Performance analysis of a stand-alone thermal energy storage system based on CSM plates filled with phase change material

In this study, experimental investigations on a Phase Change Material (PCM) based thermal energy storage system (TES) were carried out. The TES system was designed and tested as a first step of developing a potential TES product which can be integrated with commercially available ventilation system (VEX308) to provide cold intake air for space cooling applications. The system consisted of wedge-shaped air flow regions before and after an array of Compact Storage Module (CSM) plates filled with PCM and arranged vertically with air gaps between the plates. Two design configurations of the TES system were investigated based on air gap size between PCM plates (1.5 mm and 3 mm) in order to compare them for pressure loss through the system and thermal performance of the PCM storage. Investigations were done at two air flow rates of 400 m3/h and 800 m3/h which were within the working range of VEX308 for fixed air inlet temperatures of 27 °C and 13 °C for heating and cooling cycles of the PCM storage, respectively. The temperatures ranges were chosen to investigate the application of the TES system during summer season in Denmark. Parameters investigated were: pressure loss through the TES system, pressure distribution from top to bottom in the TES system before and after the PCM stack, temperature distribution in the TES system from top to bottom, and melting and solidification rates of the PCM. Results showed that pressure drop through the system, for both configurations, was well within the desired limits (<180Pa) for a successful integration of the TES system with VEX308. Temperature distribution was relatively fair from top to bottom of the PCM stack indicating an adequate inlet manifold design. The 1.5 mm gap configuration (55 CSM plates and 110 kg PCM) showed faster heating and cooling rates at both flow rates as compared to 3 mm system (50 CSM plates and 100 kg PCM). Both systems showed almost same system efficiency (78.3%) for the utilization of the PCM. The 1.5 mm system provided approximately 8.7% more energy storage potential than the 3 mm system because of the presence of 10 kg of extra PCM.