The Salt Cavern Process
The UK’s ambitious journey to Net Zero requires a new energy infrastructure capable of handling massive volumes of renewable power.
“Salt cavern storage is the only proven, cost-effective solution available at the scale required to facilitate Hydrogen to Power.”
DESNZ-commissioned report from international energy consultants Baringa LLP
The Salt Cavern Process
What is a Salt Cavern?
Salt caverns are not natural caves but man-made chambers created deep underground within thick naturally occurring salt (halite) deposits.
Such caverns have been used to store natural gas and hydrogen in the UK since the 1970s.
Only three areas in Great Britain have suitably thick and extensive salt deposits suitable for such caverns: Dorset, Yorkshire and Cheshire.
How are salt caverns created?
The caverns are created through a process called solution mining.
Wells are drilled deep into thick, underground salt layers (like the Permian Zechstein salt found beneath the UK’s East and South Coasts, or the Triassic salt underlying Dorset and Cheshire).
Fresh or sea water is pumped down through the well to dissolve the salt. The resulting saltwater (brine) containing the dissolved salt is pumped back up to surface enabling the cavern to grow until it reaches the required size.
A single large cavern is around one hundred metres high and wide, providing an immense storage volume (332,000 m3 useable cavern volume per cavern).
Where are the salt fields located in the UK?
The UK mainland is blessed with thick rock salt (halite) deposits suitable for large-scale cavern construction in three primary geological regions.
These areas are strategically important because they coincide with major industrial decarbonisation and hydrogen demand clusters, namely:
- The South & South West
Dorset contains the South’s only regionally extensive and thick Triassic salt deposit capable of providing the necessary energy storage to facilitate decarbonisation, H2P and pipeline support in the South of England. - The North West (Cheshire & West Lancashire)
Contains an age equivalent Triassic salt deposit within the Cheshire Basin which is already being utilised to store natural gas and can support the storage needs of the Hynet cluster. - The North East (East Yorkshire & Teeside)
Contains the eastern most extension of the Permian Zechstein salt deposit which extends eastwards across the North Sea and further into Northern Europe. It is ideally situated to support the East Coast Cluster.
By harnessing the stability of salt geology, the UK can confidently build the backbone of a resilient, Net Zero energy system.
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Salt is naturally impermeable (does not let gas pass through) and self-sealing under pressure. This makes salt caverns the safest, most secure, and most effective geological option for storing vast quantities of compressed hydrogen gas over long periods.
Geological storage facilities are inherently capital-intensive, requiring substantial initial investment (CAPEX) due to the complexity of subsurface development. Even relatively small salt cavern sites, designed for high-pressure storage of substances like hydrogen, are likely to have capital costs in excess of £100 million, with larger multi-cavern sites costing several times that amount. Projects utilising vast, low-pressure formations, such as depleted gas fields or deep aquifers, which offer significantly larger storage volumes, can see their total capital expenditure surpass £1 billion.
East Coast of Yorkshire / Teesside & Humber Regions is one of the most significant areas, with active salt cavern sites currently used for storing natural gas and ethylene. The region around Portland and South Dorset is a major focus for developing new salt cavern facilities specifically for hydrogen energy storage. This development is crucial for supporting the nearby Solent Cluster and creating the necessary energy buffer for the entire Southern England grid.
The locations are determined entirely by geology, not population or demand. The salt deposits must be thick enough to allow for the creation of a cavern hundreds of meters high. Plus, they must be deep enough to withstand the high pressures needed to compress and store large volumes of gas securely. The impermeable nature of the salt in these specific areas ensures the gas is safely contained indefinitely.
The creation and operation of salt caverns for storage is considered highly safe. The process, known as solution mining, is a mature, low-risk technology that has been successfully used globally for decades, backed by rigorous regulatory oversight and decades of operational data. Crucially, the process does not rely on high-pressure fluid injections to fracture rock layers like fracking, but instead, it involves the controlled, monitored dissolution of soluble salt rock to create secure, naturally self-sealing storage chambers. This established geological method offers a safe and resilient solution for the UK's long-term hydrogen energy security needs.