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Renewable hydrogen implementations for combined energy storage, transportation and stationary applications
Journal Pre-proofs Renewable hydrogen implementations for combined energy storage, transportation and stationary applications Barbara Widera PII: DOI: Reference:
S2451-9049(19)30262-8 https://doi.org/10.1016/j.tsep.2019.100460 TSEP 100460
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Thermal Science and Engineering Progress
Received Date: Revised Date: Accepted Date:
28 September 2019 5 December 2019 8 December 2019
Please cite this article as: B. Widera, Renewable hydrogen implementations for combined energy storage, transportation and stationary applications, Thermal Science and Engineering Progress (2019), doi: https://doi.org/ 10.1016/j.tsep.2019.100460
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Renewable hydrogen implementations for combined energy storage, transportation and stationary applications Title:
Author names and affiliations: Barbara Widera PhD, DSc, Assoc. Prof. Faculty of Architecture,
Wroclaw University of Science and Technology Corresponding author: Barbara Widera, [email protected] Highlights:
The key distinguishing feature of hydrogen energy storage is the flexibility and possibility to provide multiple services Renewable hydrogen has a significant potential for stationary applications in buildings such as combined heat and power (CHP) plants or fuel cell electric generators Hydrogen energy storage should be used in sustainable architecture The versatility of possible applications of stored hydrogen puts this technology in the centre of R&D related to renewable energy infrastructure With the latest technologies green hydrogen can be produced using seawater, in an faster and environmentally safe solar-driven process
Abstract The purpose of this paper is to discuss the potential of hydrogen obtained from renewable sources for energy generation and storage systems. The first part of analysis will address such issues as various methods of green hydrogen production, storage and transportation. The review of hydrogen generation methods will be followed by the critical analysis and the selection of production method. This selection is justified by the results of the comparative research on alternative green hydrogen generation technologies with focus on their environmental impacts and costs. The comparative analysis includes the biomass-based methods as well as water splitting and photo-catalysis methods while water electrolysis is taken as a benchmark. Hydrogen storage and transportation issues will be further discussed in purpose to form the list of recommended solutions. In the second part of the paper the technology readiness and technical feasibility for joint hydrogen applications will be analysed. This will include the energy storage and production systems based on renewable hydrogen in combination with hydrogen usage in mobility systems as well as the stationary applications in buildings such as combined heat and power (CHP) plants or fuel cell electric generators. Based on the analysis of the selected case studies the author will discuss the role of hydrogen for the carbon emission reduction with the stress on the real value of carbon footprint of hydrogen depending on the gas source, storage, transportation and applications.
Keywords renewable hydrogen, hydrogen energy storage, RES, VRE, water electrolysis, hydrogen applications, resiliency, climate change, fuel cells, hydrogen energy storage in architecture, sustainable architecture
1. Introduction In the light of the Paris Agreement the development of sustainable energy technologies is a necessary part of tackling climate change action. Renewable hydrogen has a promising potential as an energy storage medium. As such, it can be used to ensure the energy system security and to cover the demand for energy in the periods of lower availability of variable renewable energy (VRE), namely wind and solar energy. Appropriate methods of energy storage help to deal with the
intermittency of renewable energy sources (RES) and thus contribute to the decarbonization of multiple sectors, including mobility and building industry. Hydrogen power to gas storage systems offer a feasible opportunity for the electricity transformation from the fossil fuels to RES, balancing variable renewable energies, especially at the local and regional level [26]. The paper will focus on the combination of hydrogen production based on water electrolysis and solar energy methods with the possibility of hydrogen implementations for energy storage, transportation and stationary applications such as combined heat and power (CHP) plants or fuel cell electric generators. Scientific articles published last years are mainly concentrated on renewable hydrogen production methods [1, 2, 4, 5, 11, 14, 29]. The literature review reveals that only a few authors address the hydrogen energy storage [7, 16, 19, 23, 26, 31]. The concept of combination of hydrogen production, storage, transportation and utilization for low carbon heat, power and mobility is described very fragmentarily in the literature [19, 27, 28]. As the topic attracts a lot of attention, the electrolysers have been tested worldwide for integrated generation of renewable electricity and the alternative energy carriers production (hydrogen or synthetic methane) in about 50 pilot and demonstration plants. 1 MW electrolysers (or larger) have been used in most of test sites [9]. Still, the combined applications of hydrogen from electrolysis for energy storage, sustainable transport and stationary purposes are rare and limited to particular locations. Some of the main nontechnological obstacles are related to policy regulations, not adjusted to the specific demands of hydrogen usage. Therefore, the pilot projects strive for better understanding of the opportunities and challenges of the hydrogen technology, including the electrolyser operation, plant selection, necessary permissions and regulations, as well as power and gas grid connections [5, 17]. In this paper the author aims to discuss the ability to reach improved efficiency and costeffectiveness in the energy transition on the example of the three selected case studies. Two of them are positioned in Europe and one in the United States of America. The analysed European projects are: the world’s first full-scale wind power and hydrogen plant on Utsira (Norway) and the most upto-date on-going project (chosen by Fuel Cells and Hydrogen Joint Undertaking) aimed to put in place fully integrated model of hydrogen production, storage, transportation and utilization for low carbon heat, power and transport (Orkney Archipelago, United Kingdom). The American demonstration scenario is the Wind-to-Hydrogen Project housed at the National Wind Technology Center (Boulder, Colorado), developed by the National Renewable Energy Laboratory's (NREL) and aimed to be a demonstration project integrating wind turbines and photovoltaic arrays with hydrogen production in electrolyzer.
