# Reduction of Dust on Solar Panels through Unipolar Electrostatic Traveling Wave
## 1 Introduction  
The power produced by solar panels varies according to the incident radiation, which varies with location, climate, and installation. Although there is high radiation in equatorial regions, especially in desert areas, these may experience high losses due to dust and other factors, with reduction in energy obtained. The distribution of dust in different parts of the world has been investigated and significant dust accumulation is observed in the Middle East and North Africa [1]. Whilst the Middle-East is a suitable place to collect solar energy; there is an abundance of sand and dust [2]. The effects of dust accumulation have been investigated in detail and the cleaning cycle and methods based on the PM10 world map for dust removal are discussed in [3]. Turkey also has an abundance of dust due to its location that affects energy production in solar power plants. Such problems were observed in a study in Iraq [4], in which the accumulation of dust on the surface of solar panels in solar power plants (SPP) significantly reduced panel performance. The aqueous panel cleaning system of Europe is often used in Turkey, as it is recommended to clean the panel surfaces monthly with an automatic cleaning system [3]. In Middle East regions, the diameter and form of dust particles varies from region to region due to environmental and climatic factors [5]; in some regions the dust is dry, whereas in other regions it is small and sticky, causing a decrease in power [6]. Dust on photovoltaic panels can reduce the solar radiation by half [7] and has been shown to reduce the amount of electricity generated by 40% [8] and 85% [9]. For example, dust accumulation on solar panels caused a decrease in performance of 32% after 8 months in Riyadh and 17% after 6 days in Kuwait [10]; periodic cleaning of panels is essential. Moreover, cleaning solar panels in this region can be problematic due to the scarcity of water [2], and such aqueous and manual cleaning is expensive for large-scale power plants [11]. Alternative cleaning methods to the traditional water or mechanical assemblies should be investigated [2; 12; 10; 13; 14; 15; 16]. A new four-stage automatic 'dry cleaning' method for solar panels has been reported [2]; [17] investigated dust removal methods including natural tools, mechanical tools, electrostatic tools and self-cleaning nano-film; apiezoelectric actuator-based cleaning system with a light weight and compact structure was reported in [18]. An ultrasonic cleaning method has been proposed that can access hard-to-reach surfaces that are not normally accessible [19]. A moving wave electric charge has been investigated as a method to clean small particles from solar panels [20]. The electrostatic method is based on cleaning dust by applying high voltage to parallel electrodes embedded in the glass plate of the panels [21]. Cleaning systems using a similar method have been developed to remove dust and sand from the surfaces of solar panels [22; 23]. The glass plate of a solar panel is embedded with parallel wire electrodes for single-phase [21], two-phase [23; 24], three-phase [8; 25] or four-phase [23; 24; 25; 26], with a high voltage being applied. In this approach, power consumption is very low [21]. This system is especially suitable for use in the very large SPP built in deserts because it can clean automatically in a way that is low-power, cheap, and avoids water cleaning [21]. However, cleaning panels by an electrostatic method requires very high voltages to work efficiently, which can be difficult practically and dangerous to working staff [2]. One study [21] found that the electrostatic method removed more than 90% of the dust particles from the surface of an inclined panel [21]. This system is reliable because it has no moving parts [23]. The electrostatic method has been shown to be capable of cleaning a panel surface loaded with sand up to 300 g/m\({}^{2}\), giving high performance corresponding to a sand layer thickness of about 0.3 mm.