Energy, exergy, and techno-economic performance analyses of solar dryers for agro products: A comprehensive review

Due to continuous growth in population and sharp increase in energy and food demand, research on alternative energy sources independent of fossil fuels has increased over the last decade. Moreover, limitations on greenhouse gas emissions by developed and developing countries are imposing much pressure on the energy sector worldwide to use renewable energy sources such as solar, wind, biomass, hydro, and geothermal. Food production is one of the biggest industries in the world, and it consumes a large amount of energy in the form of heat and electricity. In this work, agro-product drying technologies powered by solar energy are presented and discussed. Different types of solar dryers based on direct, indirect and mixed modes are described. Moreover, energy, exergy, economic, and environmental analyses for these technologies are presented to determine the main parameters affecting the dryer performance. The results indicate that the air mass flow rate, temperature, moisture content, and drying time are the most important parameters in solar dryer performance. Finally, a comparative assessment of the performance of different existing solar dryer has been highlighted with a detail scope of future works.