There are several types of heat pump. All use the same basic principle of extracting heat from an external source and concentrating it to obtain a higher temperature. This is usually then applied to water for domestic heating and hot water.
Heat pumps work in much the same way as a domestic fridge or vehicle air conditioning unit. In a fridge or vehicle, the heat is transported from inside to outside. The same principles are used for the heat pump to take heat stored in the air or below ground and transport it via pipework to radiators, heat pads, delta pipes or a hot water store.
Some heat pumps can be operated both ways allowing heat to be extracted from buildings in summer: one use is cooling pads for farrowing sows. The key feature of a heat pump is that the amount of heat energy delivered is several times more than the electrical energy used to drive the system.
Ground source heat pumps use a buried ground loop, collecting heat from the ground. The heat exchanger then transfers it into the water feeding the heat emitters in the same way as a heating boiler. The ground loop is comprised of lengths of pipe buried in the ground, either in a borehole or a horizontal trench, typically 1–4m below ground.
Ground source heat pumps are most efficient when the temperature between the collector fluid and water being heated is not too great. Therefor they are more relevant where hot water below 40°C is required rather than 65°C. Thus they are applicable for use in underfloor heating or heat pads in well insulated buildings.
Air source (and water source) heat pumps are also available. These work on the same principle but extract heat from the air using a fan that passes the air through an induction loop assembly all contained in a unit usually placed outside the building demanding the heat.
Warm exhaust air from building ventilation is a good source of heat. However, air from livestock buildings is very corrosive so the loops and foils within the unit must be made from non-corrosive materials.
Both types of heat pump are only really suitable in new build or refurbished properties due to the high level of insulation required.
The government’s Planning Portal website contains up to date information with regard to planning permission, particularly with regard to domestic appliances.