Solar, Biomass and Hybrid Dryers - BioEnergy Discussion Lists

Package 7: Solar-Biomass Hybrid Cabinet DryerThe hybrid cabinet dryer (Figure 7.1) consists of an air-heating solar collector, adrying chamber, a biomass stove-heat exchanger-chimney assembly, and a chimneyattached to the drying chamber at the top. During daytime, ambient air is heated bythe solar collector, and the hot air is passed through trays kept inside the dryingchamber where products to be dried are loaded. During poor weather conditionsand at night if required, the biomass stove provides the hot air required for drying.A heat exchanger is used to avoid direct contact of flue gas with the product. Directcontact of flue gas might contaminate the product as the flue gas generally containssmoke, soot, and other harmful gases.Figure 7.1: The solar-biomass hybrid cabinet dryerThe stove can be operated using fuels such as fuelwood, wood chips, twigs, andbriquettes. As honeycomb briquette is a popular fuel in certain parts of Nepal,production of honeycomb briquette is explained in detail in this package.The products are spread in thin layers on several trays inside the drying chamber.Warm moist air from inside the drying chamber exits to the atmosphere through thechimney at the top, assisted by draft created in the chimney. Technical specificationsof the solar-biomass hybrid cabinet dryer are given in Table 7.1. The dimensions ofthe drying chamber are optimized for convenient loading and unloading of theproducts. The drying chamber was also partitioned to minimize heat losses duringhandling of the product during the drying process.Design DetailsThe hybrid dryer is a modified version of the solar cabinet dryer described inPackage 5. The design of the flat plate solar collector, drying chamber, and36