Study explores potential of North Sea rocks to store renewable energy

Rocks in the seabed off the UK coast could act as stores for renewable energy on a large scale, a study suggests.

Researchers have been exploring ways to store renewable energy produced in the summer for use in winter, when demand is at its highest.

Engineers and geoscientists from the universities of Edinburgh and Strathclyde used mathematical models to assess the potential of a process known as compressed air energy storage (CAES) – a method which uses compressed air to store energy generated at one point for use at a later date.

Described as an advanced technique, CAES works by using electricity from renewable sources 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 in the North Sea.

During times of energy shortage, the pressurised air could later be released from the well, powering a turbine to generate large amounts of 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, the experts said.

Using mathematical models and a database of geological formations in the North Sea, researchers concluded that porous rocks beneath UK waters could store about one-and-a-half times the UK’s typical electricity demand for January and February.

The approach could help to deliver steady and reliable supplies of energy from renewable sources, such as wind and tidal turbines, and aid efforts to limit global temperature rise as a result of climate change, the team said.

They added that locating wells close to sources of renewable energy, such as offshore wind turbines, would make the process more efficient, cheaper and reduce the number of undersea cables required.

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.”

The study has been published in the journal Nature Energy.