Syngas-fed membrane-based and steam and water-fed electrolysis-based hydrogen production systems: Renewability, sustainability, environmental and economic analyses and optimization

Abstract

Emergy analysis is an effective technique to scrutinize the sustainability of energy systems. In this study, the renewability, sustainability, environmental impacts, and economic aspect of three common hydrogen production systems are studied applying emergy analysis. Hydrogen is produced by (a) biomass gasification and membrane-assisted hydrogen separation, (b) steam electrolysis in a solid oxide electrolysis cell, and (c) water electrolysis in a proton exchange membrane electrolysis cell. A geothermal plant is integrated with the mentioned hydrogen production systems as the prime mover; in case the input power is insufficient/excess, the extra power is received from or injected into an electrical grid. The systems are analyzed and compared for thermodynamic performance (exergy), sustainability, economic dependency, and environmental impacts at a constant hydrogen production capacity, and eventually, they are optimized employing NSGA II algorithm considering three optimization scenarios. In addition, the influence of hydrogen production mass flow rate and the solid oxide electrolysis cell temperature on the aforementioned parameters is evaluated. The results of optimizing the sustainability index and exergy efficiency showed that the sustainability index of the system based on biomass gasification was 8 times and 10 times higher than the sustainability index of the systems based on steam electrolysis and water electrolysis, respectively.