Experimental Investigations of a Simple and Cheap Passive Solar Dryer for Preserving Agricultural Products

In this study, a simple passive solar dryer was designed and built with low-cost materials, then tested to determine its drying performance. Developing a sustainable solar dryer using low-cost materials sourced locally to outperform open sun and direct solar drying techniques readily used for preserving agricultural products is novel in this work. The passive solar dryer features a single-pass solar collector, a drying chamber with multiple trays for drying food, and a chimney. The drying performance of potatoes was compared to that of open sun drying (OSD) and direct solar drying methods based on the solar collector's thermal efficiency and air outlet temperature. The drying tests revealed that collector efficiency varied with time, peaking at 1:00 pm with a maximum outlet temperature of similar to 54.2 degrees C. In addition, the efficiency of the solar collector is found to increase as the airflow rate increases. Potatoes were dried from an initial moisture content (MC) of 82% to below 10% using the passive solar dryer. Compared to direct solar and open sun drying methods, the studied passive dryer was more efficient, resulting in 11.1% and 20% less drying time, respectively. The drying rate was seen to be higher at the start of the drying process and decreased at the end. The average drying efficiency was found to be 4.3, 14.4, and 18% using samples of 100, 300, and 500 g, respectively. Sensory tests revealed that potatoes dried using the passive solar dryer were more appealing in colour, taste, and flavour.