Ground source heat pumps

Ground Source Heat Pumps (GSHP) use pipes which are buried underground to extract the constant heat which is generated in the ground, hence the name “ground source” heat pumps.

A GSHP pumps a mix of water and anti-freeze around a loop of piping, which is called a ground loop which is buried wherever you have decided to have the system installed. The ground stays at a reasonably constant temperature under the surface, so the pump will be effective throughout the year, including in the middle of winter.  The heat in the ground is then absorbed by the passing liquid which then passes through a heat exchanger into the heat pump.

The length of the pipe is determined based upon two main factors; the size of your home, and the amount of heat which you need. It goes without saying that longer loops can draw in more heat due to a larger area from which to absorb, but they also need more space to be buried into. If you have a limited amount of space available, you can always have a borehole drilled instead.

After passing through the heat exchanger the liquid is cool again, so it goes around the loop again, picking up more heat on the way. This is a continuous process, which goes on for as long as the heating is required. The loop is usually laid flat or coiled in trenches which are dug to a depth of around two metres, but if there isn’t enough room for this, you can have a vertical loop instead, this can go up to around 100 metres deep for a typical domestic residence.

GSHPs don’t need fuel, just a little electricity to keep the pump going, but this is a very small amount of electricity compared to an electric heating system. For every unit of electricity used for the pump, three to four units of heat are returned, so it is very efficient. This type of renewable energy can heat your home and give you hot water as well as lowering your fuel bills and your homes carbon emissions, but by how much depends on what fuel you are replacing.

If you are thinking about getting this system installed for your home, it is imperative that your home is properly insulated and the building envelope is completely sealed. This is because the ground source heat pump produces heat at a lower temperature than traditional boilers. They can perform better with underfloor heating, or warm air systems because lower water temperatures are required of it. It also doesn’t require much attention in the way of maintenance, it’s called ‘fit and forget’ technology.

Getting a ground source heat pump installed could also provide you with additional income through the governments scheme ‘Renewable Heat Incentive’ (RHI).

Written by Jade Turney – Building Tectonics.

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