Introduction of small-scale 4th generation district heating system. Methodology approach

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16th 16th International International Symposium Symposium on on District District Heating Heating and and Cooling, Cooling, DHC2018, DHC2018, 9–12 September 2018, Hamburg, Germany 9–12 September 2018, Hamburg, Germany th generation district heating system. Introduction of small-scale 4th Introduction of small-scale 4 generation district system. The 15th International Symposium on District Heatingheating and Cooling Methodology approach Methodology approach

Assessing the feasibility using aathe heat demand-outdoor a a Ieva Francescoof Romagnoli ,, Dagnija Ieva Pakere Pakerea*, *, Francesco Romagnoli Dagnija Blumberga Blumbergaa temperatureInstitute function forandaEnvironment, long-term district heat demand forecast of Energy Systems Riga Technical Univeristy, Azenes street 12/1, Riga Institute of Energy Systems and Environment, Riga Technical Univeristy, Azenes street 12/1, Riga a a

Abstract Abstract

I. Andrića,b,c*, A. Pinaa, P. Ferrãoa, J. Fournierb., B. Lacarrièrec, O. Le Correc

a

IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco requires Pais 1, 1049-001 Lisbon, Portugal In efficiency in and reduced thermal energy consumption innovative solutions and b In nowadays, nowadays, increased increased energy energy efficiency in buildings buildings and 291 reduced thermal energy consumption Veolia Recherche & Innovation, Avenue Dreyfous Daniel, 78520 Limay,requires France innovative solutions and appropriate district heating system development planning process. 4th generation district heating system is one of the key c appropriate district heating system development planning process. 4th generation district heating system is one of the key Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France solutions for improved overall system efficiency by decreased heat losses, improved heat generation efficiency, more efficient solutions for improved overall system efficiency by decreased heat losses, improved heat generation efficiency, more efficient use use of of renewable renewable energy energy sources sources and and other other advantages. advantages. The The article article describes describes the the approach approach and and the the methodology methodology for for development development of strategy to transform the existing DH system to 4GDH system particularly in cases with low DH systems loads. of strategy to transform the existing DH system to 4GDH system particularly in cases with low DH systems loads. Two Two factors factors (low heat Abstract (low heat load load and and low low temperatures) temperatures) are are becoming becoming more more and and more more actual. actual. The the particular particular small-scale small-scale DH DH system system in in aa parish parish located located in in the the East East part part of of The article article analyses analyses the the transformation transformation process process of of the Latvia. As a result, several transformation scenarios are identified. The technical solutions include replacement of a boiler, Latvia. a result, severalare transformation scenarios inaretheidentified. technical includesolutions replacement of a boiler, DistrictAsheating networks commonly addressed literature The as one of the solutions most effective for decreasing the heating network network reconstruction, reconstruction, heat heat supply supply temperature temperature lowering and and solar solar panel panel installation. installation. Further Further technical technical analyses analyses is is heating greenhouse gas emissions from the building sector. Theselowering systems require high investments which are returned through the heat carried out out for system system development development evaluation evaluation and strategy strategy implementation. implementation. Results Results shows shows that that it is essential essential to to evaluate evaluate the the carried sales. Duefor to the changed climate conditionsand and building renovation policies, heat demand itinisthe future could decrease, future energy efficiency measures in buildings when such small scale system is evaluated as it results in lower heat density and future energythe efficiency measures in buildings when such small scale system is evaluated as it results in lower heat density and prolonging investment return period. higher specific specific heat heat losses. losses. higher The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand forecast. Theinsert district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 Click here andAuthors. your abstract text. © 2018 The Published by Elsevier Ltd. Click here and insert your text. that vary in abstract both by construction and typology. Three weather scenarios (low, medium, high) and three district ©buildings 2018 Theopen Authors. Published Elsevier Ltd.period This is an access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) ©renovation 2018 The Authors. Published by Elsevier Ltd. scenarios were developed (shallow, intermediate, deep). To the error, obtained heat values were Peer-reviewand under responsibility of the scientific committee of the International Scientific Conference “Environmental anddemand Climate Selection peer-review under responsibility of the scientific committee ofestimate the 16th International Symposium District Heating Peer-review under responsibility of the scientific committee of the International Scientific Conference “Environmental andon Climate compared with results from a dynamic heat demand model, previously developed and validated by the authors. Technologies. and Cooling, DHC2018. Technologies. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications Keywords: 4thth in generation district heating, energy planning, solar power, primary energy, shrinkingconsidered). municipalities (the error annualdistrict demand wasenergy lower than 20% for allprimary weather scenarios Keywords: 4 generation heating, planning, solar power, energy, shrinking municipalities However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the Nomenclature Nomenclature decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the DHdistrict heating DHdistrict heating The values suggested could be used to modify the function parameters for the scenarios considered, and coupled scenarios). th 4GDH –– 44th Generation District Heating 4GDH District Heatingestimations. improve theGeneration accuracy of heat demand PEF –Primary Energy Factor PEF –Primary Energy Factor PEF solar – Primary Energy Factor for system with integrated PV panels; PEF Primary Energy Factor for system with solar –The © 2017 Authors. Published by Elsevier Ltd.integrated PV panels; E j – the amount of the primary energy for heat production consumed; EPeer-review of the primary energy for heat production consumed; j – the amount under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and E el – the amount of primary energy for power consumption coverage; ECooling. el – the amount of primary energy for power consumption coverage; ƒƒp,j -- the primary energy factor related to an energy source; p,j the primary energy factor related to an energy source; ƒƒp,el -- the primary energy factor the plants; energyForecast; factor for for the power power plants; p,el the primary Keywords: Heat demand; Climate change E Edel -- the the amount amount of of energy energy delivered delivered to to the the consumers. consumers. del

