Thermodynamic assessment of a cogeneration system with CSP Driven-Brayton and Rankine cycles for electric power and hydrogen production in the framework of the energy and water nexus

Abstract

In increasingly energy-dependent world, there is a question mark over the viability of fossil fuel resources. To tackle this issue, an integrated poly-generation system based on concentrated solar power is proposed to feed in the city grid and produce hydrogen as a clean energy carrier. Concerning the COVID-19 outbreak, all countries are in dire need of oxygen. Therefore, the produced oxygen in this system can be considered as an added value. The introduced scheme applies solar energy to supply thermal energy to a Brayton cycle. Two bottoming Rankine cycles are employed to empower a PEM electrolyzer using the residual heat from the gas turbine. The system is modelled using the Engineering Equations Solver for a comprehensive thermo-economic analysis. The exergy destruction analysis proved a significant loss of exergy by the solar field, illustrating the necessity to address this in future research. Afterwards, six design variables were selected and then optimized for the proposed system using the NSGA-II. Based on the TOPSIS approach, exergy efficiency, and capital cost rate, the objective functions were 22.2% and 272.6 $/h, respectively. Finally, a case study was performed to investigate the impact of solar irradiation and ambient temperature on system outputs.