Air source heat pumps are based on the same principal as Ground Source Heat Pumps but, as the name suggests, use heat from the air rather than the ground to heat buildings. There are essentially two types of air source heat pumps, air-to-air and air-to-water. Air-to-air provide warm air to be circulated in the building whilst air-to-water heat water to be used in radiators or under-floor heating (in this case they are usually more efficient with under-floor heating due to the lower temperatures produced than those from a standard boiler).
Air source heat pumps are made up of three main components. The evaporator coil absorbs heat from the air, the compressor pumps refrigerant through a heat pump and compresses the gaseous refrigerant to the temperature required for the heat distribution circuit, and the heat exchanger transfers the heat to the air or water. The first question many people will no doubt ask is whether it is warm enough in the UK for air source heat pumps. The answer is ‘yes’, as it is possible to extract heat from air at temperatures as low as -15°C!
Air source heat pumps take up much less space than ground source heat pumps and can be very effective. It is essential, however, that the building be well insulated and draught proofed. In this case the heat provided should be adequate to heat the building completely and they are a particularly cost effective option for properties without a mains gas supply.
Typical 5KW domestic air source heat pumps cost between £6,000 and £8,000 to install and there are grants available towards this in Scotland from the Scottish Community and Householder Renewables Initiative.
