We usually associate geothermal energy with areas along the major tectonic boundaries, where the majority of volcanic activities and earthquakes are concentrated – the so-called “Ring of Fire”.
But capturing underground energy doesn’t have to be about huge differentials in heat.
A Glasgow housing project is successfully using mine water at 16degC to provide hot water and heating to its residents using a simple-to-operate heat pump.
In addition to heat, the first electricity to be generated from geothermal energy was at Larderello in northern Italy in 1904.
There are now geothermal plants in 24 countries, with deep geothermal energy systems currently being developed and tested across Europe in France, Germany, Switzerland as well as the UK.
Guy MacPherson-Grant, managing director of EGS Energy, the firm behind the world famous Eden eco-project, said: “The UK is not going to become Iceland – but if we can find the heat in granite then we could build (generation) plants.”
“A four-megawatt plant would create electricity for thousands of homes and if you can send the heat to a hospital or schools, that is when you become really efficient.”
Almost half of all energy consumed in the UK is used to generate heat, so if government intends to meet its carbon reduction commitments, successful implementation of low carbon heating is vital.
The Scottish Government has set a target of ensuring 11% of heat demand comes from renewable sources by 2020.
In terms of geothermal electricity production in the UK, Jim Hart, business manager at the Edinburgh Centre for Carbon Innovation, said the British Geological Survey (BGS) has suggested that the deep geothermal resource in Scotland might have been underestimated.
He said: “However, there are no onshore boreholes (yet) of sufficient depth in Scotland to definitively prove the case either way.”
The generation vision would be to tap into temperatures of 150degC a few miles underground to heat water to turn electricity-producing turbines.
A distinct advantage of this form of renewable power over others is that it can be run as baseload, and turned on and off as required.
Hart added: “More accessible, though, is the not-so-deep geothermal energy that might be tapped into through the extensive redundant mine workings throughout the Central Belt.
“Existing at depths from near the surface down to around 900m at some mines, huge volumes of water, (with) temperatures from about 12-35degC, can be abstracted at depth, passed through a heat pump, and returned – cooler – to a point nearer the surface.”
There are already a couple of fairly shallow schemes using mine water in Scotland, such as the Glenalmond Street project in Shettleston, Glasgow.
BGS is working on a publicly-funded project to investigate the potential of these resources and how the heat can be utilised by local communities such as the heat energy from mine waters beneath Glasgow.
Dr Ryan Law, managing director of Geothermal Engineering, said UK support plans for geothermal are “too low to stimulate domestic investment”.
He said: “We should be at the forefront of this industry, given the strength of British engineering skills.
“If the UK wants to seize a share of the booming global market for geothermal we must prove our competence at home.”
He points to Germany, which has similar sub-surface temperatures to the UK, and is building 150 geothermal heat and power plants, representing a £3.4billion investment and creating 9,000 jobs.
Law added: “We are now watching from the side-lines while others forge ahead in a global market estimated to be worth £26billion by 2020.”
A UK-wide survey in 2011 by the Renewable Energy Association (REA) found that so-called “hot rocks” could lie below Peterhead, Inverurie and areas around Stonehaven. These are granites where temperatures may reach 210degC only a few kilometres below ground.
Granites have very little free-flowing water unless naturally fractured. Hydro-fracturing appears possible to encourage flow.
Although hyped at the time as a project that could attract millions in investment, it still remains, as Aberdeenshire Council puts it, “a potential investment opportunity for the future”.
The first deep geothermal exploration borehole (995m) to be drilled in the UK for over 20 years was completed at Eastgate (Weardale, Co. Durham) in December 2004.
Abundant brine (46DegC) was encountered within natural fracture networks of very high permeability within granite.
The Eastgate borehole was said to have significant exploitation potential for direct heat uses; it demonstrated the potential for hydrothermal vein systems within radiothermal granites as targets for geothermal resources.
But why is progress so slow in the British Isles?
Gaynor Hartnell, of the Renewable Energy Association, said the UK needed to urgently develop a comprehensive geothermal exploration licence regime, similar to those used in the oil and gas industry.
She said: “These licences would grant the exclusive right to exploration and exploitation of geothermal resources over a defined area for a defined period of time and are essential to provide investor confidence as the industry develops and grows.
“Legislation has (already) been adopted by most countries within Europe.”
Even with more modest projects like the district heating possibilities in Scotland’s Central Belt being explored by the BGS, which it is doing in partnership with professional services firm Aecom, there are a welter of barriers.
Aecom said that part of the reason for the lack of take-up for geothermal heating projects was the lack of information on development costs. Even though Scotland has a £103million renewable energy investment fund, investor confidence is lacking.
Typical obstacles include; inconsistent planning laws, opposition to the road closures necessary for city projects and resistance to modify historic tenement buildings in cities such as Edinburgh.
Aecom said: “Further consideration around the policies addressing the economics, operation, ownership and regulation of district heating infrastructure is necessary.”
But all may not be lost. In May last year, the UK Government signed a memorandum of understanding with Iceland to explore importing Icelandic geothermal electricity by cable to our shores. If we are unable to capture our own geothermal energy, we may at least be able to buy it one day.
Recommended for you
