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The use of heat pumps in district heating systems

The use of heat pumps in district heating systems. Joe Grice Energy capital projects manager 24/11/2015. Why Decentralised Energy. Heat Networks. CHP & Heat Pumps. Urban Waste Heat. Green gas.

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The use of heat pumps in district heating systems

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  1. The use of heat pumps in district heating systems Joe Grice Energy capital projects manager 24/11/2015

  2. Why Decentralised Energy Heat Networks • CHP & Heat Pumps • Urban Waste Heat • Green gas... Offers a long term approach to heating for our residents giving flexibility of heat source and providing: Reduced heating costs A long-term flexible and expandable solution Reliable and secure energy supply Efficiencies of scale Look to move away from gas

  3. Combined Heat and Power CHP is typically sized to meet baseload demand Generates heat and power simultaneously Most cost effective to run when electricity is most expensive

  4. Heat Pumps Efficiency is heat source and heat sink dependent. More efficient at higher temperatures for heating. Closer the heat source is to the heat sink, the higher the efficiency Coefficient Of Performance (COP): COP 8 ≈ Z Factor 8

  5. District Heating the ‘Heat Interconnector’ Commercial Chilled Water ICE Store Homes HP HP Retail The Network Waste Heat HP Waste Heat Industry Biogas Electricity Biomass

  6. Thermal Storage Used to improve the viability of the district heating scheme by adding storage to the network Can store large quantities of heat, with very low losses. Further the flowtemperature of storage is from the returntemperature of the network, the greater the thermal energy stored RETURN TEMPERATURE of network is of greatest importance

  7. Why use heat pump • Adds greater resilience to the network. • Energy input to a heat pump is electricity which can be fed from the power generated by CHP engine • More efficient to use for heating when ambient temperatures are high • CHP better when ambient temperatures are lower as export prices for electricity tend to be higher • Common in Norway where hydro generated electricity is much cheaper than in the UK • Main barrier to expansion in UK is electricity price and capital cost • Eligible for government support in the form of RHI

  8. Network temperatures • Heat pumps are more efficient at lower temperatures • Consideration should be given at an early stage as retrofitting into existing network is complex and expensive • Secondary networks are often standard 82c/71c flow and return systems • This can be relatively easily achieved at new build stage but existing buildings looking to connect may need to be incentivised • Lower flow and return temperatures also reduce losses through the network • An allowance would be required for larger distribution pipework

  9. Operating Temperatures Increased H&S risk High Flow Temperature Increases heat loss – reduces system efficiency Increases capital cost High Return Temperature • Plant runs inefficiently • Plant ‘trips’ off • Plant fails Can increase return water temperatures – especially in oversized systems

  10. Return Temperatures • Low temperature heat emitters • Plate based calorifiers/DHW generation NOT coils • Correct energy estimations based on realistic assumptions NOT peak demand. Part L is not appropriate – CIBSE TM 54 energy model recommended. • High quality pumps – multiple pump design – pressure controlled • Temperature controlled Bypasses Return Temperature More important than flow temperature

  11. Electrical Demand/Supply Mismatch High CO2 Electricity Low CO2 Electricity Credit: Paul Woods @ AECOM

  12. District Heating Network Response High CO2 VARIABLE HEAT LOAD +2 MWe / 2.5 MWth 2.5 MWth 2.5 MW Electrical Swing Low CO2 -0.5 MWe / 2.5 MWth

  13. District Heating Network Response High CO2 VARIABLE HEAT LOAD +2 GWe / 2.5 GWth 2.5 GWth 2.5 GW Electrical Swing Low CO2 -0.5 GWe / 2.5 GWth

  14. Islington Celsius ProjectBunhill Phase 2 – Capturing heat

  15. What is Bunhill Heat and Power? A 1.9MW CHP plant based in Central Street that generates heat and electricity. It provides heat to: 720 council homes 162 private homes 2 leisure centres Electricity generated is sold the national grid Phase will be a second energy centre with 2 x 350kW CHP engines and 1MW heat pump. - Additional 800 council homes - Additional commercial buildings

  16. Bunhill extension objectives • To demonstrate innovative solutions to the technical challenges of using low temperature heat to supply heat to new and existing homes. • To connect a further 500 existing council homes and more new homes: • Reducing energy costs by at least 10% to connected residents to tackle fuel poverty • Reduce carbon emissions • Improving the security of heat supply • To help London develop a replicable vision for how to evolve into a truly energy-smart city. • To demonstrate and to promote roll-out of Smart District Heating through-out Europe and support 50 new cities by 2016 & another 100 cities by 2026.

  17. Development – How we got here • Policies and guidance • Well developed • Council and member commitment • Officer understanding • Communication • Consultation • Information & Knowledge • Spacial opportunities • Strategic opportunities • Best Practice

  18. District Heating and Electrical Networks

  19. The heat pump • 1MW thermal output heat pump • Electrical input of 345 kW (Met by CHP engine) • Coil located within London Underground shaft as ambient temperatures are higher • Ammonia refrigerant selected for highest COP possible operation at higher temperatures • Ammonia is toxic and a fire risk. Safety features need to be engineered into design

  20. Ground and water source heat pumps • Higher efficiency that air-source heat pumps • More complex and expensive to install that air-source heat pumps • Very expensive and complex to retrofit into existing networks • Can be integrated into new development and could possible supply a district heating scheme

  21. Conclusions • CHP and Heat pumps are complementary technologies • Heat Pumps with a COP ~ 8 are competitive with CHP • It is easy and cheapto store large quantities of heat • District heating is a technology agnostic energy distributor • District heating facilitates the efficient utilisation and sharing of diverse energy sources including waste heat • Waste heat includes conventional cooling plant • In combination, these technologies facilitate the use and balancing of low carbon heating, cooling AND electrical demands

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