© Storag Etzel
The H2CAST Etzel consortium completed the filling of two underground salt caverns in northern Germany with approximately 90 tons — or one million standard cubic meters — of hydrogen in mid-March, marking a significant operational milestone for the country’s nascent hydrogen storage infrastructure.
A Test Bed at a Critical Moment for German Hydrogen Policy
The completion comes as Germany presses ahead with building a 9,000km core hydrogen pipeline network, to which the Etzel site could eventually be connected. Underground storage is widely regarded as essential for managing the intermittency of renewable energy supply, particularly for storing electrolytic hydrogen produced during periods of excess wind and solar generation.
How the Caverns Were Filled
The two caverns, converted from existing natural gas storage facilities, were filled using 200 trailer deliveries of hydrogen. Plug Power, the US hydrogen firm, supplied the gas, while Hy2Gen’s 2.3MW green hydrogen plant in Werlte provided additional volumes during the project period. Filling began in May 2023, though early procurement proved difficult: high-pressure trailer infrastructure was scarce, and some deliveries travelled over 1,000km, pushing up costs significantly. By the project’s later stages, a nearby supplier had been secured, materially reducing both logistics and production expenses.
Infrastructure Now Under Construction Above Ground
With the underground caverns now full, attention has shifted to the above-ground facilities. A purpose-built pilot plant — incorporating gas purification, compression, and quality monitoring systems — is currently under construction and is expected to be ready for its first tests in 2026. The plant will assess the efficiency of various hydrogen purification methods and trial cyclical injection and withdrawal operations, which are critical for commercial viability.
What the Operators Say
Carsten Reekers, project manager at STORAG ETZEL, said the filling process had underscored how early-stage the German hydrogen market remains, but noted meaningful progress. “Meanwhile, the market has evolved, allowing us to secure a delivery from a nearby hydrogen producer during the project period — significantly lowering both logistics and production costs,” he said. Eddy Kuperus, business development manager for hydrogen storage at Gasunie, expressed confidence in the consortium’s ability to advance the project, citing the technical expertise within the partnership.
Implications for Investors and Policymakers
The Etzel pilot is one of several early-stage underground hydrogen storage projects emerging in Germany. EWE plans to convert one of its seven natural gas caverns in Huntorf for hydrogen storage, while Uniper began operating a salt cavern pilot in Krummhörn in 2024. If H2CAST’s trials confirm that existing caverns are suitable for hydrogen — a conclusion Reekers said the project’s experience since 2022 already supports — it could reduce the cost and timeline for scaling storage capacity across the country. For policymakers designing Germany’s hydrogen infrastructure, demonstrable proof of cavern integrity and purification efficiency at Etzel would strengthen the case for integrating storage into the approved core network.
