A comparison between solar tunnel driers and conventional fuel dehydrators for on-farm drying

A simulation and experimental study of a small solar tunnel drier has been made to determine its performance compared to a conventional dehydrator for drying horticultural crops on-farm. Over a three day drying period, the solar tunnel drier is predicted to reduce energy consumption by 29% and achieve a 16% reduction in drying time. The load ratio in the solar tunnel drier is inferior to the dehydrators surveyed, but the capital and recurrent costs are less. Variations in drying rate and product quality due to uneven levels of solar radiation and temperature gradients within the solar drier have been overcome by the use of a rotating tray system, which also simplifies the on and off loading of fruit. Sultana grapes, apricots and tomatoes are particularly suitable crops for drying in solar tunnel driers because their final product quality is enhanced by the direct exposure to solar radiation.