Cold thermal energy storage for industrial CO refrigeration systems using phase change material: An experimental study

Abstract

Refrigeration systems in industrial food processing plants are large users of electric energy and often show high peak power consumption. Cold thermal energy storage (CTES) technology integrated into refrigeration systems can reduce the peak power requirement and achieve peak shifting by decoupling the supply and demand of the refrigeration load. This paper presents the design and performance of a CTES unit consisting of a pillow plate heat exchanger (PP-HEX) immersed into a low-temperature phase change material (PCM) as the storage medium. It is one of the first experimental investigations featuring a large-scale technical solution that allows for coupling the evaporation and condensation processes of the refrigeration system with the melting and solidification of a low-temperature PCM in the same heat exchanger. The charging and discharging performance of the plates-in-tank CTES unit was extensively tested using CO as the refrigerant and a commercial PCM with phase change temperature of -9.6 °C. The charging time was found to be mainly affected by the refrigerant evaporation temperature, while the discharging rate and discharged energy over the cycle was higher when increasing the refrigerant condensing temperature. Using a plate pitch of 30 mm resulted in the highest mean discharge rate and total discharged energy over the cycle with 9.79 kW and 17.04 kWh, respectively. The flexible CTES-PCM unit can be adapted to fit several refrigeration load characteristics and temperature levels by changing the PP-HEX geometry and type of PCM used as the storage medium.