Ground Source Heat Pumps
The Earth acts as a huge thermal store absorbing around 50% of the sun's energy and maintaining a temperature of around 12ºC throughout the year.
Heat pumps extract this energy which is stored in the ground, water courses and in the air.
These systems require electricity to drive the pump, and could be integrated with other technologies to make it almost completely renewable.
Domestic refrigerators are similar to heat pumps and work by the same principle, moving heat from where it's cold to where it's warm.
Ground source heat pumps are a very energy efficient technology, with every unit of electricity used to drive the compressor producing between 3 and 4 units of heat.
GSHPs work most efficiently in combination with low temperature heat distribution systems, such as underfloor heating.
For a 4-person household the annual electricity use might be reduced by 75% compared to a conventional electrically heated system.
In addition, a heat pump could reduce CO2 emissions by 30-50% compared with an efficient oil or gas boiler system.
This type of heat pump can supply all of your heating needs (with underfloor heating); but for hot water as well, you will probably need to supplement it with solar panels, or a fossil fuel alternative, such as a gas condensing boiler.
Ground Source Heat Pumps consist of three important elements:
The ground loop.
This comprises buried lengths of pipe, either in a borehole, or a horizontal trench. The pipe is usually a closed circuit and is filled with a mixture of antifreeze and water, which is then pumped around the pipe, whilst absorbing heat from the ground.
The heat pump.
This has three main constituents:
- the evaporator - which takes the heat from the water in the ground loop;
- the compressor - moves the refrigerant round the heat pump and compresses the gaseous refrigerant to the temperature needed for the heat distribution circuit; (this is what makes the noise in your fridge)
- the condenser - (the hot part at the back of your fridge) gives the heat to a hot water tank which feeds the distribution system.
The heat distribution system.
This usually consists of underfloor heating or radiators for space heating and in some cases water storage for hot water supply.
What options are available?
The ground loop can be:
- a borehole,
- a straight horizontal trench costs less than a borehole, but needs more land area,
- spiral horizontal (or 'slinky coil') - needs a trench of about 10m length to provide about 1kW of heating load.
To discuss more options or for a quote, please contact us.