Design Construction and Testing of Indirect Type passive Solar Dryer for Groundnuts (Arachis hypogaea Linnaeus)

Abstract

The objective of this research was to design an indirect type passive solar groundnut dryer constructing its prototype and evaluating the performance of the dryer compare to sun and shade drying. The dryer designed consists of three units: air-heating solar energy collector, drying chamber, and Chimney. The performance evaluation was conducted using Completely Randomized Design (CRD) with a total number of 27 observations (3 depths x 3 drying methods x 3replications) .Greater drying rates were obtained with the solar dryer at similar drying depths for all drying methods used. Drying of groundnut in solar dryer from around 25% (wet basis) to the final moisture content about 10% has taken 24hrs, 29hrs, and 38hrs at 5, 10, and 15 cm depth of drying respectively; and this reduced the drying time by 9hrs and 54hrs at 5cm depth, by 13hrs and 53hrs at 10cm depth, and by 16hrs and 52hrs at 15cm depth for sun and shade drying respectively. Average dryer efficiency was estimated to be about 25 %, 20.68%, and 15.78% at 5, 10, and 15cm depth of drying respectively. Physical and proximate content analysis of the dried groundnut showed drying method and drying depth affects the proximate content and germination capacity of groundnuts. shade dried groundnuts samples has resulted in the highest crude fat content (45.93%), crude protein content (26.58%) and germination capacity (89.33%) at 10cm depth; solar dried groundnuts has resulted in the next highest crude fat content (42.91%) and statistically similar crude protein content with the sun dried samples at all 5, 10 and 15 cm depths of drying. The highest crude fiber content was obtained in the groundnuts samples dried in solar dryer (7.27%) and shade drying with the next highest value (6.84, 4.82%). The best drying depth for high crude fiber content was 15cm. The groundnuts samples dried with solar dryer at 15 cm depth have the highest ash content (3.5%) and sun dried samples have the lowest ash content with statistically similar value at all depths. High Carbohydrate content was obtained in groundnuts samples dried in open sun drying (33.76%) and solar dried samples with the next highest value (27.8%)