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Storing hydrogen – HyCAVmobil research project

In Rüdersdorf near Berlin, EWE is building an underground storage cavern in the salt rock. For the first time, 100% pure hydrogen will be stored underground – a first in Europe. EWE wants to explore how climate-friendly energy sources can be integrated into regional energy supply systems.

Storage is at the core of the hydrogen economy

It is technically possible to store hydrogen in gaseous form for a long time. This is its great advantage over electricity from wind or solar power, from which it can be obtained. The HyCAVmobil project will research how this might work.

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 for the success of the energy revolution. We can only achieve the UN’s and the European Union’s climate goals with hydrogen technology.

Construction site 1,000 metres underground

EWE will create a test cavern for the storage and relocation of hydrogen in Rüdersdorf. EWE has already built natural gas caverns on the site. Caverns are giant hollows in underground salt domes, where gases such as natural gas can be safely stored.

The building of the test cavern will begin in February 2021, when 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.

1,000 metres below the earth’s surface: here in the salt rock is where the test cavern will be built.© EWE / C3 Visual Lab 1,000 metres below the earth’s surface: here in the salt rock is where the test cavern will be built.

Capacity: 1,000 tankfuls

The cavern will have a capacity of 500 cubic metres. Up to six tonnes of hydrogen can be stored there once it has been prepared. For comparison: These six tonnes could fill up the tanks of 1,000 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 expected in the second half of 2022

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 for the use of hydrogen in mobility, with the focus 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.

After research comes application

If everything goes as planned, EWE will expand the generation, storage and potential uses of hydrogen in the mobility sector. At some point, hydrogen storage will be as normal as the storage of natural gas, which has been well-established for decades.

Hydrogen storage in Rüdersdorf – questions and answers about the project

How do you build a cavern underground?

Geological conditions deep in the earth under Rüdersdorf are optimal for building caverns because 150 million years ago, there was a sea here. Today, what remains of it is a layer of salt rock that begins at 600 metres below the surface and continues down to 2,500 metres.

A hole that leads down to the salt rock has already been bored. A pipe will be pushed into this hole and cemented in place. This is slightly wider than a ring binder and extends down to where the test cavern will be built, at a depth of 1,000 metres.

Water is pumped into the hole through the pipe. The water dissolves the salt and a dome 500 cubic metres in size and filled with salt water – “sole” – is formed. This is the size of a swimming pool that is 25 metres long, 10 metres wide and 2 metres deep. This makes 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. There, 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. It will continue to operate – for example, for expansion measures such as this.

What happens on the surface at the cavern facility?

The overground facility above the bore hole and the storage cavern pumps hydrogen into and out of the cavern.

It has pipes and fittings, which are like valves to open and shut the pipes. They function like a tap in a bathroom.

Compressors inject the hydrogen into the storage facility (comparable to an air pump increasing the pressure in a ball) and increase 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 tanks of trucks, buses and other vehicles.

Who is involved in the project?

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.

To determine the quality of the hydrogen (for example, the degree of purity and moisture components), its quality is measured comprehensively prior to injection into the cavern storage facility and after its offtake from the cavern.

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