Performance evaluation of an enhanced fruit solar dryer using concentrating panels

Concentrating solar panels (CSP) improve the process of solar drying Roma tomatoes. This paper presents a performance comparison between two mixed-mode solar dryers. The dryers were identically constructed, however one of the dryers utilized mobile and easily adjustable flat concentrating solar panels to maximize incident solar energy on the dryer. Temperatures inside the dryer that utilized the concentrating solar panels were approx. 10 °C higher than those in the normal dryer during the majority of a sunny day testing period. This increase in temperature led to shorter Roma tomato drying times in the dryer with CSP. The concentrating solar panels showed a considerable increase in drying rate on sunny days, with a 27% decrease in total drying time as compared to the normal dryer to reach the target dimensionless moisture content of 0.2. A less significant increase in drying capacity was achieved when the dryer was tested in simulated cloudy conditions. The faster drying rate achieved in the dryer utilizing solar concentrators, under both sunny and simulated cloudy conditions, demonstrates the ability to dry produce to an acceptable moisture content in a reasonable time, with the objective of reducing postharvest loss and preventing spoilage.

► Concentrating panels increase solar dryer temperature and relative humidity.
► Increased vapor pressure deficit increased drying rates, reducing drying times.
► Lightweight, locally available materials may be used as concentrating panels.