A comprehensive review on solar drying using paraffin wax as PCM.

This article reviews the use of thermal energy storage (TES) materials, particularly phase change materials (PCMs) like paraffin wax, in solar drying technologies for fruits, vegetables, and agricultural products. It discusses various types of solar dryers—natural and forced convection, direct, indirect, mixed, and hybrid modes—and highlights how integrating TES, especially latent heat storage via PCMs, enhances drying efficiency, extends operational hours beyond sunlight availability, and improves product quality and nutrient retention. Advances in PCM technology, including encapsulation and nano-enhancement with nanoparticles of different dimensions (0D to 3D), are examined for their role in improving thermal conductivity, stability, and reducing leakage. The review concludes that solar dryers employing PCMs can significantly reduce drying time and increase energy efficiency, with paraffin wax being a widely used, stable, and effective PCM for temperatures between 45–70 °C. Future research is suggested to explore nano-enhanced PCMs and combined sensible and latent heat storage to further optimize drying performance.