Electrodynamic Dust Shield Research Articles

Electrodynamic dust shield efficiency characterisation under UV in vacuum for lunar application

Dust mitigation is one of the most crucial aspects of extraterrestrial exploration. This paper presents a series of experiments on the electrodynamic dust shield (EDS) and how UV radiation affects its efficiency on selected lunar simulants (LHS-1 and LMS-1) across a range of particle sizes, quantities, and surface materials. In this experimental study, VUV is used with a 1500 V AC electric field to mobilise the dust particles resting on either glass, Kapton, or Beta cloth inside a vacuum chamber at ∼10-6 mbar. The dust removal efficiency is characterised by two quantifying methods: weighing and solar array light transmission. The experimental results show that EDS activation under continuous UV exposure on the simulant particles improves the dust removal rate by 40 to 80 percentage points across all surfaces, with the exception of certain particle size ranges on Beta cloth. The primary force facilitating particle mobilisation was identified as the repulsive electrostatic force, enhanced by ionising mechanisms such as photoemission.

Dust Mitigation on Solar Panels in the Desert Environment by Single-Phase Electro-Dynamic Dust Shield: Optimization Using Electrical and Geometrical Parameters

Dust Mitigation on Solar Panels in the Desert Environment by Single-Phase Electro-Dynamic Dust Shield: Optimization Using Electrical and Geometrical Parameters

Performance of chemically modified reduced graphene oxide (CMrGO) in lunar electrodynamic dust shield (EDS) applications

Electrodynamic Dust Shield (EDS) technology is a dust mitigation strategy that is commonly studied for rigid applications such as photovoltaics or thermal radiators where soiling of the surfaces can reduce performance. The goal of the current work was to test the performance of a flexible, patterned nanocomposite EDS system produced through spray-coating and melt infiltration of chemically modified reduced graphene oxide (CMrGO) traces with thermoplastic high-density polyethylene (HDPE). The EDS performance was tested for a dusting of lunar regolith simulant under high vacuum conditions (∼10−6 Torr) using both 2-phase and 3-phase device configurations. Uncapped (bare) devices showed efficient dust removal at moderate voltages (1000–3000 V) for both 2-phase and 3-phase designs. Further tests carried out while illuminating the dust surface with a UV excimer lamp showed that the EDS voltage needed to reach the maximum cleanliness was reduced by almost 50% for the 2-phase devices (500 V minimum for rough and 1000 V for smooth), while the 3-phase devices were unaffected by the application of UV. However, the performance of the uncapped devices degraded after several sequential tests due to erosion of the traces caused by electric discharges and dielectric breakdown. Capping the CMrGO traces with low-density polyethylene (LDPE) eliminated breakdown of the materials and device degradation, but larger voltages (3000 V) coupled with UV illumination were required to remove the grains from the capped devices.

Parametric Optimization of an Unmanned Three-Phase Electrodynamic Dust Shield for Sustainable Photovoltaic Panel Operation for Dusty Environments and Space Applications

Parametric Optimization of an Unmanned Three-Phase Electrodynamic Dust Shield for Sustainable Photovoltaic Panel Operation for Dusty Environments and Space Applications

Field evaluation of two types of EDS-integrated PV modules with different configurations and surface properties

In this study, two prototypes of PV modules with integrated electrodynamic dust shield (EDS) were characterized in the lab and tested in the field to determine their effectiveness in soiling mitigation. The surface properties of the prototype modules’ front cover were measured to evaluate their effects on the EDS dust removal performance. The soiling of each EDS-PV module was assessed based on its PV power output, from which the EDS cleaning efficiency was quantified in field conditions during winter and summer periods. The dust removal efficiency of glass-surface EDS-PV modules was approximately 30%, about three times higher than that of polymer-surface modules. The EDS technology cleaned more effectively in dry and windy weather conditions. The EDS modules’ front surfaces varied significantly with respect to thickness, hydrophobicity, and the electrostatic potential pattern, contributing to the variation of the EDS efficiency of modules. The EDS-PV module with a hydrophobic polymer surface had a higher soiling rate and lower cleaning efficiency than a thinner, hydrophilic glass surface. The results of this study may help improve design and manufacturing methods for more efficient and robust EDS devices integrated into PV modules.

