Seabed Rocks in Scotland Could Offer Renewable Energy Storage

January 22, 2019 by Scott McMahan

Researchers from the Universities of Edinburgh and Strathclyde have looked into an innovative method that could be used to trap compressed air in porous rock formations found in the North Sea using electricity from renewable technologies. The researchers looked into the use of the rocks to store pressurized air that could later be released to drive turbines that would generate large amounts of electricity.

Engineers and geoscientists from the Universities of Edinburgh and Strathclyde utilized mathematical models to evaluate the potential of the process, called compressed air energy storage (CAES). The researchers estimate that using the method on a large scale could store enough compressed air to meet the UK's winter electricity needs. Winter in the UK is when demand is the highest. The above image (ID 122453481 © Juan Vilata | is of sandstone formations off the coast of Scotland.

They speculate that the procedure could help provide steady and reliable energy supplies from renewable sources including wind and tidal turbines. This type of energy storage could help compensate for the intermittent nature of many renewable energy technologies that vary depending on weather conditions. Such a method might one day fill the need for new processes that can store energy reliably for months at a time, researchers say. However, so far the researchers see cost as one of the major issues of such a process.

The team combined these estimates with a database of geological formations in the North Sea to predict the UK's storage capacity. In this way, they found that porous rocks underneath UK waters could potentially store about one and a half times the UK's average electricity demand for January and February.

Compressed air energy storage would first use electricity from renewables to power a motor that generates compressed air. This air would then be stored at high pressure in the pores of sandstone, using a deep well drilled into the rock. During energy shortages, the pressurized air could be released from the well to power a turbine. The turbine would generate electricity that could be fed into the grid.

At sites in Germany and the U.S., a similar process for storing air in deep salt caverns has been employed.

Locating wells close to renewable energy sources such as offshore wind turbines would make the process cheaper, more efficient, and reduce the amount of undersea cables needed, the team says.

The study is published in the journal Nature Energy. The study was funded by the Engineering and Physical Science Research Council, Scottish Funding Council, and the Energy Technology Partnership.

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."