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 m
2
(totally 12 m
2
) 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 m
2
surface area, acted as a single glazed solar collectorwas 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,
was recorded by watt meters. To evaluate the drying system, a local variety of medium size kernel of rough rice
was selected to be dried by the dryer. One of the objectives in this research was to evaluate the effect of mass flow
rate and interval time of crop discharging on the rate of crop drying by the dryer. Two distinct factorial
experiments were conducted in a completely randomized design with three replications for each treatment. The
first experiment was conducted with two factors: mass flowrate (three levels), and discharge interval time (two
levels). The second experiment was conducted with three factors: the moisture content of diffe
