# Reduction of Dust on Solar Panels through Unipolar Electrostatic Traveling Wave
## 3 Electrode Design
Figure 5 shows the electric field distributions are very similar in M1 and M2, although the maximum value of the electric field in M2 is about 1.7 times that of M1. In addition, the  
Figure 4: 3D FEA electric field distribution: (**a**) M3 model; (**b**) M4 model. electric field of M1 is more homogeneous than M2, which is due to the shape of the line, as seen in Figure 5b. Figure 5: Electric field along the main axis of the panel: (**a**) model M1; (**b**) model M2. The curved (sine) geometry of the M3 electrode results in a varying distribution of the electric field across the plate, and this is shown by the three lines of Figure 6a, where line 1 and line 3 pass through the \"top\" and \"bottom\" of the curve, and line 2 passes through the \"zero point\" of the curve. Likewise the triangular geometry of the M4 electrode results in a varying distribution of the electric field across the plate, and this is shown by the three lines of Figure 6b, where line 1 and line 3 pass through the \"top\" and \"bottom\" vertices of the line and line 2 passes through the \"zero point\" of the line. The ratio between the maximum and minimum values of the electric field of M4 was found to be 1.23. Figure 6: Electric field along the main axis of the panel: (**a**) model M3; (**b**) model M4. Figure 9: _Cont._  
SEM image of the powder shown in Figure 9a consisted of particles of complex geometry and various shapes, although it contained a mixture of large and small particles. The elemental composition of the powder, shown in Figure 9b, was determined by energy dispersive spectroscopy. Here, Si, Fe, K, P, O etc. element distributions are shown. Figure 9c shows that various compounds are present in the powder particles, including alkaline earth metal and alkaline compounds [32]. The powder content given in Figure 9c is Fe\({}_{2}\)O\({}_{3}\), K\({}_{3}\)FeO\({}_{2}\), FeO, Cr\({}_{2}\)O\({}_{3}\), TiO\({}_{2}\), NaO\({}_{2}\), CaO, MgO, MnO, SiO\({}_{2}\), P\({}_{2}\)O\({}_{5}\), respectively. The density of the powder material is 2.51 g/cm\({}^{3}\). The powder contains properties similar to the lunar soil simulants (JSC-1A, FJS-1 and real lunar soil) [26] in terms of its oxide forms and density. The dust was distributed evenly on the four PCB electrodes as depicted in Figure 2. A voltage of 11 kV was then applied as a single channel at a frequency of 1 Hz. The air breakdown voltage depends on the electrode opening, field shape, duration of the voltage, value of the electric field, and environmental factors such as temperature, pressure and humidity [46]. No arc or jump was observed in this study. Dust was found to be collected between the copper tracks within about 3 min. On the M1 and M2 plates (Figure 10), dust was concentrated in a straight line between the electrodes. However, on the M3 and M4 plates (Figure 11), dust accumulated as a line according to the shape of the electrodes. However, the shape of the electrode on the M3 and M4 plates did not improve the cleaning process and it was determined that the M1 and M2 plates would be more successful for the cleaning process. The stationary wave produced by the single-phase excitation is not as efficient as multi-excitation for particle removal from the plate [8]. For this purpose, the M1 plate (Figure 12) and M2 plate (Figure 13) were reconfigured for multi-excitation. 0.56 g of 100-300 \(\upmu\)m dust was evenly distributed on the plates. The two plates were then subjected to 4-channel excitation for 3 min, with 1 Hz frequency and 11 kV. Figure 9: The powder analysis result pictures: (**a**) scanning electron microscope image of the powder; (**b**) Elemental composition spectrum of the powder; (**c**) X-ray diffraction intensity (cps–count per seconds) distributions for the powder content. Figure 11: Dust distribution and accumulation as a result of single channel application to: (**a**) M3 model; (**b**) M4 model. Figure 2:0 M1 model: (**a**) Before cleaning; (**b**) After cleaning.