Phase change material thermal energy storage for a large scale ammonia chiller/heat pump system.

Thermal energy storage (TES) can be applied to reduce peak heating and cooling loads in buildings and to improve the performance and reliability of the heat supply system. For short-term TES, phase change materials (PCM) are a compact and efficient alternative. At the Bergen University College in Norway, three ammonia chillers/heat pumps cover the base load for heating and cooling. To reduce the required chiller capacity, PCM cold storage tanks have been installed. The present study evaluates the PCM-TES system in detail through modelling and analysis of measurement data. To gain more understanding of the freezing and melting processes, a dynamic model for the PCM-TES was developed in Dymola. The simulation results were validated towards measurement data. The model allows better understanding of the heat transfer characteristics of the PCM-TES, and enables more sophisticated dimensioning and design of future PCM-TES systems.