Assessment of the Performance of Energy-Efficient Electric and Solar Tunnel Dryers for Drying Tomatoes
Mkumbukwa H. Nyomolelo *
Department of Food Science and Agro-Processing, Sokoine University of Agriculture, P.O. Box-3000, Morogoro, Tanzania.
Rashid Suleiman
Department of Food Science and Agro-Processing, Sokoine University of Agriculture, P.O. Box-3000, Morogoro, Tanzania.
V.C.K Silayo
Department of Food Science and Agro-Processing, Sokoine University of Agriculture, P.O. Box-3000, Morogoro, Tanzania.
Mariam Mtunguja
Tanzania Agricultural Research Institute (TARI), P.O. Box-30031, Kibaha, Pwani, Tanzania.
*Author to whom correspondence should be addressed.
Abstract
Postharvest losses of tomatoes (Solanum lycopersicum) in Tanzania have become unacceptably high, exceeding 50% due to the perishable nature of the produce, inadequate preservation practices, and the lack of affordable and effective preservation technologies. This research compares solar tunnel drying with electric drying for fresh tomato processing under critical drying conditions, including temperature, relative humidity (RH), wind speed, as well as solar radiation intensity. The study obtained fresh and defect-free ripe tomatoes directly from Mlali Ward farmers, followed by processing through the use solar drying technology at the Sustainable Green Energy Cooperative (SUGECO) situated in Morogoro Municipal and through the use of an energy-efficient electric dryer at Sokoine University of Agriculture (SUA), School of Engineering and Technology.
The electric dryer was operated under controlled conditions, including maintaining temperatures between 50 and 65°C and RH between 20 and 60%, which resulted in moisture reduction from 95% to 10.4%, within 12 hours. The solar tunnel dryer was operated under inconsistent environmental conditions where the temperature ranged between 30 and 50°C, while the Relative Humidity remained at 30 to 65%, attaining moisture content reduction to less than11% within 18 to 20 hours. Despite the environmental variability, solar drying was found to be effective during peak solar hours when solar intensity exceeded 1000 W/m² and wind speed exceeded 2.5 m/s.).
The results show that although electric dryers provide quicker and more reliable drying, small-scale farmers cannot afford them due to their high energy requirements. On the other hand, solar tunnel dryers provide rural communities an affordable and environmentally friendly substitute. To decrease postharvest losses, enhance food security, and raise household income in Tanzanian tomato-producing regions, the study suggests improving solar dryer design, encouraging local fabrication, and strengthening farmer training and policy assistance.
Keywords: Solar dryer, electric dryer, tomato (Solanum lycopersicum), humidity, temperature, moisture content, post-harvest loss