1876-6102 © 2018 The Authors. Published by Elsevier Ltd. 1876-6102 © 2018 TheThe Authors. Published by Elsevier Ltd. Ltd. 1876-6102 © 2017 Authors. Published by Elsevier Peer-review responsibility of the scientific committee of the Ltd. International Scientific Conference “Environmental and Climate Technologies. 1876-6102 under © 2018 The Authors. Published by Elsevier Peer-review under responsibility of theofscientific committee of the International Scientific Conference “Environmental and Climate Technologies. Peer-review under responsibility the Scientific Committee of The 15th International Symposium on District Heating and Cooling.

This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of the 16th International Symposium on District Heating and Cooling, DHC2018. 10.1016/j.egypro.2018.08.219

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1. Introduction Introduction of 4th Generation District Heating (4GDH) System with lower heat transfer media temperature and integrated renewable energy sources is one of the key solutions for sustainable development of existing district heating (DH) systems. In nowadays, increased energy efficiency in buildings and reduced thermal energy consumption requires innovative solutions and appropriate system development planning process [1]. Therefore, there is several other reasons for decreased heating loads such as shrinking municipalities and prosumers approach. This requires searching for economically and environmentally beneficial solutions for development of such changing DH systems. Lowered heating network temperature is one of the key aspects for improved overall efficiency by decreased heat losses, improved heat generation efficiency, more efficient use of renewable energy sources and other advantages [2, 3]. When planning lowered heat transfer temperature in the new housing areas it is relatively simple to adjust the internal space heating and domestic hot water preparation system according the required temperature levels in design phase. However, when implementing LTDH in existing buildings it requires innovative technical solutions to ensure the necessary thermal comfort [4]. Jengsten et.all [5] has studied the actual supply temperatures and heat transfer areas of radiators in Gotheburg. Those are the key parameter, which should be taken into account when lowering the supply temperature in buildings with a radiator space heating. Authors conclude that buildings in the particular district require energy efficiency measures for the heat demand reduction as well as an increase of the radiators' heat transfer surfaces to enable lower operating temperatures. Nevertheless, another study by Tunzi et.all. [6] proposes the method for the optimal regulation of the existing radiator system according the optimal temperature level which can allow reducing the space heating supply temperature without any other particular system adjustments. Kofingher et.all. [7] offer to implement the energy-cascades between different types of buildings in order to lower the return water temperature. This is possible when aligning the DH return flow from high-temperature consumers with the supply flow for low-temperature consumers. Authors conclude that energy cascades can ensure the return flow reduction up to 10K and improve the overall system efficiency. As system approach is essential to develop smart DH system, several authors have studied the transition process from traditional DH system to more efficient 4GDH system [8,9]. Ziemele et.al [10] has developed the multi-perspective methodology to compare different DH system development scenarios to move toward 4GDH. The methodology allows evaluating the development perspectives from the different interested parties’ point of view. The methodology of transition process dynamic analyses evaluation has been proposed by Volkova et.all [11]. Authors focuses on transition process monitoring in past and present in order to identify the weak links in the system. Municipalities are one of stakeholders who has important role in DH transformation