Enhanced energy-efficient drying of kaffir lime leaves using a PVT-porous solar dryer

Drying is one of the most energy-intensive industrial processes, often resulting in excessive energy consumption and inconsistent product quality. This study experimentally investigated a photovoltaic–thermal (PVT) porous solar dryer, designed to overcome these limitations by enhancing heat utilization and improving drying performance. The system integrates a PVT panel, a double-pass solar collector, and porous materials to enhance thermal and drying performance. Experiments were conducted under humid tropical conditions to dry kaffir lime leaves at air velocities of 0.07, 0.09, and 0.10 m/s using porous materials with a porosity of 0.98. Results showed that applying porous materials markedly improved drying performance. The drying rate increased by 39–44%, while specific energy consumption (SEC) decreased by 28–30% compared to without porous. The drying process mainly occurred in the falling-rate period, governed by internal diffusion. Statistical analyses using two-way ANOVA and Tukey’s HSD confirmed that both air velocity (p < 0.05) and porous material (p < 0.01) significantly affected performance, with the porous material being the dominant factor. The observed enhancements resulted from increased turbulence, an expanded heat-transfer surface, and improved thermal retention, leading to stable drying temperatures and efficient convective heat exchange. The PVT-porous dryer maintained high efficiency even under low airflow conditions, demonstrating reduced sensitivity to air velocity. Porous materials were thus identified as crucial design elements for optimizing drying efficiency and supporting the utilization of renewable energy. This study provides valuable insights into sustainable agricultural drying, contributing to enhanced energy efficiency and reduced greenhouse gas emissions under tropical climatic conditions