The thermochemical system using ammonia as energy storage carrier is investigated in this study. A mathematical model was developed to predict the behavior of both reactors in the ammonia-based closed-loop system. For the importance of the dissociation and formation process in the system, the model focused only on the solar and the synthesis reactors. The study shows that maintaining the best mass flow rate is important for achieving the maximum ammonia dissociation and formation processes and as a result the maximum thermal output. Operating the reactors at higher pressure than suggested increases the formation of ammonia at the synthesis; however, it lowers the thermal output of the system.