The success of Germany’s energy transition relies as much upon storage as it does upon the production of renewable energy. Like a suspension bridge supported between two towers, the system only works if both elements are securely in place. Substantial efforts are therefore being put into investigating the potential of green – regeneratively produced – hydrogen (H2) as an energy carrier.

Now an innovative method of storing H2 has come from an unusual quarter – the Department of Molecular Microbiology and Bioenergetics at the Goethe University of Frankfurt. A few years back, Professor Volker Müller’s team devised a method for producing small amounts of H2 using acetogenic bacteria that are found on the deep ocean floor. In their natural environment, the organisms feed on carbon dioxide (CO2) to produce formic acid from CO2 and H2, which is then digested into vinegar and ethanol. By genetically modifying the bacteria, the formic acid stage can be reversed so they start producing H2 gas.

In a new development, one of Müller’s students has designed a kind of bio-battery for storing green H2 as part of his doctoral thesis. Firstly, Fabian Schwarz fed the bacteria H2 for eight hours. The gas was produced via electrolysis powered by the excess energy generated by solar panels during daylight hours. The bacteria then metabolised it into formic acid. In a second step, he starved them of H2, causing them to release hydrogen that could then be used for immediate power needs during the night. The system ran “extremely stably” for at least two weeks claims Schwarz, as reported by Ingenieur.

The innovation provides a sustainable solution to one of hydrogen’s biggest challenge’s – how to store the volatile gas in a stable and cost-effective manner. It shows how H2 could be safely stored in solar plants for turning back into electricity when needed (at night).