gas and biomass in addition to storage facilities and the SRU scenario uses biomass plants and CSP plants with thermal storage in addition to storage facilities. Thien et al. [10] and Popp [21] assess storage demand for a scenario including only wind and solar photovoltaic. Accordingly, the amount of storage assessed varies strongly between the studies. Starting roughly from low share to high share of renewables the storage demand derived is l
l
ECORYS study [20] (with 20%/without demand response): l 40% electricity from renewables: 190/270 GW l 60% electricity from renewables: 240/325 GW l 80% electricity from renewables: 270/375 GW EWI study [11] (about 80% of electricity from renewables): 92 GW
Then, all for 100% electricity from renewables l
l
l
l
SRU study [19]: 102 GW pumped hydro, 407 GW compressed air storage Thien et al. [10]: 233 GW short-term storage, 711 GW long-term storage Popp [21]: 895 GW storage (160% of average consumption assuming an annual consumption of 4900 TWh has proved to be sufficient) International Energy Agency study [22]: 40e100 GW has to be covered by fast plants or storages
A distinction between different types of storage technologies is only made in SRU [19] and Thien et al. [10] resulting in ratios of 1/5 to 1/4 for short-term storage to long-term storage.
6.4.2 Energy Capacity Need The overall energy capacity required in an energy system is predominantly determined by the type of gaps in energy provision occurring over the year, which may last from several days to weeks. Important gaps show different characteristics and could reduce the power from variable renewables down to 20% or below. An analysis of wind data in Droste-Franke et al. [3] shows that, depending on the share of renewable energies, various gaps differing in depths and lengths can determine the maximum amount of energy required.
81
As storage has to be recharged until the next incident occurs, not only the characteristics of single gaps, but also the frequency and timing of such gaps determines the storage capacity needed. The additional, seasonal, variation influences the storage size required as shown in the derived annual loading curve of the long-term storage technologies in Klaus et al. [13]. About 40e45 TWh is required in the scenario per event, but seasonal variation and the sequence of gaps require a total storage capacity of from 65 (methane) to 75 (hydrogen) TWh. Henning and Palzer [18] produced similar results with 86 TWh of storage size required in the cost-minimal system and, with disadvantageous timing of an individual lack of 4 weeks in wind production, a maximum of 140 TWh is derived for a medium cost scenario. Difficulties arise from the analysis of the studies, because, particularly in scenario analyses, the total energy provided per year is shown rather than the storage size required. More promising in this regard are studies concentrating on the analysis of storage demand, which often assess the required storage capacity alone. The results for an energy supply with about 80% electricity produced from renewables in Germany range from 1.7 (for one incident) through 2.3e4.8 TWh and 7e8 TWh (considering long-term storage explicitly) as derived by Droste-Franke et al. [3], Hartmann and Barth [23], Kuhn and Ku¨hne [24] and Adamek et al. [15], respectively, with results that are all in the same order of magnitude. With the share of renewables increased to 100% in Germany, a larger amount of storage capacity is required. For this case the SRU [19] results indicate only 0.14 TWh storage capacity required, which represents mostly shortterm storage. However, a high amount of biomass is assumed, which can be used to tackle most balancing tasks. Electricity production from biomass in Germany is 37 TWh higher than in the scenario combining Denmark, Norway, and Germany in which a storage capacity of 31 TWh, mainly in pumped hydro storage, is assumed. As about 16 TWh was the need of Norway and Denmark in the scenario without international exchange and it is to be expected that the effects of synergy occur with the combination, presumably more than 15 TWh of storage capacity is used for balancing the German electricity production. Hartmann and Barth [23] and Adamek et al. [15] come up with almost the same numbers for energy capacity needed: 24 TWh compared to 26 TWh. Furthermore, Steinke et al. [25] assess a needed capacity of about 27 TWh if a good national electricity grid is installed. The study of Klaus et al. [13]; as already mentioned above, results in higher amounts of 40e45 TWh per case and about 65 (methane) to 75 (hydrogen) TWh as total storage size, assuming only a small amount of electricity production of 11 TWh from biomass. Henning and Palzer [18] apply gas storage of 86 TWh in the cost-optimal scenario. Furthermore, they
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
