Progress in solar dryers for drying various commodities

Uncertain price rise and rapid depletion of fossil fuels accelerated the development of renewable energy sources in the form of alternative power sources. Solar is an abundant, renewable and sustainable energy source that attracted many eminent researchers across the world to work in the field of solar energy applications. In developing countries, solar drying is capable of fulfilling the increasing demand of healthy, low cost natural foods and need for sustainable income. Solar dryers used for agricultural product drying can be proved to be most useful device from energy conservation point of view that not only save energy but also saves a lot of time, occupying less area, improves product quality and personnel life style. A solar crop drying system does not solely depends on solar energy for its functioning besides many recent advancements in drying process which combines other form of auxiliary heating source with sun energy are also in recent trends for reducing fuel consumption. In this paper, a review of various types of solar dryers namely, direct solar dryers, indirect solar dryers, hybrid solar dryers and their various drying applications are represented. (C) 2015 Elsevier Ltd. All rights reserved.