Performance evaluation of a controlled hybrid solar dryer integrated with PID-regulated furnace heating system

Abstract

This study presents the performance evaluation of a hybrid direct-mode solar dryer integrated with a PID-regulated tungsten filament furnace to maintain consistent drying temperatures under varying weather conditions. The system was tested on tomato, onion, and garlic under both passive (natural convection) and active (forced convection) airflow modes, with targeted drying temperatures of 50 °C, 45 °C, and 65 °C set for each crop, respectively. Results showed that forced convection significantly enhanced drying efficiency from 10.2% to 14.4% for tomato, 10.7% to 17.7% for onion, and 3.85% to 4.9% for garlic, while also reducing drying time by approximately 50%. The variation in drying efficiency among crops is attributed to differences in structure and moisture content, thus leading to different drying times, with garlic showing lower efficiency due to its dense texture, smaller sample size, and longer time required to reach the final moisture content, resulting in higher relative energy consumption. Overall, the system demonstrated strong potential as a reliable, efficient, and adaptable solution for sustainable food drying in off-grid and rural settings.