In this research a new approach for employing solar radiation as the main source of energy for paddy drying
was introduced. The drying test rig was designed, fabricated and evaluated. The rough rice solar dryer was a cross
flow and an active mixed-mode type with a new and an efficient timer assisted semi-continuous discharging
system. The rig consists of six ordinary solar air heaters, an auxiliary electric heating channel, a drying chamber
with an electrically rotary discharging valve and an air distributing system. The area of each collector was 2 m2
(totally 12 m2) and they were installed on a light frame tilted 45° towards the south. The drying system consisted
of: an inlet bin, a drying chamber ended with a discharging valve, an outlet bin and a plenum chamber. The dryer
bed, with 2 m2 surface area, acted as a single glazed solar collector was also tilted 45° towards the south. At the
bottom of dryer bed, an electro-mechanical rotary valve was installed which was controlled by a timer. The timer
activated the rotary valve to operate once a while to discharge the dryer bed semi-continuously. Air mass flow
rate was measured by an orifice plate, the temperatures were monitored by T type thermocouples, the solar
insolation was recorded by a solarimeter, and the electrical energy consumed by the fan and the heating channel