Hydrogen as a beacon of hope: In the climate-neutral future, the lightest element should play a key role. Produced CO2-free, it can generate electricity in new gas-fired power plants when there is a lack of wind and sunlight. In steel works, it is supposed to remove the oxygen from the iron ore instead of coal.

The main waste product is H2O, i.e. water. Large amounts of hydrogen are needed. So that there is always enough there, it must be temporarily stored. But where? Are the existing natural gas storage facilities, of which Germany has quite a lot, suitable for this?

Yes, but probably not all. This is the conclusion of a study published by energy industry associations last summer. Accordingly, cavern storage facilities with their large cavities are “particularly well suited”, explained Ingo Forstner, Head of Storage & Geothermal Energy at the Federal Association for Natural Gas, Oil and Geoenergy (BVEG). With the other type of storage, the pore storage, the suitability must be checked on a case-by-case basis. The study assumes that only four out of sixteen pore storage facilities can be used for hydrogen storage.

Association: 23 pilot projects known

Hydrogen storage is a major issue for the operators of natural gas storage facilities. The industry association INES is aware of 23 pilot projects: “They are mostly in an early project stage without a final investment decision and have significantly smaller volumes than is usual for commercial gas storage,” says Sebastian Bleschke, Managing Director of the Energy Storage Initiative (Ines).

One of the most advanced pilot projects is being developed in Rüdersdorf near Berlin in Brandenburg under the name HyCAVmobil. The operator is the energy company EWE. On a site where EWE already has two natural gas storage facilities, a cavity the size of a house, around 500 cubic meters in size, was flushed out in an underground salt dome at a depth of 1,000 meters for three months until the beginning of March. Technology is now being installed above ground. From late summer, EWE wants to fill in the first hydrogen and start the test operation.

One focus is on the quality of the hydrogen after it has been withdrawn: According to EWE, almost 100 percent purity is particularly important for applications in the mobility sector. EWE wants to transfer the findings from the operation of the small cavern to large caverns with 1000 times the volume.

Germany’s largest storage operator Uniper is also working on a pilot plant. It is to be built in Krummhörn in Lower Saxony and will be 1000 cubic meters in size. According to Uniper, the approval process is still ongoing there. «The construction of this cavern is planned for the course of this year. We want to start filling with hydrogen for the first time at the end of the year/beginning of next year,” said Matthias Schnadwinkel, project manager at Uniper Energy Storage, at an event of the industry association Zukunft Gas. Uniper also wants to later transfer its experience to large storage systems.

Use large caverns commercially right from the start

At the Bierwang storage site in Unterreit, Bavaria, Uniper wants to work with several companies to examine the suitability of pore storage more closely. Starting in June, different methane-hydrogen gas mixtures are to be stored in a former natural gas reservoir in three phases and withdrawn again after a certain period of time. HyStorage is the name of the research project.

The energy company RWE wants to use large caverns commercially right from the start. To this end, an existing natural gas storage cavern in Gronau-Epe in North Rhine-Westphalia and a cavern that has already been mined are to be made fit for hydrogen by the end of 2026. The storage volume that can be used by customers is said to be 28 million cubic meters of hydrogen. Commercial operation will not be possible before 2027, says RWE spokesman Olaf Winter. In a second construction phase, the capacity could then be further increased later.

“The development of our hydrogen storage facility in Gronau-Epe is just a first step that must be followed by many more,” says Sopna Sury, RWE hydrogen board member, when asked by dpa. “A round-the-clock supply of industrial customers with green hydrogen is only possible with sufficiently large storage capacities.”

More than doubling of storage potential necessary

But what does “sufficiently large” mean? The storage association Ines refers to long-term scenarios of the Federal Ministry of Economics. They assume that hydrogen storage with a capacity of 72-74 terawatt hours will be needed to implement the energy transition in the target year 2045. “Our studies have shown that a hydrogen storage capacity of 32 terawatt hours can be provided from the current stock of gas storage facilities,” says Ines Managing Director Bleschke. “In order to produce this capacity, the conversion of a large part of today’s gas storage facilities would be necessary.”

But according to Bleschke, that is far from enough: In order to implement the energy transition in accordance with the long-term scenarios, the storage potential that can be used today for hydrogen would need to be more than doubled. Bleschke calls this an “infrastructure challenge” and emphasizes: “In Germany, not a single commercial hydrogen storage facility is currently in operation.” Accordingly, no conclusive experience with planning, approval and implementation processes existed. In recent years, storage capacities have tended to be reduced rather than built up. “For the development of extensive new projects in the field of hydrogen, the entire value chain will have to be largely rebuilt.”