Ground source heat pumps work by using heat stored in the ground from the sun's solar radiation to supply all of the energy required for a home's heating and hot water system.
The top 15 metres of the Earth's surface maintains a relatively constant temperature of approximately 12 degrees centigrade. This energy can be used to heat buildings indirectly.
How does it work?
A pipe is buried in the ground, either in a borehole or in a horizontal trench. The pipe is usually a closed circuit and is filled with a mixture of water and antifreeze, which is pumped around the pipe, absorbing heat from the ground. In winter, the ground is warmer than the air and buildings above. The antifreeze mixture absorbs heat from the ground, which is then concentrated and transferred into your house. This heat can be used to heat domestic hot water and a low temperature heating system such as underfloor heating.
Efficiency
The efficiency of a ground source heat pump is measured in the Coefficient of Performance (CoP). This is the ratio of units of heat output for each unit of electricity used to drive the compressor and pump for the ground loop. A CoP of 4 means that for every kilowatt of electricity you put in, you get 4 kilowatts of energy in the form of warm water. The flow temperature of the warm water is typically between 35oC and 45oC; much lower than achieved by a domestic boiler. Although the system can reach higher temperatures, the CoP is then compromised. Therefore, it is much more efficient to keep the temperature at the lower end of the scale and ensures that the system operates efficiently.
Installation
There are three ways to install ground source heating. These are:
Surface collector
Ground probe
Ground water