Status: Renewable (indirect solar power)
What is it?
Ground source heat is a type of solar energy as it relies on the Sun warming the ground. It can be extracted from the low temperature heat (10–20°C) found at shallow depths within the Earth’s crust. This heat source stays at a relatively constant temperature and can be taken from the ground itself or from groundwater.
In many shallow coil systems, a looped pipe is buried just below the surface of the ground. At this depth, the soil temperature is kept reasonably stable by indirect solar power, which this system uses.
How is it used?
There is a circuit of underground pipes outside the house, and a heat pump inside the house.
Anti-freeze circulates in the pipes, absorbing the heat from the soil around it.
This heat is transferred into a liquid where it is boiled, compressed and vaporised and passed through the system to make heat.
The system can be run in reverse so it takes heat from the house and transfers it to the ground.
Where can you find it?
Anywhere you could lay a pipe just below the surface of the ground. Some systems also use boreholes and heat pumps to raise the temperature to 40-50°C for under-floor heating and radiators.
Advantages and disadvantages of using ground source energy
• It does not produce any pollution
• Running costs are very low
• It reduces heating bills and consumption of other, non-renewable, energy resources
• All pipe-work is below ground so there is minimal effect on the environment
• The effectiveness of the system will vary with the seasons. However, installing the correct amount of pipe should compensate for this variation
How many systems in the UK?
Around 250 systems are installed every year in the UK.
How much does it cost to produce?
The heat pumps cost £2,000 per coil, and the 60-metre boreholes cost around £3,000 each to drill.
What is the carbon cost?
The process does not produce any carbon dioxide.
The use of ground source energy for individual homes is likely to increase as installation prices drop.
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