Optimised design of above-ground facilities for cavern storage
Technology transfer
Optimised design of above-ground facilities for cavern storage
Results from DLR hydrogen analysis reduce investment requirements for future gas cavern of EWE GASSPEICHER GmbH at the Rüdersdorf site
Based on the results of several hydrogen (H2) analyses carried out by DLR, EWE GASSPEICHER GmbH can reduce the number of components required for gas purification at surface facilities of new gas caverns to be built and thus minimise investment costs. The Institute of Networked Energy Systems has carried out the analyses in close cooperation with the company on a gas cavern of EWE GASSPEICHER GmbH at the Rüdersdorf site in order to identify possible factors influencing the quality of hydrogen in salt cavern storage. In addition, the hydrogen quality was assessed for usage in fuel cell vehicles.
As part of the HyCAVmobil project, the Institute of Networked Energy Systems has developed test procedures to analyse materials for their suitability in relation to hydrogen and to evaluate them for use in hydrogen caverns.
In particular, moisture contained in the hydrogen after storage in the cavern represents a burden for hydrogen systems in fuel cell vehicles as well as for pipeline systems. The measurements have shown that the hydrogen still has a purity of 99.9 % after storage in the cavern and contains less than 0.01 % water (100 ppm). This value is relatively low, especially in comparison to the storage of natural gas from caverns, so that EWE GASSPEICHER GmbH can dispense with the installation of such a gas drying plant at the Rüdersdorf site. Even if the results of the analyses confirm the suitability of salt caverns for the storage of H2: To what extent the findings can be transferred to larger caverns or caverns already used for natural gas storage needs to be researched by further investigations.
Despite the good storage quality of the hydrogen, it is not sufficient for direct use in fuel cell mobility according to the high requirements of DIN 17124/ ISO 14687 (hydrogen as a fuel). Nitrogen in particular, which was used in the production process of the cavern, exceeds the required limit values in test operation. However, it is to be expected that this value will be reduced relatively quickly through dilution during further operation. Against this background, the knowledge gained about the hydrogen composition serves as a basis for further design of above-ground drying and cleaning facilities.
Material investigations in a high-pressure test reactor have also shown that hydrogen causes more corrosion on commonly used steel compared to natural gas. Newer developments of hydrogen-suitable "H2-ready steel", on the other hand, are more resistant to corrosion in a hydrogen atmosphere than the classic material. This leads to the conclusion that either optimised materials must be used in the future or shorter inspection and maintenance cycles must be planned.
"With these findings, we will be able to design new storage facilities in particular to meet future demand, which will reduce investment costs and operational expenditure," says Hayo Seeba, HyCAVmobil Project Manager at EWE GASSPEICHER GmbH. "Since the hydrogen measurements were taken during the entire injection and withdrawal cycles, this cavern can now be operated in pressure ranges in which the water content is particularly low during withdrawal, for example, based on the knowledge gained. This procedure reduces the costs for drying". According to Seeba, the collaboration with the DLR has created the basis for establishing a cavern-based hydrogen infrastructure. "These findings will also be incorporated into the design and operation of large-scale hydrogen storage facilities in the future, for example in our project at the gas storage site in Huntorf in the Wesermarsch region. We are converting a natural gas cavern there for the storage of hydrogen as part of the large-scale IPCEI project 'Clean Hydrogen Coastline'."
Although caverns have already been put into operation as hydrogen storage facilities in sporadic cases around the world, so far there was no knowledge available about the extent to which the high purity requirements from fuel cell mobility and other industrial sectors can be achieved when storing hydrogen in a salt cavern. Therefore, in addition to possible impurities from the salt cavern itself, also other materials, processes and systems along the entire hydrogen supply process – for example at refuelling stations and electrolysers or during high-pressure storage – were investigated in the HyCAVmobil project. Here, DLR has analysed the type of contamination that can be caused by the individual components. This behaviour was examined as an example in the relevant environmental parameters such as pressure and temperature.
Background to the topic
As part of the HyCAVmobil research project, a test cavern has been filled with hydrogen for the first time in Germany in order to analyse the quality of the hydrogen stored and withdrawn and to prove that hydrogen can be stored safely in underground cavern storage facilities. For the first time, the Institute of Networked Energy Systems has presented research results for the proof of quality, which are particularly important for use in mobility. The most important findings: Hydrogen storage in caverns is possible, and the H2 quality is good according to the results so far. This means that key requirements for mobility with hydrogen-based fuel cell vehicles are met, as impurities and moisture only need to be removed to a small extent before further transport to the filling station or cleaning can even be carried out on site at the filling station.
