A SOLAR CROP DRYING SYSTEM WITH ROOFINTEGRATED SOLAR COLLECTORS: EXPERIMENTAL AND MODELLING PERFORMANCE pp.311-336
Authors: (S. Janjai, Solar Energy Research Laboratory, Department of Physics, Faculty of Science, Silpakorn University, Thailand)
Abstract: In this work, a solar crop drying system comprising a drying cabinet and roof-integrated solar collectors was developed. The drying cabinet is a parallel-flow tray type dryer with a drying area of 25.2 m2. The solar collectors are flat-plate solar air heaters with a polycarbonate cover. A food processing building with a working area of 108 m2 was constructed. Two arrays of solar collectors with a total area of 144 m2 were constructed and placed on top of the building. The solar collectors serve as both a roof of the building and solar air heaters of the drying system. The solar collectors supply hot air to the drying cabinet placed inside the building. Two dc-fans powered by six 50-watt solar cell modules were used to suck air from the solar collectors to the drying cabinet. Field-level tests for drying coffee and chili demonstrated that drying these products in this system resulted in a significant reduction of drying time as compared to natural sun drying. In addition, the solar collectors performed well both as the roof of the building and the solar air heaters. The payback period of this drying system is approximately 5.4 years. Simulation models of the solar collectors and the drying cabinet were developed. The simulated air temperature at the outlet of the solar collectors agreed well with the measured temperature. The predicted and the observed moisture contents were also in reasonable agreement. This drying system is regularly used for the demonstration of the potentiality of solar drying technology in Lao PDR.