1. Heat Pumps
Reference: BSRIA BG7 / 2009

2. Heat pump

3. Heat pump components

4. Heat pump thermodynamic cycle

5. COP vs. Lift Temperature

6. Temperature-entropy diagram

7. Plant margins for heat pumps
Need to be small, compared to boiler systems:-
capital cost of heat pump closely related to size
oversize heat pumps may not perform as well
may have a shorter life due to multiple starts

8. Bivalency 90% of design load only required for 3 days/year
Supplementary heat source can be used for extreme cold periods – either separate boiler, or direct electric.
Systems where heat pump and supplementary source used together – parallel bivalent system
Supplementary source used instead of heat pump is less efficient – alternative bivalent system

9. Selection of heat sources & sinks
Internal space requirements
Local planning restrictions
Noise emission
Available ground area and soil conditions
Shading and ground cover
Geology (for boreholes, open and closed loop)
Depth of water table
Availability and cost of electricity, and other fuel supplies
Limitations to electrical supply
Occupancy profile
Proposed heat distribution
Requirement for cooling
Requirement for domestic hot water
Ventilation system
Reference: BG7: 2009, Table 4, p.14

10. Detailed design points
ASHP
low external air temp → reduction in COP
external temp ≈ 0°C causes ice formation of atmospheric moisture, needing hot-gas defrost which lowers seasonal COP.
outside location of coils may cause noise nuisance.
GSHP
horizontal collectors min. depth ≈ 1.7m
heat extraction rate varies with soil type
heat extraction decreases over years

11. Specific heat extraction from coils/boreholes
Reference: BS EN 15450, Tables A.2/7

12. Borehole geothermal pile

13. CO2 heat-pipe

14. Gas engine heat pump

15. Reversible heat pumps