Hydrogen production is expanding across the globe, but hydrogen gas remains difficult and costly to store and transport, restricting its broader use. A pilot project in Germany is demonstrating for the first time a salt-based process for long-term hydrogen storage. The reversible technology developed by AKROS Energy GmbH (Rostock-Laage, Germany; www.akros-energy.com) relies on an aqueous potassium bicarbonate salt solution to reversibly bind and store hydrogen — essentially converting hydrogen gas into a hydrogen-rich potassium formate solution. First, hydrogen gas and potassium bicarbonate solution are introduced to a proprietary fixed-bed reactor and catalyst system operating at low pressure (below 30 bars). “Hydrogen is chemically bound to the liquid carrier via catalytic conversion under moderate conditions and can be released on-demand through the reverse reaction. This enables safe, efficient and transportable hydrogen storage without the need for high pressures or cryogenic temperatures,” explains Johannes Emigholz, CEO of AKROS Energy.
To release stored hydrogen, the formate is sent back through the reactor at around 60˚ C, converting it back to bicarbonate and H2 gas. Compared to other chemical methods for hydrogen storage, such as liquid organic hydrogen carrier (LOHC) systems, the salt-based approach requires milder operating conditions and uses non-toxic and non-flammable materials, making the systems inherently safer, less complex and lower cost. The system’s liquid carrier is continually recycled within the process in a closed loop, so no byproducts or waste are generated.
“Salt-based hydrogen storage is an emerging field. While there are academic and early-stage industrial approaches, AKROS is among the first to pursue a fully integrated, scalable solution focused on practical deployment and commercialization,” notes Emigholz.
The new pilot facility in Laage, Germany is the first end-to-end demonstration of AKROS’ technology, integrating hydrogen uptake, storage in liquid form and controlled release, all at a throughput capacity of approximately 3 kg/h of hydrogen. Evonik Industries AG (Essen, Germany; www.evonik.com) and Siemens AG (Munich, Germany; www.siemens.com) are among the partners on this project, as a part of the FormaPort R&D consortium project. AKROS is already looking ahead to further scaleup and has initiated engineering work on a 100-kg/h plant, which is expected to begin construction next year. “We have also secured our first customer, who intends to use our liquid carrier to enable large-scale hydrogen imports from the Middle East to Europe,” adds Emigholz.