Current status and prospect of integrating solar air heating systems for drying in various sectors and industries

• Solar thermal drying technologies in industrial sectors are reviewed. • Economic and environmental aspects are presented. • Future scope and recommendations for air heating systems are given. • Prospect of integration of solar drying systems with existing methods are discussed. This review presents the current status of solar air heating systems in various sectors and industries and its prospect of integration with existing drying methods. Most of published review articles in this domain have focused on the use of solar drying in agricultural industries for food preservation. Many researchers have identified component level gaps and proposed various changes to solar thermal collectors for improved drying performance. Various technologies have been developed and implemented which optimised the energy requirements effectively and efficiently. However, there have been very few studies focusing on the potential integration methods in various industries where drying is an essential process during production. In this paper, a detailed review of the essential drying processes in various industries is presented to provide a perspective on the current state of available technologies and the ongoing research in the field solar drying. In addition to the agricultural industry, the paper also discusses the potential use of this technology in other emerging areas. Few industrial installations of this technology have been reviewed, and the major findings and observations have been reported. Possible integration of solar drying with the existing drying methods has been proposed to create novel drying systems for large-scale industries that can be generalised for industrial applications. Solar based drying technology can help in reducing the energy consumption of conventional dryers up to 15% to 80%, which could in turn reduce the carbon dioxide emissions annually by 20% to 80%, depending on the type of the industry and the material or product to be dried. This review will assist researchers and industries in making the drying process compatible with solar energy.