1. Copyright 2011 Elsevier Inc. All rights reserved. Chapter 5 M.K. Mazumder, R. Sharma, A.S. Biris, M.N. Horenstein, J. Zhang, H. Ishihara, J.W. Stark, S. Blumenthal and O. Sadder

2. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.1 Dust devil formation on the dry lake area of the Mojave Desert. Photo courtesy of Creative Commons Corporation, San Francisco, CA. http://www.animalu.com/pics/photos.htm Jeff T. Alu

3. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.2 Particle size distribution (shown in dark solid steps) of the test dust as measured by using a Microtrac  particle size analyzer. The line connecting the dots shows the cumulative size distribution plotted as a function of particle diameter in mm

4. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.3 Normalized output power of a single crystal solar cell as a function of mass concentration dust (mg/cm 2 ) deposited on the front cover glass. A xenon lamp was used to illuminate the solar cell. The mass median diameter of the dust sample was approximately 9  m

5. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.4 Schematic of (a) single-phase EDS and (b) three-phase EDS

6. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.5 A cross-sectional view of transparent parallel electrodes embedded in a transparent film or glass panel. The electrodes are energized by phased pulsed voltage for lifting and removing deposited dust particles from the solar panels or mirrors

7. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.6 A schematic layout of (a) single-phase (left diagram) and (b) three- phase EDS (right diagram) electrodes

8. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.7 Transparent EDS embedded in a transparent polyurethane (PU) film is placed over a solar panel. The ITO electrodes are of triangular cross-section which provides a more uniform distribution of the electric field compared with the field distribution produced by electrodes of rectangular cross-section. The figure shows an a-Si solar cell integrated with an EDS

9. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.8 A three-phase power supply on a circuit board is shown connected to a three-phase EDS screen. The electrodes are embedded in a dielectric film

10. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.9 A traveling wave of potential is applied at x = -d. A lossy dielectric layer of thickness d, permittivity , and conductivity s prevents charged dust from penetrating into the region x < 0. The x = 0 surface has reduced potential magnitude (V 1 < V 0 ) and a lagging phase b to the driving x = -d potential

11. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.10 Cross-section of an EDS made of a flexible polyethylene terephthalate (PET) film of 500  m thickness on which transparent ITO electrodes of rectangular cross-section (width 10  m, height 10  m) are deposited with an inter-electrode spacing of 1000  m. The electrodes are embedded within a PU film coating with a film thickness of 50  m. The thickness of the electrodes is varied from 10 to 100  m and the inter-electrode spacing from 100  m to 1000  m for optimization of EDS operation

12. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.11 The electric field has been modeled for three electrode configurations. The top section shows electrodes with relatively large dimensions and large inter- electrode spacing. The spatial distribution of the divergent electric field intensity is non-uniform. As the electrode dimensions and the inter-electrode spacing are reduced, more uniform field intensity distributions are achieved (middle and bottom sections)

13. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.12 A charged (+q) particle of diameter 2  m, located at A, is subjected to an AC electrical field E 0 sin(  t) applied between the adjacent electrodes as shown. The frequency of the electric field is 4 Hz

14. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.13 An uncharged dielectric particle, deposited on the surface of a dielectric film, is experiencing a dielectrophoretic force because of the induced dipole moment on the particle by the applied non-uniform electric field

15. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.14 Induction charging of conducting and semi-conducting particles deposited on a dielectric screen with embedded electrodes.  1 and  2 are the relative dielectric constants of the screen and the particle, respectively

16. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.15 Three-phase voltages (a) in sinusoidal waveforms and (b) in square waveforms

17. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.15 (continued) Three phase square wave forms

18. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.16 Block diagram of an EDS power supply

19. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.17 Schematic diagram of an experimental EDS power supply based on 1.2-kV MOSFETs

20. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.18 MOSFET-based EDS power supply (a) in a housing and (b) circuits in a PCB

21. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.19 Linear-amplifier-based EDS power supply (a) in a system test setup and (b) block diagram

22. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.20 Power vs. voltage curves for a three-phase PCB EDS with 1-mm electrode spacing

23. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.21 Power curves for a three-phase ITO electrode-EDS with 1-mm electrode spacing

24. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.22 A 3D view of the test chamber for studying the performance of the electrodynamic screens. The environmental conditions can be adjusted (temperature up to 50 degrees and relative humidity (RH) up to 80% can be achieved) inside the chamber. The solar panels can be tilted at different angles

25. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.23 An experimental setup for testing transparent electrodynamic screens against mass loading of test dust under normal atmospheric conditions

26. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.24 Experimental arrangement for testing the EDS under Martian atmospheric conditions (0.5 to 1.0 kPa pressure, CO 2 atmosphere) to determine the dust removal efficiency as a function of dust loading. For each experiment, the total power requirements for removal of the dust layer were measured as functions of applied voltage pulses and the frequency of operation

27. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.25 Maximum power point operation of a solar panel

28. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.26 Application of an integrated circuit (IC) to control the output voltage for MPP operation

29. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.27 Voltage converter for MPP operation

30. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.28 Size distribution of Mars dust simulant measured by an ESPART analyzer

31. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.29 Charge distribution of Mars dust simulant as measured by an ESPART analyzer. The particles were bipolarly charged as shown in the figure

32. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.30 The net charge-to-mass ratio in  C/g of Mars dust simulant particles measured using an ESPART analyzer varied depending on the process conditions. The particles became charged primarily during the dispersion process

33. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.31 Dust removal efficiency of a three-phase EDS operating at 750, 1000, and 1250 volts (electrode spacing = 1.27 mm, electrode width = 0.127 mm, f = 4 Hz, cleaning operation time = 60 s)

34. Copyright 2011 Elsevier Inc. All rights reserved. FIGURE 5.32 Dust removal efficiency of a three-phase EDS with and without charge neutralizer (electrode spacing = 1.27 mm, electrode width = 0.127 mm, peak-to-peak voltage = 1250 V, f = 4 Hz, run time = 60 s, count median (aerodynamic) diameter of the dust particles = 3.66 mm, d 10 = 1.22 mm, d 50 = 9.06 mm, d 90 = 38.45 mm)