Experimental characterisation of a cold thermal energy storage unit with a pillow-plate heat exchanger design
Håkon Selvnes, Yosr Allouche, Armin Hafner
Abstract
Cold Thermal Energy Storage (CTES) technology can be introduced to refrigeration systems for air conditioning and process cooling to reduce the peak power consumption by decoupling the supply and demand of refrigeration. In these systems, the refrigeration demand can vary significantly over a day, resulting in a challenging peak and valley load pattern on the electrical grid. This paper presents the design, development, and experimental performance investigations of a novel plates-in-tank CTES unit design intended for integration into pump-circulated CO2 industrial refrigeration systems. The CTES unit is composed of a stainless steel container filled with water as the latent storage medium and fitted with a pillow plate heat exchanger. The refrigerant (CO2) circulates within the heat exchanger to transfer heat with the storage medium. The current study demonstrates the feasibility of implementing a latent CTES unit directly into the primary refrigerant circuit for peak shaving of the refrigeration load. The results show that the evaporation and condensation temperatures of the refrigerant are the most critical parameters influencing the performance of the charging and discharging cycles, respectively. The unit demonstrated a mean discharge rate of 7.90 kW over a total discharging cycle time of approximately 4.5 h. The resulting maximum discharged energy was calculated to 35.29 kWh.