Different systems of air solar collectors were used with an active solar dryer to study the drying options of a thin layer of
lemon-grass (Cymbopogon citratus). Three air solar collector systems were tested by outlet air temperature, absorbed energy,
gained energy and thermal efficiency. The results indicated that, the additional collector plate to the most common air solar
collector and the additional air flow passing upper and lower the absorbed plate, increased outlet air temperature by
18.5%, followed by increasing the energy gained by 41%, and increasing of the thermal efficiency of the air solar collector
by 69%. That system increased the drying rate of lemon-grass by 37.5%.