Optimization of thermal energy storage system in residential scale solar thermal driven adsorption cooling system is based on criterion to have a minimum size of storage tanks correspondence to maximum system performance. It found that the optimum size of the hot storage tank in a solar driven adsorption cooling system in hot arid area is ranging between 55 to 66 l/m2 per collector area with the height to diameter (H/D) ratio ranging from 2.4 to 2.75. The optimum size of the cold storage tank can be obtained according to the cooling load pattern and the required number of air conditioning working hours.