Non thermal plasma surface cleaner and method of use

Described herein are plasma generation devices and methods of use of the devices. The devices can be used for the cleaning of various surfaces and/or for inhibiting or preventing the accumulation of particulates, such as dust, or moisture on various surfaces. The devices can be used to remove dust and other particulate contaminants from solar panels and windows, or to avoid or minimize condensation on various surfaces. In an embodiment a plasma generation device is provided. The plasma generation device can comprise: a pair of electrodes positioned in association with a surface of a dielectric substrate. The pair of electrodes can comprise a first electrode and a second electrode. The first electrode and second electrode can be of different sizes, one of the electrodes being smaller than the other of the electrodes. The first electrode and second electrode can be separated by a distance and electrically connected to a voltage source.

BACKGROUND

Dust accumulation, particle deposition due to moisture evaporation, and moisture formation on dielectric surfaces such as windows, tubes, lamps, signboards, solar panels, and imaging sensors is problematic for proper function. Such accumulation is usually removed manually. Further, many dielectric surfaces are often in areas that cannot be readily accessed for cleaning. Thus, there is a need for devices and methods that can adequately clean these surfaces.

SUMMARY

Described herein is a plasma generation device and methods of use of the devices. The methods of use include use of the devices for the cleaning of various surfaces and/or for inhibiting or preventing the accumulation of particulates, such as dust, or moisture on various surfaces. In an aspect, the devices can be used to remove dust and other particulate contaminants from solar panels and windows. The devices can also be used to avoid or minimize condensation on various surfaces. In an embodiment a plasma generation device is provided. The plasma generation device can comprise: a pair of electrodes positioned in association with a surface of a dielectric substrate, wherein: said pair of electrodes comprises a first electrode and a second electrode; said first electrode and second electrode are of different sizes, one of the electrodes being smaller than the other of the electrodes; said first electrode and second electrode are separated by a distance; and said first electrode and second electrode are electrically connected to a voltage source.

In any one or more aspects, the first and second electrodes can be provided with separate alternating current voltage sources, and the voltage source provided to at least one of the electrodes is switched. The first electrode and the second electrode can be comprised of indium tin oxide. A means for canalization of airflow can be included. The electrodes can be positioned on or a distance above the surface of the dielectric substrate. The distance between the first and second electrodes can be about 1 mm to about 10 cm. A rail can be positioned in relation to the surface and at least one of the electrodes positioned in connection with the rail, and a motor affixed directly or indirectly to said electrode, wherein activation of said motor can move said electrode along an axis of said rail. The other electrode of the pair of electrodes can be connected with the rail and activation of the motor can move both of said electrodes along an axis of said rail.

In an embodiment a method of dust removal or removing moisture (e.g., water) is provided. The method can comprise the steps of: providing the plasma generation device of any one or more of the above aspects; and applying a voltage to the electrodes of said plasma generation device. The method can create a plasma or corona discharge. The discharge can create ions. The ions can be accelerated by an electric field in the direction from the smaller electrode towards the larger electrode and past the larger electrode along the surface, thereby creating a flow of wind (or an ionic wind) along the surface.

In an embodiment, a plasma generation kit, is provided. The kit can comprise: a first electrode and a second electrode, wherein said first electrode and second electrodes are different sizes; an AC power supply; a means for electrically connecting said first electrode and said second electrode to said AC power supply; and a means for affixing said first electrode and said second electrode to a dielectric surface.

DETAILED DESCRIPTION

Discussion

Description

Presented herein are devices and methods of use of the devices for inhibiting or preventing the accumulation of particulates (such as dust) and/or moisture onto various surfaces. In one or more aspects, the devices and methods can be used for removing dust and other particulate contaminants from various surfaces and avoiding, and minimizing, if not preventing, condensation on various surfaces. In a non-limiting example the devices and methods of use remove dust and other particulate contaminants from solar panels.

Solar power is the conversion of sunlight from the sun into electricity. Solar power has a variety of end uses, from powering extraterrestrial reconnaissance crafts (such as satellites, planetary probes, lunar and planetary rovers) to powering terrestrial power grids to powering individual homes to powering small personal electronics (such as calculators) to powering solar/thermal panels and solar cells. In most cases this conversion is done directly by a solar panel that consists of photovoltaic cells arranged in an array. The power output of the solar panel[s] is dependent on the number and surface area of the photovoltaic cell[s] therein, and can be scaled up or down by increasing or decreasing the number of interconnected photovoltaic cells or the number of interconnected solar panels themselves respectively.

Most recently, solar power has become a growing terrestrial alternative energy segment. The costs of solar panels have dropped dramatically over the last two to three decades, which encourages the deployment of solar panels for alternative energy production. While use of solar panels is on the rise, the efficiency of energy conversion by solar panels is one factor preventing widespread adoption of solar energy. Over time, dust and other contaminants can deposit and accumulate on the surface of solar panels drastically reducing their efficiency by 50% or more and ultimately preventing sunlight from reaching the photovoltaic cells.

