Introduction
Solar power generation has grown drastically in recent years
owing to increasing energy demand as well as the environmental
and economical concerns associated with fossil fuel consumption
[1], and many mega solar power generation plants are being
planned and constructed, especially in deserts at low altitudes,
where the sun shines the brightest. However, sand storms occur
frequently in deserts, and solar panels can become covered by
stirred-up sand, causing a drastic decrease in the output power of a
photovoltaic power generation plant [2e7]. Because sand on solar
panels is not cleaned by rain over a long period of time in an arid
region, the capacity utilization of the power plant is reduced if the
panels are not cleaned frequently.
To mitigate this problem, we have developed an automatic
cleaning system that does not need scarce cleaning water but
instead utilizes an alternating electrostatic force [8]. Transporting
particles using electrostatic force was first developed and implemented
by Masuda et al. [9], and many investigations of this
technology have subsequently been conducted mainly as a toner
supplier in electrophotography [10e21]. Numerous other applications
for the electrostatic particle transport have been proposed,
including control of bubbles in dielectric liquid [22], removal of
radioactive dust in a fusion reactor [23], transport of liquid droplet