carry out a sensitivity analysis with different timings of wind gaps lasting about a month with similar data that result in a maximum of 140 TWh storage size required if the gap occurs in February. These numbers compare to the amounts of electricity from storage aggregated over 1 year in other scenarios of 54.7 TWh [17] and 69 TWh [14]. For the European scale many studies provide numbers for aggregated energy produced with energy storage, but only four of the analyzed studies give numbers for energy capacity required. Steinke et al. [25] assess 2 days to 4 h with increasingly better grid extension from good national to good European grid that are used additionally for 10% backup capacity. This results in 27e2.2 TWh with about 490 TWh of backup capacity if 4900 TWh of electricity production is assumed [26]. Thien et al. [10] come up with numbers of 320 TWh energy capacity representing 450 h (19 days) of full load required and additionally about 2 TWh (9 h) for short-term storage for Europe plus the Mediterranean region and North Africa. Results from Ref. [21] indicate 6e30 days of electricity production as the range of storage size developing with different assumptions on the available grid connections and the wind technology applied and assuming a production reserve of 30%. This lies in about the same range as the estimates from the studies discussed above. For the SRU study Scholz [19] comes up with a value of 17 TWh energy capacity required for the same regions, including 16 TWh from pumped hydro storage and 1 TWh from compressed air storage. This study additionally assumes a large amount of electricity from biomass per year of 360 TWh together with 1080 TWh of annual electricity production from CSP plants in the system while allowing for 15% of import with respect to the annual balance in all countries. All in all one can see that the amount of energy storage capacity required strongly depends on the assumptions made in the studies. With a higher amount of biomass and a larger share of import assumed, less storage is needed.
6.4.3 Transferability of the Results to Other Regions The changes in results depending on the different assumptions for the energy system and the different regions considered in Europe show that a simple transfer of the findings to other regions is not possible. However, some influences and dependencies that can be identified from the analyzed studies are discussed in the following.
6.4.3.1 Weather Conditions The weather conditions have the highest influence on storage power and energy capacity required. Thus, results for regions with similar weather conditions to those in Europe could be similar, but for a good transferability of
results, beside the general conditions, additionally specific weather phenomena in the region that may lead to stable weather conditions over several days and even weeks have to be considered. Such extremely stable conditions determine especially the requirements for energy capacity. As an example from the studies, it can be seen that enlarging the region of Europe by adding also the Mediterranean region and North Africa leads to less variable electricity production from solar irradiation and wind and, thus, to more reliable production (s., e.g., [10,19]). The reason is that in the additional regions, in general, less frequent changes between low and high pressures occur than in Europe and, thus, more stable weather conditions are experienced in general. Figure 6.3 gives an overview of the general wind and weather systems. While Europe lies to a large part within the West wind drift zone, Northern Africa lies in the subtropical high-pressure belt. The regions with overall similar weather conditions to those in Europe are particularly those between about 30 and 60 latitude all over the world. In order to have comparable situations, the regions in focus should also be of comparable spatial extension to the regions analyzed. A more detailed correlation of storage demand with specific weather events and an analysis of historical weather data with respect to their occurrence, together with projections on how the extreme weather events and their influence on wind and solar irradiation will prospectively develop within the next decades, could help to get a better understanding and more robust estimates for the future energy supply, also for other regions.
6.4.3.2 Topological and Geological Conditions The topological and geological conditions of the regions analyzed strongly influence the technological and economical storage potential with respect to pumped hydro, compressed air, and hydrogen/methane storage underground. Europe has great potential for pumped hydro particularly in Scandinavia, in the Alps and some highlands spread over Europe. Furthermore, some regions like Germany show good conditions for building salt caverns that can be used for the storage of air or other gases. Topological conditions also have influence on the optimal distribution of wind power plants over the region. Slightly increasing altitude from the coasts with some highlands and higher mountain areas as existing in Germany is generally a good situation for efficient wind power installations spread over the whole country. In contrast, with high coasts or completely flat land or only slightly increasing altitude without additional highlands the best potential for wind power is mainly at the coast. Having high coasts, as found in Norway, pumped water is, furthermore, a good option for the storage of electricity close to the converters.
