Case study 3 / Mr VJ Patel, Raynes Park, London SW20
Description of system
A development of two flats one three bedroom 90m2 and the second 1 bedroom 50m2.
The initial proposal was to provide heating through electric storage heaters. The planners asked for a significant contribution from renewables and efficiency savings . We carried out a study demonstrating the long term efficiencies and potential payback from the Renewable Heat Incentive and The Feed in Tarif.
The flats are heated entirely with standard steel panel radiators sized accurately for the heat load and the lower operating temperatures to maximise the efficiency of the air source heat pumps . Each systems comprises a Calorex Aw45002 air source heat pumps and Gledhill 150 litre unvented hot water cylinders – special design for air source heat pumps.
2 kw photovoltaic system comprising 10 sungrid STP20018/UD solar polycrystalline pv panels and Fronius IG20
Performance of ASHP System - Flat A
- Dwelling floor area 90.22m2
- space heating requirement 3490 kwh/year
- water heating requirement 2198.92 kwh/year
- Total energy requirement heating hot water 5688.92
- 1st proposal heat source electric storage heaters and electric immersion
- 5688kwh / cost of fuel £0.13 annual cost £739.44
- annual cost gas alternative ie combination boiler 5688x0.04 £227.52
- Actual total heating hot water requirement provided by Calorex AW4502 Air Source Heat Pump Average COP 3.5
- Energy input at COP3.5 £1625 kwh
- Cost of energy input £211.00
- Yield from RHI if 7.5p/kwh proposed rate confirmed £426.67
- Annual benefit from installing ASHP system over electric alternative £955.11 (with RHI at proposed rate)
- Annual benefit from installing ASHP system over electric alternative £528.44 (without RHI)
- Annual benefit from installing ASHP system over gas alternative £443.19 (with RHI at proposed rate)
- Annual benefit from installing ASHP system over gas alternative £16.52 (without RHI)
Performance of Solar PV
- Annual SAP output 1713 kwh
- Electricity required for lighting 653.81 kwh
- Electricity required for pumps and fans 364kwh
- FIT annual yield inc savings and export £899.64
- Note: system installed before dec 11 2011. Current FIT rate 0.45p
Performance of ASHP System - Flat B
- Dwelling floor area 51.78 m2
- space heating requirement 3071.84 kwh/year
- water heating requirement 1636.67 kwh/year
- Total energy requirement heating hot water 4708.81 kwh/year
- 1st proposal heat source electric storage heaters and electric immersion
- 4708.81kwh / cost of fuel £0.13 annual cost £612.14
- annual cost gas alternative ie combination boiler 4708.81x0.04 £188.35
- Actual total heating hot water requirement provided by Calorex AW4502 Air Source Heat Pump Average COP 3.5
- Energy input at COP3.5 £1345 kwh
- Cost of energy input £174.85
- Yield from RHI if 7.5p/kwh proposed rate confirmed £353.16
- Annual benefit from installing ASHP system over electric alternative £790.45 (with RHI at proposed rate)
- Annual benefit from installing ASHP system over electric alternative £437.29 (without RHI)
- Annual benefit from installing ASHP system over gas alternative £366.66 (with RHI at proposed rate)
- Annual benefit from installing ASHP system over gas alternative £13.50 (without RHI)