course. Therefore, the DH system development strategy can be a significant changing point to create the energy efficient energy supply system [12-13]. The article describes the methodology for development of strategy to transform the existing DH system to 4GDH system. The main focus group is municipality who has the opportunities to support innovative solutions. The methodology includes several modules, which allows identifying most suitable development scenarios. The particular scenarios are compared with the existing DH system scenario (Base scenario) in order to evaluate the technical feasibility. 2. Methodology The transformation of the existing DH system to 4GDH requires careful planning process from the involved stakeholders. The municipalities are one of main interested parties of this system development. Therefore, local authorities should follow the methodology to achieve effective heat supply in accordance with specific local conditions. As a first step, it is important to analyse the overall heat supply system of the municipality to obtain the information about main networks, building structures, heat densities, heat production plants etc. Such analyses can also include the building age, depreciation periods and the upcoming investments. Therefore, it is important to identify the main stakeholders and key actors that have an impact on the overall DH system development. When the general overview of the particular urban or rural area is obtained, the next step is to search for the most suitable long-term development path of heat supply. When comparing different technological solutions it is necessary to consider if the framework conditions will change in future, what are the economical, ecological, and social implications involved. When the common guiding principles for DH transformation are designed, the particular district as a pilot case study can be chose. There are several selection criteria such as high energy efficiency and renewable energy implementation potential, suitable framework conditions, need for reconstructions etc. Further, more detailed analyses needs to be carried out for the particular pilot case in order to set the goals, develop strategies and evaluate technical alternatives. The onsite measures, input data analyses and mathematical model development are the main methods used for such investigation. Figure 1 shows the methodology for pilot case analyses. The main input data for this stage are building state of modernisation, total and specific heat and power consumption. In addition, the heat production data is required (CO2 emissions, type of heat supply, production efficiency etc. technical information). The energy balance sheet is one of the main outputs that should include both heat demand and CO2 emissions.



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Author name / Energy Procedia 00 (2018) 000–000 Analyses of existing situation

Initial data

Alternative solutions

3

551

Technologies. Data basis

Technological calculation

No

Economical calculation

Benchmarking indicators

Environmental calculation

Is alternative feasible?

Platform of results

Yes

Accepted technological solution

Fig.1. Pilot case investigation methodology The transformation potential and different development alternatives can be determined after the technological calculations of the particular pilot case. In order to compare those alternatives, different indicators can be used. For particular pilot case analyses, primary energy factor has been calculated. Primary energy factor (PEF) is an energy indicator used for quantifying the primary energy use of a system [14]. PEF is defined as follows:

PEF =

∑𝑗𝑗 𝐸𝐸ℎ,𝑗𝑗 ∙𝑓𝑓𝑝𝑝,ℎ +𝐸𝐸𝑒𝑒𝑒𝑒 ∙ƒ𝑝𝑝,𝑒𝑒𝑒𝑒 𝐸𝐸𝑑𝑑𝑑𝑑𝑑𝑑

(1)

where Ej – the amount of the primary energy for heat production consumed, MWh; Eel – the amount of primary energy for power consumption coverage, MWh; ƒp,j - the primary energy factor related to an energy source; ƒp,el - the primary energy factor for the power plants; Edel - the amount of energy delivered to the consumers MWh.

