Here we look at the 2 most common heat pumps: air and ground source:
Air Source Heat Pumps
An air source heat pump distributes heat via your central heating system. This heat is generated by the air around your house, the air is passed over a heat exchanger and then through a system similar to that you find in fridges although in reverse; this means the temperature is increased to a temperature you can heat your house and hot water with.
Ground Source Heat Pumps (GSHPs)
GSHPs use pipes that are buried in the ground to extract heat from the ground. These pipes can either be put in trenches that have been dug or in bore holes that have been drilled. When the pipes have been laid in trenches these make up the ground array and effectively turns the ground in to a big heat exchanger. A common misconception is that taking heat out of the ground can turn the ground into a large ice block. If installed correctly this will not happen. If space is a bit of an issue then it is possible to drill holes into the ground. These holes may need to be 100m or more deep depending on what is needed to meet the heat pumps requirements. With this flexibility open it does mean that a GSHP can be installed in most properties.
A GSHP circulates glycol, a mixture of water and antifreeze, around the ground array or vertical boreholes to absorb heat from the ground. This is then pumped back to the heat pump and passed through a heat exchanger. The ground stays at a fairly constant temperature under the surface, so the heat pump can be used throughout the year.
You can use a GSHP to provide heating and hot water to numerous dwellings, just like you would find on a normal district heating system. You can have one main GSHP carrying out the hard work with the individual dwellings connected to the system. Using this system may entitle you to benefit from the commercial RHI.
Things to consider
- How well insulated is the property? A heat pump works most efficiently at a lower temperature than a conventional boiler. Having good levels of insulation in a property is very important.
- Properties need to have good draught-proofing, so no big gaps around windows and doors.
- Space available to install system.
- If in a listed building or in a conservation area permission may be required, especially with an air source heat pump.