In recent years much has been made of the efficiency of Ground Source Heat Pumps. These systems offer a highly efficient alternative to more traditional boilers operating on fossil fuels. As the heat source is located below ground or underwater, temperatures will always be above zero centigrade, thus ensuring efficient operation of the heat pump year round. These systems are divided into two basic types, those being ground loop and bore hole.
Ground loop systems require the installation of a piping loop either below ground or submerged under water. The length and area covered by the pipe loop will depend directly on the size of heat pump required. It is essential that the area selected is first surveyed to ensure that any ground works will not disturb the water table nor will the area selected be subject to any further development which may impact on the installation.
Bore Hole installations require the drilling of deep bore holes by a specialist drilling company. This type of installation is ideally suited to a site with limited space for ground loops and the right geological characteristics. It is essential that a full geological survey is carried out before any drilling takes place.
Due to the extensive civil engineering and geological surveying required, both types of installation involve a considerable capital outlay and can have extremely long payback periods, (typically 25 years). Ground source heat pumps will always be better suited to large installations where the capital cost is more justifiable.
Air to water heat pumps
Air to water heat pumps have been around for some time, however with major manufacturers such as Toshiba Carrier, Daikin and Mitsubishi entering the market, more advanced technology has become available. This has meant that COPs are now significantly higher and the effective operational range is much greater. Typically systems have COPs greater than 4.0 and with the Toshiba 11kW Estia unit achieving a market leading COP value of 4.66.
These systems benefit much lower installation costs and consequently shorter payback periods. They also require little more than a suitable location for the outdoor unit and adherence to any local planning legislation.
Systems of this type are generally best suited to small and medium sized installations; however it is possible to obtain systems up to 500kW in capacity.