2. Demand for renewable energy storage in 2030 and 2050 perspective 2.1 RES penetration, intermittency and the excess energy The share of RES in the European electric power generation is expected to grow considerably, contributing to the greenhouse gas emissions reduction [18]. The prognosed share of RES production in electricity demand should reach about 36% by 2020, 45-60% by 2030 and over 80% in 2050, while up to 65% of EU power generation will be covered by photovoltaics and wind sources. These variable renewable energy (VRE) production is subject to significant variability. Therefore, it is necessary to develop adequate strategies and tools to ensure energy system security and flexibility as well as to provide an effective integration to the power grid. Among available technological options for the VRE integration, the four main kinds can be distinguished: dispatchable generation (hydro, biomass, fossil), expansion of transmission and distribution, demand side management, and energy storage [7]. Energy storage systems have three purposes, i.e. charging, holding and discharging energy. The main types of storage technologies are taken into account:
Power to Power (P2P) (e.g. pumped hydro, batteries such as Li-ion, electrolytic hydrogen production and reconversion to electricity) This method is based on the concept of electricity production (charging) during the high supply and low demand period, then storing energy and using it (discharging) when electricity is needed at times of low supply and high demand. By reducing the difference in demand peaks and troughs, electricity time shift contributes to the stability of the power grid. It also allows to capture renewable energy (that would otherwise be curtailed) and provide it to the grid when necessary. Power to Heat (P2H) (heat storage and consumption) The main concept of this method lies in conversion of electricity to other energy carriers. During the periods of high supply and low demand, electricity is transformed into an energy carrier such as heat and/or hydrogen. This carrier is being stored and used in other sectors, including building, mobility and industry. Heat may be used in multiple industrial processes as well as in all kind of buildings to provide the required range of indoor temperatures and/or for domestic water heating. Power to Gas (P2G) (especially power to hydrogen) This idea based on the conversion of electricity to hydrogen which can be used in sectors other than the power (e.g. mobility) and thus contribute to their decarbonization. In this study the option of VRE integration and electricity conversion to hydrogen through water electrolysis was particularly emphasised as it allows for the effective usage of nearly all excessive renewable energy that would be curtailed in other scenarios. Hydrogen can serve as fuel for various vehicles (land or marine vehicles, aircrafts), can find applications in industry (e.g. chemical industry), in buildings, or can be used as admixture into the natural gas grid. In this light the possibility of the combination of the three energy storage options with the use of hydrogen looks truly promising. However, the crucial condition to take full advantage of the renewable sources is to provide sufficient capacity to absorb the power into the grid through the adequate transmission and distribution network. In another case, the output energy may be curtailed. Taken that the European potential for installed electrolyser capacity in 2050 high-RES scenarios would be in the hundreds of GWs, it is necessary to match the local production of hydrogen with demand or to develop appropriate (safe and economically efficient transportation system to deliver gas to a demand site [7]. 2.2 Hydrogen potential for energy storage Hydrogen energy storage systems (HES) create numerous potential benefits regarding decarbonization and resiliency of energy supply network. From the late 1990s it is known that hydrogen can be successfully used to store the energy which can be again transformed to electricity [20]. This is particularly important in the case of generating surplus energy from renewable sources, which cannot be used for current needs [13]. Then the ability to store energy using hydrogen is vital to ensure the stability of electricity supply. HES contribute to energy costs reduction and more efficient use of renewables. Similarities and differences between hydrogen and electricity as energy carriers were described by Yang in 2008 [30]. Additionally, hydrogen can be used in natural gas pipeline systems as well as in marine and land transportation as fuel, thereby contributing to lower consumption of conventional fossil fuels. The key feature distinguishing HES systems from other forms of energy storage (e.g. batteries or compressed air energy storage systems) is their flexibility and possibility to provide multiple services. This characteristics is crucial for the grid operators to ensure the system reliability and RES integration into multiple energy end-users within the power, heating, and transportation
infrastructure [16, 15]. With HES systems energy can be stored in the large scale i.e. 1 GWh to 1 TWh, while batteries typically range from 10 kWh to 10 MWh, and compressed air storage and pumped hydro range from 10 MWh to 10 GWh [16]. Other interesting opportunities of hydrogen usage are associated with fuel cell electric vehicles or devices such as fuel cell forklifts, range-extenders for battery electric vehicles, backup power supply, remote power systems and feedstock supply to multiple industrial processes (e.g. biorefineries). The degree to which HES systems can penetrate the energy storage markets will depend on various factors, including non-technological barriers, such as policy, safety and economic issues [3]. Hydrogen can be used for short-term and long-term energy storage. Actual research and development activities are focused on biological conversion of hydrogen to methane and other hydrocarbons. Therefore, if the adequate fuelling infrastructure is provided, hydrogen can be profitably applied in transportation and mobility, being introduced for fuel cell electric vehicles. The analysed scenarios, i.e. projects combining the wind power and hydrogen plant, prove that the green hydrogen from electrolysis can improve the efficient use of variable and intermittent renewable energy for diverse purposes. The integrated model of hydrogen production, storage, transportation and utilisation for low carbon heat, power and mobility has been further explored within the paper.
3. Green hydrogen generation technologies 3.1 Review of hydrogen production methods Case studies selected for the analysis in this paper use the notion of green hydrogen in the understanding of Fuel Cells and Hydrogen Joint Undertaking (FCH JU). According to this definition solely renewable energy input is used within the whole hydrogen production process. In the case of green hydrogen from water electrolysis, the electricity is exclusively renewable [2]. As it is defined in the EU Renewable Energy Directive (RED) it means “from renewable non-fossil sources, namely wind, solar, aerothermal, geothermal, hydrothermal and ocean energy, hydropower, biomass, landfill gas, sewage treatment plant gas and biogases” [6]. CO2-free electricity such as nuclear energy was excluded from this research. In the process of traditional production, hydrogen has been obtained from fossil sources by steam methane reforming of natural gas. Nowadays, the sustainable production method, strongly supported by FCH JU, is based on water electrolysis using renewable electricity. In this process electrical energy is used to split water molecules into gas: hydrogen and oxygen. Electrolysis units typically involve alkaline or polymer electrolyte membrane (PEM) conversion [4]. Multiple projects are focused on research and development of electrolyser technology with aim to increase the energy efficiency and cost effectiveness of electrolytic hydrogen production from renewable sources. Review of green hydrogen generation technologies revealed the main opportunities and constraints arising from the use of alternative methods, namely: a) biomass-based methods: pyrolysis and gasification of biomass, raw biomass reforming, fermentation and photofermentation, supercritical water gasification of biomass, b) processes involving plasma: plasma-supported gasification, plasma-based carbon black process c) water splitting: thermochemical water splitting based on renewable high temperature heat, photo-biological water splitting including algae bioreactors and photosynthetic microbes, photo catalysis,
electrohydrogenesis (biocatalysed electrolysis). Optional electrolysis method, especially beneficial for countries struggling with the shortage of fresh water, is the salt water electrolysis. Until now, the production of hydrogen directly from sea water using electrolysis was associated with difficulties arising from the appearance of significant amounts of chlorine as a chemical reaction product (instead of oxygen as in the case of fresh water electrolysis). Since the second decade of the 21st century, research has been intensified to develop safe and efficient methods for hydrogen production from salt water. One of the most promising approaches is the electrolysis of sea water in a H2/O2 cell with the use of oxygen-selective electrodes. [1]. With the latest technologies electrolysis can be carried out directly using seawater, in an environmentally safe solar-driven process, at a faster rate than current fresh water electrolysis [14, 24]. Hydrogen produced from electrolysis can be easily stored as a gas under high pressure (up to 900 bar), in the tanks or in underground piping systems. Underground hydrogen storage is suitable for large amount of gas (usually exceeding 100.000 m3). Another popular option is to store hydrogen as a liquid at very low temperature. Hydrogen can also be adsorbed or chemically bonded to hydride complexes. 3.2 Critical analysis and the selection of production method The review of hydrogen production methods followed by the critical analysis allowed for the selection of production method. This selection is justified by the results of the comparative research on alternative green hydrogen generation technologies with focus on their environmental impacts and costs. The comparative analysis includes the biomass-based methods as well as water splitting and photo-catalysis methods while water electrolysis is taken as a benchmark. For the analysed scenarios cost comparison showed that the price of hydrogen production using the biomass-based methods is similar to water electrolysis as well as water splitting and photo-catalysis. Solely the costs of dark fermentation of wet biomass combined with anaerobic digestion are considerably higher. The numbers are similar also in relation to the primary energy consumption [2]. Differences are more noteworthy in terms of greenhouse gas emissions. In this case only the hydrogen production using the solar energy offers similar GHG reduction potential to the water electrolysis while the biomass based methods generate significant emission levels [2]. This applies also to sea water electrolysis. Consequently, the sites that offer the opportunity to combine the hydrogen production using electrolysis and solar energy methods with the possibility of hydrogen implementations for energy storage, transportation and stationary applications, such as combined heat and power (CHP) plants or fuel cell electric generators, are particularly promising and should be selected for the pilot projects.