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Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
Polar high Circum-polar East winds Subpolar lows Polar front West wind dri zone
Arc fall winds
Sub tropical high pressure belt
Descending air in highs
83
Rising air in lows Ferrel-circulaon
Northern Hadley cell Nord-East trade wind
Inner-tropical convergence zone
Rising air in convecon cells
Equator
South-East trade wind
Southern Hadley cell
Sub tropical high pressure belt
Descending air in highs
West wind dri zone Polar front Subpolar lows Circum-polar East winds Polar high
Ferrel-circulaon Rising air in lows Arc fall winds
FIGURE 6.3 General global wind and weather patterns (source, Ref. [27]), “H” means a high-pressure area (high) and “T” means low-pressure area (low).
6.4.3.3 Political Conditions Politically installed funding schemes and (legal) framework conditions in the countries influence the future development of energy systems. Furthermore, exchange between countries and between regions within a country depends on the level of collaboration in setting up an energy system. Therefore, the right political conditions and adjusted political strategies are crucial elements for the realization of technological or economical optimal solutions. Differing political situations could lead to differences in all areas in the energy system including among other things the energy demand, installed power technologies, grid installation, and usage of technologies.
6.4.3.4 Electricity Grid The electricity grid is the technical precondition for electricity exchange between countries and within countries. The studies show that grids can only help with balancing demand if excess and demand occur in different regions at the same time. Temporal shift between production and demand cannot be tackled by grids alone. Even with an optimal grid covering large regions there still exists need for balancing, which can be covered by energy storage or alternative balancing technologies (s., e.g., [25]). Grid extensions are particularly needed if the structure of the
electricity system is strongly changing. Especially low potential for renewable energy or little usage of existing potential in a country or in parts of the country leads to an increasing need for spatial exchange between countries or within a country. It can be seen from the studies that storage demand decreases with decreasing net restrictions. The dependence of the results for storage demand on the realization of the electricity grid can be seen in the work of Steinke et al. [25] who vary the size of regions with good grid connection, assuming no external exchange. The storage demand is clearly decreasing with an increasing size of the areas with good grid connections. Another example is shown in the SRU study (s., e.g., [19]). Here, three scenarios of the three countries Germany, Denmark, and Norway are compared to each other differing in the amount of electricity exchange allowed. Relying on exchange of electricity, strongly changes the electricity production mix and the usage of energy storage. Exchange here leads to an even larger use of storage capacities because of opening the potential for storing electricity produced in Germany in storage facilities in Scandinavia instead of extending other domestic alternatives like, e.g., electricity production from biomass in Germany. However, balancing the need-per-total-power installed in the region is decreasing and this can be even better observed in the case of the extension of the area to Europe plus Mediterranean countries and North Africa.
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Electrochemical Energy Storage for Renewable Sources and Grid Balancing
6.4.3.5 Competing TechnologiesdBiomass, CSP, Backup Capacities, Curtailment, and Demand Side Measures Biomass, CSP (with thermal storage) and other existing backup capacities (including CCS technologies) can take over the tasks of balancing to a large amount if the usage of excess electricity production from renewable sources is not an issue. Particularly, competing technologies using renewable sources are in direct competition with the installation of photovoltaic and wind power together with storage. Further options are, of course, curtailment to cut peaks of wind and solar electricity production and demandside measures that can temporally reduce or increase the load. Having all the alternative options in mind, it becomes clear that storage facilities are only one of several options to balance variable electricity production and the storage need is therefore very dependent on the design of the remaining electricity system. Thus, in general, it is much easier to discuss or transfer results on balancing need than results on storage demand.
