This storage project makes EWE a pioneer in Europe. EWE is the first German company to build and test infrastructure that will be essential for the storage of renewable energies in the form of pure hydrogen and thus an essential component of a sustainable and climate-friendly energy supply system. We can only achieve the UN and European Union’s climate goals with hydrogen technology.
Construction site 1,000 metres underground
EWE has already built natural gas caverns on the site in Rüdersdorf. Caverns are giant hollows in underground salt domes, where gases such as natural gas can be safely stored.
Construction of the test cavern commenced in February 2021. The first step involves EWE erecting a drilling rig on top of the existing borehole. Then EWE will flush out the salt dome 1,000 metres underground with water to create the cavity.
The goal of HyCAVmobil is to see how storage and relocation affect the quality of the hydrogen.
Capacity equivalent to one single family house or 1,000 tankfuls
The cavern will have a capacity of 500 cubic metres, roughly equivalent to the volume of a single family house. Once completed, the cavern can store up to six tonnes of hydrogen, enough to fill the tanks of a thousand hydrogen-powered cars.
After a construction time of about a year, the cavern will be filled with hydrogen for the first time in spring 2022.
Premiere in the hydrogen economy – first underground storage of pure hydrogen
Following construction, a premiere will take place in the hydrogen economy: 100 per cent pure hydrogen will be stored in an underground cavern for the first time, in Rüdersdorf. The investment volume of the project is nearly ten million euros, four million of which are from EWE’s own funds. EWE and its project partner, the DLR Institute of Networked Energy Systems, are receiving the rest of the funds as a grant from the German Federal Ministry of Transport and Digital Infrastructure through the National Innovation Programme for Hydrogen and Fuel Cell Technology.
Findings can be applied to large-scale technical applications
EWE expects initial findings in the second half of 2022 regarding how storage affects the purity of the hydrogen and how the integration of hydrogen into the German energy supply system can succeed. The test in Rüdersdorf is designed to look at the use of hydrogen in mobility, focusing on how storage affects the quality of the hydrogen. Before being used in heavy-duty transport, it goes through a drying plant to remove moisture from storage.
The findings produced by the small research cavern should be easily transferable to caverns with a volume a thousand times larger. Our aim is to use caverns with a capacity of 500,000 cubic metres for large-scale hydrogen storage in the future.
From research to real-world application
If everything goes as planned, EWE intends to expand generation, storage and potential uses of hydrogen in the mobility sector. EWE’s 37 salt caverns represent 15 per cent of all German storage caverns that could be suitable for storing hydrogen in the future.
At some point, hydrogen storage will be as normal as the storage of natural gas, which has been well-established for decades.
Q&A on the HyCAVmobil research project
Geological conditions deep below Rüdersdorf are optimal for building caverns, because 150 million years ago there was a sea here and what remains of it today is a layer of salt rock between 600 and 2,500 metres under the surface.
In February 2021, EWE erected a drilling rig on an existing borehole that leads down to the salt rock.
A pipe, slightly wider than a ring binder, is pushed down through the borehole, down to where the test cavern will be created at a depth of 1,000 metres, and cemented into place.
Water is pumped underground through the pipe, dissolving the salt and forming a 500-cubic metre cavity filled with salt water (called a “sole”), about the size of a swimming pool 25 by 10 metres across and 2 metres deep. This would make the test cavern only around one thousandth of the size of the natural gas cavern most recently built on the Rüdersdorf site.
When the cavern is later filled with hydrogen, the salt water is removed and disposed of in a climate-friendly manner. A pipeline transports the sole to a brine operating station in Heckelberg, where it is piped into a natural underground salt-water reservoir.
EWE built this station in the late 1990s when the first cavern was built in Rüdersdorf and will continue to operate for expansion measures such as this.
The facility above the borehole, and the storage cavern, pumps hydrogen into and out of the cavern. It has pipes and fittings like valves that open and shut the pipes similar to a bathroom tap.
Compressors inject the hydrogen into the storage facility (comparable to an air pump increasing the pressure in a ball), increasing the pressure in the cavern.
When the hydrogen comes out of the cavern, it goes through a hydrogen drying plant. Since water was used in the construction of the cavern, the hydrogen, which in itself is dry, may contain residual moisture. This moisture must be removed before the hydrogen can be used in the fuel tanks of trucks, buses and other vehicles.
The quality of the hydrogen (for example how pure it is and how much moisture it contains) is measured carefully prior to injection into the cavern storage facility and after its offtake from the cavern.
The investment volume of the project is nearly ten million euros, four million of which are from EWE’s own funds. EWE and its project partner, the German Aerospace Center’s Institute of Networked Energy Systems, are receiving the rest of the funds as a grant from the German Federal Ministry of Transport and Digital Infrastructure through the National Innovation Programme for Hydrogen and Fuel Cell Technology.
Hydrogen Ambassador at EWE