Thermodynamic performance analysis and comparison of a combined cooling heating and power system integrated with two types of thermal energy storage

Energy storage is an effective method to match the incompatibility of the ratio of heat to electricity between a combined cooling heating and power (CCHP) system and its users. This paper proposes an internal combustion engine CCHP system integrated with two types of thermal energy storage, which are accorded with energy levels of the waste heats of jacket hot water and exhausted gas after power generation. Correspondingly, two types of storage technologies including a hot water tank and a molten salt tank are introduced into the CCHP system. Then, the thermodynamic models are constructed, and two operation strategies are established to coordinate the operation of the thermal energy storage tanks. Through a case study, their performances are compared from three aspects: primary energy ratio, adjustable area of ratio of heating/cooling to electricity and application in different building loads. The results in summer work condition indicate that the CCHP system integrated with the jacket water storage tank achieves a primary energy ratio of 83.8% and a ratio of cooling to electricity of 2.24, which are both better than the integration of exhausted gas storage tank. These characteristics show that the CCHP system with thermal energy storage tank is more suitable to adopt the operation strategy in which the exhausted gas is adopted to drive the absorption chiller/heater, while the jacket water is used to store heat when the waste heat is larger than the heat demand.