6.5 CONCLUSIONS The discussion of studies shows that the large number of influencing parameters and differences in the studies make it difficult to give precise estimates for the storage capacity required dependent on the share of renewable energies in the system. In order to get at least an idea about the storage need, three major tasks and specific requirements were distinguished: very short-term balancing (reserve energy, time-scale: below 1 h) and short-term balancing (load leveling, timescale: 1 h to several hours), which determine the requirements for storage power as well as long-term balancing (daily to weekly or even seasonal timescale), which determines the required storage size with respect to energy capacity. Furthermore, because the potentials for wind, photovoltaic, and biomass are varying geographically, the region in focus (Germany, Europe) has to be considered so that values can only be derived for certain specific framework conditions. Many studies concentrate on the assessment of total power required for balancing, which is determined by steep gradients in the wind and photovoltaic electricity supply. With respect to the reserve market in Germany it can be said that the requirements may slightly increase. In Ref. [14] the installed capacity is rising from 5 to 7 GW. The reserve energy is used to level out very short-term effects with a timescale of less than an hour, which are occurring anyway, at least in part, because of unforeseen variations in the load. These variations are prospectively similar to those in other regions so that a slight increase in the need for reserve capacity could be expected also for
other regions in the world. By varying the estimation methodologies and discussing technological options Ref. [13] shows the potential range assessed, which starts from about 7 GW (hourly calculation) to about 15 GW (concept of secured power) for the balancing need, when additionally 7% imports are considered. Besides assessments for the typical reserve requirements, which aim at a timescale below 1 h, an additional analysis with hourly resolution can cope with the further power required to react on an hourly scale for load leveling. This is the resolution chosen in most of the selected studies. The studies concentrating on hourly load leveling in Germany result in a controllable power installed (plus energy storage) of about 60e70 GW for an 80% share of renewables in the electricity supply. Adding also the potential imports, the power increases to about 70e90 GW. Although consistently assessed studies result in a higher amount of dispatchable power with a higher share of renewables in the electricity supply, some studies give lower estimates than others. Including imports, which are very important in some of the studies, the estimated values for approximately 100% power production from renewable sources lie between about 50 and 130 GW. Thus, in total, it can be concluded that the control power needed for Germany with a share of renewable energies of about 80% and more of the electricity supply in order to cope with hourly variations is assessed to be in the range of about 50e130 GW. Depending on the scenario composition, the installed storage power is in the order of 20e35 GW for 80% and 20e80 GW for 100% renewables used. One study concludes that electricity storage is not needed at all for balancing up to 40% of electricity from renewable sources. Looking in detail into the studies for Europe shows that a relationship between the share of variable renewables and the balancing need in terms of power is likely from the results of the four applicable studies. However, the derivation of a sound correlation would require a more detailed analysis. The results indicate that, below about 28% of varying renewables, extra balancing need does not exist in the European electricity system. From this percentage onward the need could increase up to approximately 50% for the ratio of dispatchable power to total production power if power production from variable renewable sources reaches 70%. With higher shares of variable renewables the balancing need would prospectively increase further. Scholz [19] and Thien et al. [10] show that the share of variable renewables can be increased without any higher relative balancing demand by increasing the region considered to Europe plus Mediterranean countries and North Africa. Assuming that the balancing demand in these studies solely results from the installations in Europe indicates that with further investigations a correlation between the share of variable renewables and balancing demand could potentially be established. The ratio of
