A comparative experimental study of orange drying in an indirect and greenhouse-solar dryers

Aliment drying is amongst the most natural, efficient, economical, and energy-saving techniques to preserve food by inhibiting internal bacterial growth. In this context, we conduct in this work an experimental thermal performance assessment and analysis of two different drying systems under natural convection: a greenhouse-based solar dryer and an indirect solar dryer. Both were conceived in the Mohammed V University’s Laboratory for Solar Energy and the Environment in Rabat (Morocco). The first system is made up of a solar collector roof, a drying chamber, and a water storage system. The second system comprises a solar air collector, a drying chamber, a heat exchanger, and a water storage tank. Fresh high water content oranges were chosen to perform the study. At nighttime, the greenhouse solar dryer achieves higher performance by maintaining a temperature of 11 °C higher and relative humidity 18% lower than the indirect solar dryer. To dry oranges from 76% to 24% moisture content, the latter took 5 days compared to the former (3 days). The solar greenhouse dryer’s payback period was calculated to be 2.39 years, compared to 3.5The results of this study provide key insights regarding the implementation and performance of both systems in drying an aliment of high worldwide interest.