Metal hydride-based hydrogen production and storage system for stationary applications powered by renewable sources

In this work, a compact and low-cost electrochemical laboratory prototype for the storage and production of hydrogen, based on metallic hydrides, with high reversibility in the charge/discharge process is demonstrated, using electricity either from the grid or by direct coupling to renewable energies as power source. The reactor is a 316 L stainless steel vessel with a capacity up to 15 bar internal pressure. It includes working electrodes of alloy LaNi4.3Co0.4Al0.3 and counter-electrodes of Ni foam in an electrolyte solution of 35% KOH. The reactor uses unicellular/multicellular configurations, so that the overall capacity of the system can be extended by increasing the number of working electrodes, resulting in a highly modular system. Results show excellent linearity, reversibility, and stability under cycling at room temperature and pressure, demonstrated either when powered by the grid or by off-grid renewable energy. Furthermore, criteria were established for the quantification of the state of full charge and full discharge. The system was integrated with a custom electronic system, developed inhouse for monitoring and control the reactor and to optimize the performance and energy efficiency of the hydrogen storage and discharge processes.