Hopes that heat stored in rocks buried deep beneath the north-east soil could bring a new energy boom to the region have been dismissed in a new government report.
Only a handful of places around the globe provide the special geological conditions needed to produce the green power.
At these locations, deep fractures in the Earth’s crust allow the molten rock to surge close enough to the surface to heat liquid underground and power turbines.
It had been thought that the north-east – the Grampian mountains in particular – could be Scotland’s best hope of cashing in on the new energy source because of the granite which propped up the region’s economy for 200 years.
A new report, produced for the UK Government by Atkins, confirms that a source of heat does lie beneath the hills.
However, it concludes that the region only has “moderate geothermal gradients” at the depths which can currently be reached. The Grampian granites have been considered as providing a potential resource, but the likelihood of geothermal temperatures sufficient to generate electricity is considered low,” it says. Four miles underground, the Earth’s temperature typically rises by 150C – but in areas where there is granite the temperature can rise by 210C.
However, the report does leave the door upon for further exploration should technology develop in the future.
It says the drilling depths required currently render potential geothermal schemes as “economically unviable”, but adds the “technical advancement may supersede this presumption in the future.”
To create geothermal energy, a pump is used to send the fluid through the warm ground, and wells similar to those used to produce oil and gas are drilled to recover it.
Once captured, steam and hot water are separated.
The steam is cleaned and sent to the power plant to drive a turbine, and generate electricity.
The separated water is returned underground.
It is renewable because it is based on a practically limitless resource – natural heat within the Earth.
EGS Energy has been given permission to build the UK’s first geothermal plant at the Eden Project, in Cornwall.
It will consist of a two-borehole system – one injection well and one production well – both around three miles deep.
Water will circulate between the bottoms of the two wells, where it will be heated by the hot rocks and returned to the surface at a temperature of approximately 180C.
At the surface the heat will be extracted to drive a binary turbine to create electricity and provide hot water.
The report does leave the door upon for further exploration
