(Strausberg) – The Oldenburg energy supplier EWE AG reports construction progress on its planned hydrogen storage facility in Rüdersdorf near Berlin. The company has now installed and cemented 160 steel pipes to a depth of 1.000 meters. In a cavern in the salt dome, EWE wants to “test the safe storage of 100 percent hydrogen” (we reported). Findings from the project could be transferable to large cavern storage facilities.
Double pipe tour for large-scale storage
However, before large-scale hydrogen storage is possible, EWE wants to use this pilot project called “HyCAVmobil” to demonstrate that the gas can be safely stored in cavities underground. A pipe-in-pipe system was installed for this purpose. “We put a small and a large steel pipe together to form a double pipe tour,” describes EWE project manager Hayo Seeba. In order to be able to use the inner tube for material testing, a flexible system was developed together with its service provider UGS from Mittenwalde. This is used to be able to remove the inner tube again without destroying the material. The tests are important for future long-term applications. In the case of large-scale hydrogen storage, it must be proven that hydrogen is compatible with the materials used.
Rock salt rinse in autumn
In the next few months, EWE will prepare to create the underground cavity. “To clean out the test cavern, we first set up the surface technology,” says Seeba. The rock salt should be rinsed out from autumn onwards. The layer beneath the storage area begins at around 600 meters and extends up to 3.200 meters deep. The salt comes from a sea that existed in Rüdersdorf 150 million years ago. 
The cavern is designed to have a volume of 500 cubic meters – “a single-family home can fit in it,” says the project manager. The cavity is washed out with water from our own pond and from the mill river flowing past. 4.000 cubic meters of fresh water will be used for brining over a period of three months. “We pump the salt water created during the brining process via an existing underground pipeline to our sinking station in Heckelberg.” There, the brine is piped into a sandstone formation 1.000 meters deep, which already naturally contains salt water.
Natural gas storage since 2007
In Rüdersdorf, EWE has built two of its 37 caverns in salt rock and has been storing natural gas in the cavities since 2007. The drilling for another cavern was already in place. EWE is now using this to build the hydrogen test cavern. “As part of the research project, we are particularly hoping to find out what level of purity the hydrogen from the cavern has after it has been stored there for a while,” says EWE hydrogen expert Paul Schneider. This criterion is particularly important for hydrogen use in the mobility sector.
The BMVI is funding the project with six million euros
In the project, EWE is cooperating with the Institute for Networked Energy Systems of the German Aerospace Center (DLR), which will, among other things, examine the quality of the hydrogen after it is removed from the cavern and the materials used. The investment volume amounts to around ten million euros. Of this, six million euros come from the Federal Ministry of Transport and Digital Infrastructure (BMVI) from the pot of the National Innovation Program for Hydrogen and Fuel Cell Technology.
The findings from the research cavern will be used in later projects with 1.000 times the volume for large-scale hydrogen storage.
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EWE installed and cemented 160 steel pipes to a depth of 1.000 meters / © EWE, Andreas Prinz
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Pipe-in-pipe system / © EWE, Andreas Prinz
