EWE Gasspeicher GmbH has completed a key step in the conversion of a natural gas cavern at its Huntorf site (Wesermarsch district, Lower Saxony). The borehole, which has been technically modified for future hydrogen storage, has passed the tightness test. Testing was first carried out with nitrogen and subsequently with hydrogen. According to the company, this fulfils a key prerequisite for converting the storage facility. From 2028, the cavern is to hold around 16 million standard cubic metres of hydrogen, equivalent to roughly 1,440 tonnes. Injection and withdrawal capacity is set to total 35,000 standard cubic metres per hour.
"With the successful proof of tightness, we have reached another important milestone. In Huntorf, we are showing how existing energy infrastructure can be developed further for the climate-neutral energy supply of tomorrow," says Peter Schmidt, Managing Director of EWE Gasspeicher GmbH.
New cement and additional sealing element
Because of the small size of hydrogen molecules, sealing the borehole against the surrounding rock places particularly high demands on the materials used. EWE has therefore equipped the existing borehole with a new, cemented casing string. A further developed cement and an additional sealing element were used.
"We first checked the tightness with nitrogen and then also successfully confirmed it with hydrogen. All measured values are within the specified test criteria. We also did not detect any unusual pressure changes in the monitored areas," explains project manager Hayo Seeba.
For the conversion, EWE is drawing on findings from the HyCAVmobil pilot project, which was completed at the end of 2024. Together with the German Aerospace Center (DLR), the company built a 500-cubic-metre test cavern at the Rüdersdorf site near Berlin and demonstrated underground hydrogen storage there over several operating cycles.
Compressors and drying unit in preparation
From mid-November onwards, EWE plans to carry out further work on the borehole. This will include installing the pipe system for subsequent injection and withdrawal of hydrogen as well as additional safety equipment. In parallel, foundations, cable routes, drainage systems and operating buildings are being constructed on the storage site.
EWE has ordered two hydrogen compressors from Neuman & Esser. The company has commissioned the industrial service provider Bilfinger to handle the engineering, installation and commissioning of a drying unit. The unit removes moisture from the hydrogen withdrawn from the cavern before it is fed back into the grid. According to the company, Bilfinger's H2Dry technology will be used on a commercial scale for the first time.
Connection to hydrogen core grid by 2028
Alongside the storage conversion, EWE group companies GTG Nord and EWE Netz are working on connecting the facility to the hydrogen core grid. The link is part of the H2Coastlink 2 pipeline project. The connection between Huntorf and Sandkrug is around 34 kilometres long. Of this, approximately 28 kilometres of existing natural gas pipelines will be converted and six kilometres of new hydrogen pipeline will be built. According to EWE, the line is scheduled to be operational by the end of 2027.
A further pipeline, H2Coastlink 1, will create a new 24-kilometre hydrogen line between Emden and Leer. It is intended to transport hydrogen produced in Emden into the supra-regional grid.
Part of Clean Hydrogen Coastline
The storage conversion is part of EWE's "Clean Hydrogen Coastline" project. This also includes a 320-megawatt electrolysis plant currently under construction in Emden. The project is funded under the European IPCEI programme (Important Project of Common European Interest) by the German federal government and the state of Lower Saxony.
Looking ahead to the broader hydrogen ramp-up, Schmidt calls for reliable framework conditions: "Investments in further hydrogen storage facilities must be economically viable and plannable. At the same time, production, grid expansion, storage and demand must go hand in hand. Only in this way can a high-performance hydrogen economy develop."
