H2 Underground Storage
Salt Caverns
Researchers in Germany have identified salt caverns as a feasible and flexible solution for hydrogen storage. They also revealed that Europe has the potential to inject hydrogen in bedded salt deposits and salt domes, with a total storage capacity of 84.8 PWh.
The researchers said the storage of hydrogen in salt caverns is similar to that of natural gas, as they have similar needs for cavity design, construction and operation. They differ only in the materials in access wells, cavern heads, and transmission infrastructure.
“Natural gas storage in underground cavities has been practiced for decades,” the researchers said. “The knowledge gained by this can be easily transferred to the case of hydrogen storage.”
Hydrogen injection.. Compared to depleted oil and gas reservoirs, salt caverns offer the advantage of lower cushion gas requirements to avoid rock breakage, as well as the large sealing capacity of rock salt and the inert nature of salt structures. Salt caverns are also a more flexible solution because they can ensure high hydrogen injection rates and withdrawal cycles.
In order to ensure safe storage operations, the minimum thickness of the hanging wall in a salt cavern should be 75% of the cavern diameter, while for the foot wall this percentage is reduced to 20%. “A minimum salt thickness of 200 meters and a range of minimum to maximum depth of 500 meters to 2,000 meters were selected as being suitable for salt cavern construction,” the scientists explained.
The energy density of salt caverns can vary between 214 kWh and 458 kWh per cubic meter. By multiplying the energy density by the cavern volume, the researchers found that the capacity of salt caverns in domal salt structures is the highest at 210 GWh, while that of caverns located in bedded salt deposit ranges from 65 GWh to 160 GWh. Deeper salt structures can increase the amount of storage capacity, they said.
Alvera, The Hydrogen Revolution
The petrochemical industry in Texas need[ed] a continuous supply of hydrogen to its refineries and their solution has been to store it in caverns. The Chevron Phillips Clemens Terminal in Texas, for example, has stored hydrogen in a disused salt cavern since the 1980s. Meanwhile, in the UK, there are three salt caverns safely storing hydrogen... Underground gas storage involves compressing and injecting the gas into a cavity of some sort. Gas is released under pressure when needed. For natural gas, underground storage in disused fields is remarkably cheap, at something like $10/MWh even if you only use it once a year...
Pipe Storage
Alvera, The Hydrogen Revolution
[Another] intriguing option is pipe storage. We already know that pipelines can hold hydrogen gas at pressure, but what’s to stop you from laying down a series of cheap, standardised pipelines with sealed ends and using them as storage? A kilometre of pipeline (of the same diameter and pressure that you’d use for natural gas) could hold approximately 12 tonnes of hydrogen.
Lined Rock Cavern
Alvera, The Hydrogen Revolution
Another clever idea is to line a rock cavern with a thin layer of steel. This has been done in Skallen, Sweden, for use with natural gas. It allows you to ramp up the storage pressure to 200 atmospheres, because the rock formation carries the main structural load, and would be cheaper and easier than a massive tank.
Construction of the 100-cubic-meter.. rock cavern storage facility 30 meters below ground is done by Vattenfall AB in collaboration with Swedish steel company SSAB AB..
The cavern is being built via the so-called lined rock cavern (LRC) approach, which involves covering the walls of the cavern with a selected matter. The technology for storing gas in a lined rock cavern (LRC) is well proven and has been used in southern Sweden for about 20 years for storing natural gas. However, the technology is now taking another step forward as it’s being developed for the first time with hydrogen gas on a large pilot scale... The finished plant will contain hydrogen gas pressurized up to 250 bar