Novel hybrid solar dryer for medicinal plants: An experimental evaluation (Tithonia diversifolia Gray)

Abstract

The present study examines a hybrid solar drying (HSD) system designed to dry the medicinal plant species, Tithonia diversifolia Gray, via both natural and forced convection. The dryer was built and tested at the Polytechnic University of Chiapas, Mexico. The hybrid solar technology used in the present research comprise a flat solar collector, a solar water heater, and the paraffin wax HS-58, which was used as a phase-change material. The solar dryer was experimentally tested both with and without a thermal energy storage system. Experimental tests were carried out to evaluate the energetic profitability and the quality of the drying produced by the system proposed. Energetic profitability was evaluated based on exergy indicators, the sustainability index, and the quality of drying. The results show that, used with the flat solar collector, the solar dryer was able to operate for only 4 h, while, used with the proposed auxiliary subsystem, the system was able to continually operate for 14 h. The total autonomy of the HSD was 71.42% higher than that recorded for a simple solar dryer. The exergetic efficiency of the HSD ranged from 17.68% to 57.66%. The HSD reduced the moisture content of the T. diversifolia by 90%.