What’s next for long duration storage?: Air batteries

As the UK adds more renewable energy generation to its grid, some of the sector’s most important questions remain around how to harness it efficiently, and particularly: how can we store this energy for long enough to deploy it when needed most?

Having been at the forefront of the UK energy storage market for more than a decade, from the earliest stages of the battery energy storage system (BESS) to carbon capture and storage (CCS), pumped hydro and beyond, Burges Salmon have seen firsthand the exciting developments in technology which have evolved as energy storage has emerged as a critical part of British energy infrastructure. 

And now, “air batteries” are beginning to gather some momentum, building on a 50-year-old concept to present an interesting option in the next chapter of UK energy storage.

What is an “air battery”?

“Air battery” is an umbrella term used for long-duration technologies that store energy using air, or gases derived from air, rather than electrochemical cells. Two of the most prominent forms are liquid air energy storage (LAES), and compressed air energy storage (CAES). 

LAES uses surplus electricity generated by renewables at times of low demand to cool air to approximately minus 196°C, turning it into a liquid that can be stored in insulated, low-pressure tanks. During periods of high demand, the liquid air then is pumped to a higher pressure and warmed so that it expands back into a gas. That expansion drives a turbine and generates electricity. 

CAES uses a similar principle to store compressed air in underground salt caverns, depleted reservoirs or purpose-built storage facilities to be released and expanded through turbines at points of peak-demand. 

Why does it matter?

Lithium-ion BESS will continue to play a major role in supporting the grid. However, air-based technologies may be particularly valuable where electricity must be stored for six hours or more. Their potential advantages include long asset lives, limited reliance on scarce battery minerals and the ability to increase storage capacity by expanding tanks or underground storage rather than adding electrochemical cells. 

This could help renewable generators capture electricity that might otherwise be curtailed and may improve system flexibility, support security of supply and reduce reliance on fossil fuel generation during periods of peak demand.

From concept to commercial deployment

A project attracting particular attention is Highview Power’s Carrington facility at Trafford Energy Park in Greater Manchester. The project is under construction and is expected to provide 50MW of output and 300MWh of storage, equivalent to six hours of discharge. It is intended to become the UK’s first commercial-scale LAES plant and is planned to become operational from 2026. 

The project secured £300 million of investment in 2024 from a group including the UK Infrastructure Bank and Centrica and is an important test case of the commercial scalability and integration of LAES. Highview Power has plans for two more UK LAES plants, one in Hunterston, Scotland with planned storage of 2.5 GWh.

Supporting the next generation of storage

New technologies like these bring novel issues around bankability, procurement, grid connection, revenue models, interface risk and long-term operation. At Burges Salmon, our reputation is built on supporting first-of-a-kind projects, and with more than 100 dedicated energy specialist lawyers working across development, financing, regulation, construction, planning, real estate, environment and disputes, we pride ourselves of providing expert advice throughout project life cycles in all UK jurisdictions.

Our experience is clear in seeing novel technologies through to completion: from supporting MeyGen’s pioneering commercial  tidal array deployment in the Pentland Firth over a decade ago to recent market leading projects including advising on carbon capture storage schemes, hydrogen and heat developments, and Firefly Green Fuels first commercial scale sustainable aviation fuel project. We are well placed to help clients turn innovative energy storage concepts into deliverable and financeable projects. 

“Air batteries” may prove part of the answer to the grid’s long-term storage needs, but the demand for innovative renewable technologies will no doubt continue to evolve, presenting promising opportunities, and interesting new challenges, for all parties in the sector. We are excited to use our knowledge across all technologies and our market leading BESS, PSH and storage experience to support the next wave of long duration storage projects.

If you have and queries or would like to discuss any of the topics in this article further, please don’t hesitate to get in contact with Lloyd James. 

This article was written by Lloyd James and Sophie Pace-Bonello.