Microcontroller-based solar tunnel dryer for sustainable drying in Northeast India

Abstract

The growing world population necessitated enhanced food availability and reduced waste. Drying has been a popular technique for extending food storage for a long time since it minimizes volume and lowers moisture and enzymatic activity, reducing food loss. This project sought to create a microcontroller-driven solar tunnel dryer designed for the prevalent rainfall and elevated humidity conditions in Northeast India. The designed solar tunnel dryer is equipped with two DHT22 sensors that assess ambient humidity inside and outside the dryer, deciding whether to let airflow with the environment or isolate it. It controls fan operation based on real-time monitoring. The dryer has 12 trays on a six-tray structure that holds 100 kg of sliced turmeric in every batch. An additional tray with a load cell was provided to record turmeric weight during drying. Without any load, the maximum internal temperature exceeded the outside by 27.1°C, while the minimum internal humidity was 30% lower than external values. The turmeric was dried from an initial moisture content of 71.62% to less than 10% (wet basis) over 101 hours and 40 minutes (5 days) with 28.63 effective bright sunshine hours. The developed solar tunnel dryer's average efficiency was 19.20%, demonstrating its ability to dry turmeric in Meghalaya, India.