Ground Source Heat Pumps
Ground source heat pumps work in much the same way as air source heat pumps, but instead of taking energy from the air, they take solar energy which is stored naturally in the ground throughout the year. This energy is used to increase the temperature in your home.
The heat pump uses pipes which are filled with an anti-freeze fluid that absorbs energy from the ground heat and transfers it to the heat pump indoors. This ground heat warms a refrigerant to the point that, because of its extremely low boiling temperature, it boils and turns into gas. Once it has boiled, the refrigerant is pushed through a compressor, which heats it further to temperatures of around 60-70°C. This is then used to heat your hot water, radiators and underfloor heating.
While this process does require some input of electrical power, you can typically expect to get 4 units of heat out, for every unit of electricity you put in. Because of this cost effective ratio, ground source heat pumps remain one of the most efficient forms of renewable energy in the UK, especially when combined with solar PV.