“One year later – one year further” - Underground storage of hydrogen

In the future, hydrogen will play an immensely important role in providing short and long-term flexibility to volatile renewable energies in an increasingly decarbonized energy system. However, it is important to keep an eye on the technical challenges throughout the entire system. In 2023, the German Scientific Society for Sustainable Energy Sources, Mobility and Carbon Cycles (DGMK) and the German Association for Natural Gas, Petroleum and Geoenergy (BVEG) held their first project day on the topic. It was relaunched last December. Dr. Gesa Netzeband, Managing Director of the DGMK, introduced the project day by saying that this would have been obvious “after the success and the great interest”.

This year, the focus was once again on current technical research and application projects. Ingo Forstner, Head of Storage & Geothermal Energy at BVEG, who moderated the project day, referred to the development process that the industry has undergone. “One year later, one year further on,” said Forstner, the presentations showed not only what is being done, but also what project results and know-how can be shared. “It’s crunch time,” said Forstner, assessing the progress. What had initially been vague ideas had now, among other things, become projects that had ‘been confirmed by the Brussels desk.’ New projects had been added. Forstner pointed out the fundamental importance of such projects: ”If we want an energy transition, we need hydrogen storage.”

The hydrogen core network can come
On October 22, the Federal Network Agency approved the application for a hydrogen core network submitted by the transmission system operators. This means that the implementation of the H2 core network, with a length of 9,040 kilometers, can begin with legal certainty. The core network is to connect central hydrogen sites in all federal states by 2032 – from production centers and import points to storage facilities and future customers in industry and power plants.
Dr. Janina Zittel from the Zuse Institute in Berlin explained what the transition from natural gas to hydrogen also means in terms of network control. Two-thirds of the core hydrogen network is already backed by specific projects, and the transport network is to be phased in by 2032, according to Zittel. The German gas transmission network has a length of around 40,000 kilometers, so the German hydrogen core network will have a significantly lower capacity than the current gas transmission network.
The experts at the Zuse Institute have carried out calculations based on specific transport data. They took 333 natural gas transport scenarios as a basis, i.e. for almost every day, based on measured flows and pressures in a section of the German transmission network. They modeled how the network would have to be controlled in the future to meet these transport requirements, assuming that hydrogen would have to be transported instead of natural gas.

More control interventions required
In view of the specific characteristics of hydrogen (including a lower energy density by volume compared to gas and higher flow rates), the calculations showed, according to Janina Zittel, that hydrogen compression will require significantly more space unless new compressor technology is available. In addition, the network’s lower storage capacity would place higher demands on the balancing of transport orders, and more control interventions would be necessary. And a greater compressor output would be needed: to transport the same amount of energy, about four times the amount of energy would have to be used for compression.

The role of hydrogen storage for the energy system
Prof. Dr. Mario Ragwitz from the Fraunhofer IEG explained the role that hydrogen storage could play in the energy system in the future. One of his core messages was that a system dominated by green hydrogen would require a storage capacity of 13 to 29 percent of annual consumption. With an expected hydrogen demand of 90 to 130 TWh in 2030, the cumulative storage capacity in the pipeline is less than 1 TWh. The functioning of hydrogen networks thus depends on the storage facilities. In times of scarce renewable generation, the entire demand, including for hydrogen power plants, would have to be covered from storage. In addition to the technological component, Ragwitz also pointed to the economic and legal framework conditions for hydrogen storage, which are uncertain and impair the conversion. While natural gas in Europe worked on a market basis, there is still no certainty about the market model for H2 storage.

Demonstration projects and practical examples
Gasuni, RWE and Uniper provided specific insights into various hydrogen storage projects. According to Eddy Kuperus, Business Development Manager at the Dutch company, transmission system operator Gasuni tested whether hydrogen can be stored safely and reliably in salt caverns in the demonstration project (A8) in Zuidwending, the Netherlands, from 2021 to 2023. The effects of hydrogen on equipment, material, cement and salt wall were investigated. According to Kuperus, the conclusion of the project, which ended last year, was positive. There were no signs of H2 leakage or negative effects on the materials used, and the storage of hydrogen went without incident. Gasunie is taking this a step further with the HyStock project. In this project, which is also located in Zuidwending and has a connection to the national gas transmission network, Gasuni is using four salt caverns for hydrogen storage. Preparations for commercial operation are underway and the company plans to start in 2029.

