Abstract

The aim of the study was to design and construct a solar grain dryer integrated with a simple biomass burner using locally available materials. This was to address the limitations of the natural sun drying for example drying exposure, liability to pests and rodents, over-dependence on sun and escalated cost of mechanical dryers. This became beneficial especially in reducing post-harvest losses as well as helping in the preservation of agricultural product. The dryer is composed of solar collector, drying chamber, back-up heater and airflow system. The design was based on the study area of Mau summit located in Nakuru County, Kenya. The average ambient conditions were 26°C air temperature and 72% relative humidity with daily global solar radiation incident on horizontal surface of about 21.6 MJ/m2/day. A minimum of 3.77 m2 solar collector area was required to dry a batch of 100 kg maize grain in 6 h with natural convection from the initial moisture content of 21% to final moisture content of 13% wet basis. A prototype dryer designed was fabricated with minimum collector area of 0.6 m2 and used in the experiment. Forced convection was employed to reduce drying time. The thermal efficiencies of the solar and solar assisted dryer were 39.9 and 57.7%, respectively. The back-up heating system improved the efficiency of the dryer by 17.8% and reduced drying time substantially.

Keywords:

Back-up heater, design, grain, solar collector, solar drying,

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Competing interests

The authors have no competing interests.

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