Design and construction of solar-biomass hybrid dryer for curing tobacco.

Abstract

Hybrid solar biomass dryer for curing tobacco was designed, constructed and evaluated. The study mainly tried to address the problem associated with long hours of drying and inefficient barns that use up a lot of biomass (firewood). The dryer looked at addressing the solar energy as the main source of energy and backup heater using biomass to enable continuous drying at night and during bad weather or low solar isolation. The dryer uses the readily available raw material to enable availability of costly dryer as compared to the current dryers. The dryer was designed based on climatic conditions of Arua located in West Nile Uganda. The average ambient conditions were 26◦C air temperature and 67% relative humidity with the global solar radiation incident on the horizontal surface about 2400MJ/m2/day. This study describes the design considerations and results of calculation of design parameters. The tobacco fresh from the garden has moisture content 80% and is dried to moisture content of 8% in 2 days. The dryer mainly consists of a solar thermal collector panel, drying chamber, fans powered by 15W solar panel and gas to gas biomass backup heater. The solar collector is made up of single glazing glass, 2mm black painted steel absorber plate and 4mm plywood insulation which is enclosed in a casing made from wood. The drying chamber is made from plywood with 4mm thickness. The backup heater uses a gas to gas heat exchanger and uses wood chips as the biomass source. The total cost of the dryer was estimated to be Ug SHS. 1.2million