Exergoeconomic and multi-objective optimization of a solar thermochemical hydrogen production plant with heat recovery

•An integrated solar thermochemical plant with heat recovery is investigated.•High temperature PCM is used for thermal energy storage.•Hydrogen and electricity are produced at a rate of 0.10 kg/s and 50.5 MW.•Optimal solution has an exergy efficiency of 50.1% and product cost of $11.9/GJ. A solar hydrogen production plant based on a four-step copper-chlorine (Cu-Cl) thermochemical cycle is presented and analyzed in this paper. The integrated system includes a pressurized solar power tower, gas turbine unit, phase change material (PCM) for thermal energy storage (TES), Cu-Cl cycle, regenerative steam Rankine cycle (SRC), and a heat recovery unit. A predictive model is developed for energy, exergy, and exergo-economic analyses of the proposed system. A parametric study is also conducted to investigate the effect of major parameters on the system performance. The system is optimized with a non-dominated sorting genetic algorithm-II (NSGA-II) considering exergy efficiency and product cost per unit exergy as the two objective functions. The results indicate that the energy and exergy efficiencies of the overall system are 48.2% and 45%, respectively, while the total product cost per unit of exergy is found to be $10.97/GJ. The integrated solar system produces hydrogen, electricity, and steam at a rate of 0.1 kg/s, 50.49 MW, and 13.93 kg/s, respectively. Pareto solutions for multi-objective optimization indicate that the optimal design point of the system has an exergy efficiency and total product cost per unit of exergy of 50.1% and $11.94/GJ, respectively.