The containerised hydrogen storage systems developed by AMBARtec can be deployed quickly. They require no structural changes to the infrastructure and can be transported and handled using standard logistics such as trucks, trains or cranes. AMBARtec will therefore enable industrial companies to supply themselves with hydrogen at comparatively low cost from as early as 2025. This will give them a significant strategic and time advantage, allowing them to prepare for the transition to the hydrogen network. The hydrogen economy in Saxony is picking up speed! 'We have a large number of companies in Saxony that want to use hydrogen in the future and want to gain initial experience now,' said State Secretary Kralinski. 'It is therefore all the more important that storage solutions are already available today to enable companies to adapt to the new energy source.'  

Significant reduction in authorisation effort
The storage material consists of iron oxide nuggets that resemble small stones. During storage, the added hydrogen reduces the iron oxide to iron. For discharging, steam is added which reacts with the iron. This produces iron oxide and hydrogen again. As no hydrogen can escape from the storage systems, even when loaded, and they are therefore not dangerous goods, the approval procedures are greatly simplified. No permits are required under the Industrial Safety Ordinance (Betriebssicherheitsverordnung) or the Hazardous Incident Ordinance (Störfallverordnung). 'We feed the water vapour produced during loading back into the electrolysis process,' explains Technical Director Uwe Pahl. 'Thanks to this closed water cycle and the up to 90 per cent reduction in water consumption during hydrogen production, our unique technology eliminates all requirements for electrolysers arising from the Water Resources Act (Wasserhaushaltsgesetz).'

Successful support of the hydrogen industry by the Free State
In addition to numerous economic policy measures, Saxony also provides its companies with considerable support in the development and implementation of suitable hydrogen technologies. 'For example, we receive support in the area of STEM employee retention and innovation bonuses,' says Matthias Rudloff, CEO of AMBARtec. 'Without these important subsidies, we would not be able to advance the development of storage systems to the same extent, or at least not as quickly, as we are still a small company. We are pleased that the government will continue to support the domestic hydrogen industry in the future.'

Since September 2023, AMBARtec has been testing its 7.5 kg H₂ storage system in full operation with hydrogen. The aim was also to optimise the plant control and find the best system configuration in terms of energy balance.  

Maximum energy efficiency: AMBARtec's storage system + SOEC
The energy balance analysis shows that the AMBARtec storage system is ideally suited for combination with a SOEC. The determined efficiency is over 80 % - a very high value compared to other H₂ storage systems. This is due to the system integration of electrolysis and storage.

The H₂ produced in the electrolysis process leaves at a temperature level of over 500°C, which is also required for storage - this significantly reduces the heating energy required.

The water vapor produced during the reduction of the iron oxide can be fed back into the high-temperature electrolysis. This means that water evaporation is no longer required in the electrolysis process. This greatly increases the efficiency of the electrolysis process.

Use case: Electricity storage
If the SOEC/AMBARtec storage system combination is supplemented with a solid oxide fuel cell (SOFC), the efficiency for the entire electricity-to-electricity process is around 60%. By comparison, the efficiency of electricity-to-electricity-systems using PEM electrolysis and conventional storage systems such as liquid hydrogen, LOHC or pressurized hydrogen is less than 40%.  
Durable storage material
Examinations of the iron oxide nuggets used show the high mechanical and chemical stability of the material. There are no changes in the storage capacity or other signs of wear.  

Safety concept validated
AMBARtec has updated all tests and documents required for explosion protection. The basic plant safety concept is applicable to all storage tank sizes up to the planned 6,000 litre storage tanks and does not require any significant changes.  

Further development of the system design
The test operation also served to improve the plant control, the heating system and the flow conditions in the storage system. AMBARtec used the results to derive an optimized design and optimized operating conditions for the next generation of storage tanks.  

Outlook
AMBARtec is currently scaling up the hydrogen storage system to a volume of 1,000 litres. It has a storage capacity of 90 kg of hydrogen. Commissioning and testing will take place in the coming months. In the future, AMBARtec will integrate its 1,000-litre modules into a standard 20-foot container that can be handled and transported using standard transport logistics such as cranes, trucks, trains and ships, with a capacity of 600 to 900 kg H2 (20 to 30 MWh) per container.