We need hydrogen energy storage to reach net zero, so it’s essential we start building it now

If you think of the UK’s renewable energy market as a jigsaw puzzle, electricity storage is the missing piece. While December 2023 saw a 6.8% increase in renewable energy generation (30.1 TWh in Q3), thanks to higher wind speeds and increased onshore and offshore capacity, the reality is that unless we find a way to store that energy, our renewable supply will remain as unpredictable as the weather. And that means a continued reliance on fossil fuels, regardless of how much money is thrown at hydrogen production, wind farms and solar panels.

For Sir Chris Llewellyn Smith, a former director-general of CERN (the Large Hadron Collider accelerator was approved during his tenure), Emeritus Professor of Physics at the University of Oxford and a Royal Society fellow, this has become something of a mission. In September 2023, he co-authored a Royal Society report on large-scale electricity storage that highlighted the need to support large-scale wind and solar power generation with large-scale hydrogen storage, and to start building that storage now.

Flawed strategies

The government issued a hydrogen strategy in August 2021, which was followed by announcements of specific steps and consultations in December 2023 and January 2024, accompanied by extravagant press statements. Llewellyn Smith says these contain some good proposals to encourage the production and use of hydrogen. Some of these would, however, be blue hydrogen rather than electrolytically produced green hydrogen. Blue hydrogen inevitably leads to leakage of methane, which is a dangerous greenhouse gas, and Llewellyn Smith says that blue hydrogen production plants could well become stranded assets by the time we reach net zero.

The government’s analysis of the use of hydrogen to buffer the variability of wind and solar is also based on studies of separate years, says Llewelyn Smith. He explains that such studies cannot cast any light directly on the need to store energy for over 12 months, which they seriously underestimate while overestimating the need for other flexible supplies.

Llewellyn Smith adds that consequently the analysis does not reveal the true scale of the need to store green hydrogen to buffer variations in wind, solar and demand, which may well be the major use of hydrogen. Also, hydrogen produced by excess wind and solar is not included in the analysis of the future hydrogen to power market, while the discussion of incentivising investment in long duration energy storage explicitly excludes storage as hydrogen.

Finding a business model

The Department for Energy Security and Net Zero aims to have two hydrogen storage projects, whose volumes and purpose are not specified, in operation or construction by 2030. However, Llewellyn Smith says this will not happen unless or until the market provides incentives or there are government subsidies.

“The companies we talk to, including the likes of SSE and Inovyn, say they’d love to build large hydrogen stores but at the moment there is no viable business model for it,” he says. “They’re not going to do it for fun, that’s for sure. They’re businesses, and would only do it to make money.”

He also notes that the government package does not include any encouragement for development of ways to turn hydrogen into electricity, which is the least developed link in the chain of electricity → hydrogen → electricity.

The time to start is now

By contrast Llewellyn Smith cites the US Inflation Reduction Act, which has earmarked billions of dollars as incentives for energy storage development projects. However, Great Britain (excluding Northern Ireland which has its own integrated market with the Republic of Ireland) has not even reached the starting line for funding the multi-year and multi-decadal storage that the Royal Society report suggests will be needed.

In order to store energy on such long timescales, it will be essential to have stores with low capital costs per unit of energy stored. Hydrogen is the only real option here other than ammonia, which would be more expensive.

“If the government announced we’re going to build several terawatt hours of hydrogen storage, starting as soon as possible, it would trigger innovation and investment”

The Royal Society’s report finds that apart from very short term/rapid response storage provided by hydrogen, the UK could be powered at what appears to be an acceptable cost (higher per MWh than in the last decade, but less than in the last two years) by wind and solar supported by some 90 TWh of hydrogen storage. This is an extreme case, he says, but even allowing for the contributions of nuclear and the addition of other types of storage that are more expensive than hydrogen per unit of energy stored but have higher round-trip efficacies, Llewellyn Smith says that tens of TWh of hydrogen storage will be needed.

“If we’re going to get that built in time, we need to start now,” he says. “If the government announced we’re going to build several terawatt hours of hydrogen storage, starting as soon as possible, it would trigger innovation and investment. I bet if you said that in eight years’ time, there’s going to be a very large need for electrolysers, INEOS, ITM and Ceres will be there saying, we can do that. And if you said we’re going to have a very large need for converting the hydrogen back to power, ITM, Ceres and JCB will be there. Those things will happen if we start building storage. The priority is to get it started.”

Llewellyn Smith notes that until we’ve actually done it, we won’t know with any accuracy what it’s really going to cost, and this may be where government caution becomes an issue. Yet the longer-term costs of not doing anything are much greater, while starting now can create jobs and start a learning process that will drive down costs.

Pressure on salt caverns to deliver

Llewellyn Smith says that if we want to store hydrogen at the scale that the Royal Society report says will be needed, the only way to do it is in very large underground, solution-mined salt-caverns at high pressure. This has been successful in the US where  three very large caverns have been used to store hydrogen in Texas for over 40 years and there’s experience in the UK too where  caverns on Teesside have been used to store hydrogen for  chemical feedstock.

“We’ve been worrying about how fast these underground caverns can be built because we’d like a large enough number to be there in time for us to get to net zero by 2050,” says Llewellyn Smith.

Inovyn, he adds, has planning permission to build a half-million cubic metre natural gas storage plant in Cheshire, and has applied for planning permission to use it for hydrogen. There are, however, concerns over what to do with the brine when it is removed from the salt cavern. Some could be sold, but this would slow down construction as the market is limited.

“The [government’s] analysis does not reveal the true scale of the need to store green hydrogen to buffer variations in wind, solar and demand”

“In Texas, I think they stored the brine in saline aquifers,” says Llewellyn Smith. “An alternative is to take it far enough out to sea and make sure it disperses quickly. It’s a possible concern, and it needs more study, but I don’t think it’s a showstopper.”Potential UK sites for salt caverns are limited to East Yorkshire, Cheshire and Wessex, but ammonia could be stored in large tanks almost anywhere. Hydrogen could possibly be stored in aquifers in many places, but this has never been done and the potential storage capacity is unknown. A more promising possibility, which is being trialled for the first time in Austria in the Underground Sun Storage project, would be to store hydrogen in depleted gas fields. Centrica is confident that it will be possible to store hydrogen in the depleted Rough gas field off Yorkshire and the Kinsale Head field off Cork. While probably not cheaper than using solution-mined salt caverns, Rough could store 17 TWh at a relatively early date, and using gas fields with terminals in Norfolk would – if it’s possible ­– provide valuable geographical diversity.

Moving forward with hydrogen storage

“The electricity that comes into your house will be a mix of power directly generated by wind and solar and stored electricity,” says Llewellyn Smith. “The directly generated wind and solar power will be relatively cheap and meet demand maybe 85% of the time. However, the remaining 15% of power will have to come from storage or other flexible sources that would also operate with a very low duty factor. While the first lot would be pretty cheap, the second lot would be very expensive – but without it the system would not work.”

Under present market conditions, the ‘second lot’ won’t get built. This is just one of the market issues that Llewellyn Smith says needs to be urgently addressed. In order to attract the investment required to ensure that the storage that will be needed is available, when it is needed, we have to start now.