north sea coast

Porous North Sea rocks could store surplus renewable energy in compressed air

Image credit: Dreamstime

Renewable energy could be stored in the form of compressed air trapped inside porous rocks off the coast of the UK in the North Sea according to researchers from the University of Edinburgh.

The study proposes a technique that uses excess energy generated from renewable sources, which do not operate 24 hours a day due to varying weather conditions, to power a motor to force compressed air into the rocks.

This air would be stored at high pressure in the pores found in sandstone, using a deep well drilled into the rock.

This pressurised air could later be released to drive a turbine to generate large amounts of electricity whenever demand requires it.

Using the technique on a large scale could store enough compressed air to meet the UK’s electricity needs during winter, the study found.

The approach could help deliver steady and reliable supplies of energy from renewable sources – such as wind and tidal turbines – and aid efforts to limit global temperature rises due to climate change.

There is a need for new processes that can store energy cheaply and reliably for months at a time, researchers say.

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 UK waters could store about one and a half times the UK’s typical electricity demand for January and February, they found.

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 cabling required, the team said.

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.”

In 2017 E&T looked at the most promising storage technologies for smoothing out the flow of renewable electricity. 

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