Table 1. Primary energy factors used for scenario evaluation Energy source Primary energy factor Biomass 0.2 Power from grid 1.5 Power from solar energy 0 Table 2 shows the primary energy factors used for calculations. PEF are compared and those are further justified in order to find the most feasible technical solution, which can be then implemented, into the particular district. 3. Results The methodology is applied and tested on the particular DH system in Latvia. The chosen case study is a parish located in the East part of country. Due to decreasing number of inhabitants and recently accomplished energy efficiency measures in building it was necessary to redesign the existing inefficient DH system. Detailed analyses according methodology described above has been applied for the particular parish. As a result, several transformation scenarios are identified. The technical solutions include replacement of boiler, heating network reconstruction, heat supply temperature lowering and solar panel installation. Further technical analyses is carried out for system development evaluation and strategy implementation. The DH network scheme of the parish can be seen in Fig.2. The DH network has been redesign completely in order to increase the heat density and reduce heat loses. In order to optimize the heat pipe length, four private houses has been switched from the DH network to individual heating system. In addition, the location of boiler house has been changed and new pellet boiler house is integrated into the system.

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Signs

Existing heating network Heating network after reconstruction

Existing firewood heat plant

Avotu street 2

Vienibas street 1 New pellet boiler house

Vienibas street 2

Vienibas street 3

Vienibas street 5

Fig.2. Pilot case DH network before and after reconstruction After the DH network reconstruction only five buildings will be connected to the system. The heat density increases from 1.1 MWh/m to 2.8 MWh/m after reconstruction. Table 2 shows the overview of the building types, area and specific heat consumption for space heating. Most of buildings experienced energy efficiency measures recently, therefore only apartment building has high specific heat consumption compared to standard in new buildings in Latvia that is 80 kWh/m 2 per year. Therefore, two different scenarios are analyzed for further development of scenarios. In Base scenario the heat consumptions remains constant. In energy efficient (EEF) scenario it is assumed that heat losses from apartment building will be reduced due to insulation works and the specific heat consumption will decrease by 60% to 80 kWh/m2. Table 2. Overview of buildings connected to DH system after reconstruction

Nr.

Address

1

Avotu street 2 Vienibas street 2 Vienibas street 1 Vienibas street 3 Vienibas street 5

2 3 4 5

Type

Kindergarten Mail Local authority Shop Recreational, utility room Cultural house Apartment building

Insulated

Area, m2

Specific heat consumption, kWh/m2

Yes

1614

75

Yes No Yes No

229 277 723 1224

88 65 125 192

Figure 3 shows the heat load duration curves for both scenarios. It can be seen that heat capacity in EEF scenario reduces to 150 kW by comparing to 200 kW in Base scenario. In the particular parish heat is provided only for space heating and there is no heat load in summer period.

Heat capacity, kW

250 200

150 100 50 0

0

1000

2000

3000 Base scenario

4000

5000

6000

Energy efficient scenario

Fig.3. Heat load duration curve

7000

8000



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5

Heat carrier temperature, oC

An essential aspect to aproach 4GDH is to lower heating network temperature. Therefore, it is considered to reduce supply and return water temperature from 90 oC/60 oC to 60oC/35oC.The heating network temperature curve is shown in Figure 4. It has been considered that heating system in renovated buildings remains the same as before the renovation. Therefore, the surface area of installed heating elements would allow to reduce the supply water temperature without any other additional change of operational parameters [6]. In case of appartment building in BS when no energy efficiency measures are considered, it would require to consider energy cascade [7] or other solutions for supply temperature lowering to be possible. 100 80 60 40 20 0

-25

-20

-15

Supply (90/70)

-10

-5

0

Outdoor temperature Return (90/70)

Supply 60/35

5

8

Return (60/35)

Fig.4. Heat carrier temperature curves for standard and low temperature system Therefore, four different technical alternatives regarding building heat consumption and temperature levels in DH network have been identified for the further development of particular parish. In order to compare and evaluate those alternatives, the heat losses and heat density have been used as technical indicators. In addition, it has been considered to install the PV panels for power production and building power consumption coverage. The total power consumption in buildings and boiler house is 33 MWh per year. It would require 9 kW of PV panel to cover such consumption in summer period (see Figure 5). The assumed PV efficiency is 15% and annual solar radiation is 973 kWh/m 2.