4. Green hydrogen production based on water electrolysis in combination with hydrogen energy storage - case studies analysis The paper covers the most actual initiatives addressing the combination of hydrogen production based on water electrolysis and solar energy methods with the possibility of hydrogen implementations for energy storage, transportation and stationary applications such as combined heat and power (CHP) plants or fuel cell electric generators. The opportunity to reach improved efficiency and cost-effectiveness in the energy transition is presented on the example of the three selected case studies:
The world’s first full-scale wind power and hydrogen plant (Utsira, Norway) The most significant American project of National Wind Technology Center (NWTC) by National Renewable Energy Laboratory (NREL), using electricity from wind turbines to produce and store hydrogen to be further used for energy storage (Boulder, CO, USA),
The most up-to-date on-going project (chosen by Fuel Cells and Hydrogen Joint Undertaking) aimed to put in place fully integrated model of hydrogen production, storage, transportation and utilization for low carbon heat, power and mobility (Shapinsay and Eday, Orkney Archipelago, UK).
The case studies selection for the analysis was based on the particular role of these projects in the development of renewable hydrogen production and storage systems, designed to provide the clean energy for the buildings. In all analysed scenarios hydrogen is produced in the proximity of the point of use. Selected projects offer the implementation in the building industry (heat and power supply). The purpose of analysis is to draw conclusions related to the opportunities and limits of the actual renewable hydrogen storage systems tested in the real life situation. 4.1 Lessons from the first full-scale wind power and hydrogen plant Norwegian island, Utsira, situated about 20 km from the west shore of Haugesund, was selected for the world’s first full-scale combined wind power and hydrogen plant, operated in the period 2004 - 2008. The island, inhabited by approximately 200 persons, has a ferry connection to the mainland. Difficult weather conditions often disturb the transportation, including the fossil fuel delivery. This increases the cost of energy production. However, the strong winds, characteristic for the island, contribute to the favourable conditions for the wind energy production. The Utsira Wind Power and Hydrogen Plant was financed by Statoil ASA and operated together with wind turbine manufacturer Enercon GmbH. The project was aimed to demonstrate hydrogen production from wind energy through fresh water electrolysis. The research and development tasks were focused on safe, continuous, and efficient energy supply while testing a full-scale, windhydrogen energy system [12]. The second purpose was to check the possibilities of costs reduction and technical solutions optimization in order to commercialize the production method. The energy generated from two Enercon E40 wind turbines (600 kWh each), installed at Utsira, fully covered 10 households' electricity demand. The plant was operated from the mainland control centre and the back-up power was available through the existing 1 MW subsea cable. According to the testing concept the first turbine would produce electricity directly for the external grid and the other was connected to the autonomous system through a 300 kW one-directional inverter (Fig. 1). It was
possible to redirect the surplus of energy (above 300 kW) from the autonomous system to the local grid.
On windy days, when the power production from the wind turbines would exceed the demands of the households, Hydrogen Technologies electrolyser (10 Nm3/h, 50 kW) was switched on. The produced hydrogen was compressed by the Hofer compressor (5 kW) and stored in a standard 200 bar tank (capacity 2400 Nm3). When the weather conditions would prevent the operation of wind turbines (with either too weak or strong wind), the electrolyser was switched off and the hydrogen engine was switched on. The continuous power supply was enabled by the 55 kW MAN hydrogen internal combustion engine and a 10 kW IRD fuel cell, using the stored hydrogen for the electricity production. During the short term increases in power the flywheel was charged to cover short term decreases in power with the stored energy (Fig. 2). In the prolonged period of the excess power, when the battery was fully charged, the electrolyser would be switched on and the hydrogen engine was switched off. A 5 kWh flywheel was installed for the frequency control to provide the grid stabilization in the autonomous system, together with a 100 kVA master synchronous machine for voltage control. Moreover, a Ni-Cd battery was added for extra redundancy. During the four years of testing period the plant was in continuous operation while for more than 50% of the time it would work in stand-alone mode.
Fig. 1. Utsira wind/hydrogen demonstration plant system schedule, drawing based on Harg [10].
Fig. 2. Utsira demonstration plant operational data, March 2007, drawing based on Ulleberg et al. [25].
Utsira Wind Power and Hydrogen Plant was successful, the quality of produced power was good and the project achieved a customers’ positive evaluation and a high level of satisfaction. In spite of some technical problems, it was demonstrated that the wind power energy generation can be effectively combined with renewable hydrogen production in electrolyser. It was also proven that it is possible to use the green hydrogen as the energy storage medium in purpose to provide reliable energy supply, especially for the communities inhabiting distant locations [27]. Among the most important technical issues the low durability of the fuel cell (less than 100 hours) was reported. Other difficulties were related to the leaking of coolant fluid and the voltage monitoring system damage during assembly, which was followed by numerous false grid failure alarms to remotely operated plant [12]. Proper operation of the hydrogen engine lasted 3 years and afterwards the
pistons have been damaged. In selected analysed periods (e.g. 1-30 March 2007) the stand-alone operation achieved 65% of time [25]. During the whole project duration the wind energy utilization reached only 20%. Additionally, it was hard to predict the electrolyser lifetime and one of the main conclusions from the project was that it is necessary to develop high-performance electrolyser (more efficient, with small footprint) and to improve the hydrogen-electricity conversion efficiency [10]. Another conclusion addressed the suggested inclusion of multiple renewable energy sources (e.g. wind, solar, bioenergy) in future projects [12]. 4.2 American leading project oriented towards multidimensional optimization of hydrogen production with electricity from wind turbines and hydrogen energy storage The Wind2H2 project (2008-2009) was oriented towards multidimensional optimization of hydrogen production with electricity from wind turbines and hydrogen energy storage. This project was developed by National Renewable Energy Laboratory (NREL) as a part of research in National Wind Technology Center (NWTC) in Boulder (Colorado, USA). The main goals of project were defined as follows: Reduce capital costs of electrolysis system through improved designs and lower cost materials • Develop low-cost hydrogen production from electrolysis through integration with renewable electricity sources • Develop strategies for low cost hydrogen production from electrolysis through utility coordination (Fig. 3).
Fig. 3. Wind2H2 R&D project, National Wind Technology Center (NWTC) in Boulder (Colorado, USA) (2008-2009), drawing based on NREL: Ramsden et al. [22].
The research covered the analysis of cost and capability of “time shifting” wind and PV energy through utility scale hydrogen-based energy storage as well as evaluation of synergies from
electricity and hydrogen co-production. Other activities involved the comparison of response and performance of alkaline and PEM electrolyzer technologies and assessment of efficiency gains through simplified and integrated power controllers. Multiple efforts have been undertaken towards optimization of wind to hydrogen conversion including simplifying PEM common controls, closely coupling wind input to stack and electricity regulation [22]. One of the identified issues was the necessity to work out a compromise between “the device being capable of handling an over-capacity beyond the rated input power (e.g. 2MW), and the subsequent additional cost associated with the balance of plant needed to facilitate an over-capacity capability” [23]. The electrolyzer system requires over-sizing of the power supply and thermal management systems that generate extra costs and complexity. In purpose to make a large-scale generator cost efficient the new membrane technologies that increase conductivity and reduce the thickness were evaluated. Consequently, the fluorinated membrane material that maximizes conductivity at the desired thickness was identified. Another conclusion addressed the exchanging of platinum group metals (PGMs), currently used as catalysts in electrolysers, with new catalyst materials and advanced electrode structures, developed in cooperation with 3M and the Brookhaven National Laboratory. Using nanostructures and core cell catalysts allowed to reduce the amount of PGMs in a working catalyst by more than 50% [23]. The analysis of system efficiency at rated stack current showed that the PEM electrolyzer system had efficiency of 57% while the maximum alkaline system efficiency reached 41%. It was also noted that the hydrogen production was about 20% lower than the manufacturer’s rated flow rate and if rated flow were achieved, 50% system efficiency would be realized [22]. Moreover, the energy transfer improvement was possible due to the implementation of the Maximum Power Point Tracking (MPPT) power electronics system that captured between 10% and 20% more energy than the PV direct-connection to the electrolyzer stack [23].
