Low-Temperature District Heating System. for Low-Energy Buildings

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1 Low-Temperature District Heating System for Low-Energy Buildings + Peter Kaarup Olsen COWI, Energy Department pko@cowi.dk # 1

2 Repetition from yesterday.. Why District Heating (DH) to Low-Energy Houses? Renewable energy sources can be used directly or in combination with large scale heat storages. It is flexible system suitable for all kind of energy sources Waste heat from CHP plants, refuse incineration and industrial processes can utilized Reliable and easy operation for the consumers Easy operation for the heat consumers # 2

3 Why District Heating (DH) to Low-Energy Houses? The number of low-energy houses is increasing!!!! The European energy policy focuses on energy savings and use of renewable energy. In Denmark the government has decided that energy use in new buildings must be reduced stepwise by 25% in 2010, 2015 and # 3

4 Finalised R&D-project (EFP2007) Title: Development and Demonstration of Low-Energy District Heating for Low-Energy Buildings Period: Financing: Supported by the Danish Energy Authority's Energy Research Programme (EFP2007) Participants: Danish Technological Institute (Project responsible) DTU Byg (Technical University of Denmark) COWI A/S LOGSTOR A/S DANFOSS District Heating Energy Service Denmark (Energitjenesten) # 4

5 Project description To investigate if DH is suitable for low-energy houses To design a cost-effective ti DH system for low-energy houses by reducing heat losses and minimize the total investment costs Development and testing of prototypes (make the design concept ready for real demonstration!) District Heating Storage Unit Optimised i district i heating pipe New smaller dimension flexible twin pipe Ø14/14 Aluflex (by Logstor) New type of unit: District Heating storage 120 eller 175 liter (by Danfoss) # 5

6 Space heating consumption in reference house 20 C in all rooms: 24 C in the two bath rooms and 22 C in de øvrige rum: 20.1 kwh/m²/year * 30.7 kwh/m²/year ** -> 50% higher heating consumption Calculated in Bsim (programme for thermal building simulations): * Standard indoor temperature used in documentation (BE06 calculations in correlation with the Danish Building Regulation) ** More common / realistic indoor temperatures Reference house: 145 m² low- energy class 1 house (Danish Building Regulation) Reference house: Peak heat demand of 3.7 kw and a yearly heat consumption of 6750 kwh (incl. domestic hot water) # 6

7 Investigated scenarios Different DH consumer units Scenario Consumer unit type Design Design temperatures load T supply T return 0 Domestic hot water (reference) storage 8 kw 80 C 40 C DH storage (new type) * Heat exchanger (no heat storage) Domestic hot water storage 3.7 kw 50 C 22 C 32 kw 50 C 22 C 8 kw 60 C 30 C * Low constant DH flow, because peak demand for domestic hot water is levelled out ~ 0.3 kw # 7

8 District Heating Network Design assumptions 6 or 10 bar system (maximum pressure) Holding pressure: 2 bar Maximum velocities: 2 m/s Bypass flows (in the end of a "street" pipe) No bypass flows in the units Simultaneity factor = 1,00 for DH storage Twin-pipes pp (lower total heat loss, lower investment costs both regarding pipes and digging) Simultaneity factors No. of consumers Heat exchanger Domestic hot (no heat storage) water storage , ,00 2 0,66 0,75 3 0,56 0,63 4 0,47 0,60 5 0,39 0,53 6 0,34 0,50 7 0,31 0,49 8 0,30 0,48 9 0,28 0, ,25 0, ,19 0, ,12 0,19 "Re-thinking"!!! # 8

9 Simulation Example of supply temperatures Supply temperatures in a case of a heat demand of 1.53 kw pr. house (Scenario 1) Temperature profile in twin pipes # 9

10 Calculation results Energy in DH network Scenarie 0 Reference* Scenario 1 DH storage Scenario 2 Heat Scenario 3 D. hot water unit exchanger unit unit Electricity to pumping, MWh p /year total network Heat delivered, total network MWh/year Heat consumption, 92 houses MWh/year Heat loss, MWh/year total network Heat loss, % total network * Domestic hot water units and "traditional" DH network with single pipes # 10

