Abstract Solar drying of fruit materials often suffers from low thermodynamic efficiency, extended drying time, and quality deterioration caused by fluctuating solar radiation. Despite the development of hybrid solar drying systems, limited studies have examined how multi‐stage pulsed thermal regimes influence second‐law thermodynamic behavior and exergy‐based environmental sustainability indicators. This study investigates a pulsed multi‐temperature drying strategy implemented in a hybrid solar dryer (HSD) integrating a solar air collector, photovoltaic power supply, and automated control. Fresh orange slices of three thicknesses (3, 5, and 7 mm) were dried under outdoor conditions in Aswan, Egypt, and the effects of slice thickness and tray position on drying kinetics, energy performance, exergy efficiency, and environmental sustainability indicators were evaluated. The pulsed drying regime accelerated moisture removal and improved drying uniformity compared with conventional continuous heating. The solar collector (SC) achieved a maximum energy efficiency of 58.22% at peak solar radiation, whereas exergy efficiency remained lower (maximum 21.49%, average 9.28%) due to significant exergy destruction in the collector. In contrast, the drying chamber exhibited substantially higher thermodynamic performance, with an average exergy efficiency of 53.6% and a sustainability index of 2.9, indicating effective conversion of available energy into moisture evaporation. Exergy‐based environmental indicators revealed that the collector contributed the largest environmental burden (WER ≈ 0.90; EEF ≈ 19.6), while the drying chamber operated with comparatively low exergy losses (WER ≈ 0.50; EEF ≈ 1.2). Overall, the system improved drying performance and enhanced thermodynamic sustainability by promoting more effective utilization of solar‐derived exergy during moisture removal.
Elwakeel et al. (2026) studied this question.