Ground Source Heat Pumps (GSHP) extracts heat from the ground by circulating a mixture of water and antifreeze around a ground loop. Heat from the ground is absorbed into the fluid and then passes through a heat exchanger into the heat pump. Trenches are usually between 1-2m deep and boreholes between 15-100m, depending on energy needs. The longer the coil, the more energy it produces. A well designed GSHP system provides the lowest running cost of any heating system - because it uses a small amount of electricity to transfer a large amount of naturally occurring heat from the ground.
The heat pump in a water source heat pump system is identical to that for a "ground source heat pump" system. The difference is that a WSHP receives water through pipes that absorb heat from contact with water. The water may be from a river, open water or even the sea in the case of a "marine source heat pump". Usually a closed loop is used. However, if clean water is available from an aquifer it may be possible for an open loop to be used. In this case water is drawn from the aquifer and passed directly through pipes into the heat pump and discharged back to the aquifer though another pipe.
An advantage of a WSHP is that a constant temperature will be available to the WSHP even if a large amount of heat is required - provided the WSHP is heat exchanging with a large body of water.
Air Source Heat Pumps (ASHP) absorb heat from the outside air, in the same way that a fridge extracts heat from its inside. There are two main types of ASHP - an air-to-water system distributes heat via your wet heating distribution system, while an air-to-air system produces warm air which is circulated by fans to heat your building.
Generous RHI are driving GSHP's, see complete polytunnel deals
Growers are using the generous GSHP RHI to fund complete new heated poly tunnels for rent to multiple growers. The case study below shows how a landowner has a heated 1Ha of heated polytunnels with a guaranteed income of £200,000pa from the RHI.
The rental income from commercial growers (renting individual tunnels) adds to this producing a return on investment of less than 5 years.