The cave is huge, and Uniper wants to carry out one of its biggest technical tasks in it. This is where the energy company will store green hydrogen as a test in the foreseeable future. This Monday, the company, which is currently almost entirely state-owned, presented an underground pilot plant in an East Frisian salt dome. “With a volume of around 500,000 standard cubic meters of green hydrogen, this storage facility will be one of the first of its kind,” said Uniper CEO Michael Lewis on Monday in front of press representatives and Lower Saxony’s Environment Minister Olaf Lies (SPD). He spoke of “real pioneering work”. Although the project is only a test, it could be crucial for the energy transition, the sore point of which is the lack of deposits. During so-called dark lulls, for example, stored hydrogen could be converted back into electricity. Industry also urgently needs the green molecules. “Hydrogen storage should fulfill several important functions in the future energy system,” says Jan Hendrik Kopp, who works intensively with the gas at the Energy Economics Institute (EWI) in Cologne. “Firstly, they should balance supply and demand. Secondly, they can be used to make other capacities in the energy system more efficient, for example pipelines or import terminals. And thirdly, they help to reliably supply industry and power plants with hydrogen, for example.”Two-year test Uniper would now like to use an existing borehole in Krummhörn, Lower Saxony, for two years to examine under real conditions how the technical equipment and material are used Cope with hydrogen. This is supposed to happen in a so-called salt cavern, which is a formation made of salt stone that the company has converted into a kind of cave so that it can be filled with hydrogen and stored in it. Many questions are still unanswered, as Lewis said in his opening speech. For example, the question of what quality the stored hydrogen will have, but also questions about thermodynamics and mountain mechanics. The planned hydrogen core network will pass close to the cavern and enable the gas to be transported further. Uniper is investing a low double-digit million amount in the project, and the Lower Saxony Ministry of the Environment is funding the storage facility with around 2.4 million euros. Michal Lewis announced at the opening of the facility that it will undergo the crucial leak test in around a month. The cavern will be filled for the first time next year. It is expected that a pending approval will have been granted by then, says Uniper. According to the technical manager of the Uniper gas storage division, Frank Holschumacher, green hydrogen from various manufacturers will be used for filling, which will be delivered by tanker trucks. Next year, Uniper also wants to operate a demonstration plant with stored hydrogen and test various injection and withdrawal cycles. Uniper sees itself as a pioneer. If hydrogen storage becomes economically worthwhile after the two-year test phase, Uniper wants to expand the cavern for commercial use. According to Holschumacher, the so-called brining is expected to take three to five years. The usable amount would then be 250 gigawatt hours of hydrogen. He expects costs of between 350 million and 500 million euros to fill this new cavern. Uniper is already Germany’s largest natural gas storage operator and sees itself as one of the pioneering companies in building a European hydrogen economy. The energy company is planning large projects in other countries – but also in Germany, not far from Krummhörn. In Wilhelmshaven, for example, Uniper is building a large electrolyzer to produce hydrogen with a capacity of one gigawatt. It is scheduled to be completed at the end of this decade. Uniper also wants to build a terminal in Wilhelmshaven to receive imported green ammonia. Green ammonia can be converted into green hydrogen. In general, the majority of hydrogen will come from abroad in the coming years. Exactly how much storage will be needed in the future is not yet entirely clear in research. The Federal Ministry of Economics shows a demand for Europe of 7 to 13 terawatt hours in 2030 and 243 to 412 terawatt hours in 2045 – so the ranges are still very large. For comparison: 286 terawatt hours of natural gas can be stored in Germany today. However, only a small proportion of the natural gas caverns have the potential to be converted to store hydrogen. Therefore, many underground storage facilities will have to be rebuilt in the coming years. Basically, this works in caverns – like at Uniper in East Frisia – or in porous rock. Uniper has been testing the latter in Bierwang, Bavaria, for several months. “While there is still a need for further research into pore storage, research shows that salt caverns are suitable for storing hydrogen,” says Kopp. In cavern storage, the huge cavities in which the gas is subsequently stored are artificially flushed into salt domes. The geological potential for this is particularly great in northern and central Germany; more than 40 percent of the potential deposits in Europe are located here. The energy supplier EWE has also been testing the operation of such a cavern storage facility in Rüdersdorf near Berlin since 2019. RWE is also experimenting with converting a cavern in Gronau-Epe, Westphalia, which is scheduled to go into operation in 2026. “Salt caverns have the advantage that they are impermeable to gas, so the hydrogen cannot escape into other rock layers,” says Kopp. “The salt structure does not pose an increased risk of hydrogen contamination. Caverns are also suitable for the rapid storage and removal of hydrogen.” However, one difficulty could be the disposal of the brine that is created during the construction of the cavern.More on the topicThe Federal Ministry of Economics wants to have presented a strategy for dealing with hydrogen storage by the end of the year. The industry hopes that this will provide information on how planning and approval procedures can be accelerated in the future. The storage association Ines estimates that it currently takes more than six years to convert a gas storage facility to hydrogen, and even ten years to build a new one.
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