Granite could be about to trigger a second industrial boom in the north-east – thanks to the heat it generates below the surface of the Earth.
Business chiefs are investigating whether a geothermal energy plant – which would utilise high temperatures found between three and six miles underground to generate electricity – can be built between Aberdeen and Peterhead.
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.
But Aberdeen and Aberdeenshire 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.
Four miles underground, the Earth’s temperature typically rises by 150C – but in areas where there is granite the temperature can rise by 210C.
Scientists believe that so-called “hot rocks” could lie below Peterhead, Inverurie and areas around Stonehaven.
Scottish Enterprise is now funding a major study to establish if a test plant could be built in the north-east.
Chevron is the world’s largest producer of geothermal energy and has plants in California, the Philippines, and Java, Indonesia.
Several countries, including Scotland and Australia, are now working to develop deep geothermal power’s potential.
The Scottish plans would be part of the multimillion-pound Energetica project, which is aimed at creating a corridor of new businesses between Aberdeen and Peterhead to radically transform the local economy.
Project leaders Aberdeen City and Shire Economic Future (Acsef) say it could attract £750million of investment in its first 10 years.
Energetica project director Sara Budge said: “As part of our quest to make Energetica a world-class, all-energy destination, we are exploring various avenues for generating renewable energy in the corridor which stretches north from the Bridge of Don up to Peterhead and west to Aberdeen Airport.
“Geothermal is one source we are considering.”
She added: “We have just issued a tender to appoint an appropriate organisation to undertake a feasibility study into the potential for geothermal heat generation within Energetica but also in other locations across Aberdeenshire.” For more than two centuries, mining, exporting and building with granite formed the cornerstone of the north-east economy.
After the first quarry opened at Loanhead, Rosemount, in 1730, the industry boomed with the discovery of granite in Rubislaw Quarry, which became the deepest man-made hole in Europe at 450ft.
At the industry’s peak at the turn of the 20th century, there were 127 working quarries in Aberdeenshire and 2,500 jobs in Aberdeen’s yards.
The quarries which gave Aberdeen the Music Hall, Marischal College, HM Theatre and the town house began to decline soon after World War I. Nick Schofield, a volcanologist with the Volcanic and Natural Environmental Systems group at Aberdeen University, said it was “perfectly feasible” that the granite deep underground could hold geothermal potential. He said: “Peterhead sits on a big chunk of granite, as does Inverurie.
“I think they will be targeting the granites in the north-east, because when they decay, the radioactive minerals within granite give off heat.”
Last night the Scottish Government said it believed that geothermal had huge potential.
“Geothermal energy represents a substantial and as yet almost entirely untapped potential resource in Scotland,” a spokesman said.
“It offers scope to regenerate brownfield sites as well as opportunities to create jobs.
“Following on from our Routemap for Renewables, we are commissioning further work to provide certainty for the industry to fully exploit this potential, putting Scotland at the forefront of this emerging industry in the UK.”
****
What is geothermal?
Geothermal is translated from the ancient Greek words for “Earth’s heat”.
The temperature of the Earth’s core – 4,000 miles below the crust – is around 5,500C, roughly the same as the sun.
As a result, the upper parts of the surface stay warm throughout the year.
This heat can be used directly for heating buildings and for a number of commercial and industrial uses.
How does it work?
There are three types of power plant that can convert geothermal energy to electricity, depending on the temperature of the geothermal fluid used.
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.
Is it a finite resource like oil and gas?
Geothermal energy is a reliable source of power that can reduce the need for imported fuels to generate power.
It is renewable because it is based on a practically limitless resource – natural heat within the Earth.
Why the north-east?
For every kilometre (two-thirds of a mile) below the Earth’s surface the temperature increases by around 25C.
This is known as the geothermal gradient.
In areas where there are high concentrations of granite, which is formed from magma, the geothermal gradient increases to 35C per kilometre.
This is because radioactive particles in the stone give off heat as they decay.
Parts of the north-east, such as the Peterhead and Inverurie areas, have granite beneath them and therefore could be perfect for geothermal energy.
What about radon gas?
Radon is a naturally-occurring gas that seeps up from the ground.
It is attributed with being the second-largest cause of lung cancer in the UK.
Parts of Aberdeenshire, the Highlands and Orkney are the worst-affected areas of Scotland, but it is not considered dangerous unless there is long-term exposure at high concentrations.
Radon is a known pollutant emitted from geothermal power stations but it disperses rapidly and no health hazards have been proven.
The trend in geothermal plants is to pump all emissions back underground.
