Solar drying of fruits, vegetables, spices, medicinal plants and fish: Developments and Potentials

This paper presents developments and potentials of solar drying technologies for drying of fruits, vegetables, spices, medicinal plants and fish. Previous efforts on solar drying of fruits, vegetables, spices, medicinal plants and fish are critically examined. Recent developments of solar dryers such as solar tunnel dryer, improved version of solar dryer, roof-integrated solar dryer and greenhouse type solar dryer for fruits, vegetables, spices, medicinal plants and fish are also critically examined in terms of drying performance and product quality, and economics in the rural areas of the tropics and subtropics. Experimental performances of different types of solar dryers such as solar tunnel dryer, improved version of solar tunnel dryer, roof-integrated solar dryer and greenhouse type solar dryers which have demonstrated their potentialities for drying fruits, vegetables, spices, medicinal plants and fish in the tropics and subtropics are addressed. Simulated performances of solar tunnel dryer, improved version of solar tunnel dryer and roof-integrated solar dryers were assessed for drying fruits, vegetables, spices, medicinal plants and fish. The agreement between the simulated and experimental results was very good. The simulation models developed can be used to provide design data and also for optimal design of the dryer components. A multilayer neural network approach was used to predict the performance of the solar tunnel drier. Using solar drying data of jackfruit and jackfruit leather, the model was trained using backpropagation algorithm. The prediction of the performance of the drier was found to be excellent after it was adequately trained and can be used to predict the potential of the drier for different locations and can also be used in a predictive optimal control algorithm. Finally, prospects of solar dryers for drying fruits, vegetables, spices, medicinal plants and fish in the tropics and subtropics are discussed.