N.Georgescu-Roegen's production model for EROI evaluation. Case study: Electrolytic H2 production using solar energy

Nowadays there is a considerable interest in studying the direct and indirect energies involved in products and services. This is particularly critical when novel energy resources are exploited by complex technological chains and to determine if they can indeed guarantee an useful energy societal supply. Unfortunately, there is no universally accepted procedure for doing this. The present paper aims to suggest a new procedure to evaluate the EROI of technologies producing energy carriers based on the stocks/flows-funds/services production model of N.G. Roegen. The suggested method can uniquely identify the energy flows involved in the technology consistent with biophysical and anthropological boundaries. This analytical formulation can be used either for single technologies or combination of them in series or parallel using different energy resources. Specific recommendations in the use of the Cumulative Energy Demand and Global Energy Requirements in the Net Energy Analysis, as well as in the evaluation of both for an electrical system are reported. The approach is here applied to the analysis of electrolytic H2 production using electricity produced by a photovoltaic panel ("green hydrogen"). The resulting EROI = 0.97 means that the technology is not sustainable, requiring 3% energy from the anthropological sphere to support it. The paper is organized as follows: providing a narrative model for EROI evaluation consistent with anthropological and biophysical spheres; covering the definition of stocks/flows-funds/services model for EROI evaluation; analysing and suggesting uses of the model for energy technologies scoring and selection based on sustainability and presenting a numerical case study.