Chapter | 6
Review of the Need for Storage Capacity Depending on the Share of Renewable Energies
power installed for balancing need to total power installed in Europe could then increase to more than 60%. While a correlation for balancing need seems to be assessable with more detailed analyses, the required amount of electrical power from storage facilities strongly varies between the different scenarios. Of course, in the 100% variable renewable sources scenario only storage is used, but in other scenarios, the controllable power consists, e.g., of CSP and biomass or with lower shares of renewables of gas/oil plants and demand-side measures. The lowest estimate of storage size was derived by Fu¨rsch et al. [11] with 92 GW (70% of renewables, 44% variable renewables). The highest value was assessed by Thien et al. [10] with 940 GW (100% variable renewables). These two results already show the large range that could be expected. In order to assess the energy capacity required, the size and the timing of long gaps in wind power production are analyzed in the studies to obtain insight into the need for long-term or even seasonal balancing. Studies concentrating on Germany come up with values of about 2e8 TWh of storage size needed for a share of 80% renewable energies used in the electricity production and, thus, all are in the same order of magnitude. With 100% of electricity produced from renewable energies, the required storage size increases. However, the variations in the results of the SRU study [19] show that biomass can be used instead of storages. Estimated storage sizes range from about 15 TWh through about 25 TWh to 75 or even 86 TWh. In the case of the 75 TWh storage the single gaps in power are much smaller with about 40e45 TWh. The importance of the timing of gaps is shown with a variation carried out by Henning and Palzer [7] resulting in a maximum of 140 TWh and, thus, nearly a doubling of size is required if bad timing occurs. Studies looking at a larger region like Europe show that a smoothing effect can be observed by exchanging electricity from variable renewables internationally. Furthermore, more sources of dispatchable or more reliable production of electricity from renewables can be developed such as from CSP, photovoltaics, and wind in the Mediterranean region and in North Africa. This is impressively shown in Ref. [25], which assesses that 27 TWh (2 days) of storage size is needed if a region with a good national grid and without international exchange is assumed and 10% backup capacity exists. With no backup capacity the estimate for a good national grid and no international exchange is that 30e90 days of storage capacity is required while, with a good European grid, 7e30 days of storage capacity would be sufficient. This compares well with the results of Ref. [10], which comes up with about 3 weeks (320 TWh) of full load hours of long-term storage required and Ref. [21], which shows a range of 6e30 days of storage capacity required, depending on the grid performance and the wind power technologies used. The discussion in
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Ref. [25] emphasizes that the storage demand has to be discussed with respect to different grid conditions. With bad grid connections between regions and no backup capacity installed, which would be a worst case situation, the (average) storage demand for the regions increases to about 90 days. The review of the studies on need for energy storage capacity showed that a transfer of the results to other regions outside Europe is difficult and can only be done considering the specific circumstances in the scenarios to be analyzed. This holds particularly for long-term storage demand, which highly depends on extreme weather conditions varying strongly over different regions. The findings for very short-term balancing (reserve capacity) and load leveling could be comparable in other regions, particularly in regions also situated in the west wind drift zone (between about 30 and 60 of Northern and Southern latitude), because the wind systems and general weather conditions are similar to those in Central Europe/Northern Africa and at least part of the reserve is required to manage load variations.
ABBREVIATIONS CAES Compressed air energy storage CC Combine cycle CCS Carbon capture and storage CHP Combined heat and power CSP Concentrated solar power DSM Demand-side management HVDC High-voltage direct current RE Renewable energy
