Review and evaluation of hydrogen production methods for better sustainability

This paper examines various potential methods of hydrogen production using renewable and non-renewable sources and comparatively assesses them for environmental impact, cost, energy efficiency and exergy efficiency. The social cost of carbon concept is also included to present the relations between environmental impacts and economic factors. Some of the potential primary energy sources considered in this study are: electrical, thermal, biochemical, photonic, electro-thermal, photo-electric, and photo-biochemical. The results show that when used as the primary energy source, photonic energy based hydrogen production (e.g., photocatalysis, photoelectrochemical method, and artificial photosynthesis) is more environmentally benign than the other selected methods in terms of emissions. Thermochemical water splitting and hybrid thermochemical cycles (e.g. Cu-Cl, S-I, and Mg-Cl) also provide environmentally attractive results. Both photoelectrochemical method and PV electrolysis are found to be least attractive when production costs and efficiencies are considered. Therefore, increasing both energy and exergy efficiencies and decreasing the costs of hydrogen production from solar based hydrogen production have a potential to bring them forefront as potential options. The energy and exergy efficiency comparisons indicate the advantages of fossil fuel reforming and biomass gasification over other methods. Overall rankings show that hybrid thermochemical cycles are primarily promising candidates to produce hydrogen in an environmentally benign and cost-effective way.