In the present study, a lab-scale for closed thermochemical heat storage reactor design is performed for seasonal thermochemical energy storage using magnesium chloride hexahydrate based on dehydration and hydration processes. Firstly, the closed reactor and plate heat exchanger are studied. Then, reactor layout modifications are examined. The dehydration process is performed under 95°C. During hydration, plates’ temperature ranges from 20°C to 30°C. The impact of adding zeolite13X-4A to magnesium chloride hexahydrate is examined. The addition of zeolite13X-4A to magnesium chloride hexahydrate of 1/4 mass ratio improves the hydration process and increases its efficiency.