Sustainable House

There are several variations of heat pump technology, ground, air and water source heat pumps all work on the same principle, that of drawing thermal energy from their chosen medium. Air at ambient temperatures is passed over a heat exchanger and heat energy extracted into the evaporator of the heat pump, then the compressor circulates the gaseous refrigerant and compresses it to the desired temperature. Finally, the condenser transfers the heat to a hot water tank from which feed the heat distribution system. The heat distribution system then heats space through under-floor piping, wall mounted radiators or similar.

Heat pumps consume energy in the form of the electricity used to power the pump. This is a relatively efficient use of energy as heat pumps produce between two and four units of heat for each unit of electricity expended. To be truly sustainable however, the pump should be powered by sustainable, ideally zero carbon electricity. Therefore, electricity sourced from solar photovoltaic (PV), wind or water generation should be considered.

From a purely economic standpoint, the high cost of electricity from PV cells means that source is not currently cost effective and the use of off-peak electricity should be considered as an alternative.