The heat in the ground comes from the sun rather than the common misconception it is geothermal heat coming from the Earth’s core. Depending on where you are in the UK the temperature of the earth is around 8 – 10°c throughout the year.
An “array” of pipes filled with an environmentally friendly anti-freeze and water solution is buried 1m below the ground surface, keeping pipes apart by a similar amount. The ground source heat pump circulates the “brine” through the array which absorbs heat from the ground, increasing its temperature by 2 – 3°c. The ground source heat pump, through the refrigeration cycle, intensifies the small increase in brine temperature to a level whereby it can be used for space and hot water heating.
As heat is extracted through the winter it is important that the ground is allowed to recover this energy in the summer months to prevent it from cooling over time.