Heat storage in solar adsorption refrigeration systems: A case study for indigenous fruits preservation

The present study deals with heat storage in a solar-powered refrigeration system designed for indigenous products preservation in a cold room with a positive temperature. One of the key goals of this study is to show the importance of heat storage and the choice of the suitable coupling, position, and technology of thermal heat storage in these systems to ensure energy management and system operation flexibility. A new system configuration design where the direct connection between the solar collectors and the adsorption chiller used in the directly driven chiller without any heat storage module and in the classic storing system is suppressed and a new special regulation system is added to manage the temperature of the supplied water to the adsorption chiller. Under the same solar collectors' area, the new configuration design performs well than the existing configurations and offers more flexibility and stability to the system. It was found that, the heat storage, performed by a Hot Water Tank (HWT), enhances the system's cooling production time duration as well as offers stability and reduces the highly fluctuant hot water temperature in solar adsorption chillers. It's shown that the choice of the adsorption chiller cycle time duration is of great importance as well as the HWT volume on the system's performance. The study shows also that the system achieves better performances when considering a stratified HWT instead of a fully mixed HWT. Using a total solar collectors' area of 84.53 m2, a hot water tank of 3 m3, and a cycle time of 1200 s, a solar fraction of 86% is obtained when the proposed configuration is connected to the stratified heat storage technology however 80% is reached when the system is equipped with the mixed hot water tank.