Search

Building cooling is achieved by the extensive use of air conditioners. These mechanically driven devices provide thermal comfort by deteriorating the environment with increased energy consumption. To alleviate environmental degradation, the need for energy-efficient and eco-friendly systems for building cooling becomes essential. Evaporative cooling, a typical passive cooling technique, could meet the energy demand and global climatic issues. In conventional direct evaporative cooling, the sensible cooling of air is achieved by continuous water circulation over the cooling pad. Despite its simple operation, the problem of the pad material and water stagnation in the sump limits its usage. Moreover, the continuous pump operation increases the electrical energy consumption. In the present work, a porous material is used as the water storage medium eliminating the pump and sump. An experimental investigation is performed on the developed setup, and experiments are conducted for three different RH conditions (low, medium, and high) to assess the porous material's ability as a cooling medium. Cooling capacity, effectiveness, and water evaporation rate are determined to evaluate the direct evaporative cooling system's performance. The material that replaces the pump and sump is vermicompost due to its excellent water retention characteristics. There is no necessity to change material each time. However, the vermicompost is regenerated at the end of the experiment using a solar dryer. The passing of hot air over the vermicompost also avoids mould spores' transmission, if any, present through the air. The results show that vermicompost produces an average temperature drop of 9.5°C during low RH conditions. Besides, vermicompost helps with the energy savings of 21.7% by eliminating the pump. Hence, vermicompost could be an alternate energy-efficient material to replace the pad-pump-sump of the conventional evaporative cooling system. Further, if this direct evaporative cooling system is integrated with solar-assisted drying of vermicompost, it is possible to provide a clean and sustainable indoor environment. This system could pave the way for year-round thermal management of building cooling applications with environmental safety. [ABSTRACT FROM AUTHOR]

The adoption of phase change material (PCM) based free cooling technology in all the climatic conditions is challenging because of its site-specific nature. In order to support the implementation of free cooling concept in unfavorable climatic condition, a novel hybrid system with the combination of evaporative cooling and PCM based free cooling is proposed herewith. The present experimental work aims to compare and analyze the charging behavior of the PCM-based free cooling system without and with the integration of direct evaporative cooling (DEC) unit during the summer month (April) in an Indian city possessing hot–dry climate. By considering the local ambient conditions, PCM with a phase change temperature of 27–29 °C is opted for the present study. The time-temperature history of PCM, instantaneous heat transfer rate, charging efficiency, heat exchange between the storage tank and ambient were analyzed and the respective results are presented. It is inferred from the experiments conducted without the integration of DEC unit that PCMs did not undergo phase transition and remained in the liquid phase even after 8 h of the experimentation due to unfavorable local ambient conditions. However, in the case of experiments conducted with the integration of DEC unit, PCMs at all locations in the thermal energy storage (TES) tank got solidified irrespective of local ambient temperature and reached its freezing temperature. This is due to the reduction in heat transfer fluid (HTF) temperature and the additional temperature driving potential achieved through DEC. Better results in terms of charging duration was obtained for the experiments conducted with higher temperature driving potential than the higher HTF velocities. The main inference from the present study is that it is much possible to store the useful energy in PCM even during the summer season in the hot and dry climatic zone irrespective of local ambient temperature through the integration of DEC unit with the PCM based free cooling system. [ABSTRACT FROM AUTHOR]