Development of a Solar Dryer Incorporated with a Thermal Storage Mechanism

Abstract

This work presents the development and performance evaluation of a solar crop dryer for drying agricultural products. The dryer consists of three major parts; the drying chamber (630 mm by 610 mm by 210 mm), a solar collector (630 mm by 590 mm by 50 mm) and a heat storage device (630 mm by 590 mm by 50 mm). The dryer was designed for crops weighing a maximum of 15 kg with an ambient temperature of 33oC. The performance evaluation was carried out using unripe plantain and okra. The results of the performance evaluation for no-load test showed that the average temperatures for the drying chamber, collector and ambient without the heat storage system and the boaster mirror were recorded as 47, 69 and 32oC respectively and 55.5, 71.5 and 32oC with heat storage, while 73oC, 83.5oC, 32oC respectively with both the heat storage and boaster mirror. The boaster mirror introduction recorded a higher temperature of 73oC in the drying chamber as against 55.5oC when it was not installed. The results of the on-load test shows that the rate of moisture removal was faster in the dryer (1 to 0.24) kg after drying for four days fro plantain and (1 to 0.21) kg after drying for three days for okra as against (1 to 0.35) kg for plantain and (1 to 0.49) kg for okra with direct/open sun drying. The products were evaluated for physicochemical properties for the fresh, solar dryer dried and open sun-dried samples and results shows that solar-dried plantain and okra recorded higher percentage of nutrients over open sun-dried samples in Fibre, protein, ash content (1.89, 1.17, 0.39), (1.63, 1.14, 1.53) respectively, while the percentage of fat content was significantly higher in sun-dried samples with plantain having (0.32%) and okra (0.1%) as against solar-dried samples.