German and Dutch companies move forward with joint project to store hydrogen in underground caverns

Europe’s energy transition has just reached a strategic milestone with the advancement of the H2 CAST pilot project, which brings together the companies Gasunie (from the Netherlands) and Storag Etzel (from Germany) in a mission to transform underground caverns into safe, large-scale reservoirs for renewable hydrogen. Located in Etzel, Lower Saxony, the project pioneers the conversion of two salt caverns to store around 90 tons of hydrogen – an initiative that strengthens the energy axis between the two countries and could shape the future of energy security on the continent.

Cavern storage: underground infrastructure for European green hydrogen

With high-level political and diplomatic support – including the presence of the Dutch ambassador to Germany and two ministers from the Lower Saxony government – ​​H2CAST has reached the second phase of the project, with the initial injection of hydrogen into the caverns and the preparation of the above-ground installation. Deliveries of the green gas produced by Plug Power in Werlte (just 90 km from the site) have already begun, marking the start of practical operations of the infrastructure. Hydrogen will be a key player in the decarbonization of European industry, and large-scale storage is essential to enable an efficient and resilient market. In this context, the two converted caverns, with a combined geometric volume of 300,000 cubic meters, represent a promising solution. The final plan envisages a capacity of up to 1 terawatt-hour (TWh), which will give the regional energy system greater flexibility and stability, especially in view of the intermittency of renewable sources such as wind and solar. Etzel stands out not only for its suitable geology, but also for its strategic location: it is integrated into the future central hydrogen network and close to the Wilhelmshaven energy hub, as well as having a direct connection to the German-Dutch market. At the same time, Gasunie is already developing a similar project in the northern part of the Netherlands, HyStock, showing that the ambition goes beyond the pilot project – it involves building a robust binational ecosystem.

The validation of the geological integrity and the materials used underground allows us to glimpse a new era for hydrogen in Europe, where underground storage can guarantee continuity, efficiency and energy sovereignty. In times of accelerated transition and geopolitical instability, infrastructure like this represents more than innovation: it is a strategic commitment to the continent's energy autonomy.