Efficient solar drying techniques: a review

Abstract

In the absence of effective drying techniques, a lot of food gets wasted as there is a lack of post-harvest processes. In India, most of the agricultural produces like paddy, maize, wheat, corn, oil seeds, pulses, chillies, etc. require a temperature range of 50-80 °C for effective drying. Hence, in these conditions, solar drying techniques seem to be the most economical; also, it is safe and eco-friendly. Various types of solar dryers are used across India and worldwide; these are direct solar dryer, green house dryer and indirect solar dryer. Nowadays, indirect type solar dryers are most commonly used because of their several advantages over direct solar dryers. In case of indirect type solar dryers, the products to be dried are kept inside a separate compartment known as drying chamber. Hot air is obtained from the solar collectors either by direct heating method or by using a secondary heating medium and then supplied to the drying chamber for heating of the products. This paper presents a detailed review of various innovative designs of indirect type solar dryers and compares the performance of different types of dryer configuration in terms of collector efficiency, dryer efficiency, drying time and maximum air temperature. Also, the effects of various operating parameters on the thermal performance of such dryers have been discussed.

Solar Drying of Herbal Wealth in Eastern Himalaya: A Review

“…Among all the other types of solar dryer techniques, indirect use of solar radiations for drying plant products is most commonly used in present scenario for removal of moisture content from plant products. It has proven one of the best techniques over the direct use of solar radiations for drying agricultural products (Jangde et al, 2021).Some limitations for the use of indirect solar dryer are mentioned in table 2. It cannot be used in those areas where electricity is not available.…”

Selección de tecnología apropiada para el secado solar de productos agrícolas

“…La eficiencia térmica del secador solar relaciona la energía utilizada para la evaporación de la humedad contenida en los productos agrícolas a una temperatura determinada con la energía total suministrada al secador y se determina utilizando la siguiente ecuación (Abdellatif et al, 2018;Lopez et al, 2020;Jangde et al, 2022). En relación a la evaluación económica, las determinaciones de los costos de secado están en función del tiempo y de los insumos (Inversión construcción del secador, energía eléctrica, depreciación del equipo, volumen de producto, salarios por carga, costo del terreno y de administración).…”

Solar Cookers and Dryers: Environmental Sustainability and Nutraceutical Content in Food Processing

“…In the following decades, solar drying technology has been the subject of research and improvements, both using natural and forced circulation, and with regard to heating from auxiliary sources [15,24,25] Sun drying is still the most common method used to preserve agricultural products in many countries of the world: if advanced techniques are not available, farmers spread their products in thin layers on open ground or on mats where they are exposed to the sun and wind to be dried. Several authors report that significant losses can occur during natural sun drying mainly due to rodents, birds, insects, rain, storms and microorganisms [26]. It has been calculated that about 40% of food loss in less-developed countries derived from post-harvest handling including bad or incomplete drying practice.…”