Geothermal power
How can the technology be used?
What is geothermal power?
Beneath the surface of the earth the temperature steadily increases the closer you get to the molten core. Geothermal technology allows the explotation of this thermal energy
Warm Aquifers
Where the geological conditions are right, it is possible to harness geothermal heat by drilling into warm aquifers.
Hot Dry Rocks
Hot dry rocks exist everywhere under the earth's surface and current research is attempting to extract heat from this resource.
Ground source heat pumps
Ground source heat is a different form of geothermal energy. At a few metres below the surface, the temperature of the earth tends to remain constant, with a few degrees of variation between the air and surface temperature. This constant source of heat can be harnessed by ground source heat pumps.
How does the technology work?
Warm Aquifers
Energy is derived from warm aquifers by drilling bore holes to draw the heated liquid up to the surface. The water can be up to 100°C.
Hot Dry Rocks
Wells are drilled down to depths of up to 6000m and a large fracture is opened up to join up adjacent wells. A fluid is injected into one well under high pressure and the heat from this fluid is extracted when it reaches the surface through the other well. Hot dry rocks could produce steam at up to 250°C.
Ground source heat pumps
Ground source heat pumps work by extracting the low temperature heat near the surface, which is between 8°C and 14°C in the UK.
A heat pump is used to transfer the heat from the ground through a pipe buried in the ground and filled with fluid to absorb the heat, which is then distributed to the heating system for a building.
How can the technology be used?
Warm aquifers
Warm aquifer geothermal energy is particularly suitable for district heating schemes due to the localised nature of the phenomenon.
Hot dry rocks
This technology is suitable for electricity generation for the national grid.
Ground source heat pumps
This technology can deliver 4kWh of useful heat to a house for each kWh extracted from the ground. The system can be connected to a normal radiator or underfloor heating system.
Suitable for the UK?
Warm aquifers
The potential for warm aquifer geothermal energy in the UK is limited as most sources are too far from major cities or are not commerically exploitable. It has been used successfully in Southampton since 1986.
Hot dry rocks
An experimental well project was carried out at Camborne School of Mines in Cornwall. The project came up against some difficulties that made it less successful than hoped. However, there is still great potential from this source, estimated at 210TWh per year.
Ground source heat pumps
The technology is commerically available, widely tested and already proven in Europe and North America. It has the potential to replace traditional heating heating systems and is easily connected to existing radiator pipework in homes.
Ground source heat pumps are also suitable for commercial and industrial buildings.
The DTI has estimated that there is the potential for 1,550 large industrial sites to use ground source heat pumps.
According to an Energy Saving Trust report, domestic uptake of ground source heat pumps could be installed in 537,000 homes in the UK by 2030.
This was only based on a comparison with electric heating, and ground source heat pumps have the potential to go much further than this with the correct support. The increasing price of gas, improvements in technology and increases in production will make ground source heat pumps even more competitive in the future.
The benefits
Ground source heat pumps
The environmental impacts of this technology are very low. If you use it with green electricity to run the heat pump it is carbon-neutral. Heat pump installations are noise- and pollution-free.
Access to a suitable piece of ground or body of water would be required to use a heat pump. Potentially every home in the UK with a garden could use a ground source heat pump.
In a well-insulated bungalow, of approximately 100 square metres, the annual running costs and carbon dioxide emisions compare as follows (source: Powergen/Calorex):
- Ground source heat pump: £280; 1.6t of carbon dioxide
- Condensing gas boiler: £340; 3.2t of carbon dioxide
- Non-condensing gas boiler: £375; 3.6t of carbon dioxide
- LPG (non-condensing) bottle gas: £780; 4.6t of carbon dioxide
- Oil (non-condensing): £545; 5.5t of carbon dioxide
- Electricity (storage & panels): £720; 6.3t of carbon dioxide
- Smokeless coal (stove/back boiler): £1080; 10.3t of carbon dioxide
There are obvious benefits for tackling fuel poverty with this technology. The cost of initial installation is higher compared with a traditional boiler replacement on a radiator or underfloor heating system, but the running costs are substatially lower when compared with traditional forms of space and water heating at the current price of electricity. But, installing ground source heat pumps will increase electricity use at a time when we need to be reducing our demand. With the price of natural gas increasing, the cost of electricity will also rise, so the cost of running a ground source heat pump will increase.
The Green Party would like to see the renewables industry properly supported by Government and grants for the costs of installation available to those who are in fuel poverty to allow them to switch to a form of heating that is less costly to run.
Links to suppliers and manufacturers
Other green energy sources
Ground source heat pump ground collector installation
Viessmann Ground source heat pump system
Hot dry rock geothermal project at Cambourne School of Mines