Fig. 3. BIG HIT Building Innovative Green Hydrogen Systems in an Isolated Territory: a Pilot for Europe (2016-2020). The combination of wind and tidal energy with hydrogen production and storage, drawing based on Fundación Hidrógeno Aragón [8].
The key conclusion from Wind2H2 R&D was that hydrogen provides a complete storage solution for wind and solar energy and the subsequent work should concern further improvements of system efficiency, taking into account the cost reduction in the next years. 4.3 Analysis of the cutting edge on-going project selected by FCH JU The wide range of stored hydrogen possible applications means that it occupies a central position among research on the development of renewable energy infrastructure. The project BIG HIT Building Innovative Green Hydrogen Systems in an Isolated Territory: a Pilot for Europe was submitted under Horizon 2020 and selected by the Fuel Cells and Hydrogen Joint Undertaking (FCH JU). BIG HIT, as the world leading pilot and demonstration project, is designed to create and implement a fully integrated model of hydrogen production, storage, transportation and utilisation for low carbon heat, power and mobility (Fig. 3). BIG HIT has 12 participants from 6 EU countries and was inaugurated in May 2018. However, the basis for this project were developed within the Orkney Surf 'n' Turf program which started hydrogen production through water electrolysis process powered by the wind and tidal energy on the Orkney archipelago, namely on the Eday and Shapinsay islands. The 2 by 4 kilometres EMEC tidal test side has 8 tidal test berths, situated near Eday, at the range of depths from 12 to 50 meters, in an area of strong marine currents (up to 4 m/sec). This test side is connected via 11 kV sub-sea cables to the substation at Caldale (Eday). The substation is equipped with the main switchgear and back-up generator in purpose to provide connection to the grid and to control the supply from tidal devices. The main idea of BIG HIT is to combine the renewable energy from community-owned Enercon E44 wind turbines, 900 kW each, located Shapinsay and Eday, with hydrogen production and storage. The two state-of-the-art ITM Power proton exchange membrane (PEM) electrolysers have the capacity of 1 MW and the other of 0.5 MW. They characteristics involve rapid response, high operating efficiency and high pressure output capability as well as the compact size (Fig. 4). The electrolysers use the otherwise curtailed capacity to produce each year about 50 tonnes of ultra-pure hydrogen which will be used for the energy storage, so that it can be converted to electricity and heat [8]. The majority of hydrogen will be transported in 5 tube-trailers to Kirkwall, except for the small amount that is planned to be used in two hydrogen-powered boilers that will provide zero carbon heat for the local buildings [21]. Due to the excessive weight of standard tube trailers, in which the hydrogen is stored as high pressure gas, a new tube model was designed by Calvera so that the gas can be safely transported on Orkney roads and by the sea. All the rigorous safety tests required for marine transportation of hydrogen were successfully passed [10]. In Kirkwall, a 75 KW hydrogen fuel cell, installed in 2017 as part of the Surf 'n' Turf project, uses the hydrogen and oxygen for the electricity production. The hydrogen refuelling station in Kirkwall delivers fuel for the 5 zeroemission hydrogen vehicles operated by the Orkney Islands Council. It is planned to enlarge this fleet to 10 hybrid Symbio vans based on the Renault Kangoo ZE Maxi (combined electric and hydrogen). The cars are fitted with a 22 kWh Li-Ion battery and a 5 kW hydrogen fuel cell range extender. The extender system will double their operational range and additionally there will be no impact from the cabin heating on the range [8]. The 3 Proton Motor PM 400 fuel cell stacks, with nominal electrical power of 4.0 - 30.0 kW each, are suitable for maritime stationary applications. The electricity is used by the local premises and vessels in the harbour, while the heat, as a by-product of the chemical reaction in the fuel cell, is send to the nearby buildings. The project has already produced substantial social, environmental and economic impact and significantly contributes to the development of integrated model of hydrogen production, storage, transportation and utilisation for low carbon heat, power and mobility.
Fig. 4. Proton exchange membrane (PEM) electrolyser by ITM Power installed on Orkney [8].
5. Conclusions Hydrogen is one of the most universal energy carriers. The versatility of possible applications of stored hydrogen is the reason why research on this technology occupies an important place among R&D works related to renewable energy infrastructure. Green hydrogen may be used in large-scale fuel cells to produce electricity on-site, or it can utilize existing infrastructure, such as natural gas pipelines. Small amounts of hydrogen may be added into the gas grid or a natural gas can be replaced with synthetic gas obtained through hydrogen methanation. The results of FCH JU research showed that in the nearest future a very large amounts of storage will be necessary to reduce the required fossil backup to a renewable energy network [7]. Therefore, it is expected that nearly all of the RES technologies will have to be re-oriented towards locations suitable for high-capacity hydrogen storage, elevations for pumped hydro, etc. [7]. To achieve requisite reduction in the backup capacity in would be essential to have the energy storage capacity of 50 TWh and more, so that it can be charged throughout the year with the excessive renewable energy production and discharged when necessary, instead of fossil fuel backup. However, to achieve such a high level of energy storage capacity, it would be required to keep the costs of storage technology very low. At this moment only chemical storage (notably hydrogen storage) could potentially fulfil the requirements. The opportunity to reach improved efficiency and cost-effectiveness in the energy transition was presented on the example of three selected case studies: the world’s first full-scale wind power and hydrogen plant, the American leading project oriented towards multidimensional optimization of hydrogen production with electricity from wind turbines and hydrogen energy storage, and the most up-to-date on-going European project aimed to put in place fully integrated model of hydrogen
production, storage, transportation and utilisation for low carbon heat, power and mobility. The analysis of the case studies allows to conclude that the use of renewable hydrogen, produced in highly efficient PEM electrolysers, powered by the wind, tidal and solar energy, represents substantial environmental and economic advantages as an energy storage medium. It may significantly contribute to more stable, efficient and sustainable energy systems. Nevertheless, the hydrogen production should be based on local renewable energy generation, with large-scale, highperformance and cost effective electrolysers, preferably located in proximity of power plants and well connected to the demand site. Taken the new opportunities to carry out salt water electrolysis, it is recommended to locate the electrolysers in the harbour area to have an easy access to the sea water as well as to the marine and land transportation. To take full advantage of the hydrogen benefits, selected sites should offer the opportunity for the hydrogen implementations for energy storage, transportation and stationary applications, including hydrogen refuelling station for vehicles and sea vessels. Combined CHP plants or fuel cell electric generators are strongly recommended. As the hydrogen system requires over-sizing of the power supply and thermal management systems, it is vital to keep the hydrogen production costs on the acceptable level. Thus, the new membrane technologies increasing conductivity and reducing the thickness (e.g. the fluorinated membrane material) may be used. Furthermore, the technologies of nanostructures and core cell catalysts allow to reduce the amount of PGMs in a working catalyst by more than 50%. It is also recommended to use Maximum Power Point Tracking (MPPT) systems to improve the energy transfer that allow to capture 10-20% more energy than the PV direct-connection to the electrolyzer stack. The final conclusion is that the electricity conversion to hydrogen through water electrolysis and usage of this hydrogen as an energy storage medium, fuel for mobility sector and the heating systems in the buildings can productively utilise nearly all excess of renewable energy by 2050 (taken 80% RES scenario), contributing to the decarbonisation of these sectors.
