Drying Kinetics of Coffee Cherries From Two Varieties Using a Solar Cabinet Dryer Coupled With Underground Thermal Energy Storage

ABSTRACT Coffee is a vital cash crop in Ethiopia, yet substantial postharvest losses and quality degradation which limit its market value and export potential. This study explores drying of coffee cherries in a solar cabinet dryer integrated with an underground rock bed thermal energy storage system (TES) as a novel approach. Experiments were conducted using two beds with different particle sizes (36 and 56 mm) at an airflow rate of 0.75 m 3 /s. Results showed that the solar cabinet dryer with TES considerably reduced drying time, maintained higher and more consistent drying temperatures during off‐sunshine periods, and improved overall drying efficiency. Bed 1's smaller rocks enhanced heat retention, increasing drying rates by 6%–11% despite slightly lower efficiency (32%) than Bed 2 (33.88%). Nine thin‐layer drying models were evaluated based on R 2 , RMSE, and SSE values. The Modified Midilli model best fits Zegie cherries, while the Midilli‐Kucuk model fits Dangela cherries. Zegie cherries exhibited higher moisture diffusivity (6.16 × 10 −11 m 2 /s), mass transfer coefficients (4.71 × 10 −8 m/s), and heat transfer coefficients (1.20 × 10 −5 W/m 2 K). The activation energy was 23.91 kJ/mol for Zegie and 46.27 kJ/mol for Dangela. Statistical analysis revealed significant ( p < 0.05) effects of coffee variety and bed effect. This integrated system provides a sustainable, energy‐efficient solution for agricultural drying, reducing fossil fuel reliance while enhancing decentralized renewable energy and supporting smallholder farmers in agro‐industrial value chains. Future research should focus on system scale‐up, cost–benefit analysis, and integration with other postharvest technologies to maximize impact.