Geothermal

Geothermal Cogeneration
The interior of the earth is very much hotter that its surface and there are some places where the hot rock is very close to the surface and the geothermal steam can be used to create electricity or for heating applications. This form of energy is not strictly renewable but it is low in greenhouse gas emissions. Suitable sites in the UK are limited to areas Wessex, Hampshire and Yorkshire and cogeneration plants have been built at Marchwood, Southampton and Cleethorpes.

Geothermal Heat Pumps
Geothermal energy can however be used to power efficient heating or cooling systems in homes and offices. In a process that works like a domestic refrigerator, another technique relies on the fact that the temperature of the earth one meter below the surface remains constant throughout the year, and water is pumped through two circuits of pipes, one of which is underground and another on the surface, and heat exchanger between the two circuits can extract the thermal energy. Whilst this is not sufficient to power an electricity generator, it is sufficient to heat a building. The only draw back is that plenty of land is needed to either lay the pipes underground or create deep bore holes.

How a heat pump works