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CRediT author statement Barbara Widera: Methodology, Research, Writing, Graphical Presentation and Editing
S2451-9049(19)30262-8 https://doi.org/10.1016/j.tsep.2019.100460 TSEP 100460
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Please cite this article as: B. Widera, Renewable hydrogen implementations for combined energy storage, transportation and stationary applications, Thermal Science and Engineering Progress (2019), doi: https://doi.org/ 10.1016/j.tsep.2019.100460
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Renewable hydrogen implementations for combined energy storage, transportation and stationary applications Title:
Author names and affiliations: Barbara Widera PhD, DSc, Assoc. Prof. Faculty of Architecture,
Wroclaw University of Science and Technology Corresponding author: Barbara Widera, [email protected] Highlights:
The key distinguishing feature of hydrogen energy storage is the flexibility and possibility to provide multiple services Renewable hydrogen has a significant potential for stationary applications in buildings such as combined heat and power (CHP) plants or fuel cell electric generators Hydrogen energy storage should be used in sustainable architecture The versatility of possible applications of stored hydrogen puts this technology in the centre of R&D related to renewable energy infrastructure With the latest technologies green hydrogen can be produced using seawater, in an faster and environmentally safe solar-driven process
Abstract The purpose of this paper is to discuss the potential of hydrogen obtained from renewable sources for energy generation and storage systems. The first part of analysis will address such issues as various methods of green hydrogen production, storage and transportation. The review of hydrogen generation methods will be followed by the critical analysis and the selection of production method. This selection is justified by the results of the comparative research on alternative green hydrogen generation technologies with focus on their environmental impacts and costs. The comparative analysis includes the biomass-based methods as well as water splitting and photo-catalysis methods while water electrolysis is taken as a benchmark. Hydrogen storage and transportation issues will be further discussed in purpose to form the list of recommended solutions. In the second part of the paper the technology readiness and technical feasibility for joint hydrogen applications will be analysed. This will include the energy storage and production systems based on renewable hydrogen in combination with hydrogen usage in mobility systems as well as the stationary applications in buildings such as combined heat and power (CHP) plants or fuel cell electric generators. Based on the analysis of the selected case studies the author will discuss the role of hydrogen for the carbon emission reduction with the stress on the real value of carbon footprint of hydrogen depending on the gas source, storage, transportation and applications.
Keywords renewable hydrogen, hydrogen energy storage, RES, VRE, water electrolysis, hydrogen applications, resiliency, climate change, fuel cells, hydrogen energy storage in architecture, sustainable architecture
1. Introduction In the light of the Paris Agreement the development of sustainable energy technologies is a necessary part of tackling climate change action. Renewable hydrogen has a promising potential as an energy storage medium. As such, it can be used to ensure the energy system security and to cover the demand for energy in the periods of lower availability of variable renewable energy (VRE), namely wind and solar energy. Appropriate methods of energy storage help to deal with the
intermittency of renewable energy sources (RES) and thus contribute to the decarbonization of multiple sectors, including mobility and building industry. Hydrogen power to gas storage systems offer a feasible opportunity for the electricity transformation from the fossil fuels to RES, balancing variable renewable energies, especially at the local and regional level [26]. The paper will focus on the combination of hydrogen production based on water electrolysis and solar energy methods with the possibility of hydrogen implementations for energy storage, transportation and stationary applications such as combined heat and power (CHP) plants or fuel cell electric generators. Scientific articles published last years are mainly concentrated on renewable hydrogen production methods [1, 2, 4, 5, 11, 14, 29]. The literature review reveals that only a few authors address the hydrogen energy storage [7, 16, 19, 23, 26, 31]. The concept of combination of hydrogen production, storage, transportation and utilization for low carbon heat, power and mobility is described very fragmentarily in the literature [19, 27, 28]. As the topic attracts a lot of attention, the electrolysers have been tested worldwide for integrated generation of renewable electricity and the alternative energy carriers production (hydrogen or synthetic methane) in about 50 pilot and demonstration plants. 1 MW electrolysers (or larger) have been used in most of test sites [9]. Still, the combined applications of hydrogen from electrolysis for energy storage, sustainable transport and stationary purposes are rare and limited to particular locations. Some of the main nontechnological obstacles are related to policy regulations, not adjusted to the specific demands of hydrogen usage. Therefore, the pilot projects strive for better understanding of the opportunities and challenges of the hydrogen technology, including the electrolyser operation, plant selection, necessary permissions and regulations, as well as power and gas grid connections [5, 17]. In this paper the author aims to discuss the ability to reach improved efficiency and costeffectiveness in the energy transition on the example of the three selected case studies. Two of them are positioned in Europe and one in the United States of America. The analysed European projects are: the world’s first full-scale wind power and hydrogen plant on Utsira (Norway) and the most upto-date on-going project (chosen by Fuel Cells and Hydrogen Joint Undertaking) aimed to put in place fully integrated model of hydrogen production, storage, transportation and utilization for low carbon heat, power and transport (Orkney Archipelago, United Kingdom). The American demonstration scenario is the Wind-to-Hydrogen Project housed at the National Wind Technology Center (Boulder, Colorado), developed by the National Renewable Energy Laboratory's (NREL) and aimed to be a demonstration project integrating wind turbines and photovoltaic arrays with hydrogen production in electrolyzer.
