Process dynamics in a hydrogen-based energy storage system

Abstract

The BioGenerator is a technology that was recently invented and is used for the biological conversion of hydrogen to electricity. Its main application is in the re-electrification of hydrogen in hydrogen-based energy storage systems for the smoothing of the variability in wind and solar power generation. Therefore, BioGenerator operation is highly dynamic. The core of the BioGenerator is a bioreactor where principal microorganisms Leprospirillun ferriphilum oxidize Fe2+ to Fe3+. The dynamics of the process of energy storage affects the temporal characteristics of the bioreactor. The BioGenerator remains idle during the peaks of power generation of renewable power where Fe2+ remaining in the bioreactor is continuously consumed biologically. Likewise during the valleys in power generation Fe3+ is consumed electrochemically and Fe2+ accumulates. The effect of periodic interruption on the operation of the iron-oxidizing bioreactor was studied in this work. Our results show that idling of the BioGenerator for less than half a day has no negative effect on returning to the initial performance, while longer idling periods result in a small temporary reduction in bioreactor performance. Similar dynamics were observed in both stand-alone bioreactor as well as in a bioreactor incorporated in a complete BioGenerator system for hydrogen re-electrification. Additionally, operation of the closed loop BioGenerator system revealed hysteresis effects on the steady state bio-oxidation rate correctable with brief interruption of operation.