Heat pumps in rural off gas grid buildings

Completed

Energy Efficiency(Other)

Final stage Development and Demonstration

ENGINEERING AND TECHNOLOGY (General Engineering and Mineral & Mining Engineering)

Not Cross-cutting

Mr J Ellis-Tipton
Shropshire County Council

3

Carbon Trust

01 August 2003

30 July 2004

12 months

£42,000

West Midlands

Mr J Ellis-Tipton, Shropshire County Council

Project Contact, Marches Energy Agency

To demonstrate the utility of heat pumps in schools and other public buildings not connected to the gas grid, and for which conventional electrical storage heaters would otherwise be the only heating choice.

Heat produced by the sun at the soil surface over time migrates downwards and is insulated from the prevailing surface temperature by the intervening soil layers. As a result, a region exists at a particular depth where appreciable renewable heat energy is stored, with a temperature essentially invariant with the ambient surface temperature. It is this stored heat energy that heat pumps exploit and tap into when they transport heat from the relatively cold outside soil to a building with a heating requirement. When compared with heating by conventional electricity resistance heating, heat pumps are very much more efficient. In conventional electrical heating for every one unit of electrical energy put into the heater, one unit of heat energy is produced. In contrast, for a heat pump, for every one unit of electrical energy put into the heat pump up to four units of heat energy can be transferred from the outside to the inside of a building. This means that for the same amount of heat put into a building, far smaller CO2 emissions occur. The environmental benefits of heat pumps are being put to good use at Buntingsdale School in Shropshire. A horizontal coil has been installed at a depth of 1.3 metres, appropriate to tap into the heat energy stored at the subsurface. The coil contains an aqueous working fluid (with a natural anti-freeze) which is kept at a temperature lower than the surrounding soil. Heat is thus transferred from the soil to the working fluid. This fluidis pumped to the heat pump which, through the use of a refrigerant, transfers this heat content to the interior of the building. It is anticipated that the heating system will save approximately 52,000kWh of electricity annually (out of a total consumption of 73,500kWh). This will result in a reduction in CO2 emissions of approximately 22 tonnes for this school alone

01/01/07