2. Demand for renewable energy storage in 2030 and 2050 perspective 2.1 RES penetration, intermittency and the excess energy The share of RES in the European electric power generation is expected to grow considerably, contributing to the greenhouse gas emissions reduction [18]. The prognosed share of RES production in electricity demand should reach about 36% by 2020, 45-60% by 2030 and over 80% in 2050, while up to 65% of EU power generation will be covered by photovoltaics and wind sources. These variable renewable energy (VRE) production is subject to significant variability. Therefore, it is necessary to develop adequate strategies and tools to ensure energy system security and flexibility as well as to provide an effective integration to the power grid. Among available technological options for the VRE integration, the four main kinds can be distinguished: dispatchable generation (hydro, biomass, fossil), expansion of transmission and distribution, demand side management, and energy storage [7]. Energy storage systems have three purposes, i.e. charging, holding and discharging energy. The main types of storage technologies are taken into account:
Power to Power (P2P) (e.g. pumped hydro, batteries such as Li-ion, electrolytic hydrogen production and reconversion to electricity) This method is based on the concept of electricity production (charging) during the high supply and low demand period, then storing energy and using it (discharging) when electricity is needed at times of low supply and high demand. By reducing the difference in demand peaks and troughs, electricity time shift contributes to the stability of the power grid. It also allows to capture renewable energy (that would otherwise be curtailed) and provide it to the grid when necessary. Power to Heat (P2H) (heat storage and consumption) The main concept of this method lies in conversion of electricity to other energy carriers. During the periods of high supply and low demand, electricity is transformed into an energy carrier such as heat and/or hydrogen. This carrier is being stored and used in other sectors, including building, mobility and industry. Heat may be used in multiple industrial processes as well as in all kind of buildings to provide the required range of indoor temperatures and/or for domestic water heating. Power to Gas (P2G) (especially power to hydrogen) This idea based on the conversion of electricity to hydrogen which can be used in sectors other than the power (e.g. mobility) and thus contribute to their decarbonization. In this study the option of VRE integration and electricity conversion to hydrogen through water electrolysis was particularly emphasised as it allows for the effective usage of nearly all excessive renewable energy that would be curtailed in other scenarios. Hydrogen can serve as fuel for various vehicles (land or marine vehicles, aircrafts), can find applications in industry (e.g. chemical industry), in buildings, or can be used as admixture into the natural gas grid. In this light the possibility of the combination of the three energy storage options with the use of hydrogen looks truly promising. However, the crucial condition to take full advantage of the renewable sources is to provide sufficient capacity to absorb the power into the grid through the adequate transmission and distribution network. In another case, the output energy may be curtailed. Taken that the European potential for installed electrolyser capacity in 2050 high-RES scenarios would be in the hundreds of GWs, it is necessary to match the local production of hydrogen with demand or to develop appropriate (safe and economically efficient transportation system to deliver gas to a demand site [7]. 2.2 Hydrogen potential for energy storage Hydrogen energy storage systems (HES) create numerous potential benefits regarding decarbonization and resiliency of energy supply network. From the late 1990s it is known that hydrogen can be successfully used to store the energy which can be again transformed to electricity [20]. This is particularly important in the case of generating surplus energy from renewable sources, which cannot be used for current needs [13]. Then the ability to store energy using hydrogen is vital to ensure the stability of electricity supply. HES contribute to energy costs reduction and more efficient use of renewables. Similarities and differences between hydrogen and electricity as energy carriers were described by Yang in 2008 [30]. Additionally, hydrogen can be used in natural gas pipeline systems as well as in marine and land transportation as fuel, thereby contributing to lower consumption of conventional fossil fuels. The key feature distinguishing HES systems from other forms of energy storage (e.g. batteries or compressed air energy storage systems) is their flexibility and possibility to provide multiple services. This characteristics is crucial for the grid operators to ensure the system reliability and RES integration into multiple energy end-users within the power, heating, and transportation
infrastructure [16, 15]. With HES systems energy can be stored in the large scale i.e. 1 GWh to 1 TWh, while batteries typically range from 10 kWh to 10 MWh, and compressed air storage and pumped hydro range from 10 MWh to 10 GWh [16]. Other interesting opportunities of hydrogen usage are associated with fuel cell electric vehicles or devices such as fuel cell forklifts, range-extenders for battery electric vehicles, backup power supply, remote power systems and feedstock supply to multiple industrial processes (e.g. biorefineries). The degree to which HES systems can penetrate the energy storage markets will depend on various factors, including non-technological barriers, such as policy, safety and economic issues [3]. Hydrogen can be used for short-term and long-term energy storage. Actual research and development activities are focused on biological conversion of hydrogen to methane and other hydrocarbons. Therefore, if the adequate fuelling infrastructure is provided, hydrogen can be profitably applied in transportation and mobility, being introduced for fuel cell electric vehicles. The analysed scenarios, i.e. projects combining the wind power and hydrogen plant, prove that the green hydrogen from electrolysis can improve the efficient use of variable and intermittent renewable energy for diverse purposes. The integrated model of hydrogen production, storage, transportation and utilisation for low carbon heat, power and mobility has been further explored within the paper.
3. Green hydrogen generation technologies 3.1 Review of hydrogen production methods Case studies selected for the analysis in this paper use the notion of green hydrogen in the understanding of Fuel Cells and Hydrogen Joint Undertaking (FCH JU). According to this definition solely renewable energy input is used within the whole hydrogen production process. In the case of green hydrogen from water electrolysis, the electricity is exclusively renewable [2]. As it is defined in the EU Renewable Energy Directive (RED) it means “from renewable non-fossil sources, namely wind, solar, aerothermal, geothermal, hydrothermal and ocean energy, hydropower, biomass, landfill gas, sewage treatment plant gas and biogases” [6]. CO2-free electricity such as nuclear energy was excluded from this research. In the process of traditional production, hydrogen has been obtained from fossil sources by steam methane reforming of natural gas. Nowadays, the sustainable production method, strongly supported by FCH JU, is based on water electrolysis using renewable electricity. In this process electrical energy is used to split water molecules into gas: hydrogen and oxygen. Electrolysis units typically involve alkaline or polymer electrolyte membrane (PEM) conversion [4]. Multiple projects are focused on research and development of electrolyser technology with aim to increase the energy efficiency and cost effectiveness of electrolytic hydrogen production from renewable sources. Review of green hydrogen generation technologies revealed the main opportunities and constraints arising from the use of alternative methods, namely: a) biomass-based methods: pyrolysis and gasification of biomass, raw biomass reforming, fermentation and photofermentation, supercritical water gasification of biomass, b) processes involving plasma: plasma-supported gasification, plasma-based carbon black process c) water splitting: thermochemical water splitting based on renewable high temperature heat, photo-biological water splitting including algae bioreactors and photosynthetic microbes, photo catalysis,
electrohydrogenesis (biocatalysed electrolysis). Optional electrolysis method, especially beneficial for countries struggling with the shortage of fresh water, is the salt water electrolysis. Until now, the production of hydrogen directly from sea water using electrolysis was associated with difficulties arising from the appearance of significant amounts of chlorine as a chemical reaction product (instead of oxygen as in the case of fresh water electrolysis). Since the second decade of the 21st century, research has been intensified to develop safe and efficient methods for hydrogen production from salt water. One of the most promising approaches is the electrolysis of sea water in a H2/O2 cell with the use of oxygen-selective electrodes. [1]. With the latest technologies electrolysis can be carried out directly using seawater, in an environmentally safe solar-driven process, at a faster rate than current fresh water electrolysis [14, 24]. Hydrogen produced from electrolysis can be easily stored as a gas under high pressure (up to 900 bar), in the tanks or in underground piping systems. Underground hydrogen storage is suitable for large amount of gas (usually exceeding 100.000 m3). Another popular option is to store hydrogen as a liquid at very low temperature. Hydrogen can also be adsorbed or chemically bonded to hydride complexes. 3.2 Critical analysis and the selection of production method The review of hydrogen production methods followed by the critical analysis allowed for the selection of production method. This selection is justified by the results of the comparative research on alternative green hydrogen generation technologies with focus on their environmental impacts and costs. The comparative analysis includes the biomass-based methods as well as water splitting and photo-catalysis methods while water electrolysis is taken as a benchmark. For the analysed scenarios cost comparison showed that the price of hydrogen production using the biomass-based methods is similar to water electrolysis as well as water splitting and photo-catalysis. Solely the costs of dark fermentation of wet biomass combined with anaerobic digestion are considerably higher. The numbers are similar also in relation to the primary energy consumption [2]. Differences are more noteworthy in terms of greenhouse gas emissions. In this case only the hydrogen production using the solar energy offers similar GHG reduction potential to the water electrolysis while the biomass based methods generate significant emission levels [2]. This applies also to sea water electrolysis. Consequently, the sites that offer the opportunity to combine the hydrogen production using electrolysis and solar energy methods with the possibility of hydrogen implementations for energy storage, transportation and stationary applications, such as combined heat and power (CHP) plants or fuel cell electric generators, are particularly promising and should be selected for the pilot projects.
4. Green hydrogen production based on water electrolysis in combination with hydrogen energy storage - case studies analysis The paper covers the most actual initiatives addressing the combination of hydrogen production based on water electrolysis and solar energy methods with the possibility of hydrogen implementations for energy storage, transportation and stationary applications such as combined heat and power (CHP) plants or fuel cell electric generators. The opportunity to reach improved efficiency and cost-effectiveness in the energy transition is presented on the example of the three selected case studies:
The world’s first full-scale wind power and hydrogen plant (Utsira, Norway) The most significant American project of National Wind Technology Center (NWTC) by National Renewable Energy Laboratory (NREL), using electricity from wind turbines to produce and store hydrogen to be further used for energy storage (Boulder, CO, USA),
The most up-to-date on-going project (chosen by Fuel Cells and Hydrogen Joint Undertaking) aimed to put in place fully integrated model of hydrogen production, storage, transportation and utilization for low carbon heat, power and mobility (Shapinsay and Eday, Orkney Archipelago, UK).