REFERENCES [1] dena. Studienlotse. Analysen zur Umgestaltung des Energiesystems. Deutsche Energie-Agentur (dena), http://www.effiziente-energie systeme.de/nc/studien-statistiken/studienlotse.html, 2012. [2] J. Eyer, G. Corey, Energy Storage for the Electricity Grid: Benefits and Market Potential Assessment Guide. A Study for the DOE Energy Storage Systems Program, Sandia Report, SAND20100815, Sandia National Laboratories, Albuquerque, 2010. [3] B. Droste-Franke, B.P. Paal, C. Rehtanz, D.U. Sauer, J.-P. Schneider, M. Schreurs, T. Ziesemer, Balancing Renewable Electricity. Interdisciplinary Perspectives on Energy Storage, Smart Grids, E-mobility and Network Extension, in: Ethics of Science and Technology Assessment, vol. 40, Springer, Berlin, 2012. [4] U. Bu¨nger, F. Crotogino, S. Donadei, C. Gatzen, W. Glaunsinger, M. Kleinmaier, M. Ko¨nemund, H. Landinger, T.J. Lebioda, W. Leonhard, D. Sauer, H. Weber, A. Wenzel, E. Wolf, W. Woyke, S. Zunft, Energiespeicher in Stromversorgungssystemen mit hohem Anteil erneuerbarer Energietra¨ger, ETG Task Force Energiespeicher, Energietechnische Gesellschaft im VDE (ETG), VDE, Frankfurt, 2009. [5] J. Nitsch, T. Pregger, Y. Scholz, T. Naegler, M. Sterner, N. Gerhardt, A. von Oehsen, C. Pape, Y.-M. Saint-Drenan, B. Wenzel, Langfristszenarien und Strategien fu¨r den Ausbau der erneuerbaren
86
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
Electrochemical Energy Storage for Renewable Sources and Grid Balancing
Energien in Deutschland bei Beru¨cksichtigung der Entwicklung in Europa und global, 2010. Leitstudie 2010‘. Deutsches Zentrum fu¨r Luft- und Raumfahrt (DLR), Fraunhofer Institut fu¨r Windenergie und Energiesystemtechnik (IWES), Ingenieurbu¨ro fu¨r neue Energien (IFNE), BMU - FKZ 03MAP146, German Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), Bonn. J. Nitsch, ‘Leitstudie 2008’eWeiterentwicklung der ‘Ausbaustrategie Erneuerbare Energien’ vor dem Hintergrund der aktuellen Klimaschutzziele Deutschlands und Europas, 2008. Ivestigations in collaboration with the German Aerospace Center (DLR), German Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), Bonn. H.-M. Henning, A. Palzer, 100% Renewables for Electricity and Heatea Holistic Model for a Future German Energy System, in: 7th International Renewable Energy Storage Conference (IRES 2012), November 12e14, 2012, Fraunhofer Institute for Solar Energy Systems ISE, Berlin, 2012b. J. Nitsch, B. Wenzel, Langfristszenarien und Strategien fu¨r den Ausbau erneuerbarer Energien in Deutschland unter Beru¨cksichtigung der europa¨ischen und globalen Entwicklung, Leitszenario 2009, Investigations on behalf of the German Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), Bonn, 2009. D. Lindenberger, M. Bartels, F. Borggrefe, D. Bothe, R. Wissen, B. Hillebrand, H.G. Buttermann, M. Bleul, Energiewirtschaftliches Gesamtkonzept 2030, Institute of Energy Economics at the University of Cologne (EWI), Energy Environment Forecast Analysis GmbH (EEFA), Bundesverband der Energie- und Wasserwirtschaft (BDEW), Berlin, 2008. T. Thien, M. Leuthold, F. Steinke, D.U. Sauer, Speicher- und Netzausbaubedarf in einem europa¨ischen Elektrizita¨tsversorgungssystem mit 100% EE-Versorgung, in: Paper for the VDE Conference ‘Smart Grid’, November, 5e6, 2012, Stuttgart, 2012. M. Fu¨rsch, S. Hagspiel, C. Ja¨gemann, S. Nagl, D. Lindenberger, L. Glotzbach, E. Tro¨ster, T. Ackermann, Roadmap 2050ea Closer Look. Cost-efficient RES-e Penetration and the Role of Grid Extensions, Final Report, Institute of Energy Economics at the University of Cologne (EWI), energynautics, Ko¨ln, 2011. D. Heide, L. von Bremen, M. Greiner, C. Hoffmann, M. Speckmann, S. Bofinger, Seasonal optimal mix of wind and solar power in a future highly renewable Europe, Renewable Energy 35 (2010) (2010) 2483e2489. T. Klaus, C. Vollmer, K. Werner, H. Lehmann, K. Mu¨schen, Energieziel 2050: 100% Strom aus erneuerbaren Quellen, Umweltbundesamt, Dessau-Roßlau, 2010. J. Nitsch, T. Pregger, T. Naegler, D. Heide, D.L. de Tena, F. Trieb, Y. Scholz, K. Nienhaus, N. Gerhardt, M. Sterner, T. Trost, A. von Oehsen, R. Schwinn, C. Pape, H. Hahn, M. Wickert, B. Wenzel, Langfristszenarien und Strategien fu¨r den Ausbau der erneuerbaren Energien in Deutschland bei Beru¨cksichtigung der Entwicklung in Europa und global, 2012. German Aerospace Center (DLR), Fraunhofer IWES, IFNE, Schlussbericht, BMU - FKZ 03MAP146, German Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), Bonn.