Power, MWh

4 3 2 1 0

jan

feb

mar

apr

may

jun

Power from PV panels

jul

aug

sep

oct

nov

dec

Power consumption

Fig.5. Power consumption and solar power production duration Table 3 shows the results of technical calculations. It can be seen that in EEF scenario, when energy efficiency measures are considered, the heat consumption and heat density decreases, therefore specific heat losses in heating network increases. Reduced heating network temperature is a solution for optimal operation of DH system in such conditions.

Scenario BS (90/60) BS (60/35) EEF (90/60) EEF (60/35)

Table 3. Technical calculation for different scenarios Heat Heat Heat Heat Power Solar consumption, density, losses, losses, consumption, power, MWh per MWh/m MWh % MWh MWh year 491 2.8 41.3 8% 491 2.8 34.5 7% 33 8.7 347 2 41.3 12% 347 2 34.5 10%

PEF 0.322 0.319 0.350 0.345

PEF Solar

0.347 0.344 0.384 0.380

In order to compare the scenarios when PV are installed for power production, the primary energy factor is calculated for all scenarios (PEF –without solar power and PEF solar – with solar power considered). Results shows that lowest value is for base scenario with lowered temperature regime and solar panel installation as primary energy is low and delivered energy remains high. Therefore, PEF for EEF scenarios is higher than for BS scenarios as heat consumption decreases and the specific heat losses are higher.

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4. Conclusions The article provides the methodology for municipalities to transform the existing DH system to 4GDH system with lower heat supply temperature and integrated alternative energy sources. Therefore, the main steps of the transformation process is to evaluate the overall DH system of particular region/city, identify the most suitable transformation path and further select the relevant district/area for pilot case study which needs to be analyzed more detailed. The example of such analyses has been provided in the article with the comparison of different technological alternatives for particular parish. The analyzed example is a small-scale DH system with few buildings connected in order to achieve optimal heat density and operational conditions. The calculation of technical indicators allows evaluating the possible development scenarios, which includes the energy efficiency measures, reduction of heat supply temperature and installation of solar PV panels for power production for selfconsumption coverage. The heat losses, heat density and primary energy factor have been calculated for all scenarios. The results shows that when energy efficiency measures are considered, the overall heat consumption reduces by around 30%. This effect the heat density of network and it decreases from 2.8 to 2 MWh/m. Therefore, in considered EEF scenario, the specific heat losses increases from 8% to 12%, but reducing the heat supply temperature from 90oC to 60oC allows decreasing the specific heat losses to 10% level. For the particular parish it is considered to install the 9kW PV panel power station for self-consumptions coverage of buildings and boiler house. Therefore, such power station can cover around 27% of total power consumption. The calculated primary energy factor allows comparing the primary energy consumption with and without integrated solar panels. Integration of solar panels reduces the PEF by around 7% in BS scenarios and by 9% in EEF scenarios. Therefore, the methodology allows identifying and evaluating potential technical solutions for particular district to approach 4GDH concept. The municipality should than ensure the suitable conditions for the implementation of desirable solution in pilot case district. However, afterword it requires monitoring the results of particular pilot case to evaluate the achievement or identify improvements for the further transformation process and application to larger scale (region or district). Acknowledgement This work is supported by the European Commission through the EU INTERREG Baltic Sea Region Project Number #R063 „Low Temperature District Heating for the Baltic Sea Region” (LowTEMP).

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