Design of a cold thermal energy storage unit for industrial applications using CO2 as refrigerant

Abstract

Natural refrigerants such as ammonia, hydrocarbons and CO2 are becoming increasingly popular due to favorable thermo-physical properties, low environmental impact and low cost. Industrial refrigeration systems are often installed in applications where the difference in peak and average cooling load is substantial. Cold thermal energy storage (CTES) integrated into the system enables shifting of the load from peak hours to off-peak hours, which enables design of the system capacity closer to the average load rather than the peak load. This paper describes the design and development of a CTES unit and associated experimental test rig. The CTES unit consists of a stack of heat exchanger plates contained in a steel tank, initially filled with water as the phase change material (PCM). CO2 circulates within the plates to freeze and melt the water during charge and discharge cycles, respectively.