Assessment of energy and cost analysis of packed bed and phase change material thermal energy storage systems for the solar energy-assisted drying process

Abstract

In this study, an evaluation of energy and economic analysis of two different energy storage systems for the drying process was presented. These systems were the packed bed (PBTES) and phase change material (PCM) thermal energy storage systems, respectively. Pebble stones were utilized as energy storage material in PBTES, while paraffin wax with a melting temperature of 55–60 °C was used in PCM. The main objective of this study was to compare two energy storage materials whose physical and chemical properties were completely different, in terms of performance and costs and to determine the ideal energy storage medium for the solar energy-assisted drying process. For this purpose, two different energy storage mediums of similar capacity were developed and examined experimentally. When the systems were investigated in terms of energy analysis, it was determined that the maximum thermal energy stored during the charging period was 52.59 MJ and 49.52 MJ for PBTES and PCM, respectively. With this energy stored during the discharge period, average 5 mm thick lemon slices were dried and the drying process lasted an average of 6.27 h in PBTES and 6.23 h in the PCM. During the drying process, the moisture content of the lemon slices was reduced from 94.8% to 10% on wet basis. As a result of the experimental studies, the average energy efficiencies were detected as 68.2% and 68.55% for PBTES and PCM, respectively. When the systems were considered economically, it was observed that PBTES had a 10.47% lower initial investment cost compared to PCM.