Hybrid Greenhouse Dryer for Paddy

Abstract

A forced convection greenhouse dryer was developed and used for drying of freshly harvested paddy. The solar greenhouse dryer of size 4.47 × 2.13 m with 2.59 m central height was constructed and covered with 6 mm polycarbonates sheet. Photovoltaic power driven direct current fans were used to provide forced ventilation. Freshly harvested paddy was dried at 50, 100 and 150 mm bed thickness in the hybrid greenhouse dryer and open sun drying during kharif and rabi seasons of 2016. The kharif harvested paddy was dried from 25.3 % to 12.0 % (w.b.) moisture content at 100 mm bed thickness within 21 h, 28 h of drying in the hybrid greenhouse dryer and open sun drying, respectively. Highest drying rates were 1.54 kg.h-1 and 1.35 kg.h-1 in greenhouse dryer and open sun drying, respectively. During rabi season, paddy was dried from 22.8 % to 12.0 % (w.b.) moisture content within 19 h and 25 h with highest drying rates of 1.65 kg.h-1 and 0.97 kg.h-1, respectively, in the hybrid greenhouse dryer and open sun drying. Thermal efficiency of the greenhouse dryer was 28.15 % and 22.15 %, and pickup efficiency was 15.49 % and 14.88 % during kharif and rabi seasons, respectively.