An Investigation of Solar Dryers with Different Covers for Solar-Dried Cultivated Bananas

Abstract

This research made comparison studied of the efficiency of a solar dryer covered with polycarbonate sheet and glass sheet under the same ambient environment. The experiment was carried out during the period of February-March, 2022 in Thailand. Cultivated bananas were dried from 8:00 a.m. to 4:00 p.m. for four consecutive days and the experiments were repeated twice. Data collected from the experiment were irradiance, temperature, and banana mass from both solar dryers and the controlled sample under natural sunlight exposure. The results from the repeated experiments showed that the maximum global solar radiation was 928.96 W/m², with mean value of solar radiation of 549.05 and 543.39 W/m² for round 1 and 2; respectively. The temperature inside the solar dryer covered with glass sheet was found higher than the one covered with polycarbonate sheet by 3-5°C, and higher than the ambient air temperature by 25-28°C. As a result, the bananas in the solar dryer covered with glass sheet was dried quicker than the one covered with the polycarbonate sheet. The final moisture contents for dried bananas from round 1 and 2 were 4.34, 5.22% (wet basis, wb); 5.07, 6.21% (wb); and 12.01, 14.37% (wb) for the solar dryer covered with glass sheet, dryer covered with polycarbonate sheet, and the sample directedly exposed to sunlight; respectively. According to the same drying time comparison, the solar dryer covered with glass sheet was 3% faster than the dryer covered with the polycarbonate sheet and was also around 45% faster than the sample under natural sun drying.