Scientists at the universities of Strathclyde and Edinburgh believe rocks in the seabed off the UK coast could provide long-term storage locations for renewable energy production.
In a paper in Nature Energy, Dr Julien Mouli-Castillo of the school of geosciences at Edinburgh University described a technique that could be used to trap compressed air in porous rock formations found in the North Sea using electricity from renewables. The pressurised air could later be released to drive a turbine to generate large amounts of electricity.
Using the technique on a large scale could store enough compressed air to meet the UK’s electricity needs during winter, when demand is highest, the scientist’s study found and could help deliver steady and reliable supplies of energy from renewable sources – such as offshore and onshore wind and tidal turbines – and help efforts to limit global temperature rise as a result of climate change.
The engineers and geoscientists at the universities 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 1.5 times the UK’s typical electricity demand for January and February, they found.
Compressed air energy storage 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 said.
The study described in Nature Energy was funded by the Engineering and Physical Science Research Council, Scottish Funding Council, and the Energy Technology Partnership. The analysis described in the paper, Inter-seasonal compressed-air energy storage using saline aquifers, found that the potential storage capacity available to the UK was equivalent to approximately 160% of its electricity consumption for January and February 2017 (77–96 TWh), with a ‘roundtrip’ energy efficiency of 54–59%. They said UK storage potential is achievable at costs in the range US$0.42–4.71 kWh.
Dr Mouli-Castillo said, “This method could make it possible to store renewable energy produced in the summer for use in winter. It can provide a viable, though currently 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.”