So far, dust on solar panels is usually removed manually. However, in an area where it is difficult to reach the panels, cleaning is not performed as often as necessary to obtain peak performance. Directed airflow, such as a wind, is one way to remove dust and particulate matter or contaminants from solar panels which are placed in areas not readily accessible for routine maintenance. While a directed air flow can remove particulate matter from the surface, surface charges on the panels and surface charges on the particulate matter or particles can create static or ionic cling between the solar panel surface and dust (or other particulate matter) that cannot be overcome by the force of the airflow. An ionic wind can be used to remove dust and particulate matter to overcome this limitation.

Described herein are non-thermal plasma generation and/or discharge devices and methods of their use. In an aspect the devices can generate an ionic wind that can be used to inhibit accumulation of particulate matter and/or moisture onto surfaces. For example the devices can be used to remove particulate matter, such as dust, from various surfaces, including the surfaces of solar panels.

In an aspect, as depicted inFIG. 1, the non-thermal plasma generation and/or discharge device can include a pair of electrodes1,2positioned on or adjacent to a same side of a dielectric substrate3. Alternatively, the electrode pair can be embedded in the dielectric substrate3or in the surface of the substrate3. The electrodes in the pair of electrodes (electrode1and electrode2) can be of different sizes. For example, they can be of different height and length. The electrodes can be separated by a distance. The space or distance between the electrodes is herein sometimes referred to as the inter-electrode space. The inter-electrode space can vary. For example, the inter-electrode space can be in the range of 1 mm to 10 cm (and any range in between).

In one or more aspects, one electrode, for example depicted as electrode1in the figures is smaller than electrode2. The smaller electrode can have one dimension in the range of 30 nm (nanometer) to 5 mm, and can be as long as necessary, for example like a wire. In various aspects the larger electrode can be at least 2 times larger than the small electrode and can be up to 100 times larger (and any range in between). By larger, the second electrode can be larger in terms of surface area or it can be larger in terms of volume. The length of both electrodes can be similar.

The electrodes can take any one of a number of shapes. In an embodiment the electrodes can have a center or middle portion that is raised or higher than the peripheral edges of the electrodes, thus having a middle or center portion having a greater dimension than the outer or peripheral edges in a perpendicular direction or axis from the surface of the substrate. In an aspect the outer surface of the electrodes can be concave shaped in relation to the surface of the substrate providing a middle or center portion that has a surface that is a greater distance from the substrate surface than the outer or peripheral edges of the electrode, such as illustrated inFIG. 1.

The electrodes1,2can be applied to the substrate3or the surface of the substrate3in any of a number of ways. For example, the electrodes can be printed, painted, slot-die coated, blade or spray coated, affixed by adhesive or vacuum deposited (e.g., E-beam lithography, sputtering, and/or thermal evaporation) on the dielectric surface and can have different sizes and geometries.

The electrodes1,2can be made of any material that is electrically conductive or serves as an electrical conductor. The electrodes1,2can be optically transparent or opaque and can include optically transparent materials such as indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) The electrodes1,2can be formed of any type (nanoparticles, nanowires, nanoflakes, etc.) of electrically conductive elements (e.g., Ag, Cu, W, Cr) and/or alloys (e.g., Cu:Ag) and/or pristine and doped oxides (e.g., ITO, FTO, AZO, ZnO) and/or sulfides (AgS, Fe1-xS). The electrodes1,2can be printed onto the substrate from an ink formulation. The ink formulation can be any organic and inorganic compound in any ink formulation type. Examples of suitable ink formulations include nanoparticles and/or nanoflakes and/or nanowires and/or other elemental complexes including or incorporating the conductive elements, oxides or sulfides. The electrodes can have a thickness between 30 nm-10 mm (and any range in between). The thickness can be measured in a vertical dimension perpendicular to the substrate.

The electrodes1,2can be deposited on any dielectric substrate/superstrate. In one or more aspects the substrate/superstrate can be a rigid dielectric material. For example, the substrate/superstrate can be formed from glass, sapphire, quartz and/or mica. In one or more aspects, the substrate/superstrate can be formed of a flexible material. Suitable flexible materials include but not limited to polyimides (e.g., KAPTON), polyethylene terephthalates (PET), polyurethanes (PU), polyethylene naphthalates (PEN) (e.g., Teonex), andior polycarbonates (e.g., LEXAN).

The electrodes can be deposited on either or both surfaces of the substrate/superstrate (asymmetrically) in order to create Dielectric Barrier Discharge (DBD) actuators and/or on the same side of the surface in order to create non-thermal plasma surface discharges, such as corona discharges. Our various plasma generating devices can generate an ionic wind. An ionic wind is defined herein as a flow of gas surrounding the electrodes by ion collision with neutral particles.