Working with lunar surface materials: Review and analysis of dust mitigation and regolith conveyance technologies

The Moon's dusty surface environment threatens any equipment that operates there, especially for long-duration infrastructure needed for a sustained lunar presence. This is doubly true for systems that convey regolith, which by agitating the soil are certain to generate dust. Here, we provide a comprehensive review of technologies that have been proposed to convey regolith on the lunar surface, and to mitigate against dust hazards that are generated by such transport systems. We define functional taxonomies for both regolith conveyance and dust mitigation, then carry out quantitative trade studies in several categories for each. Examples include passive and active dust mitigation, and horizontal and near vertical conveyance. Conveyance technologies that scored particularly high include wheeled haulers, conveyor belts, and auger/hopper transfer points. High scoring dust mitigation technologies include the lotus leaf passive coating, Electrodynamic Dust Shield, and boots or bellow made of fiberglass fabric. We also explore novel or unconventional concepts and describe how dust mitigation and regolith conveyance can be combined using a systems approach with multiple technologies layered together. The results from the trade studies and the subsequent recommendations constitute a practical guide that can be used for designing and developing systems that must perform efficiently and reliably to carry out useful tasks on the Moon or Mars, such as resource extraction, construction, and additive manufacturing.

Effect of relative humidity on dust removal performance of electrodynamic dust shield

In this study, the dust removal efficiency of a two-phase, standing-wave electrodynamic dust shield (EDS) was investigated as a function of relative humidity (RH) in single operation mode under constant RH and in cyclic operation mode with alternating RH conditions. It was found that in single-operation mode with a nominal dust loading of 200 mg m−2, the EDS efficiency decreased from 22% to 9% when the RH increased from 10% to 80%. This could be attributed to the effect of RH on particle adhesion force and its effect on the dissipation of electrostatic charges. In cyclic-operation mode under alternating RH mimicking diurnal humidity patterns in the field and the timing of EDS activation, the cycle type had some effect on the EDS efficiency. The EDS efficiency was found higher with humid activation than with dry activation, while only the “long-humid-short-dry” cycle had statistically lower EDS efficiency than the other cycles. The findings of this study suggest that the effect of humidity on EDS efficiency depends on the diurnal RH cycles and the mode of EDS operation, and it is possible to maximize the soiling mitigation benefits of EDS by properly timing the activation in cyclic operations.

Effect of Voltage Rise Time on the Efficiency of Electrodynamic Dust Shield

Electrodynamic dust shield (EDS) has been proposed as a potential anti-dust solution for terrestrial solar photovoltaic (PV) power generation in dusty environments. EDS typically uses square wave alternating high voltage, but the actual voltage waveform on the EDS is trapezoidal, with the voltage rise time dependent on the high voltage source's current capacity, especially for real-world applications, where the EDS devices’ dimensions are large. It is therefore necessary to address the effect of voltage rise time on EDS efficiency. In this study, we measured the EDS efficiency by keeping the peak-to-peak voltage constant at 6 kVpp while varying the voltage rise time by adjusting the high voltage source's maximum output current from 0.2 to 40 mA, corresponding to voltage rise time from about 100 ms to a fraction of a millisecond. The EDS was operated in both the single-operation mode and the cyclic-operation mode. In the single-operation mode, voltage rise time affected the EDS efficiency in a complex manner and showed interactions with other factors. In the cyclic-operation mode, with the three faster voltage rise times the EDS efficiency was statistically indistinguishable at about 33%, but it became significantly lower, at 14%, with the slowest voltage rise. The finding shows that high voltage sources should be able to provide sufficiently fast voltage rises for EDS to be efficient in removing dust from solar PV modules.

