Heat Pumps

The purpose of a heat pump is to absorb heat from one source (ground, water or air) and transfer it for use where it is needed – either for space or water heating.

The heat extracted is usually at a temperature too low to be useful, so this is boosted by the pump to a useful level.

Although the pump itself uses electricity to run, for every kW of energy it uses, it produces 3 to 5kW of energy in return.

As a result, these systems also work very well in tandem with solar photovoltaic systems.

The most common forms of heat pump are as follows.

• Ground Source Heat Pumps

These do not use geothermal heat, but solar heat that has been stored in the earth.

The heat collector consists of a long loop of piping, plumbed in a closed loop, and buried about a metre deep. The length of loop required varies according to heating needs, but averages 200m for a domestic situation.

It is therefore mainly an option when there is plenty of land available.

• Water Source Heat Pumps

These work in the same way as Ground Source Heat Pumps, but the closed plumbed heat collector is placed at the bottom of a large pond or lake.

The minimum size of water source needs to be about half an acre by 3 metres deep – so not generally suitable for urban or suburban homes….

• Air Source Heat Pumps

These present an advantage over ground and water source pumps in that they are cheaper to install, and you don’t need to have your own estate in terms of space requirements.

The pump absorbs heat from the outside air to warm water or heat buildings.

All heat pumps are most efficient when they are operating a low temperature distribution system such as under-floor heating rather than conventional radiators.

This can only be classed as a renewable technology if the energy source running the pumps is also renewable. The simplest way to achieve this is to sign up with an energy provider who guarantees their energy comes from renewable sources (see our links page for the best ones).