Regenerative Fuel Cells for Energy Storage Application: Performance Limitation Studies

Redox flow batteries are a potentially versatile and attractive solution to store and deliver energy over the kW/kWh to MW/MWh range. A variety of redox flow chemistries exist, with all-vanadium battery being the most mature and developed.  Nonetheless, all-vanadium systems suffer from a relatively low power density, specific energy and high cost, associated with the use of vanadium based electrolytes. These issues can be circumvented by replacing the vanadium anolyte or catholyte with a cheaper alternative. Particularly, novel regenerative fuel cells have been developed that utilise a combination of a liquid and a gaseous redox reactions; either hydrogen oxidation reaction on the anode side or oxygen reduction reaction on the cathode side.  Previous work by the authors has demonstrated a regenerative fuel cell based on hydrogen/vanadium redox reactions whichachieved a specific power of 200 mW/cm². Further optimisation of this system has increased the power density to more than 400 mW/cm². This paper will present a study of the performance limiting factors in the Regenerative Hydrogen Vanadium Fuel Cell, showing how this information can be generally implemented in other energy storage systems utilising hydrogen and metal redox couples.