Global advancement of solar drying technologies and its future prospects: A review

Global energy demand continues to increase with the expansion of the economy activities and sustainable development. Meanwhile, the world is suffering from pollution and harmful greenhouse gases originated from burning of fossil fuels where the consequences of climate changes are also alarming. Solar energy is an alternative energy source that is abundant, safer and cleaner. This article provides a comprehensive review of works pertaining to solar thermal energy utilization in the drying process. In this article, the classification of solar dryers, the main components which includes solar collector, drying chamber and auxiliary systems, prospects, challenges, recent advancement and performance are discussed. The existing literature reported that solar dryer and solar collector maximum efficiency of 54% and 81% respectively, with superior products quality than the open solar drying. Solar drying is economical method with the payback period of 0.54-4.69 years. Solar dryer can also reduce 34% of CO2 emission to the atmosphere with less consumption of fossil fuel. Improvements such as in the design of solar collector, drying chamber, new auxiliary system, and material are essential to elevate the solar drying system performance. A review of the technologies can provide a base for the next generation of sustainable solar drying systems and helps policymakers to frame strategies aiming for clean technology and sustainable development.