11 DH network Total investment costs DKK per hou use Installation of unit Consumer unit Consumer supply line installations Main pumps Pipe system 0 Scenario 0 Scenario 1 Scenario 2 Scenario 3 Reference* DH storage unit Heat Domestic hot exchanger unit water unit * Domestic hot water units and "traditional" DH network with single pipes Maybe a combination of DH storage units and Heat exchanger units in the network? # 11

12 Socio-economics Objective To compare low-temperature district heating with alternative heating systems Investigated scenarios Low-temperature district heating (district heating storage unit) Heat pump, ground coil Heat pump, air-to-water vs. vs. # 12

13 Socio-economics Costs per 30 years DKK / house Low-temp. DH unit Heat pump, ground coil Heat pump, air-to-water Fuel, taxes, emissions etc. Investments (Incl. re- investment and salvage value) Low-temperature DH is fully competitive with the heat pump technology! # 13

14 Environmental analysis Emissions CO 2 -equiv valent [ton] Low-temp. DH unit Heat pump, p, Heat pump, p, ground coil air-to-water Also environmentally Low-Temperature DH looks fully competitive with Heat pumps! In these calculations Low-Temperature DH comes out with the lowest CO 2 -emissions, and the Heat Pumps with the lowest emissions of SO 2 and No x # 14

15 Environmental analysis Emissions DH Waste (combined heat &power) DH Natural Gas (combined heat & power) DH Biogas - boiler DH Biomass (wood) - boiler DH Biomass (straw) - boiler Heat pump, ground coil average electricity Heat pump, air-to-water average electricity CO 2 -equivalent [ton] With biofuels, it is possible to achieve almost CO 2 -neutral DH supply and to reduce the emissions of SO 2 og NO x to the same level as the Heat Pumps Moreover, solar heat and waste heat can deliver heat supply almost without t emissions, just as extension of wind power can result in lower emissions for the heat pumps # 15

16 Main conclusions for this case-study Heat density is of great importance for the feasibility Very low DH network heat loss (down to 12-16%) despite the low heating demand in the low-energy buildings Little difference between different DH unit types Optimisation of network (pipe length and heat density) can give even better economy for DH With an sufficient supply temperature of 50 C at the consumers, it is possible to use many different heat ressources like waste heat (from industries etc.) and Renewable Energy Low-energy DH is fully competitive with the heat pump technology both economically and environmentally Demonstration results will indicate if a low-temperature DH network should be designed with a combination of DH storage units and Heat exchanger units! # 16

17 On-going R&D-project Title: "CO2-reductions in low energy buildings and communities by implementation of low temperature district heating systems. Demonstration cases in EnergyFlexHouse and Boligforeningen Ringgården Period: Financing: Supported by the Danish Energy Authority's Energy Research Programme (EUDP 2008 II) # 17

18 Ongoing R&D-project Participants: Energy Service Denmark (Energitjenesten), Project responsible COWI A/S Danish Technological Institute LOGSTOR A/S DANFOSS District Heating DTU Byg (Technical University of Denmark) AffaldVarme Århus, Århus Kommune Kamstrup A/S Lystrup Fjernvarme Lystrup Fjernvarme A.m.b.A. Boligforeningen Ringgården Høje Taastrup Fjernvarme Høje Taastrup Fjernvarme A.m.b.A. Ribe Jernstøberi (radiators) # 18

19 Ongoing R&D-project Testing of DH storage unit and DH pipe in Energy Flex House Demonstration ti and monitoring i of low-temperature t DH system for 40 dwellings in Ringgården Housing Association, Lystrup Assessment of the potential for CO 2 -reductions and energy savings in both new and existing buildings (in the municipalities of Århus and Høje Taastrup) Phase 4: (New R&D project application) Large scale demonstration on basis of experiences from Phase 3 The municipalities i of Århus and Høje Taastrup are obvious opportunities # 19

20 Energy Flex House Demonstration in Høje Taastrup, Danish Technological Institute Plan of the Energy Flex House(s) (3 new low-energy test house) # 20

21 Boligforeningen (Housing association) Ringgården Demonstration in Lystrup New low-energy class 1 terraced (row) houses # 21

22 Questions and discussion # 22