H2 storage in Gronau-Epe to be ready in 2027
Sebastian Cichowski, Operations Manager at RWE Gas Storage West GmbH, gave a practical example of future energy storage at RWE. An underground hydrogen storage facility is being built in Gronau-Epe in North Rhine-Westphalia. The framework in which the storage project is being realized is the Get H2 joint project, which represents the complete value chain. The hydrogen to be stored is produced from North Sea offshore electricity in electrolysers in Lingen.
Construction work at the storage facility in Epe is in full swing, with the first compressor being delivered on December 4. The storage facility is to be operated commercially from 2027; capacities are already being marketed.

Uniper aims to start commercial operation in 2030
Uniper’s H2 storage plans are also progressing. Maxim Stein-Kholov, Head of Subsurface Facilities Storage at Uniper, explained that the company has been investigating gas storage facilities for their suitability for years. The company aims to start commercial operation in 2030. Uniper has set itself the goal of providing a quarter of the predicted hydrogen storage demand in 2030, which is expected to be 2 TWh. In northern Germany, Uniper is testing the operation of a hydrogen storage facility in the salt cavern storage facility in the HPC Krumm-hörn project, which has not been in commercial use since 2017. The storage facility is conveniently located at the hub of the planned hydrogen core network, and the first hydrogen is currently being transported underground.
In the Bavarian town of Bierwang, Uniper is working with partners Open Grid Europe, RAG Austria, SEFE and NAFTA on the HyStorage research project to test the integrity of pore storage facilities with regard to hydrogen storage. HyStorage is based on a multi-stage concept that will investigate the effects of different admixture ratios, with the hydrogen content to be gradually increased. In three project phases, different natural gas/hydrogen gas mixtures with 5 percent, 10 percent and 25 percent hydrogen content in the natural gas will be injected into the former natural gas storage site and then withdrawn after a three-month holding period. The second project phase is currently underway, with tests running with a hydrogen content of 10 percent. According to Stein-Kholov, the fact that the tests at the cavern storage facilities could be seamlessly transferred to commercial use is a fundamentally optimistic factor.

Sharing knowledge
The information situation is becoming denser, was the conclusion of storage expert Ingo Forstner from BVEG. The presentations by Remco Groenenberg, Udo Lubenau, Christian Belting-Clar and Daniel Bick also contributed to this at the DGMK and BVEG project day. Remco Groenenberg, Scientific Lead at the Dutch science organization TNO, provided information about TCP Task 42 of the International Energy Agency (IEA). The TCP Task 42 has set itself the task of arriving at a comprehensive assessment of the general technical and economic feasibility of underground hydrogen storage. The results of TCP Task 42 are expected to be available in the first quarter of 2025, when a final report will be published.
Udo Lubenau, authorized signatory of the DBI Group, reported on the European project MefHySto, which dealt with metrological and thermodynamic issues in the large-scale storage of hydrogen in underground gas storage facilities.
Christian Belting-Clar, Senior FEED Manager Decarbonization & Innovation at Siemens Energy, presented in his lecture “Hydrogen and the challenges of the energy mix transformation using current examples” which solutions from industry are already available for problems regarding compression, pressure losses and performance with hydrogen.
Dr. Daniel Bick, a specialist in hydrogen technology at transmission system operator OGE, pointed out the requirements that have to be met by components and the entire pipeline system, which has to be H2-ready. This is a broad topic that, in addition to complex individual technical aspects such as material properties, also takes into account questions of system suitability such as gas qualities or flexibilities.

No showstoppers
The most important projects have been completed or are in progress, said Forstner in his closing presentation. There are now nine projects involving hydrogen caverns in Germany. He concluded that a great deal of research has already been carried out for underground applications. However, there is still a long way to go. Nevertheless, no general showstoppers have been found to date with regard to the compatibility of materials for hydrogen storage.