Evaluation of Modular Polycarbonate Solar Dryers for Coffee: Technical Performance and Economic Feasibility

Abstract

Solar drying is the most common method for drying parchment coffee on smallholder farms due to its low cost. However, traditional dryers often suffer from long drying times, moisture reabsorption, and material degradation, which can reduce coffee quality. This study evaluates two modular, self-supporting solar dryers covered with polycarbonate sheets, one solid (3 mm) and one alveolar (6 mm), compared to a traditional control dryer covered with Prosolar 140 g/m² plastic fabric. Trials were conducted in Gigante and San Agustín, Huila, Colombia, measuring drying time, environmental conditions, and sensory quality. Both polycarbonate dryers included an automated ventilation system and a retractable curtain to improve moisture control. The solid polycarbonate dryer reduced drying time by up to 47.8% and maintained the highest internal temperatures. The alveolar dryer reduced drying time by 43.2% and showed slightly better uniformity in sensory scores. Despite the accelerated drying, cup quality was preserved, with no typical defects linked to rapid or uneven drying. The ventilation system maintained low humidity levels, and no nighttime moisture reabsorption was observed, unlike in the control dryer. Economic analysis showed that while the polycarbonate dryers had higher initial costs, they offered better long-term returns due to greater drying capacity and lower maintenance. These systems processed more coffee per cycle and had longer service lives, improving overall profitability. Polycarbonate-based drying systems present an efficient, scalable, and sustainable alternative for coffee producers, particularly in regions with variable climates. They reduce drying time, preserve product quality, and enhance economic feasibility.