A standalone solar thermochemical water splitting hydrogen plant with high-temperature molten salt: Thermodynamic and economic analyses and multi-objective optimization

Abstract

Alternative methods for clean production of hydrogen have been proposed recently. Some of these methods utilize water instead of hydrocarbons as the hydrogen source. The copper-chlorine (Cu–Cl) thermochemical cycle is one of the most promising methods that attracted the attention of numerous researchers and organizations in recent years. In this paper, the design and integration of a standalone solar power tower (SPT) system with LiNaK high-temperature carbonate molten salt with a four-step Cu–Cl cycle is investigated. The integrated system does not rely on external or auxiliary energy sources such as grid electricity or natural gas. The proposed system is investigated in terms of thermodynamic and economic analyses, and the system performance and hydrogen production cost are determined. For the base case, the thermal efficiencies of the Cu–Cl cycle, supercritical steam Rankine cycle, and overall system are 40.4%, 45.74%, and 28.77%, respectively. The hydrogen capacity of the system is 1530.4 kg/h, and the total capital investment is 811.04 million dollars. The levelized cost of hydrogen is estimated as $9.47/kg H2. Based on the multi-objective optimization results, the optimal system design has an overall thermal efficiency and levelized cost of hydrogen of 29.18% and $7.58/kg H2, respectively.