The demand for clean and sustainable energy resources is rapidly increasing. Consequently, solar energy storage using reversible chemical reactions has emerged as a modern and reliable option. The aim of this research is to design, simulate, and optimize thermochemical cycles based on ammonia and decalin in order to evaluate and compare their capacities for solar energy storage and recovery. In this study, a thermochemical cycle for thermal energy storage based on ammonia and decalin, as two distinct chemical carriers, is investigated. In this cycle, the endothermic decomposition reaction of ammonia takes place in a fixed-bed reactor with a metallic wall exposed to solar heat, where ammonia is converted into hydrogen and nitrogen. The hot gaseous products from this reactor exchange heat with liquid ammonia in a heat exchanger, leading to a reduction in temperature. In fact, solar energy is stored in the form of chemical energy in the ammonia storage tank. The gaseous mixture of hydrogen and nitrogen then enters a synthesis reactor, where the reverse exothermic reaction occurs, producing ammonia again along with a significant amount of heat that can be used for power generation. This characteristic makes such cycles highly suitable for long-term thermal energy storage and application in solar thermal systems. In this research, numerical and pseudo-homogeneous models were developed to simulate the thermal and kinetic performance of fixed-bed decomposition and synthesis reactors for both hydrogen carriers (ammonia and decalin). Subsequently, the reactor operating conditions were optimized to enhance thermal energy production. In addition, this study investigates the application of these cycles in concentrated solar power (CSP) plants and aims to facilitate the development of advanced thermal energy storage systems.
The results showed that the ammonia-based thermochemical cycle, in the modeling of the synthesis process, could store a reaction heat rate of 10.61 W/cm wit