Design, exergy analysis, and optimization of a hydrogen generation/storage energy system with solar heliostat fields and absorption-ejector refrigeration system

In the current work, a solar-based energy plant that includes an organic Rankine cycle, an NH3 -LiNO3 operated refrigeration system, reverse osmosis desalination, and hydrogen production device are integrated, modeled, and optimized. A parametric examination is designed with Matlab software to show the impact of varying primary system variables on outputs like system total energy, exergy efficiency, and total exergy output. All processes have been carried out for different working fluids, namely iso-butane, Propane, n-octane, and the results are compared. Parametric analysis reveals that at solar radiation of 800 W/ m2, which is reasonable for the sun in most of the Middle East, selecting n-Octane as a working media results in an increase in the hydrogen production rate of about 150%. This also confirms the importance of selecting the right working fluid for the ORC unit. More-over, the influence of substantial decision variables on the hydrogen production, net out pout power, exergy efficiency indicated that multi-criteria optimization is necessary. The multi-objective optimization strategy suggests the TIP = 1753 kPa, Toil = 99 degrees C, htur is = 0.9, hpump = 0.87, and AHeliostat = 2800 m2, for the optimum state of the studied system. Addi-is tionally, the scatter distribution and sensitivity analysis for optimum point introduced by multi-criteria optimization utilized for better understanding the optimization process.(c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study integrated, modeled, and optimized a solar-based energy plant, showing the impact of different working fluids on system performance parameters, and highlighting the importance of choosing the right working fluid. Parametric analysis revealed that selecting n-Octane as the working media can significantly improve hydrogen production under specific solar radiation conditions. A multi-objective optimization strategy yielded the optimal state parameters for the system.