**3. Importance of solar drying**

Solar energy is a renewable and clean source of power that harnesses sunlight to generate electricity or heat. Using solar panels made of semiconductors, photons from sunlight are absorbed, releasing electrons and creating an electric current. This energy is environmentally friendly, as it does not produce harmful emissions or deplete finite resources. Solar energy can be deployed at various scales, providing energy independence and resilience, particularly in remote areas. Although initial costs can be high, advancements in storage technologies are improving efficiency and overcoming limitations associated with weather conditions. Overall, solar energy offers a sustainable solution for our energy needs, contributing to a cleaner and more sustainable future [9, 10]. Solar drying methods offer several advantages compared to conventional drying techniques. Energy efficiency [8], cost-effectiveness [11], environmental sustainability [12], preservation of nutritional quality [13], and enhanced product quality [14] are the advantages of using solar dryers.

In this regard, Ekechukwu et al. conducted a comprehensive review of various solar energy drying system designs, construction details, and operational principles. Their findings indicated that properly designed forced convection (active) solar dryers are generally more effective and controllable than natural-circulation (passive) types. However, due to the need for electricity or fossil-fuel-driven fans and auxiliary heating sources, active solar dryers are unsuitable for remote rural village farm use in most developing countries, given their high capital, maintenance, and operational costs. On the other hand, for large-scale applications in rural areas, the "ventilated greenhouse dryer" offers the advantage of being cost-effective and simple to construct and operate on-site [15].

Fudholi et al. gave the technical directions for developing solar-assisted drying systems for agricultural produce [16]. Jairaj et al. reviewed solar dryers exclusively for grape drying on a normal scale. They included various pre-treatment and drying methods for good-quality grape drying [17]. For the Malaysia location, the air-based solar collectors integrated solar drying system was reviewed by Fudholi et al. They have included the energy, exergy, economic and environmental aspect of the various solar dryers [18]. Mustayenp et al. presented a study on various solar dryers' design, performance, and application. This review focused on solar dryer models suitable for producing high-quality dried products [19]. Hicham El Hage et al. extensively reviewed the economic and environmental aspects of the solar drying system. The critical parameters, such as payback period and CO2 mitigation, were compared [20].

Om Prakash et al. reviewed the various modeling technics, including computational fluid dynamics (CFD), adaptive-network-based fuzzy inference system (ANFIS), artificial neural networking (ANN), FUZZY, thermal, mathematical, drying kinetic, and energy modeling [21]. Azwin Kamarulzaman et al. reviewed the global advancement of solar drying technologies and their prospects. They discussed various performance parameters, including energy assessment, payback period, and CO2 mitigation [22]. Aprajeeta Jha et al. reviewed the recent advancements in design, application, and simulation Studies of hybrid solar drying technology. The review discussed the various software used for simulating the solar drying system, including PHOENICS, FLUENT (general purpose software with Multiphysics capabilities), FIDAP (modeling complex physics), ANSYS CFX, COMSOL Multiphysics, TRNSYS [23]. Nukulwar et al. focused on various materials used to construct solar dryers and their performance evaluation for agricultural products [24].

The literature shows that various authors reviewed the performance evaluation of some specific food commodities, the use of simulation software, various modeling, and economic and environmental aspects of solar drying systems. However, the performance evaluation of various ranges of fruits, vegetables, marine food products, and other commodities was not reported exclusively. This chapter mainly focused on the review of the performance of solar drying techniques for a range of food substances which is widely used in India, including vegetables (bottle gourd, carrot, potato, ivy gourd, and onion), fruits (banana, cucumber, Tomato, and grapes), marine food products (Fish, shrimp, and prawn), and other commodities (Ginger, Chili, and Jaggery). The drying parameters such as moisture diffusivity, activation energy, drying rate, operating temperature, size, and shape of the drying product were compared for mentioned food substances. A suitable mathematical thin-layer model for food substances was also presented.
