An Investigation into Hohenheim Solar Tunnel for Drying Maize in Sub-Saharan Climate

This paper presents experimental performance of a polyethylene covered large-scale solar tunnel dryer type of Hoheinheim. Studies were conducted to investigate the performance of Hohenheim-type solar tunnel dryer for drying agricultural products under Togo climatic condition. However, in the sub-Saharan crop producers rely on open-air drying under the sun, this means that this method depends on good dry weather conditions. Tests of drying have been undertaken in experimental research station at Gapé Kpodji (latitude 6°25N, longitude 1°12E) in Togo on the two devices the more used: the traditional sun drying device and the Hohenheim tunnel drier. There is neither electric network nor regular provision in gas butane or other shape of energy besides the biomass. The trade of materials and equipment use for dryers’ construction are non-existent and the technical level of the population is low. The great majority of the population uses the traditional techniques of drying. The obtained the results revealed that the temperature available inside the Hohenheim solar drier produce a 15,5 °C increase in the inside air temperature versus the outside temperature (33,70 °C) to considerable reduction of drying time compare to the traditional device. Besides, the products are protected against rain, the bugs and the dust. It permits to get dry products of good quality. However, its capacity is very low considering to the quantities of cereal produced. Also the cost of maintenance and of its renewal is over the financial capacity of the users. The Hoheinheim drier certainly introduces some improvements compare to traditional sun drying but doesn't answer fully to the specifications of the users.