ENERGY AND PERFORMANCE EVALUATION OF PVT-POROUS SOLAR DRYER

Drying is a critical post-harvest operation for agricultural and herbal products, but remains energy-intensive and performance-limited under humid tropical conditions. This study experimentally investigates the energy performance and drying kinetics of a photovoltaic–thermal (PVT) solar dryer integrated with porous absorber materials to enhance heat and mass transfer. The developed system consists of a 150 W PVT panel, a double-pass solar collector, and porous steel mesh absorbers with porosities of 0.98, 0.97, and 0.96. Experiments were conducted under tropical climatic conditions in Thailand at a low air velocity of 0.07 m/s using kaffir lime leaves as a representative leafy material. The results show that drying occurred entirely in the falling-rate period and was governed by internal moisture diffusion. Porous integration improved thermal uniformity and airflow turbulence, increasing the drying rate by 43.73–56.01% and reducing specific energy consumption (SEC) by 30.44–36.01% compared with the non-porous configuration. Optimal performance was achieved at a porosity of 0.96, yielding the highest Deff (8.59x10-13 m²/s) and the lowest SEC of 21.84 MJ/kg. Thin-layer analysis confirmed that the Page model best described the drying kinetics (R2 = 0.980–0.999). Statistical analysis (ANOVA) verified that porosity is a dominant factor influencing performance (p < 0.01). Overall, the integration of porous materials into a PVT solar dryer significantly enhances drying performance and represents an energy-efficient approach for drying leafy agricultural products in humid tropical regions.