Solar PV soiling mitigation by electrodynamic dust shield in field conditions

Soiling of solar photovoltaic (PV) modules by dust accumulation can cause significant loss in electricity production. Electrodynamic dust shield (EDS) is a potential anti-dust solution that can be used to repel dust from a PV module surface, but so far there have been few studies of EDS performance in the field. In this study, we fabricated prototype PV modules with integrated EDS electrodes, and carried out field tests of the EDS function. Each prototype was made by fabricating EDS electrodes on the front glass of a base module and insulating the electrodes with a polymer dielectric cover. Three units, comprising two EDS-integrated PV modules and one reference PV module without the EDS electrodes, were tested in a solar test facility at Doha, Qatar for six months. The soiling loss of each solar module was quantified by comparing the module’s temperature-corrected performance ratio to that of the clean module. The EDS efficiency was in turn assessed by comparing the soiling loss of the EDS-PV module with EDS activation to that of the EDS-PV module without activation. When activated hourly at 9 kVpp, EDS could reduce soiling loss by 16–33%, while at 6 kVpp activation voltage EDS had no observable soiling mitigation effect. Further research with larger sample sizes and longer testing time is needed to better understand the soiling mitigation capability of EDS in field conditions.

Numerical analysis of the effects of particle-particle interactions and particle size on the performance of an electrodynamic dust shield

Performance loss due to dust accumulation on solar energy collection surfaces has garnered increasing research interest in recent years. The electrodynamic dust shield (EDS) has been proposed to clean solar devices, the design of which can benefit from understanding of the microscopic interactions of individual dust particles with each other and the electric field in the system. Consequently, the objective of this work was to determine the effects of particle sizes and particle interactions on the performance and power utilization of an EDS through a discrete element simulation of the transport, collision, and adhesion of charged dust particles subject to a four-phase traveling wave on a horizontal EDS. Over a thousand monodisperse particles with diameters from 10 to 200 μm were simulated. In the presence of all types of particle-particle interactions, particles with diameters greater than 10 μm were transported in the direction of the wave with a larger average transport distance as diameter decreased. This result was due to, in general, smaller particles remaining closer to the surface to travel more closely along electric field lines toward the positive electrode, while larger particles exhibited more disordered motion. Meanwhile, 10-μm particles were transported slightly in the direction opposite to the wave due to lack of particle-particle collisions and the presence of van der Waals adhesion, which had a relatively larger effect on smaller particles than larger particles. Electrodynamic particle-particle interactions and particle images were identified to be the main interactions responsible for a reduction in the efficiency of 50-μm and 100-μm particles to travel with the wave. The average power applied to a particle while it was lifted off the surface increased as particle diameter increased in most cases, due to increased particle momentum at lifting. This power was reduced with the absence of at least one type of particle-particle interaction due to reduced velocity and distance traveled immediately after lifting from the surface. Our study identified additional important factors in EDS dust mitigation that were not suggested by previous experimental studies, namely, particle-particle collisions and large particle charge. As well, our work indicated that intermittent operation of the EDS may aid in cleaning of small particles and that the use of the lowest possible voltage that still lifts large particles may aid in cleaning of large particles.

Self-cleaning spacesuits for future planetary missions using carbon nanotube technology

Lunar dust proved to be troublesome during the Apollo missions. The powdery dust got into everything, abrading spacesuit fabric, clogging seals and other critical equipment. Even inside the lunar module, Apollo astronauts were exposed to this dust after they removed their dust coated spacesuits. The lunar dust is comprised of fine particles, with electric charges imparted by solar winds and ultraviolet radiation. As such, it adheres readily, and easily penetrates through the smallest crevices into mechanisms. While efforts are under way to figure out how to return astronauts to the Moon and set up habitats for long duration missions, the issue of lunar dust remains relevant. Consequently, NASA has identified dust as a critical environmental challenge to overcome for future planetary surface missions characterized by dusty environments.Several concepts were successfully investigated by the international research community for preventing deposition of lunar dust on rigid surfaces (ex: solar cells and thermal radiators). However, applying these technologies for flexible surfaces and specifically to spacesuits has remained an open challenge, due to the complexity of the suit design, geometry, and dynamics. In our research, we developed a SPacesuit Integrated Carbon nanotube Dust Ejection/Removal (SPIcDER) system to protect spacesuits and other flexible surfaces from lunar dust. SPIcDER leverages the efficient Electrodynamic Dust Shield concept developed at NASA for use on solar cells. It is customized for dust mitigation on flexible surfaces, using novel materials and specialized design techniques. The result is a self-cleaning spacesuit that can repel lunar dust.This paper provides an overview of the SPIcDER system and showcases our working prototypes, ranging from coupons to a scaled portion of a lunar spacesuit segment. The design is supported by parametric analysis in ANSYS Maxwell for optimizing SPIcDER integration into the spacesuit outerlayer. The paper emphasizes design considerations for astronaut safety, based on analysis and experimental results. The SPIcDER system can be optimized efficiently for potential missions to Mars and asteroids, as well as for Earth based applications.

