Solar dryers are used to enable the preservation of agricultural crops, food processing industries for dehydration of fruits and vegetables, fish and meat drying, dairy industries for production of milk powder, seasoning of wood and timber, textile industries for drying of textile materials. The fundamental concepts and contexts of their use to dry crops is discussed in the chapter. It is shown that solar drying is the outcome of complex interactions particular between the intensity and duration of solar energy, the prevailing ambient relative humidity and temperature, the characteristics of the particular crop and its pre-preparation and the design and operation of the solar dryer.Temperatures from -37 C to 71 o C kill bacteria and inactivate enzymes, although, as such temperatures are also likely to cause crop surface hardening, lower operating temperatures in the range 40 C to 45 o C as shown in Table 1 are generally more common place in solar dryers.For many crops pretreatment is recommended such as washing, blanching and cutting into thin slices. Crops are generally harvested at moisture contents ranging from 16% to 30% wet basis and must be dried to a safe storage moisture contents given in Table 1. In grain drying, fissures that can arise from excessive moisture and temperature gradients lead to broken grains during milling reducing the milled cereal yield. Prompt packing in hermetically sealed containers is essential if for consumer acceptability higher safe storage moisture are used for example as is the case for some dried fruits. Bassey MW, Oosthuizen PH and Sarr J. (1994) Using heated chimneys and reduced collector air gap height to improve the performance of indirect passive solar dryers. Renewable Energy, 4: 169-178. Basunia MA and Abe T. (2001) Thin-layer solar drying characteristics of rough rice under natural convection. J Food Engineering. 47: 295-301. Bechoff A, Dufour D, Dhuique-Mayer C, Marouze C, Reynes M and Westby A. (2009) Effect of hot air, solar and sun drying treatments on provitamin A retention in orange-fleshed sweet potato. Journal of Food Engineering, 92: 164-171. Bena B and Fuller RJ. (2002) Natural convection solar dryer with biomass back-up heater. Solar Energy, 72: 75-83. Evaluation of a rice drying system using a solar assisted heat pump. Renewable Energy, 5: 465-468. Chauhan PM, Choudhury C and Garg HP. (1996) Comparative performance of coriander dryer coupled to solar air heater and solar air-heater-cum-rock bed storage. Applied Thermal Engineering, 16: 475-486. Chavan BR, Yakupitiyage A, Kumar S. (2008) Mathematical modelling of drying characteristics of Indian mackerel (rastrilliger kangurta) in solar-biomass hybrid cabinet dryer. Drying Technology Int J, 26:1552-62, Chen H-H, Hernandez CE and Huang T-C. (2005) A study of the drying effect on lemon slices using a closedtype solar dryer. Solar Energy, 78: 97-103. Das SK and Kumar Y. (1989) Design and performance of a solar dryer with vertical collector chimney suitable for rural application. Energy Conversion and Management...