A review on hydrogen production thermochemical water-splitting cycles

Hydrogen is an energy carrier and thermochemical cycles are a sustainable and benign method for hydrogen production. This study reviews and investigates thermochemical hydrogen production cycles by detail. Promising cycles, namely Sulfur-Iodine, Copper-Chlorine, Magnesium-Chlorine, Iron-Chlorine and Vanadium-Chlorine, and a recently developed Zinc-Sulfur-Iodine cycle are discussed here. Process flow diagram of each cycle is presented along with its pros and cons. Finally, the cycles are compared in terms of thermal and power load, energy and exergy efficiency and cost of the hydrogen production. The results show that the lowest cost, highest energy and exergy efficiencies with the value of 1.77$/Kg, 57%, 78.21%, belongs to geothermal based 4-step Cu-Cl, 3-step Cu-Cl in the first option and open-loop Zn-S-I, respectively. Also, in terms of external heat required in the cycle, Zn-S-I cycle has the highest and Mg-Cl cycle has the lowest value. Mg-Cl also has the highest power load. (C) 2020 Elsevier Ltd. All rights reserved.