Hydrogen production by thermochemical water splitting cycle using low-grade solar heat and phase change material energy storage system

In this research, a novel integrated system for renewable hydrogen production, power, and hot water from solar thermal energy has been developed and precisely evaluated in terms of thermodynamics. The developed structure is comprised of a four-step Cu-Cl thermochemical cycle, and an organic Rankine cycle to generate electricity. The required heat is supplied by a concentrated solar power plant and thermal energy storage based on latent heat. Also, a high-temperature heat pump is employed to improve the thermal grade of working fluid and provide each unit with sufficient heat. System dynamics simulation has been performed using weather and irradiation input data of Tehran, Iran. The integrated structure has the capability to produce 21.75 kg/h of hydrogen, 563.6 kW of electricity, and 393.3 m(3)/h of hot water at 70 degrees C. The energy efficiency of the system reaches more than 80% based on higher heating value and the solar-to-fuel efficiency has a value of 25.8%. Moreover, an exergy analysis has been executed to determine the fundamental operating parameters of each component and the whole structure. The total exergy efficiency of the integrated structure is 34.23%, and the prime cost of the product is found to be 5.795 USD/kg H-2.