Solar Dryers for Agricultural Products, A Review

Document Type : Review Article

Authors

1 Department of Biosystems Engineering, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran.

2 Department of Mechanical Engineering, Payame Noor University, Tehran, Iran

10.22034/jrenew.2025.227722
Abstract
Considering that fossil fuels are associated with pollution and cannot be used permanently, attention has been paid to the use of other energy sources such as the sun, water and wind for drying agricultural products. Among renewable energies, solar energy has the most potential. Solar dryers are classified into two categories: active and passive. In the passive type, only solar energy is used to dry the product. But in the active type, a suction fan or blower is used to create air flow throughout the product bed. Also, in direct dryers, the product bed is exposed to direct sunlight, but in indirect dryers, the product bed is not directly exposed to sunlight and hot air passes through the entire product bed. In the mixed type, the air heated by the sun's energy passes all over the product bed, and at the same time, the bed itself is exposed to direct sunlight. The solar dryers are made in two types, open circuit and close circuit. In the close circuit type, unlike the open circuit type, the hot air exiting the dryer chamber is reused to heat the incoming air and increase the thermal efficiency of the dryer. The development of new types and optimization of existing types of the dryers using advanced engineering techniques such as artificial neural networks and computational fluid dynamics is underway at a rapid pace, and in the future, we will see the introduction of smart types of solar dryers.

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Volume 12, Issue 2 - Serial Number 24
September 2025
Pages 200-209

  • Receive Date 07 December 2024
  • Revise Date 04 March 2025
  • Accept Date 29 April 2025