ROCKS in the seabed off the Scottish coast could provide a long-term solution to the problem of how to store surplus energy generated from renewable sources.
Wind, solar and tidal power are capable of creating energy bonanza for Scotland thanks to the power of country's climate and long coastline.
But without a way to capture any excess or companies have to switch off their turbines if the grid cannot cope, while wind power winds down when turbines stop turning.
Now scientists say the answer could be found beneath the waves - in the form of compressed air pumped into porous rock formations which could later be released to drive a turbine, generating large amounts of electricity.
Researchers at the University of Edinburgh say using the technique on a large scale could in theory generate enough electricity to meet the UK’s needs during winter, when demand is highest.
READ MORE: New Moray Firth wind farm to power nearly 1m homes
It would also store energy cheaply and reliably for months at a time, delivering a steady and reliable supply of electricity aiding efforts to fight climate change and combat rising global temperatures.
Engineers and geoscientists from the Universities of Edinburgh and Strathclyde used mathematical models to assess the potential of the process, called compressed air energy storage (CAES).
The team then predicted the UK’s storage capacity by combining these estimates with a database of geological formations in the North Sea.
Porous rocks beneath the waters of the Moray Firth and the North Sea could store about one and a half times the UK’s typical electricity demand for January and February, they found.
CAES would work by using electricity from renewables to power a motor that generates compressed air.
This air would be stored at high pressure in the pores found in sandstone, using a deep well drilled into the rock.
During times of energy shortage, the pressurised air would be released from the well, powering a turbine to generate electricity that is fed into the grid.
A similar process storing air in deep salt caverns has been used at sites in Germany and the US.
Locating wells close to sources of renewable energy – such as offshore wind turbines – would make the process more efficient, cheaper and reduce the amount of undersea cables required, the team says.
The study is published in the journal Nature Energy. It was funded by the Engineering and Physical Science Research Council, Scottish Funding Council, and the Energy Technology Partnership.
READ MORE: Green energy revolution unfolds yards from Celtic Park
Dr Julien Mouli-Castillo, of the University of Edinburgh’s School of GeoSciences, who led the study, said: “This method could make it possible to store renewable energy produced in the summer for those chilly winter nights.
"It can provide a viable, though expensive, option to ensure the UK’s renewable electricity supply is resilient between seasons. More research could help to refine the process and bring costs down.”
"Technically, it's feasible. It was done in the 1980s with a test in North America where they found they could get air back from porous rock. There's still a lot of research to be done but with the expertise of the oil and gas industry in the UK it possible that we could be able to do it."
Hannah Smith, Senior Policy Manager at Scottish Renewables, added: “Renewable energy technologies like solar, wind and hydropower are already Scotland’s largest source of electricity.
“Energy storage technologies - of which batteries are the most recognisable - can take the energy created by renewables at times when it's not needed, or when bottlenecks on the grid mean it can’t get to consumers, and save it for later.
“Compressed air storage has the potential to be part of a smart energy future and we welcome this research from the University of Edinburgh as yet another sign that Scotland is leading the way on tackling climate change by cutting carbon emissions from energy generation.”
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