The UK’s ambition to transition to a renewable energy grid faces a significant challenge in the search for reliable, long-duration energy storage. Periods of low wind or solar generation often necessitate the activation of gas-fired power plants, exposing the nation to volatile fossil fuel markets and imported energy. However, new research from Durham University suggests a transformative solution lies beneath the North Sea, within its depleted oil and gas fields and salt caverns.
A comprehensive modelling study indicates that these geological formations could collectively store an estimated 3,659 terawatt-hours (TWh) of hydrogen. This represents a substantial capacity, equivalent to more than seven years of the UK’s projected electricity demand in 2040.
It is important to note that this figure represents an upper-bound scenario, combining potential from both depleted fields in the North and Irish Seas (approximately 2,582 TWh) and salt caverns (around 1,077 TWh), rather than solely North Sea fields.
Addressing Seasonal Energy Fluctuations
The intermittent nature of renewable energy sources, such as wind and solar, creates a need for storage solutions that can bridge gaps ranging from hours to entire seasons. While batteries are effective for short-term energy shifting, prolonged periods of low renewable output, particularly in winter, demand a “reservoir” rather than a mere “power bank.”
Green hydrogen, produced through electrolysis using surplus renewable electricity to split water into hydrogen and oxygen, offers this potential, and is a process which avoids direct carbon emissions associated with conventional “grey” hydrogen.
The stored hydrogen can then be converted back into electricity when needed, or directly used by industries difficult to decarbonise through electrification alone, such as fertiliser, steel, cement, and glass production.
A domestic hydrogen supply could reduce reliance on fossil fuel imports and foster new employment opportunities in coastal regions with existing offshore energy expertise.
Repurposing Existing Infrastructure
Depleted oil and gas fields offer promising sites for hydrogen storage due to their established geological integrity. These porous rock formations, sealed by caprock, have historically contained hydrocarbons and can be repurposed for hydrogen, leveraging decades of geological data. However, existing wells and pipelines would require significant upgrades and rigorous safety checks to accommodate hydrogen.
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The UK government acknowledges both depleted hydrocarbon fields and salt caverns as viable large-scale hydrogen storage options. Centrica’s Rough field in the southern North Sea, a former gas storage facility, exemplifies this opportunity. Centrica is exploring its redevelopment for hydrogen storage, with engineering work underway for new pipelines and injection equipment. This proposed investment, however, remains contingent on strategic public support.
A Path Towards Zero Gas Generation
The Durham University study, authored by Zongtai Zhang, Joseph Brown, Andrew Crossland, Roderick MacKenzie, Stuart Jones, and Christopher Groves, modelled future energy scenarios every 30 minutes, incorporating projected growth in electric vehicles, heat pumps, and data centres. Their findings suggest that by 2030, all accelerated pathways, including increased renewables, batteries, and hydrogen, could reduce the grid’s reliance on gas plants without carbon capture from approximately 4.6 per cent to around 1 per cent. Critically, the scenario featuring faster hydrogen and electrolyser deployment could eliminate the peak need for such gas plants entirely by 2040.
The researchers emphasise that hydrogen is “not a stand-alone fuel,” but rather a crucial component of a flexible energy system. They advocate for integrated planning, urging that infrastructure decisions today will determine whether depleted fields are repurposed for storage or irrevocably decommissioned. While the geological capacity appears substantial, building the interconnected system – encompassing renewable generation, electrolysers, storage, and power plants – remains the more complex undertaking.
