A Solar-regenerated Desiccant Dehumidifier for the Aeration of Stored Grain in the Humid Tropics

• Published in: Journal of agricultural engineering research 1998-11, Vol.71 (3), p.257-262
• Main Authors: Thoruwa, T.F.N., Grant, A.D., Smith, J.E., Johnstone, C.M.
• Format: Article
• Language: English
• Subjects: Air conditioning. Ventilation; Applied sciences; Biological and medical sciences; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; General. Properties of wet air; Handling, storage, packaging, transport; Heating, air conditioning and ventilation
• ISSN: 0021-8634; 1095-9246
• DOI: 10.1006/jaer.1998.0321

In many tropical countries, high ambient humidity levels during the night pose difficulties for grain storage. Typical problems are the formation 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 regenerated by solar energy during the day, has been built and tested in Kenya, where ambient conditions often demand dehumidification for 16 h out of 24 h. The desiccant was solid bentonite CaCl2, which is cheap and has a high moisture adsorption capacity, packed beneath a glazed cover for solar regeneration. Airflow was maintained by a small electric fan, powered by a photovoltaic panel and a 12 V battery. Field measurements verified that the system is fully sustainable, with complete restitution of the effectiveness of the desiccant by day. A night-time airflow of 2 m3/min m2of the collector area, with a relative humidity of 40% below ambient levels, could be maintained continuously. Certain geometric and operational parameters remain to be optimized. However, it is concluded that a simple device, built largely from local materials, can significantly enhance conditions for crop storage in humid tropical regions.