Empty North Sea oil fields could store enough green hydrogen to power the country for seven years

Stuart Jones, Andrew Crossland, Chris Groves, Durham University

Every time Britain has a still, grey week in winter, something invisible happens behind our plug sockets: gas power stations fire up to keep the lights on. That gas is often imported, with prices set by volatile global markets. This is one reason why energy bills surged during the cost-of-living crisis, despite the low cost of available renewable energy.

On very windy days, we have a different problem. The grid can’t always use all the electricity our wind farms generate, so we pay them to switch off. In effect, we throw away clean energy because we have nowhere to store it.

Our latest research, published in the journal Applied Energy, points to a solution hiding under the North Sea. The depleted oil and gas fields that powered Britain for half a century could be refilled, this time with hydrogen made from our surplus wind and solar power.

We found that suitable depleted North Sea fields could provide 3,659 terawatt-hours of hydrogen storage capacity, equivalent to more than seven years of projected UK electricity demand in 2040. Using them could also take conventional gas power stations off the grid altogether by 2040.

What is green hydrogen?

Hydrogen is the simplest and most abundant element in the universe, and can be used to produce energy without releasing carbon dioxide. Most hydrogen produced is “grey”: stripped out of natural gas in a process that releases carbon dioxide. “Blue” hydrogen is made the same way, but with some of that carbon captured and stored. “Green” hydrogen is different: it’s made by passing renewable electricity through water by electrolysis, splitting it into hydrogen and oxygen. If the electricity comes from wind or solar, the hydrogen is genuinely zero carbon.

Green hydrogen production is, in effect, a way of bottling renewable energy. When the wind blows harder than we need, that surplus electricity can be used to make hydrogen. When the wind drops, stored hydrogen can be turned back into electricity in a power station – doing the job gas does today, but without the emissions or the imports.

Green hydrogen can be particularly useful in winter when energy demand is highest, but where there can be little sun or wind to power renewables. For enough green hydrogen to get us through the winter months, we need seasonal storage – somewhere to bank huge amounts of summer and autumn surplus and draw it down through winter. For that, you need the help of geology.

The potential of underground storage

Natural gas has been stored underground for millions of years. It collects in porous rocks capped by an impermeable layer that traps it below the surface. When a gas field is depleted, that underground storage space does not disappear. The rock formations remain, and many fields are still connected to pipelines and offshore facilities. This raises the possibility of using them to store hydrogen instead.

These depleted fields are not considered in current UK plans for hydrogen storage. Instead, the focus is almost entirely on salt caverns. These are artificial voids dissolved out of thick underground salt layers, mainly in Cheshire and East Yorkshire. Salt caverns are excellent stores, but Britain simply doesn’t have enough of them to meet long-term hydrogen storage needs. Only one North Sea field, Rough, is currently being developed for hydrogen. That leaves an enormous resource untouched.

Our research assessed depleted fields across the North Sea and identified the best candidates for hydrogen storage based on their geology. We drew on previous academic and industry research to understand the quality of the cap rock and how little hydrogen would seep away in storage.

Modelling future energy needs

Working with colleagues, including PhD researchers Zongtai Zhang and Joseph Brown, we built a digital twin of Britain’s future electricity system and geological storage. Rather than using annual averages, we modelled supply and demand in half-hourly detail, capturing real weather patterns and the coming growth of electric vehicles, heat pumps and data centres.

We then tested different futures. With more renewables but without more hydrogen, the grid still leaned on gas during windless winter weeks. In a low-storage scenario using only planned storage sites, hydrogen stores quickly filled to capacity, preventing additional surplus renewable electricity from being converted into hydrogen during summer months.

Only the high-storage scenario, adding depleted North Sea fields, eliminated the need to use conventional gas power stations entirely by 2040. Across all scenarios, gas fell to just 1% of generation by 2030.

More than electricity

The prize goes well beyond keeping the lights on. Hydrogen at this scale is important to supply industries that are challenging to electrify or rely on international supply chains. That includes the production of fertiliser, steel, cement and glass. All of these need intense, high-temperature heat. Burning hydrogen produces a very high-temperature flame that can deliver concentrated heat directly to industrial processes helping to replace coal or natural gas in furnaces, kilns and blast furnaces, significantly reducing industrial emissions.

Local economies could also benefit. Because the hydrogen would be made close to where offshore wind lands, and stored in fields served by existing infrastructure, it could bring skilled jobs to the very coastal communities affected by the decline of North Sea oil and gas, employing similar skills and expertise.

Green hydrogen would also make Britain’s economy genuinely more home-grown: less imported fuel and reduced reliance on overseas supply chains for critical minerals. With our exceptional wind resource and significant hydrogen storage potential across the North and Irish seas, the UK has the potential to become a hydrogen exporter to Europe.

None of this will happen by accident. The challenge is no longer generating renewable electricity – it’s storing enough of it to get us through the winter when demand is high. Relying on salt caverns will not give us the capacity we need. The infrastructure decisions that determine whether our depleted North Sea fields are repurposed for hydrogen storage (or decommissioned and lost) are being made now. If Britain wants secure, affordable, clean energy in 2040, the planning has to start today.

This article is republished from The Conversation under a Creative Commons license. Read the original article.