System configuration
Parallel wire electrodes embedded in the cover glass plate of the
solar panel was employed instead of ITO electrodes to reduce the
manufacturing cost of the cleaning plate. Although the wire electrodes
create a shadow and disturb the absorption of light, this is
minimized by using a fine wire and a wide pitch configuration. The
diameter chosen for the wire electrodes was 0.3 mm, and the size
chosen for the pitch between the electrodes was 7 mm.
To mitigate the complexity of the electrode wiring, power
supply, and interconnections, we adopted a standing wave instead
of a traveling wave [34e36]. That is, a single-phase rectangular
voltage was applied to parallel wire electrodes. Because a traveling
wave is not generated by the application of a single-phase voltage,
particles are not transported in one direction but rather repelled
from the plate, and when airborne the sand particles are transported
downward by gravity. We generated a single-phase rectangular
voltage by using a set of positive and negative amplifiers
switched by semiconductor relays that were controlled by a
microcomputer. Because a high slew-rate is not required for this
system, we employed conventional low-capacity onboard amplifiers
(HUR30-6, Matsusada Precision, Tokyo).