An air source heat pump (ASHP) is a heating system that uses outside air as its heat source and heat sink. Under the principles of vapour compression refrigeration, an ASHP uses a refrigerant system involving a compressor and a condenser to absorb heat at one place and release it at another.
In domestic heating use, an ASHP absorbs heat from outside air and releases it inside during winter, and can often do the converse in summer. When correctly specified, an ASHP can offer a full central heating solution and domestic hot water up to 80°C.
Outside air, at any temperature above absolute zero, contains some heat. An air-source heat pump moves or pumps some of this heat to provide hot water or space heating. This can be done in either direction, to cool or heat the interior of a building.
The main components of an air-source heat pump are:
- An outdoor heat exchanger coil, which extracts heat from ambient air
- An indoor heat exchanger coil, which transfers the heat into a water tank or indoor heating system, such as radiators or under-floor circuits.
An air source heat pump will provide low cost space heating. A high efficiency heat pump can provide up to four times as much heat as an electric heater using the same energy. They can last for over 20 years with low maintenance requirements.
Air source heat pumps are used to provide interior space heating and cooling even in colder climates, and can be used efficiently for water heating in milder climates. A major advantage of ASHPs is that the same system may be used for air conditioning in summer and heating in winter.
With conventional boilers, 1kw of input energy provides less than 1kw of output energy or heat, but with an air source heat pump, for every 1kw of electrical energy which is put in this is converted into about 3.6kw of heat energy and this is expressed as the COP (Co-efficient of Performance) which the ratio of the heat delivered by the power consumed.
Air source heat pump offers a good alternative to LPG, oil and solid fuel.