By Nigel A-F
16th October, 2019
A ground source heat pump (GSHP) is a system of heating, or cooling, using the heat from the ground. It is made out of a series of pipes buried underground, which transfer the heat from the earth into your home.
Below the surface layer, the ground remains at a constant temperature of about 12 degrees Centigrade all year round. A GSHP system makes use of this consistent temperature by extracting heat and enhancing it to provide hot water for heating infrastructure.
For large GSHP systems it is normal to sink a number of boreholes (the ground array), which can be 200-250m deep; or use horizontal trenching if there is space on the estate.
A fluid is circulated in continuous pipes within these boreholes to absorb the ground heat. The collected heat is then transferred from the fluid to a refrigerant running through the heat pump.
The heat pump acts like a fridge in reverse, using a pump and compressor to increase further the temperature of the refrigerant. The increased heat is then transferred from the hot refrigerant to the water in the heating system.
Some power is required to run the heat pump, but its heat output is 3 to 4 times the electrical input, so the ratio between the power needed to the output is 1:3 or 1:4. This ratio is known as its Coefficient of Performance (CoP).
The more efficient the heat distribution system within the target building, the lower the required temperature of the heating water and the higher will be the CoP. But GSHPs can work well in leaky, old, listed buildings.
Water used to heat domestic hot water (DHW) systems may need to be boosted at times to raise the temperature to protect against Legionella.
Heat can also be dumped back into the ground to allow a GSHP system to be set up for cooling as well as heating.
GSHP is now a well-known, proven and reliable technology. The key to an effective and efficient system is the site-specific design. The heat pump must be adequately sized to meet the demand. The ground array must also be appropriately sized to extract enough heat from the ground whilst allowing the ground to regenerate its heat, either from the sun or underground water. The result of a poorly sized array can be frozen ground and an inability to deliver the required hot water.
To learn more about GSHP and how it can help your estate, get in touch with us.