Measurement of electrodynamic dust shield efficiency in field conditions

In this study, two electrodynamic dust shield (EDS) prototypes were tested in the field for their dust removal efficiency using an outdoor soiling microscopy (OSM) approach. Photomicrography and image analysis were used to quantify the dust on the EDS prototypes before and after EDS activation, to determine the dust removal efficiency over periods of four days. Dust accumulation on the EDS prototypes occurred continually in the ambient environment, and the EDS function was activated once every 24 h over two rounds of testing, each round lasting four consecutive days. On average, over four days the EDS efficiency (proportion of dust mass removed) decreased from 40% to 14%. It was also found that removal efficiency was lower for particles that had spent longer time on the surface, and “old” dust from previous cycles was largely immune to removal by EDS. Also, dust removal efficiency correlated with proximity to the electrode, however this correlation weakened with exposure time. This was the first successful field test of weather-resistant EDS prototypes in the Middle East, a necessary step towards field evaluation of the EDS concept.

Electrodynamic dust shield performance under simulated operating conditions for solar energy applications

Electrodynamic dust shield (EDS) uses traveling-wave or standing-wave electrodynamic effects to repel dust particles from a surface, and has been proposed as a potential anti-dust solution for mitigating soiling loss in solar energy applications. In this study, a standing-wave EDS technique was tested in a cyclic manner at field-relevant dust loading levels using dust deposited by aerosol deposition, in order to assess the EDS’ dust removal efficiency under simulated real-world operating conditions. Tests using sieve deposition and the single-operation mode were also carried out for comparison. Each single-operation test only used freshly-deposited dust with a single activation of the EDS, and the results showed that the dust removal efficiency with aerosol deposition to be moderately lower than that with sieve deposition. In contrast, a cyclic-operation test consisted of many consecutive cycles, which began with the first cycle using freshly-deposited dust, and each additional cycle having new dust added on top of the persistent dust from the previous cycle. The cyclic-operation dust removal efficiency was found to be strongly dependent on the dust deposition method. Using aerosol deposition, the cyclic-operation efficiency continually decreased as the number of cycles increased; with sieve deposition, the cyclic-operation EDS efficiency fluctuated and had a much higher average value than with aerosol deposition. The different behaviors of the cyclic-operation EDS efficiency can be modeled with two hypothetical scenarios, based on how the persistent dust from a previous cycle reacts to EDS activation. However, the physical mechanisms behind the different behaviors are not well understood. The results from this study suggest that further research is critically needed for evaluating the effectiveness of electrodynamic anti-dust solutions for solar energy applications in dusty environments.

Efficiency of Electrodynamic Dust Shield at Dust Loading Levels Relevant to Solar Energy Applications

In this study, laboratory measurement of dust removal efficiency of electrodynamic dust shield (EDS) prototypes was carried out using a real-world dust at mass loading levels relevant to solar energy applications. A removable dielectric cover method was employed to gravimetrically determine the dust removal efficiency. Three EDS prototypes with the same electrode configuration but different areas were used. The results suggest that scale-up does not negatively affect the EDS dust removal efficiency. However, the EDS dust removal efficiency decreased with decreasing dust loading, and it dropped significantly when the total dielectric cover thickness increased from 0.27 to 0.37 mm. Much of the persistent dust consisted of particles μ m, but these small particles constitute a large fraction of dust in the field. Depositing dust through a mesh sieve led to unnatural apparent size distribution, due to particle agglomeration. Future EDS studies need to use dust deposition methods that better simulate natural dust accumulation.

