Ground Source Heat Pumps

What Is A Ground Source Heat Pump?
Is A GSHP Right For My Home?

You'd never know it, but many office blocks, schools and hospitals in the UK are already tapping into energy from the ground. It could be heating your home too, with the help of a ground source heat pump.

By Josephine Smit, editor of Building4change.com

The ground beneath your feet is effectively a heat store. Even when there is snow on the ground in winter in the UK, just several metres below the surface the temperature is likely to be a fairly constant 10 to 12 degrees centigrade. A ground source heat pump allows you to harvest some of this heat and put it to good use.

What Is A Ground Source Heat Pump?

There are two key elements to a ground source heat pump (GSHP): pipes buried in the ground that collect heat from the surrounding earth, and the heat pump itself. The heat pump is a washing machine-sized box of tricks that boosts the temperature of the harvested heat to around 65 degrees centigrade and transfers it from the ground into a form that can be used in your home.

How Does The Technology Work?

A heat pump works in the same way as a refrigerator, but in reverse. While a fridge extracts heat from the air inside it to make the space colder, a heat pump extracts heat from the ground to warm your home. The heat pump circulates a mixture of water and anti-freeze through the pipes in the ground to absorb the heat.

This pipework, which is called a ground loop, is buried in the garden adjacent to your home in any one of a number of layouts. The ground loop can be laid in a relatively shallow 2 to 3m deep trench, with the pipe in either a straight line or in a looping line (often known as 'slinky'). Pipes can also run vertically in boreholes sunk much, much deeper in the ground. These will generally be more than 100m in depth.

What Are The Pros & Cons?

A GSHP does run on electricity and so is not technically completely renewable energy, but it is considered a very efficient technology. It is generally reckoned that for every kilowatt of electrical energy that you put into the system, you will get three to four kilowatts of heat out.

If you've just made your back garden picture perfect you may balk at the prospect of digging a long trench right through the middle of it. But the disturbance is temporary, and once the ground loop is beneath your lawn, it won't require further regular maintenance.