Efficient, safe, space-saving hydrogen storage

WTSH: Professor Jepsen, what kind of research is currently being conducted at the Institute for Hydrogen Technology?

Jepsen: Our research team, which consists of around fifty scientists, is focusing on the storage and compression of hydrogen. We're using a highly innovative method - the secret lies in metal. We're working with metal powders that can absorb hydrogen like a sponge. System integration, meaning the practical application of our research, is a key priority for us because the development of the hydrogen economy needs to progress. 

WTSH: How does hydrogen storage in metal actually work?

Jepsen: Certain metals and metal alloys can store gaseous hydrogen by embedding hydrogen atoms at the atomic level. This occurs in the intersitital spaces within the latice-like atomic structure. The metal and gas form a compound, resulting in a metal hydride. During hydrogen absorption, heat ist released, and a slightly elevated pressure is required - usually less than 50 bar. Conversely, for hydrogen release, heat must be applied and the pressure reduced. Unlike conventional high-pressure gas tanks, this method allows us to store hydrogen in very compact form and at a low pressure, making it extremely safe. This technology is fully operational and is continuously being advanced in Schleswig-Holstein through collaboration with national and international research communities. 

WTSH: Are metal-hydride tanks used in stationary systems, mobile applications or both? 

Jepsen: We're researching their use in both stationary and mobile systems. Our relatively heavy metal-hydride tanks are ideal for use in residential buildings and industrial settings, where weight is not a critical factor. In aviation, however, metal hydrides aren't suitable due to their weight. In shipping, on the other hand, we can turn our greatest drawback into an advantage - the weight of the metal-hydride tank can be used to stabilise the ship's hull. In general, different technologies compete across various fields of application. For heavy-duty road transport, hydrogen technologies are likely to take precedence. In contrast, conventional battery-electric drives are well-suited for smaller passenger vehicles. However, metal-hydride storage systems can provide cars with greater range and much shorter refuelling times compared to battery-electric systems. Additionally, high-capacity battery systems add substantial weight to vehicles. 

WTSH: What's the purpose of incorporating the metal-hydride tank on the research vessel Coriolis?

Jepsen: First and foremost, we want to provide our colleagues on board with a reliable hydrogen-electric propulsion system. At the same time, the Coriolis serves as a floating real-world test lab for our technology. On the ship, the metal-hydride tanks are installed on deck rather than in the hull. With this setup, we can demonstrate that the system can also be retrofitted to existing ships. It also gives us easier access to the storage system. To further optimise the overall system, we use a digital twin of the Coriolis, which provides a continuous digital simulation of the ship's behaviour. However, practical onboard testing is essential to validate these simulation and ensure they accurately reflect reality. Only then can we implement additional improvements using computer-based models. 

WTSH: What's the purpose of the on-board hydrogen-powered electrical system? 

Jepsen: A ship like the Coriolis isn't always at sea - it often spends time anchored in port, where power is still needed for shipboard operations and research tasks. Conventional ships typically rely on diesel generators produce noise, cause vibrations and emit pollutants such as CO₂ and particulate matter into the air around the harbour. The Coriolis can generate its own on-board power using a hydrogen fuel cell, ensuring that the captain hears little more than the sound of the kettle, while the surrounding air in the port remains clean. In the future, alongside their main propulsion system, ships could rely on hydrogen-powered electricity generation as a viable alternative to diesel generators or onshore power supplies. 

WTSH: How advanced is the practical application of hydrogen technologies today? 

Jepsen: Hydrogen is ready for use across various fields, both mobile and stationary. What we need is a regulatory framework that supports rapid market growth. Another key issue is fostering acceptance of hydrogen technology. We need to move out of the lab and demonstrate to the public how effective this technology already is and the benefits it brings. If we do this, the industry will show greater confidence, and visions like giga-watt-scale electrolysis capacities can be realised more quickly.