Geothermal power in the United Kingdom

The potential for exploiting geothermal energy in the United Kingdom on a commercial basis was initially examined by the Department of Energy in the wake of the 1973 oil crisis. Several regions of the country were identified, but interest in developing them was lost as petroleum prices fell.

Groundwater in Permo-Triassic sandstones in the UK has the potential to provide an exploitable geothermal resource at depths of between 1 and 3 km. Since 1979 the British Geological Survey has been investigating the nature of these sandstones using information from coal and hydrocarbon exploration boreholes and geophysical surveys, and from deep exploration boreholes which have been drilled and tested in Hampshire, Northern Ireland and South Humberside.

Aquifer-based schemes

Southampton District Energy Scheme

Geothermal energy is the natural heat of the Earth stored in rocks and fluids within them. Most of this energy is derived from the decay of radioactive materials within the Earth. As a result of this heat production, there is a flow of heat towards the Earth's surface, resulting in temperatures that increase with depth (the geothermal gradient). Heat flow and geothermal gradient are highest in volcanic and seismically active regions, but in the UK, which is generally geologically stable, the gradient is generally no different to the world average of about 25 °C/km. However there are areas where favourable conditions exist and the gradient can exceed 30 °C/km.

The British Geological Survey has investigated and estimated the UK's geothermal resources, including for aquifers in both Palaeozoic and Mesozoic rocks, and has found the most favourable for low enthalpy geothermal energy in the UK are Permo-Triassic sandstones. These are typified as extending deep into depositional basins, and in many cases are on-shore extensions of major offshore basins. The basins of principal interest are East Yorkshire and Lincolnshire, Wessex, Worcester, Cheshire, West Lancashire, Carlisle, and basins in Northern Ireland. In addition, some of these basins are in areas of elevated heat flow, or are overlain by less thermally conductive strata, providing in effect an insulating layer. The following table lists the primary UK Geothermal aquifer resources for areas where the temperature is greater than 40 °C and the transmissivity is greater than 10 Dm, except as indicated:

Aquifer/Basin name	Geologiocal Formation	Geothermal resource (Exa-joules)	Identified resource(1) (Exa-joules)	Depth (m)
East Yorkshire and Lincolnshire	Sherwood Sandstone	99	6.7	?
	Basal Permian Sands	6.7	0.9(2)	?
Wessex	Sherwood Sandstone	22.9	3.2(3)	1,700 to 2,200
Worcester	Permo-Triassic (undifferentiated)	12	1.4	2,500
Cheshire	Sherwood Sandstone	16.9	2.1	4,000
	Permian, including some Triassic	27.9	3.8	4,000
Northern Ireland	Sherwood Sandstone	35.4	4.7	?
(1) Identified resource calculated assuming an end of process heat rejection temperature of 30 °C; direct use of the fluid, and re-injection of the fluid after use. (2) Transmissivity ≥5 Dm (3) In part of area transmissivity 5 to 10 Dm Note: 1 exa-joule=1018joules

In the 1980s, the United Kingdom Department of Energy undertook a research and development programme to examine the potential of geothermal aquifers in the UK. However after some initial success drilling a well in the Wessex Basin in 1981, it was deemed too small to be commercially viable. The project was abandoned by the Department of Energy, but Southampton City Council refused to let the project fall and took the decision to create the UK's first geothermal power scheme. This was undertaken as part of a plan to become a ‘self sustaining city’ in energy generation, promoted by then leader of the city council Alan Whitehead. The scheme was eventually developed in conjunction with French-owned company COFELY District Energy and the Southampton Geothermal Heating Company was then established. Construction started in 1987 on a well to draw water from the Wessex Basin aquifer at a depth of 1,800 metres and a temperature of 76 °C.

The scheme now heats a number of buildings in the city centre, including the Southampton Civic Centre and the WestQuay shopping centre, by providing 8% of the heat distributed by a larger city centre district heating system that includes other combined heat and power sources. Geothermal energy provides 16 GWh of heat per year.

Another area with great potential for geothermal energy is in the North Sea, on the continental shelf where the Earth's crust is thin (less than 10 kilometres). The offshore platforms extract hydrocarbons from this region, but each year the output falls by 5% and soon it will be uneconomic to continue using these platforms for fossil fuel extraction. An alternate use could be geothermal power generation. A 1986 work on this was undertaken by Total Energy Conservation and Management Co. Ltd. An overview document was produced called "Single Borehole Geothermal Energy Extraction System for Electrical Power Generation".

Hot rock schemes

In addition to using geothermally heated aquifers, Hot-Dry-Rock geothermal technology can be used to heat water pumped below ground onto geothermally heated rock. Starting in 1977, trials of the technology were undertaken at Rosemanowes Quarry, near Penryn, Cornwall.

In 2008 a planning application was submitted for a hot rocks project on the site of a former cement works at Eastgate, near Stanhope in County Durham. The geothermal plant will heat the UK's first geothermal energy model village.

In 2010 planning permission for a commercial-scale geothermal power plant was granted by Cornwall Council. The plant will be constructed on the United Downs industrial estate near Redruth by Geothermal Engineering Ltd. The plant will produce 10MW of electricity and 55MW of renewable heat.

On 18 December 2010 The Eden Project in Cornwall was given permission to build a Hot Rock Geothermal Plant. Drilling is expected to in 2011 with electricity being produced from the second half of 2013. The plant will be on the north side of the Eden Project, a showcase for environmental projects at Bodelva, near St Austell. It should produce up to 4 megawatts of electricity for use by Eden with a surplus, enough for about 5,000 houses, going in to the National Grid.

See also

• Energy use and conservation in the United Kingdom
• Ground source heat pumps
• Earth warming tubes
• Renewable energy
• The Geological Society
• Geothermal (geology)
• List of renewable energy topics by country

External links

• The Geological Society: Low enthalpy geothermal options for the UK
  • The Geological Society: Map of geothermal potential in England and Wales
• Geothermal Power Generation in the UK
• Geothermal Implications in the UK by Gresham Clacy, Geophysicist
• EVALUATION OF THE PERMO-TRIASSIC SANDSTONES OF THE UK AS GEOTHERMAL AQUIFERS
• Deep Geothermal Energy and Groundwater in the UK, Jon Busby BGS
• Geothermal Prospects in the United Kingdom, Jon Busby BGS