[15] F. Adamek, T. Aundrup, W. Glaunsinger, M. Kleimaier, H. Landinger, M. Leuthold, B. Lunz, A. Moser, C. Pape, H. Pluntke, N. Rotering, D.U. Sauer, M. Sterner, W. Wellßow, Energiespeicher fu¨r die Energiewende Speicherungsbedarf und Auswirkungen auf ¨ bertragungsnetz fu¨r Szenarien bis 2050, ETG-Task Force das U Energiespeicherung, VDE, Frankfurt am Main, 2012. [16] SRU, Wege zur 100% erneuerbaren Stromversorgung, Sondergutachten, Sachversta¨ndigenrat fu¨r Umweltfragen (SRU), Berlin, 2011. [17] A. Kirchner, M. Schlesinger, B. Weinmann, P. Hofer, V. Rits, M. Wu¨nsch, M. Koepp, L. Kemper, U. Zweers, S. Straßburg, F.C. Matthes, J. Busche, V. Graichen, W. Zimmer, H. Hermann, G. Penninger, L. Mohr, H.-J. Ziesing, Modell Deutschland, Klimaschutz bis 2050: Vom Ziel her denken, Prognos AG, ¨ ko-Institut e.V, World Wildlife Fund (WWF), Basel/Berlin, O 2009. [18] H.-M. Henning, A. Palzer, 100% Erneuerbare Energien fu¨r Strom und Wa¨rme in Deutschland, Fraunhofer Institute for Solar Energy Systems ISE, Freiburg, 2012a. [19] Scholz, Mo¨glichkeiten und Grenzen der Integration verschiedener regenerativer Energiequellen zu einer 100% regenerativen Stromversorgung der Bundesrepublik Deutschland bis zum Jahr 2050, Endbericht, Deutsches Zentrum fu¨r Luft- und Raumfahrt, Materialien zur Umweltforschung, SRU, Berlin, 2010. [20] W. Lise, J. van der Laan, K. Rademaekers, F. Nieuwenhout, C. Kirchsteiger, Assessment of the Required Share for a Stable EU Electricity Supply until 2050, 2011 final report, ECORYS Nederland BV, Energy research Centre of the Netherlands (ECN), DG Energy, European Commission, Contract No TREN/R1/350-2008 Lot 2, EUR 24996, Brussels. [21] M. Popp, Speicherbedarf bei einer Stromversorgung mit erneuerbaren Energien, Springer, Berlin, 2010. [22] S.-I. Inage, Prospects for Large-scale Energy Storage in Decarbonised Power Grids, Working Paper, International Energy Agency (IEA), Paris, 2009. [23] N. Hartmann, R. Barth, Bedeutung der Stromspeicher bei hohen Anteilen erneuerbarer Energien in Deutschland, Institut fu¨r Energiewirtschaft und Rationelle Energieanwendung (IER), Universita¨t Stuttgart, 2011. VDI-Berichte Nr. 2157, 285e 303. [24] Ph Kuhn, M. Ku¨hne, Optimierung des Kraftwerks- und Speicherausbaus mit einem iterativen und hybriden Modell, TU Mu¨nchen, 2011. VDI-Berichte Nr. 2157, 305e 317. [25] F. Steinke, P. Wolfrum, C. Hoffmann, Grid vs storage in a 100% renewable Europe, Renewable Energy 50 (2013) (2012) 826e832. [26] ECF, Roadmap 2050, a Practical Guide to a Prosperous, Lowcarbon Europe, European Climate Foundation (ECF), Den Haag, 2010. [27] W. Roedel, Physik Unserer Umwelt. Die Atmospha¨re, SpringerVerlag, Berlin, 1992. [28] N. Hartmann, Data for Scenarios Used in Hartmann and Barth (2011), Personal Communication, Institut fu¨r Energiewirtschaft und Rationelle Energieanwendung (IER), Universita¨t Stuttgart, Stuttgart, 2012.