Hybrid cooling system integrating PCM-desiccant dehumidification and personal evaporative cooling for hot and humid climates

Abstract

Hot and humid climates present a challenge for implementing passive cooling practices in office spaces, due to the inherent small temperature difference between day and night, which affects the utilization of thermal storage systems. Moreover, added means are required to maintain the humidity in the space at an acceptable level for comfort. The novelty of this study is to design and implement a feasible hybrid cooling system for office spaces in such climates by uniquely combining several sustainable cooling, thermal storage, and dehumidification solutions. The proposed system integrates a phase change material (PCM) thermal storage layer with a melting temperature of 25 °C to cool the supply air and a personalized evaporative cooler (PEC) to provide cooling for the occupants. The supply air humidity is controlled using a solid desiccant wheel regenerated via an auxiliary heater assisted with a Trombe wall. Mathematical models were adopted for each system component/process, solved numerically and integrated to size the system components, simulate their operation and predict the overall system's performance in an office space during the summer months of Beirut climate. The proposed system was found to achieve acceptable thermal comfort levels in the space. Moreover, it reduced the total energy cost by 87% compared with a conventional air conditioning unit over the summer period. In addition, the Trombe wall provided energy savings of 55% compared to relying only on the auxiliary heater. Hence, integrating several sustainable solutions succeeded in implementing an effective cooling system of office spaces in hot humid climates.