Sustainability analysis of a solar driven hydrogen production system using exergy, extended exergy, and thermo-ecological methods: Proposing and comparing of new indices

Highlights: • Presenting new indices and comparing them with some ones available in the literature. • Applying the indices to a solar driven hybrid system. • Performing a dynamic analysis of the considered system. • Indicating advantages of the suggested indices. This paper aims at investigating and comparing some sustainability indices in the literature while proposing some new indices. A solar driven hybrid system made of a PV cell, an alkaline electrolyzer and a PEM fuel cell is chosen to apply these indices because renewable-based stand-alone hybrid systems for generating electricity seem to be very promising for the future. Some sustainability indices and methods, such as sustainability index, exergetic sustainability index, extended exergy accounting and thermo ecological cost analysis, exist in the literature. In addition to these indices, new indices proposed in this paper contain thermo-ecological cost (TEC) of irreversibilities, extended TEC, extended exergy-based sustainability index and the extended exergetic ecological index. A daily dynamic performance analysis is made for one year. According to the results, exergy efficiency values range from 0.027 to 0.121 while extended exergy efficiencies vary between 0.08 and 0.14. Finally, the proposed indices are classified for designing environmental cycles, assessing environmental effects under operation conditions, and evaluating sustainability in every aspect.