Reduction in Auxiliary Energy Consumption in a Solar Adsorption Cooling System by Utilization of Phase Change Materials

This study investigates the efficiency of application of phase change materials (PCMs) in a solar cooling system. The proposed system consists of an adsorption chiller and a latent heat storage unit (LHSU) containing PCMs. The PCM stores solar energy during daytime and at nighttime, the thermal energy stored in the PCM is utilized to drive the adsorption chiller. An auxiliary heater is also used to provide the required energy in addition to the LHSU. To verify the accuracy of the obtained results, the modeling of the solar adsorption system and the PCM unit are validated separately. Moreover, the whole system performance is verified by evaluation of the conservation of energy in the system. The performance of the system is compared with a similar solar adsorption chiller lacking LHSU. Also, the parameters which affect the performance of the LHSU are studied. It is found that application of LHSU decreases auxiliary energy consumption and increases solar fraction. Solar fraction goes up more if larger amount of PCM is used. However, there exists a maximum mass of PCM which can be charged during the sunshine hours. The maximum chargeable mass of PCM goes up by increasing the solar collector area, which leads to decreasing auxiliary energy consumption and increasing solar fraction. The results also show that enlargement of the hot water storage tank reduces auxiliary energy consumption and enhances solar fraction, but decreases thermal storage efficiency. In order to achieve higher thermal storage efficiency and also less auxiliary energy consumption, it is suggested to use average-sized hot water storage tanks.