EnergyPathways advances MESH salt cavern storage for UK grid
EnergyPathways is developing the Marram Energy Storage Hub (MESH), a 300 MW/55.2 GWh compressed air energy storage project in salt caverns under the East
EnergyPathways is advancing the Marram Energy Storage Hub (MESH), the UK's largest compressed air energy storage project under development. The 300 MW/55.2 GWh facility will use vast salt caverns beneath the East Irish Sea, about 18 kilometres off the coast of Lancashire, with onshore facilities at the Port of Barrow.
The project leverages a thick, pure salt formation. Ben Clube of EnergyPathways described the salt as a very thick sequence with 500 to 600 meters of vertical relief and virtually pure halite. Each planned cavern will measure 700,000 cubic meters, a volume equal to four St. Paul's cathedrals. The first phase calls for four such caverns, but the entire license area holds potential for up to 60 caverns. MESH is planned as an integrated hub, combining compressed air storage with future gas and hydrogen storage and production, plus graphite manufacturing.
First phase details
The initial stage of MESH is a major compressed air energy storage plant. This first phase is designed to deliver 300 megawatts of power with a massive 55.2 gigawatt-hour energy capacity. At full output, the facility could run for over seven days. This makes it the largest CAES scheme currently in development across the United Kingdom.
| Metric | Specification |
|---|---|
| Power Capacity | 300 MW |
| Energy Capacity | 55.2 GWh |
| Duration at Full Power | Over 7 days |
| Number of Initial Caverns | 4 |
| Individual Cavern Volume | 700,000 m³ |
Strategic positioning and government engagement
EnergyPathways strategically skipped the first application window of Ofgem's cap-and-floor support scheme for long-duration storage. In that first round, concluded in June, the regulator provisionally selected 16 projects totalling 7.6 GW and 136.9 GWh. Ben Clube stated the company was invited to apply for that round but chose not to.
The company has now been invited by Ofgem and the Department for Energy Security and Net Zero to participate in the scheme's second round. However, that second round has been pushed back by about six months from the government's original timetable. Officials attribute the delay to holdups in finalising the shortlist for the first round.
Despite the delay, EnergyPathways maintains regular communication with the government and expresses strong confidence. Clube said support to see MESH proceed is very strong within government, viewing its progression as a matter of when, not if, the second round launches. The company intends to submit a much more mature proposal for the second round, with key issues and criteria well addressed.
Context of UK energy needs
The need for a project like MESH is framed by the limitations of the first cap-and-floor round and the UK's specific energy profile. The projects selected in that first round provide about 130 GWh of storage capacity with an average duration of roughly 18 hours. Ben Clube pointed out that this hardly addresses the scale of the challenge. In the UK's wind-dominated electricity system, surplus generation events typically run well beyond 12 hours and frequently last for days.
He assessed that the first round fails to deliver the quantity or type of storage the UK urgently requires to manage these surpluses and lower consumer bills. Unmanaged, the system costs from such surpluses could reach multibillions. MESH is conceived as an integrated solution where compressed air captures surplus wind generation, paired with gas and hydrogen storage to enhance energy security.
The UK grid currently relies on dispatchable gas-fired generation to back up intermittent renewables. About half of this gas supply comes from UK North Sea production. However, during peak winter demand periods, the nation may need to import up to 90% of its gas needs. The UK currently holds very little gas storage capacity, under six days of national supply. This contrasts sharply with around 80 days of storage in the European Union and over 40 days in other large importers like China.
EnergyPathways attributes MESH's low-cost proposition to the enormous scale of the caverns that can be developed. The company is targeting a final investment decision in 2028 and commercial operations by the end of 2031. This timeline is contingent on securing the necessary consents and successful participation in Ofgem's second cap-and-floor support round.
