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Features|November 3, 2015 16:38

Unleash the heat

Pat Barnsdigs out the facts on ground source heat pumps – the next untapped resource

Perhaps it’s their clumsy name, or the fact that once they’re buried under the ground you can’t actually see them working, but despite being one of the most efficient forms of renewable energy, the humble ground source heat pump receives little public recognition in the UK.

Yet for over 30 years Scandinavians have been tapping into the free, natural heat under their feet, with the vast majority of all new homes now heated this way. Germany too has been installing heat pumps since the 1980s, and the French are also embracing them.

‘It’s not a new technology, that’s what people must remember,’ explains Sean Sowden of specialist heat pump suppliers Go Geothermal. ‘It’s been in Europe for years. It’s only because we’ve had access to cheap gas and oil that it hasn’t come to the fore in this country.’

How it works

It’s a little known fact that just one metre below the earth’s surface, the ground remains at around 10˚C all year round, and ground source heat pumps are designed to take advantage of this heat. A long coiled tube, filled with a mixture of water and anti-freeze, is buried under the ground and as the solution is pumped through, it absorbs heat.

The solution then passes through a heat exchanger, where it is concentrated to reach a much higher temperature, before being pumped into the house to heat radiators and under-floor heating. As a closed loop system, it then returns to the underground coil to begin the process again.

The ground loop is usually buried in the garden or, in a commercial setting, under a car park.  Where space is limited, bore holes are drilled and the loop used vertically rather than horizontally.

According to Jaryn Bradford, senior technology manager at the Energy Saving Trust, to work efficiently, it is critical that the building is properly insulated. Then, for every one unit of electricity used to run the pump, the system can give around three units of energy back, whereas a house heated by electricity, operates on a 1:1 ratio.

‘It provides more heat in terms of energy that it uses,’ explains Bradford. ‘Heat pumps can save consumers money, and they can also save carbon by replacing fossil fuels.’

In fact, a well-installed system can provide up to 80 per cent of a household’s hot water and heating needs…

Read the full feature in issue eight or in our digital edition by clicking here.

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