A SOLAR-REGENERATED DESICCANT DEHUMIDIFIER FOR THE AERATION OF STOREDGRAIN IN THE HUMID TROPICS

In many tropical countries, high ambient humidity levels during the ni ght pose di difficulties for grain storage. Typical problems are the f ormation of wet and hot spots within the stored grain mass, with mould growth and mycotoxin contamination. A prototype device that provides a supply of dehumidified air at night, using desiccant which is regene rated by solar energy during the day, has been built and tested in Ken ya, where ambient conditions often demand dehumidification for 16 h ou t of 24 h. The desiccant was solid bentonite CaCl2, which is cheap and has a high moisture adsorption capacity, packed beneath a glazed cove r for solar regeneration. Airflow was maintained by a small electric f an, powered by a photovoltaic panel and a 12V battery. Field measureme nts verified that the system is fully sustainable, with complete resti tution of the effectiveness of the desiccant by day. A night;time airf low of 2 m(3)/min m(2) of the collector area, with a relative humidity of 40% below ambient levels, could be maintained continuously. Certai n geometric and operational parameters remain to be optimized. However , it is concluded that a simple device, built largely from local mater ials, can significantly enhance conditions for crop storage in humid t ropical regions. (C) 1998 Silsoe Research Institute.