Integrated optimization of a solar multigeneration plant employing iron-chromium redox flow battery and thermal management

This study examines a solar polygeneration system which provides a variety of energy products, as well as providing the means for integrating a linear Fresnel photovoltaic/thermal collector array, thermal energy storage, an iron–chromium redox flow battery, and a hybrid subsystem comprising both a heat pump and absorption cooling technology. The integrated solar polygeneration system operates using a dynamic control methodology that adjusts both the thermal and electrical distribution in response to changes in available solar irradiance and changing end-user demands. From an energetic perspective, an exergetic perspective, and from an economic perspective this research assesses the total system performance relative to a reference tri-generation pathway consisting of a power-to-hydrogen-to-power scheme to simultaneously produce heat, cooling, and electricity. Additionally, the effects of two primary design variables, namely the collector allocation ratio and the battery capacity are evaluated to elucidate their contributions toward the total system’s efficiency, exergy use, and economics. Furthermore, this research develops a multi-objective optimization approach using the firefly optimization algorithm coupled with simulated annealing to simultaneously maximize the exergy efficiency of the system, minimize the delivered energy cost, and minimize the annual operational carbon dioxide emissions associated with grid electricity imports. The study indicates that the incorporation of an iron-chromium battery into the solar polygeneration system enhances its ability to dispatchable energy resources and to maintain equilibrium between supply and demand during fluctuating operating conditions without degrading the system’s thermodynamic performance. Compared with the hydrogen-based reference case, the proposed polygeneration configuration has favorable economic advantages including lower delivered energy costs, faster pay-back periods, and greater investment attractiveness. Tri-objective optimization identified a compromise design (coverage ratio of 0.935 with a 337 kWh battery) attaining 31.27% exergy efficiency, an LCOE of $0.04567/kWh, and a 4.1% reduction in annual operational CO 2 emissions relative to the base design.