Draft PPS18: Renewable Energy
Annex 1 Ground, Water & Air Source Heat Pumps: Air Source Heat Pumps
H11. Air source heat pumps, are often used in moderate climates, they use the difference in outdoor and indoor air temperatures to cool and heat the building. Air source heat pumps extract the heat in air and use a fan to draw air over coils that extract energy. This energy is then transferred to a home or building and used as part of a heating supply. Although they are less efficient than ground source heat pumps, and likely to be more variable because air temperatures fluctuate both daily and seasonally. Even when the outside temperature drops, air source heat pumps can still produce 2-3 times as much energy as they use to run. However in cold weather the evaporator coil is likely to need defrosting. The air source heat pump does have advantages in terms of lower installation costs and the fact that no ground loop negates the need for trenching.
H12. Air source heat pumps can be used for a wide variety of applications such as cooling for lofts, restaurant kitchens and hotel plant rooms where the hot water can easily be used for other applications. They can provide hot water using waste heat in the air. By using waste heat, they can also remove heat from an area, such as a loft space, where it is not needed.
H13. Air source heat pumps can be located in the roof space or on the side of the building. They look like air conditioning boxes. Where these are proposed for listed buildings or in conservation areas, it will be important that they are sensitively designed and sited.