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The study was conducted on a knapsack sprayer powered by a DC motor through a 12 V lead acid battery charged from a solar panel (photovoltaic) directed to sun rays. The system was installed and tested in the western desert on a small-scale farm at Frafra Oasis (New valley). This study aimed to evaluate and develop a knapsack sprayer powered by a solar energy for overcoming operator fatigue and shortage of traditional energy in Egypt's western desert. The experiments were conducted during the period which starts in August 2019 till February 2020. The main parts of the system consist of photovoltaic (PV) or solar cells, charger controller, rechargeable battery, and DC motor speed control with dimmer and pump which was attached with a tank 20 liters capacity for sucking and pressurizing the liquid to the boom of the sprayer through a flexible hose. The main results of experiments were as follows: The time for recharging the battery completely was found 330 minutes (5.5 hours) to charge completely from 10.55 V -13.85 V, with current intensity 1.67 Ampere. The battery discharge time was varied due to drop the battery voltage from 13.85 -10.55 Volts. Depending on the motor speed, which is the time for discharging the battery was found 4 -9 hours, when motor pulled 0.85 -1.85 Amps at 2000 -3400 rpm and this time at deferent speed is enough to spray area 3 -6.82 fed/day "day work = 6 hours" with application rate 67 -104.7 l/fed. The number of droplets and the area coverage percentage ranges from 30 -146.33 drops and 13.96 -27.97% for one cm 2 of simulator targets at a speed ranging from 2000 -3400 rpm, respectively.

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