Simulation of microscale particle interactions for optimization of an electrodynamic dust shield to clean desert dust from solar panels

Abstract A largely neglected aspect necessary to prevent energy losses of photovoltaic (PV) panels is efficient and cost-effective mitigation of dust soiling. A potential solution is an electrodynamic dust shield (EDS) to lift and transport dust off the PV panel via electrodynamic waves generated by electrodes on the panel surface. Accordingly, the objective of this research was to determine the effects of EDS parameters on the optimal cleaning efficiency of PV panels soiled by desert dust. A discrete element method was used to computationally simulate the transport, collision, and adhesion of charged particles, representative of dust in Doha, Qatar, subject to two-phase waves on an inclined EDS. Results showed that under given conditions, the optimal distance between electrodes (pitch) was 14 mm, which resulted from a balance between increasing pitch that aided dust transport and concomitant decreasing electric field strength that hindered transport. Optimal voltage was 2.8 kVp-p, while particles remained adhered to the surface at small voltages (0.7 kVp-p) but were repelled and attracted by the same electrode at high voltages (11.8 kVp-p). Dust transport distance per 10 cycles generally decreased as cycle frequency increased from 0.5 to 10 Hz; however, transport distance per time was largest with an intermediate frequency of 1 Hz. Our study revealed various ways in which individual dust particles were repelled and attracted by electrodes under different conditions that produced different transport patterns, which can be used to improve the efficiency of dust mitigation for PV panels.

Active dust control and mitigation technology for lunar and Martian exploration

Mars is covered with a layer of dust that has been homogenized by global dust storms. Dust, levitated by these storms as well as by the frequent dust devils, is the dominant weather phenomenon on Mars. NASA's Mars exploration rovers have shown that atmospheric dust falling on solar panels can decrease their efficiency to the point of rendering the rover unusable. Dust covering the surface of the moon is expected to be electrostatically charged due to the solar wind, cosmic rays, and the solar radiation itself through the photoelectric effect. Electrostatically charged dust has a large tendency to adhere to surfaces. The Apollo missions to the moon showed that lunar dust adhesion can hinder manned and unmanned exploration activities. In this paper, we report on our efforts to develop an electrodynamic dust shield to prevent the accumulation of dust on surfaces and to remove dust already adhering to those surfaces. The technology uses electrostatic and dielectrophoretic forces to carry dust particles off surfaces and to generate an electrodynamic shield that prevents further accumulation of dust. The concept of the electrodynamic dust shield was introduced by NASA in the late 1960s and later reduced to practice during the 1970s for terrestrial applications. In 2003, our laboratory, in collaboration with several universities, applied this technology to space applications, specifically to remove dust from solar panels on Mars. We show how, with an appropriate design, we can prevent the electrostatic breakdown at the low Martian atmospheric pressures. We are also able to show that uncharged dust can be lifted and removed from surfaces under simulated Martian environmental conditions. We have also been able to develop a version of the electrodynamic dust shield working under hard vacuum conditions that simulate the lunar environment. We have implemented the electrodynamic dust shield on solar arrays, optical systems, spectrometers, viewports, thermal radiators, batteries, and power systems, as well as on fabrics for spacesuits. We present data on the design and optimization of the electrodynamic dust shields and provide data on the performance of the different implementations of the technology for lunar and Martian exploration activities.

Controlled particle removal from surfaces by electrodynamic methods for terrestrial, lunar, and Martian environmental conditions

An Electrodynamic Dust Shield to remove already deposited micron-size particles from surfaces and to prevent the accumulation of such particles on surfaces has been developed. In addition to terrestrial application, our NASA laboratory is adapting this technology for the dusty and harsh environments of the Moon and Mars. The Apollo missions to the moon showed that lunar dust can hamper astronaut surface activities due to its ability to cling to most surfaces. NASA's Mars exploration landers and rovers have also shown that the problem is equally hard if not harder on Mars. In this paper, we show that an appropriate design can prevent the electrostatic breakdown at the low Martian atmospheric pressures. We are also able to show that uncharged dust can be lifted and removed from surfaces under simulated Martian environmental conditions. This technology has many potential benefits for removing dust from visors, viewports and many other surfaces as well as from solar arrays. We have also been able to develop a version of the electrodynamic dust shield working under hard vacuum conditions. This version should work well on the moon. We present data on the design and optimization of both types of dust shields as well substantial data on the clearing factors for transparent dust shields designed to protect solar panels for Martian exploration.