Comment by Frank Bridge, Digital Delivery Manager, and Dr. Daniel Curry, Systems Engineer (Hydrogen Networks), at Energy Systems Catapult.

Hydrogen is set to play a crucial role in decarbonising the energy sector. By 2030, the UK aims to have 10 GW of low carbon hydrogen production capacity (at least half produced through green hydrogen production), with a potential estimated demand of over 100 TWh of hydrogen per year by 2050

The UK currently has around 30 TWh of natural gas based storage, this helps to manage seasonal variation in demand and provide resilience to the energy system. In a Net Zero world it is likely that this will be replaced by hydrogen storage.

Through the IUK funded Hydrogen Innovation Initiative (HII), Energy Systems Catapult has worked with Arup and the British Geological Survey (BGS) to explore the barriers to building and operating salt caverns for hydrogen storage and areas where innovation and support may help to remove them.

Is this a new technology?

Hydrogen salt cavern storage in the UK started in the 1970s in Teesside where hydrogen is stored as a feedstock for chemical processes. This was because salt caverns can retain large volumes of pressurised hydrogen for extended periods of time with only a limited loss of volume. Salt caverns require infrastructure above ground including: hydrogen process facilities; infrastructure to transport the hydrogen to/from the facility; the well cap; and a buffer gas/liquid storage Salt caverns as a storage technology, are understood, developed, and commercially operated globally and so are a good candidate as a hydrogen storage technology for decarbonised energy systems.

Does the UK have enough storage capacity for salt caverns?

A study by Arup, BGS, and Imperial College London estimated the UK might need 1,000 new salt caverns to replace gas consumption, with an upper-bound theoretical hydrogen storage capacity of 2,150 TWh onshore. However, subsequent analysis suggested only 10% (215 TWh) of this capacity may be practically usable due to geological and land constraints. The Royal Society projects a 2050 electricity demand of 570 TWh/year, and that this would require 60–100 TWh of hydrogen storage. Even at 10% of theoretical capacity, the UK could meet this upper demand, ensuring sufficient onshore hydrogen storage for future needs.

How can salt caverns be used?

Salt caverns are well suited for long-term, large scale energy storage due to their low loss rates relative to other storage technologies. This means they can provide energy security to an energy system by storing large amounts of energy for months or even years, then providing this energy to the system consistently (until the allocated, available, hydrogen gas has been depleted).

Additionally, at least part of the UK’s future hydrogen production will be through electrolysis, which can use electricity which may otherwise be curtailed during periods of high renewable supply and low demand.

What is needed to get hydrogen salt cavern storage in the UK to be deployed?

Barriers to deployment include:

• Uncertainty around the demand for hydrogen and the associated need and role for hydrogen storage

There is a need for long duration energy storage. Understanding the uncertainties around the right size of storage, where it is needed, and the roles salt caverns will play in a future decarbonised energy system is crucial in defining the case for salt cavern hydrogen storage. Additionally, understanding the future profile of demand for hydrogen, including demand spikes will help plan storage needs, to ultimately provide increased energy security.

• Business case certainty and pricing

Salt caverns take a long time to construct and commission, and capital costs, maintenance and operational expenses can be substantial. Without clear payback periods, operational and capital costs, and reduced uncertainty around the commitment to hydrogen, investment into salt caverns for hydrogen storage will be impacted. Clarity over how costs will be recouped once the site is operational is a key barrier to the construction of storage. Strong financial performance, maximising return of investment (ROI), would make investing in storage more promising and fruitful. Continued government investment around hydrogen storage will reduce risk and increase funding and investment opportunities.

• Access to specific technical data for new commercial hydrogen storage applications

Whilst there are existing pilots and projects, there is yet no commitment for learnings from these to be shared beyond those involved. Not having access to this data impacts the design, commissioning and operation of salt caverns, and can impact project economics and funding. Establishing a means for data to be made more widely available, to create greater business to business collaboration and communication, would reduce the re-work needed to deploy salt caverns and help to reduce the timeframe from design to operation.

• Supply Chain readiness

Early investment in skills and equipment will be vital to operate and maintain both salt caverns and supporting infrastructure. Reduced availability of these in the market will drive the cost of ownership higher and could contribute to project delays with further economic impacts.

• Social and environmental impact

Understanding the current public views around the technology, its safety and impact will help to facilitate technology deployment. Once understood, stakeholders can work to address public concerns or worries that might present barriers to deployment. A clear strategic plan will aid this and working with local communities will help towards public perception and acceptance of the technology. Environmental concerns also need to be considered and managed. The brine solution (that results from the construction of a salt cavern) will need to be stored and/or safely disposed of. In addition, the above ground infrastructure needs to be positioned so it doesn’t impact wildlife. Working with local organisations and groups will help to understand the best infrastructure position to minimise environmental impact.

• Planning and regulation

Project programmes and investment decisions can be impacted by the planning process being slow and cumbersome. A strategic planning function which recognises the role of hydrogen storage would be beneficial. If this is addressed, there could be increased investor confidence as the planning stage may be completed more quickly and with less uncertainty than would otherwise be expected.

As our energy system decarbonises, salt caverns are likely to play a critical role in providing large-scale, long-duration energy storage, enabling hydrogen produced from excess renewable energy to be utilised. Hydrogen salt caverns can bolster UK energy security and support the transition to a Net Zero carbon future. However, as outlined, significant challenges and barriers remain and innovation and collaboration between stakeholders is essential.

Energy Systems Catapult and HII aim to build on the work described here and continue to support the development of innovative solutions to these challenges. This will also require Government, industry, and the public to come together to align priorities and drive forward the deployment of salt cavern technology.