A size-dependent financial evaluation of green hydrogen-oxygen co-production

Producing green hydrogen by electrolysis is a goal at European and international level. But hydrogen production by water electrolysis is currently more expensive respect the steam methane reforming. Based on our previous studies, extra revenues in order to reduce the production costs could be obtained by considering the co-produced oxygen. Starting from the point of view of a hypothetical enterprise that needs gaseous oxygen for its activity, in order to meet a variety of requests or applications, a financial evaluation of different sizes of RES-based electrolytic plant (100 kW - 10 MW) is proposed. The most relevant result that emerged from our research is the economic sustainability of the investment if the market price of oxygen is at least 3 EUR/kg. In this case, the self-production of oxygen results to be convenient, whatever the size of the electrolyser. This is valid for both the two scenarios assumed, with the exceptions of the smaller electrolyser sizes (<300 kW), for which the threshold is 4 EUR/kg. This finding is obtained considering a selling price of hydrogen at 10 EUR/kg but, according to our analysis, this condition would not change even with a price of 6 EUR/kg.