Innovating an electrostatic charging unit with an insulated induction electrode for air-assisted orchard sprayers

Abstract

Orchard pesticide applications using electrostatic spraying technology enhance droplet deposition and reduce environmental pollution. However, the incorporation of charging systems into conventional air-assisted sprayers remains limited. This is primarily due to challenges such as the necessity for high air velocity to prevent droplet adherence to electrodes, electrode-nozzle design flaws, and safety concerns related to the high voltage used for charging. To address these issues, this study developed five charging units that employ insulated induction electrodes, eliminating exposure to external elements. These units were incorporated into an air-assisted sprayer to assess their effectiveness in charging spray droplets and improving deposition. The units successfully limited electrical leakage, even under high-voltage conditions (up to 18 kV) and in the absence of airflow. At an electrode voltage of 14 kV, and an air velocity of 27 m s−1, the electrostatic units achieved an average charge-to-mass ratio of up to 0.67 mC kg−1. Activation of the charging units significantly enhanced droplet deposition with an increase of 90% on the front and 3250% on the back surfaces of the artificial targets (aluminum plates). On real plant leaves, the increase was 54% on the front and 112% on the back surfaces compared with uncharged standard spraying.