This summer a pioneering energy system was put into service at Owen Square, Bristol. Solar panels on the top of Easton Community Centre are used extract heat from the air using an air source heat pump, pass it through the ground and store it as heat in the soil. The heat is stored in pipes in Owen Square and radiated through the soil before other pipes pump the heat back into the community centre through water.

2. The problem with running heat pumps from renewables

3. The ‘holy grail’ for integrating heat pumps into the grid
If we ‘spend’ 1 kWh on summer
electricity can we reduce winter heat
pump electricity use by 1 kWh?

4. CHOICES ‘timeshifts’ heat pump electricity use from winter to summer

6. .

10. Interseasonal heat
storage energy centre
Solar microgrid
Owen Square Community Energy

12. CHOICES developed a TRNSYS model to answer this question

13. We are modelling very promising active recharge COP
Scenarios 1 – 3
Illustrates increase in CoP when the same charge is spread over a
longer time period (charging most efficient at low speeds)

14. But the max economic level of seasonal shift is limited by borehole design
Owen Square park, Bristol (£168,000):
● 12 x 150m boreholes (1.8km)
● 7m distance between boreholes
● 1 u-pipe per string, 12 strings
● 50,000m3
volume
● Low temperature array
● Grid benefits: ~4500 kWh/year
Braedstrup, Denmark (£188,000):
● 48 x 50m boreholes (2.4km)
● 3m distance between boreholes
● 12 u-pipes per string, 16 strings
● 19,000m3
volume
● High temperature array
● Grid benefits: Potentially much higher
Similar size/cost
but very different
designs
Further research will explore other borehole designs seeking further grid benefits