Underground storage: Germany's hydrogen backbone

This may sound like a silver bullet, but there's a catch: hydrogen-based energy systems hydrogen require a massive amount of energy themselves. According to calculations made by the Fraunhofer Institute, to use green hydrogen to become climate-neutral by 2050, Germany would need four times the amount of renewable energy produced today. In practical terms, that would mean a wind farm the size of the Netherlands. That's simply impossible, so instead, the country would have to rely on imported energy, for example, from Africa. 

Currently, Germany's annual demand for hydrogen is up to 60 terawatt-hours (TWh). This is produced by burning fossil fuels. The Fraunhofer Institute expects this figure to hit 700 TWh by 2050 – ideally produced using entirely carbon-neutral methods. Germany would only be able to produce a quarter of this by electrolysis; the rest would have to be imported. 

Apart from producing and importing energy, one crucial factor in creating a hydrogen economy is technical infrastructure. A comprehensive network of pipelines makes this more feasible than extending the traditional power lines. Gas pipelines can efficiently pump captured hydrogen around Germany – from offshore wind farms in the North Sea to Bavaria in the foothills of the Alps. 

The alternative is to bulk up the existing electricity grid – a proposal that has been fiercely resisted by many communities not wanting their landscape blighted. Policymakers' hopes revolve around existing gas grids, which already crisscross the country like a spiderweb. If those pipes can form part of a hydrogen network, an essential element of the infrastructure would already be in place. The second piece in the puzzle would be enough hydrogen storage capacity. 

“The energy transition will require large-scale storage facilities, from 2030 at the latest, which is by when the supply and demand parts of the hydrogen equation will have massively increased,” explains Boris Richter, Managing Director at STORAG ETZEL.

Richter is keen to point out the unseen treasure deep below the ground in Etzel. With the deep-water port in Wilhelmshaven only 20km away, the tiny village is already one of the most crucial energy hubs in northwestern Europe, thanks to a unique layer of salt several hundred metres below the surface. Fifty years ago, huge caverns were leeched out of the salt with seawater to allow leading gas companies and international oil traders to store natural gas and crude oil. The location is also ideal for hydrogen storage.

If Richter's plans come to fruition, the Etzel caverns could play a pivotal role in Germany's green energy transition. As part of a research project called H2 CAST Etzel, a consortium of businesses spearheaded by STORAG ETZEL and EKB Storage intends to demonstrate how existing caverns and above-ground facilities can store and distribute hydrogen. 

Due to the sheer scale of the undertaking, this initiative was divided into two sub-projects: H2CAST I and H2CAST II. The first has already been approved and received €8 million in state funding. In addition to state funds, the federal government is expected to support the second sub-project. Funding applications are drafted for submission to the Federal Ministry of Economic Affairs and Climate Action (BMWK). 

"Hydrogen production is more volatile because it achieves lower calorific values than natural gas, and the storage requirements for hydrogen will be four to six times higher," predicts Richter. Germany will need high storage capacity – 75 terawatt-hours (TWh), of which the Etzel caverns can provide 22 TWh. 

The consortium has deliberately chosen to use two existing caverns for the research project for technical reasons. Both already came into contact with hydrocarbons when they were flushed out with brine water. 

If the experts meet the strict purity requirements for the two caverns (with a combined capacity of 350,000 cubic metres of hydrogen), this will mark an important milestone in demonstrating that existing caverns can be used for future energy storage. This would also extend the life cycle of the caverns under Etzel, offering corresponding benefits to the (German) economy. 

One advantage of the large-scale storage facilities in Etzel is that they are also connected to the trans-regional grid of gas pipelines in Germany. There are also plans to link up the pipelines with the energy hub in Wilhelmshaven. Once it is proven that the gas grid is suitable for transporting H2, imported hydrogen could be pumped into the caverns for subsequent distribution throughout the country. 

"Having all three sides of the triangle in place – imports, pipelines and storage – would give us a backbone for hydrogen supplies in Germany," explains Richter. Furthermore, where pipelines already exist, access rights also apply, and there is still potential to expand the existing infrastructure.

The H2 CAST Etzel project runs until 2025, after which a further two years of research are planned. The consortium wants to be as open and transparent as possible towards the general public to ensure the project succeeds. Resistance in Germany to wind energy, much of which stemmed from poor communication, already serves as a cautionary reminder. This was one reason why the test caverns were set up as demonstration facilities, so that any concerns or fears regarding hydrogen storage could be openly addressed. 

The small Lower Saxony town of Etzel is well on its way to becoming one of the most important energy hubs in Europe by 2043. No wonder there's such strong interest from other countries. In addition, H2 CAST Etzel is set to become the focal point for further international research projects.