The case studies selection for the analysis was based on the particular role of these projects in the development of renewable hydrogen production and storage systems, designed to provide the clean energy for the buildings. In all analysed scenarios hydrogen is produced in the proximity of the point of use. Selected projects offer the implementation in the building industry (heat and power supply). The purpose of analysis is to draw conclusions related to the opportunities and limits of the actual renewable hydrogen storage systems tested in the real life situation. 4.1 Lessons from the first full-scale wind power and hydrogen plant Norwegian island, Utsira, situated about 20 km from the west shore of Haugesund, was selected for the world’s first full-scale combined wind power and hydrogen plant, operated in the period 2004 - 2008. The island, inhabited by approximately 200 persons, has a ferry connection to the mainland. Difficult weather conditions often disturb the transportation, including the fossil fuel delivery. This increases the cost of energy production. However, the strong winds, characteristic for the island, contribute to the favourable conditions for the wind energy production. The Utsira Wind Power and Hydrogen Plant was financed by Statoil ASA and operated together with wind turbine manufacturer Enercon GmbH. The project was aimed to demonstrate hydrogen production from wind energy through fresh water electrolysis. The research and development tasks were focused on safe, continuous, and efficient energy supply while testing a full-scale, windhydrogen energy system [12]. The second purpose was to check the possibilities of costs reduction and technical solutions optimization in order to commercialize the production method. The energy generated from two Enercon E40 wind turbines (600 kWh each), installed at Utsira, fully covered 10 households' electricity demand. The plant was operated from the mainland control centre and the back-up power was available through the existing 1 MW subsea cable. According to the testing concept the first turbine would produce electricity directly for the external grid and the other was connected to the autonomous system through a 300 kW one-directional inverter (Fig. 1). It was
possible to redirect the surplus of energy (above 300 kW) from the autonomous system to the local grid.
On windy days, when the power production from the wind turbines would exceed the demands of the households, Hydrogen Technologies electrolyser (10 Nm3/h, 50 kW) was switched on. The produced hydrogen was compressed by the Hofer compressor (5 kW) and stored in a standard 200 bar tank (capacity 2400 Nm3). When the weather conditions would prevent the operation of wind turbines (with either too weak or strong wind), the electrolyser was switched off and the hydrogen engine was switched on. The continuous power supply was enabled by the 55 kW MAN hydrogen internal combustion engine and a 10 kW IRD fuel cell, using the stored hydrogen for the electricity production. During the short term increases in power the flywheel was charged to cover short term decreases in power with the stored energy (Fig. 2). In the prolonged period of the excess power, when the battery was fully charged, the electrolyser would be switched on and the hydrogen engine was switched off. A 5 kWh flywheel was installed for the frequency control to provide the grid stabilization in the autonomous system, together with a 100 kVA master synchronous machine for voltage control. Moreover, a Ni-Cd battery was added for extra redundancy. During the four years of testing period the plant was in continuous operation while for more than 50% of the time it would work in stand-alone mode.
Fig. 1. Utsira wind/hydrogen demonstration plant system schedule, drawing based on Harg [10].
Fig. 2. Utsira demonstration plant operational data, March 2007, drawing based on Ulleberg et al. [25].
Utsira Wind Power and Hydrogen Plant was successful, the quality of produced power was good and the project achieved a customers’ positive evaluation and a high level of satisfaction. In spite of some technical problems, it was demonstrated that the wind power energy generation can be effectively combined with renewable hydrogen production in electrolyser. It was also proven that it is possible to use the green hydrogen as the energy storage medium in purpose to provide reliable energy supply, especially for the communities inhabiting distant locations [27]. Among the most important technical issues the low durability of the fuel cell (less than 100 hours) was reported. Other difficulties were related to the leaking of coolant fluid and the voltage monitoring system damage during assembly, which was followed by numerous false grid failure alarms to remotely operated plant [12]. Proper operation of the hydrogen engine lasted 3 years and afterwards the
pistons have been damaged. In selected analysed periods (e.g. 1-30 March 2007) the stand-alone operation achieved 65% of time [25]. During the whole project duration the wind energy utilization reached only 20%. Additionally, it was hard to predict the electrolyser lifetime and one of the main conclusions from the project was that it is necessary to develop high-performance electrolyser (more efficient, with small footprint) and to improve the hydrogen-electricity conversion efficiency [10]. Another conclusion addressed the suggested inclusion of multiple renewable energy sources (e.g. wind, solar, bioenergy) in future projects [12]. 4.2 American leading project oriented towards multidimensional optimization of hydrogen production with electricity from wind turbines and hydrogen energy storage The Wind2H2 project (2008-2009) was oriented towards multidimensional optimization of hydrogen production with electricity from wind turbines and hydrogen energy storage. This project was developed by National Renewable Energy Laboratory (NREL) as a part of research in National Wind Technology Center (NWTC) in Boulder (Colorado, USA). The main goals of project were defined as follows: Reduce capital costs of electrolysis system through improved designs and lower cost materials • Develop low-cost hydrogen production from electrolysis through integration with renewable electricity sources • Develop strategies for low cost hydrogen production from electrolysis through utility coordination (Fig. 3).
Fig. 3. Wind2H2 R&D project, National Wind Technology Center (NWTC) in Boulder (Colorado, USA) (2008-2009), drawing based on NREL: Ramsden et al. [22].
The research covered the analysis of cost and capability of “time shifting” wind and PV energy through utility scale hydrogen-based energy storage as well as evaluation of synergies from
electricity and hydrogen co-production. Other activities involved the comparison of response and performance of alkaline and PEM electrolyzer technologies and assessment of efficiency gains through simplified and integrated power controllers. Multiple efforts have been undertaken towards optimization of wind to hydrogen conversion including simplifying PEM common controls, closely coupling wind input to stack and electricity regulation [22]. One of the identified issues was the necessity to work out a compromise between “the device being capable of handling an over-capacity beyond the rated input power (e.g. 2MW), and the subsequent additional cost associated with the balance of plant needed to facilitate an over-capacity capability” [23]. The electrolyzer system requires over-sizing of the power supply and thermal management systems that generate extra costs and complexity. In purpose to make a large-scale generator cost efficient the new membrane technologies that increase conductivity and reduce the thickness were evaluated. Consequently, the fluorinated membrane material that maximizes conductivity at the desired thickness was identified. Another conclusion addressed the exchanging of platinum group metals (PGMs), currently used as catalysts in electrolysers, with new catalyst materials and advanced electrode structures, developed in cooperation with 3M and the Brookhaven National Laboratory. Using nanostructures and core cell catalysts allowed to reduce the amount of PGMs in a working catalyst by more than 50% [23]. The analysis of system efficiency at rated stack current showed that the PEM electrolyzer system had efficiency of 57% while the maximum alkaline system efficiency reached 41%. It was also noted that the hydrogen production was about 20% lower than the manufacturer’s rated flow rate and if rated flow were achieved, 50% system efficiency would be realized [22]. Moreover, the energy transfer improvement was possible due to the implementation of the Maximum Power Point Tracking (MPPT) power electronics system that captured between 10% and 20% more energy than the PV direct-connection to the electrolyzer stack [23].
