Cleveland Pools: Is there a more environmentally friendly alternative to gas?

Home News & Events Latest News Cleveland Pools: Is there a more environmentally friendly alternative to gas?

Congratulations to the Cleveland Pools Trust on gaining initial development funding for the £4.1 million restoration of the pools. Given the initial proposal is to use gas for heating we thought we would look at some more environmentally friendly alternatives for the main heating system for the pools:

  • Air Source Heat Pumps
  • Water Source Heat Pumps (from the River Avon)
  • Biomass boilers (woodchip)

The current plans already include options for solar thermal and solar PV, but these are only to support the changing rooms and other facilities as there is not enough roof area to provide heating for the pools as well. The trust’s current analysis suggests using a gas boiler to provide the pools’ annual 127,000 kWh heating requirement.

Our simplistic calculations suggest by using more renewable sources the Trust could save itself up to £250,000 and almost 400 tonnes of carbon over 20 years:

Air Source Heat Pump

Water Source Heat Pump

Gas Biomass
Cost Daytime Offpeak Daytime Offpeak
Annual running costs







Renewable Heat Incentive







Annual saving over gas (with RHI)







20 year Saving







20 year CO2 Saving over gas (tonnes)







We have not taken the potential additional capital costs of these solutions into account but feel that it would be of benefit to the trust and the environment to look at these alternatives?

Update: Response from the Cleveland Pools Trust:

Subsequent to the initial publication of this article, the Trust has kindly responded:

The Trust is keen to minimise the carbon footprint of the Pools and intends to employ the best renewable options available. Both government funding and the technologies have evolved since initial proposals were drawn up in 2011 and the development phase will provide an opportunity for a fresh appraisal. Advice from groups such as Transition Bath and Bath & West Community Energy (BWCE) will be very welcome.

More details of our calculations below

Air Source Heat Pump Water Source Heat Pump Gas Biomass
Cost Daytime Offpeak Daytime Offpeak
Efficiency 320% 320% 320% 320% 85% 80%
Annual Energy Consumption kWh 39,688 39,688 39,688 39,688 149,412 158,750 kWh
Fuel cost 0.14 0.07 0.14 0.07 0.042 0.031 £/kWh
Annual Energy Cost £5,556 £2,778 £5,556 £2,778 £6,275 £4,921
CO2 intensity (20 yr average) 300 200 300 200 210 25 g/kWh
Annual CO2 (tonnes) 12 8 12 8 31 4 Co2t
20 year CO2 (discounted at 3.5%) 173 116 173 116 457 58 Co2t
20 year CO2 saving over gas 283 341 283 341 0 399 Co2t
Renewable Heat Incentive (tier 1) 0.025 0.025 0.087 0.087 0.084 £/kWh
Renewable Heat Incentive (tier 2) 0.026 0.026 0.022 £/kWh
% RHI tier 1 75% 75% 75%
RHI Income £3,175 £3,175 £9,112 £9,112 £0 £8,700
Net Energy Costs £2,381 -£397 -£3,556 -£6,334 £6,275 -£3,778
20 year cost (no discount/inflation) £47,625 -£7,937 -£71,120 -£126,683 £125,506 -£75,565
Saving over gas £77,881 £133,443 £196,626 £252,188 £0 £201,071
Downsides Potentially noisy Difficulty getting permission from the environment agency? High CO2 and higher costs Transporting the woodchips down to the site. Clean air act/pollution?
Air Source Heat PumpWater Source Heat PumpGasBiomass
Annual Energy Consumption kWh39,68839,68839,68839,688149,412158,750kWh
Fuel cost0.£/kWh
Annual Energy Cost£5,556£2,778£5,556£2,778£6,275£4,921
CO2 intensity (20 yr average)30020030020021025g/kWh
Annual CO2 (tonnes)128128314Co2t
20 year CO2 (discounted at 3.5%)17311617311645758Co2t
20 year CO2 saving over gas2833412833410399Co2t
Renewable Heat Incentive (tier 1)0.0250.0250.0870.0870.084£/kWh
Renewable Heat Incentive (tier 2)0.0260.0260.022£/kWh
% RHI tier 175%75%75%
RHI Income£3,175£3,175£9,112£9,112£0£8,700
Net Energy Costs£2,381-£397-£3,556-£6,334£6,275-£3,778
20 year cost (no discount/inflation)£47,625-£7,937-£71,120-£126,683£125,506-£75,565
Saving over gas£77,881£133,443£196,626£252,188£0£201,071
DownsidesPotentially noisyDifficulty getting permission from the environment agency?High CO2 and higher costsTransporting the woodchips down to the site. Clean air act/pollution?


  • Air and water heat pumps have roughly the same COP, because of the similar water and air temperatures during the season (12C), because only low grade heat is required COPs would be between 2.5 and 5.0, so a COP of 3.2 is probably conservative
  • If soley relying on off-peak electricity to power the heat pumps, the heat pumps would have to be oversized to take into account they are only running 8 hours per day
  • Electricity carbon emissions are assumed to be lower than they are today because of future grid decarbonisation, and overnight electricity lower still as the marginal emissions are likely to be lower than peak daytime
  • No capital cost adjustments were made as without further information we would find it difficult to estimate prices accurately, the water source heat pump and biomass are likely to have a high capital cost, but the air source heat pumps may end up with similar costs to the gas boilers largely because a gas pipe would not have to be laid
  • Portishead Outdoor pool run their heating on woodchip biomass, so it should be technically possible