Geothermal energy is heat derived from the earth. The centre of the earth is very hot. Current estimates are 5,500°C at the core, which is about as hot as the surface of the sun. It is not surprising, therefore, that the temperature of the upper layers of the Earth’s surface stay at a fairly constant 10-16°C.
There are three main ways to harness geothermal energy:
- Electricity production
A turbine is driven by steam extracted from the earth, and this drives a generator to produce electricity.
- Direct use
Geothermal heat found near the surface of the earth can be used directly for heating buildings, for example, water from hot springs is piped into buildings.
- Geothermal heat pumps
The relative constant temperature of the top 15 metres of the earth’s surface can be used to heat or cool buildings indirectly. A pump circulates fluid through a series of underground pipes. In the winter when the ground is warmer that the building above, the liquid absorbs heat from the ground, which is then concentrated and transferred to the building. This can also be used to heat domestic water. In the summer, when the ground is cooler, the pumps transfers heat from the building back into the ground.
The Government grant ‘Low Carbon Buildings Programme’ is designed to help with the cost of installing domestic ground source heat pumps.
Contacts
Energy Saving Trust Advice Centre for London
Telephone: 0800 512012
E-mail: advice@est-london.org.uk
Website: www.energysavingtrust.org.uk/london