EnergyPathways advances compressed air storage

EnergyPathways has launched front-end engineering and design for its MESH compressed air energy storage project in the East Irish Sea, advancing a proposed 300MW / 55.2GWh long-duration storage facility linked to infrastructure at Barrow-in-Furness.

The project is designed to use surplus electricity from nearby offshore wind farms and the UK grid to compress air into offshore salt caverns. When electricity is required, the stored air would be withdrawn, heated, and expanded through a turbine to generate dispatchable power. The facility is planned to provide more than seven days of sustained power output.

The MESH CAES project forms part of a wider energy storage and decarbonisation development that also includes natural gas and hydrogen storage, low-carbon hydrogen production, and associated onshore infrastructure. The wider MESH development has been designated a project of national significance by the UK government.

Pre-FEED studies carried out with Siemens Energy have confirmed the technical and commercial basis for moving the scheme into front-end engineering. The current phase will be funded through a £15 million financing agreement, comprising a £5 million secured loan note facility and a £10 million at-the-market equity placing facility. Planning, consenting, environmental impact assessment, and grid connection arrangements are also underway.

The planned CAES system would use three compression trains and two generation trains connected to four large offshore salt caverns, each of about 700,000 cubic metres. The identified grid connection is positioned between the B6 and B7a constraint boundaries, where the ability to absorb otherwise curtailed renewable electricity could support wider system operation as offshore wind deployment grows.

The project intends to participate in Ofgem’s long-duration energy storage cap and floor process, with final investment decision planned for 2028 and operational start-up targeted at the end of 2031, subject to regulatory approvals. EnergyPathways is also awaiting a decision from the North Sea Transition Authority on a gas storage licence application connected to the wider MESH development.

The UK’s flexibility requirement is moving beyond the operating window of conventional lithium-ion battery storage. Grid-scale batteries are well suited to fast response and intraday balancing, but multi-day storage remains a harder engineering and commercial challenge. Periods of surplus wind generation and tight supply can stretch beyond the duration of standard BESS assets, particularly as the electricity system becomes more dependent on weather-led generation.

Compressed air storage offers a route to larger energy capacity by using geological storage, rotating machinery, and power conversion equipment rather than relying solely on electrochemical cells. Salt cavern storage can provide scale, while turbine-based generation can offer operating characteristics that differ from inverter-based assets. The remaining challenge is to deliver those capabilities with acceptable efficiency, capital cost, construction risk, and long-term revenue certainty.

MESH also reflects the growing role of offshore and coastal energy infrastructure in the low-carbon power system. Existing pipelines, port facilities, geological storage resources, and offshore engineering capability are increasingly being examined for storage, hydrogen, and grid-support functions. The East Irish Sea location gives the project access to offshore wind resources, industrial infrastructure, and potential storage formations within the same regional energy cluster.

Long-duration storage policy is still developing, and project economics will depend on the final shape of regulatory support, market access, and grid service value. The launch of FEED gives the MESH CAES project a clearer route through engineering design, consenting, connection planning, and future investment appraisal.