Fig. 3. BIG HIT Building Innovative Green Hydrogen Systems in an Isolated Territory: a Pilot for Europe (2016-2020). The combination of wind and tidal energy with hydrogen production and storage, drawing based on Fundación Hidrógeno Aragón [8].
The key conclusion from Wind2H2 R&D was that hydrogen provides a complete storage solution for wind and solar energy and the subsequent work should concern further improvements of system efficiency, taking into account the cost reduction in the next years. 4.3 Analysis of the cutting edge on-going project selected by FCH JU The wide range of stored hydrogen possible applications means that it occupies a central position among research on the development of renewable energy infrastructure. The project BIG HIT Building Innovative Green Hydrogen Systems in an Isolated Territory: a Pilot for Europe was submitted under Horizon 2020 and selected by the Fuel Cells and Hydrogen Joint Undertaking (FCH JU). BIG HIT, as the world leading pilot and demonstration project, is designed to create and implement a fully integrated model of hydrogen production, storage, transportation and utilisation for low carbon heat, power and mobility (Fig. 3). BIG HIT has 12 participants from 6 EU countries and was inaugurated in May 2018. However, the basis for this project were developed within the Orkney Surf 'n' Turf program which started hydrogen production through water electrolysis process powered by the wind and tidal energy on the Orkney archipelago, namely on the Eday and Shapinsay islands. The 2 by 4 kilometres EMEC tidal test side has 8 tidal test berths, situated near Eday, at the range of depths from 12 to 50 meters, in an area of strong marine currents (up to 4 m/sec). This test side is connected via 11 kV sub-sea cables to the substation at Caldale (Eday). The substation is equipped with the main switchgear and back-up generator in purpose to provide connection to the grid and to control the supply from tidal devices. The main idea of BIG HIT is to combine the renewable energy from community-owned Enercon E44 wind turbines, 900 kW each, located Shapinsay and Eday, with hydrogen production and storage. The two state-of-the-art ITM Power proton exchange membrane (PEM) electrolysers have the capacity of 1 MW and the other of 0.5 MW. They characteristics involve rapid response, high operating efficiency and high pressure output capability as well as the compact size (Fig. 4). The electrolysers use the otherwise curtailed capacity to produce each year about 50 tonnes of ultra-pure hydrogen which will be used for the energy storage, so that it can be converted to electricity and heat [8]. The majority of hydrogen will be transported in 5 tube-trailers to Kirkwall, except for the small amount that is planned to be used in two hydrogen-powered boilers that will provide zero carbon heat for the local buildings [21]. Due to the excessive weight of standard tube trailers, in which the hydrogen is stored as high pressure gas, a new tube model was designed by Calvera so that the gas can be safely transported on Orkney roads and by the sea. All the rigorous safety tests required for marine transportation of hydrogen were successfully passed [10]. In Kirkwall, a 75 KW hydrogen fuel cell, installed in 2017 as part of the Surf 'n' Turf project, uses the hydrogen and oxygen for the electricity production. The hydrogen refuelling station in Kirkwall delivers fuel for the 5 zeroemission hydrogen vehicles operated by the Orkney Islands Council. It is planned to enlarge this fleet to 10 hybrid Symbio vans based on the Renault Kangoo ZE Maxi (combined electric and hydrogen). The cars are fitted with a 22 kWh Li-Ion battery and a 5 kW hydrogen fuel cell range extender. The extender system will double their operational range and additionally there will be no impact from the cabin heating on the range [8]. The 3 Proton Motor PM 400 fuel cell stacks, with nominal electrical power of 4.0 - 30.0 kW each, are suitable for maritime stationary applications. The electricity is used by the local premises and vessels in the harbour, while the heat, as a by-product of the chemical reaction in the fuel cell, is send to the nearby buildings. The project has already produced substantial social, environmental and economic impact and significantly contributes to the development of integrated model of hydrogen production, storage, transportation and utilisation for low carbon heat, power and mobility.
Fig. 4. Proton exchange membrane (PEM) electrolyser by ITM Power installed on Orkney [8].
5. Conclusions Hydrogen is one of the most universal energy carriers. The versatility of possible applications of stored hydrogen is the reason why research on this technology occupies an important place among R&D works related to renewable energy infrastructure. Green hydrogen may be used in large-scale fuel cells to produce electricity on-site, or it can utilize existing infrastructure, such as natural gas pipelines. Small amounts of hydrogen may be added into the gas grid or a natural gas can be replaced with synthetic gas obtained through hydrogen methanation. The results of FCH JU research showed that in the nearest future a very large amounts of storage will be necessary to reduce the required fossil backup to a renewable energy network [7]. Therefore, it is expected that nearly all of the RES technologies will have to be re-oriented towards locations suitable for high-capacity hydrogen storage, elevations for pumped hydro, etc. [7]. To achieve requisite reduction in the backup capacity in would be essential to have the energy storage capacity of 50 TWh and more, so that it can be charged throughout the year with the excessive renewable energy production and discharged when necessary, instead of fossil fuel backup. However, to achieve such a high level of energy storage capacity, it would be required to keep the costs of storage technology very low. At this moment only chemical storage (notably hydrogen storage) could potentially fulfil the requirements. The opportunity to reach improved efficiency and cost-effectiveness in the energy transition was presented on the example of three selected case studies: the world’s first full-scale wind power and hydrogen plant, the American leading project oriented towards multidimensional optimization of hydrogen production with electricity from wind turbines and hydrogen energy storage, and the most up-to-date on-going European project aimed to put in place fully integrated model of hydrogen
production, storage, transportation and utilisation for low carbon heat, power and mobility. The analysis of the case studies allows to conclude that the use of renewable hydrogen, produced in highly efficient PEM electrolysers, powered by the wind, tidal and solar energy, represents substantial environmental and economic advantages as an energy storage medium. It may significantly contribute to more stable, efficient and sustainable energy systems. Nevertheless, the hydrogen production should be based on local renewable energy generation, with large-scale, highperformance and cost effective electrolysers, preferably located in proximity of power plants and well connected to the demand site. Taken the new opportunities to carry out salt water electrolysis, it is recommended to locate the electrolysers in the harbour area to have an easy access to the sea water as well as to the marine and land transportation. To take full advantage of the hydrogen benefits, selected sites should offer the opportunity for the hydrogen implementations for energy storage, transportation and stationary applications, including hydrogen refuelling station for vehicles and sea vessels. Combined CHP plants or fuel cell electric generators are strongly recommended. As the hydrogen system requires over-sizing of the power supply and thermal management systems, it is vital to keep the hydrogen production costs on the acceptable level. Thus, the new membrane technologies increasing conductivity and reducing the thickness (e.g. the fluorinated membrane material) may be used. Furthermore, the technologies of nanostructures and core cell catalysts allow to reduce the amount of PGMs in a working catalyst by more than 50%. It is also recommended to use Maximum Power Point Tracking (MPPT) systems to improve the energy transfer that allow to capture 10-20% more energy than the PV direct-connection to the electrolyzer stack. The final conclusion is that the electricity conversion to hydrogen through water electrolysis and usage of this hydrogen as an energy storage medium, fuel for mobility sector and the heating systems in the buildings can productively utilise nearly all excess of renewable energy by 2050 (taken 80% RES scenario), contributing to the decarbonisation of these sectors.
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CRediT author statement Barbara Widera: Methodology, Research, Writing, Graphical Presentation and Editing