The mentioned modeling and optimization techniques are applied for optimal design of ITES system incorporating PCM as the partial cold storage to be installed in a commercial building in Ahwaz, a city in south of Iran. The working hours of the building are 7 a.m. to 7 p.m. The daily cooling load of the building is shown in Fig. 2. The chiller cooling load capacity for simple ITES (without PCM as the partial cold storage (α = 0)) and conventional (system with capability of load change steps