The electrodes can be connected to any power supply (including, for example, an AC/DC high voltage source). The alternating current (AC) source can be any commercial or custom made AC power supply and can provide any shape of AC voltage for example (sine, square, triangle, etc.). The AC voltage can have a peak to peak voltage in the range of 100V to 50 kV. The AC voltage can have a frequency of 1 Hz to 1 MHz (mega Hertz). In any one or more aspects the peak to peak range, the voltage range and/or the frequency range can be any range or value within these ranges. In one or more aspects an alternating current source4can be provided for electrode1and a separate alternating current source5can be provided in connection with electrode2, as depicted inFIG. 1. The current source5for electrode2can include a switch6. The current source for electrode2can include a ground7. In one or more aspects the same power source can be provided and used to power both electrodes1,2.

Upon voltage application to the electrodes1,2of the device, a weak plasma, or corona discharge, can be created close or closest to the smaller electrode in the electrode pair and between the pair of electrodes within the inter-electrode space. The switch can allow control of the connection to the ground of the system (for example solar panel). That means the device can work with a floating potential, or between the ground and high voltages. This can be of interest for application to electrical systems, such as solar panels. The plasma discharge can be non-thermal (i.e., does not heat the dielectric surface) and may or may not be luminous. Positive and negative ions can be created by the plasma. The ions can be accelerated by an electric field in the direction from the smaller electrode towards the larger electrode of the pair of electrodes and past the larger electrode away from the pair of electrodes. During transit or flow, ions collide with neutral molecules and/or atoms and generate a flow of wind called ionic wind.

The ionic wind flow can inhibit accumulation onto and/or remove particulates (such as dust or other contaminants) from a surface, such as a dielectric surface. Additionally, ion agglomerates present on the surface in the inter-electrode space can charge particles which can be accelerated and removed from the surface. The device may not produce vibrations and can be used for vibration-sensitive applications such as optical laser techniques.

Plasma generation on the dielectric surface upon voltage application to the device can alter the hydrophilicity or hydrophobicity of the surface. In the increased hydrophilicity case air humidity in the inter-electrode space can prevent formation of droplets (such as water droplets) or other moisture on the surface but spread evenly forming a “liquid coating” along the surface and can be repelled from the surface. The repelled humidity can drag dust or other particulate matter without leaving any stains or spots. In the case of increased hydrophobicity, our device can along the surface provide a dehumidification method in addition to another method for dust removal similar to self cleaning glass.

In an embodiment, a device of the present disclosure can be affixed to the dielectric surface of a solar panel (see, e.g.,FIG. 1). The device can generate a non-thermal plasma which in turn can create an ionic wind. The non-thermal plasma generated by the device does not heat the underlying substrate or surface of the solar panel. The device can be comprised of a pair of electrodes. The pair of electrodes can be affixed to the solar panel surface and electrically connected or coupled to a voltage source. The same power source can be applied to both electrodes, or separate power sources can be used one for powering each electrode. The pair of electrodes can be affixed to the same side of the solar panel. The electrodes of the electrode pair can be affixed to the surface by a suitable means, such as: printing, painting, slot-die coating, blade or spray coating, affixed by adhesive, or vacuum depositing, E-beam lithography, sputtering, and thermal evaporation. Alternatively, one or more of the electrodes in the pair can be embedded in the solar panel. The electrodes in the electrode pair have different sizes, where one electrode is smaller in size than the other electrode of the pair of electrodes, and the electrodes can be separated by an inter-electrode space. The electrodes in the electrode pair can be made of any material that is an electrical conductor, including transparent materials such as indium-doped tin oxide (ITO). The electrodes in the electrode pair can be of any suitable geometry. One skilled in the art will be able to recognize a suitable electrode material, size, geometry, and affixation method.

Upon application of a voltage to the electrodes by the AC source, a weak plasma, called a corona discharge, can be created close to the smaller electrode of the electrode pair and towards and past the larger electrode of the electrode pair and away from the pair of electrodes. The plasma may or may not be luminous, but in any event can be non-thermal. Positive and/or negative ions can be created in the plasma. The ions can be accelerated by the electric field in the direction of the larger electrode of the electrode pair. The accelerated ions can collide with neutral molecules and/or atoms and can generate a flow of gas, an ionic wind. The ionic wind can remove particulates from the dielectric surface of the solar panel. The ions can agglomerate on the surface of the particulates present in the inter electrode space, and additionally charge small particles nearby. Once electrically charged, the particulates can be accelerated by the electric field and removed from the solar panel surface.

One skilled in the art will appreciate the need to choose and optimize parameters described herein according to environmental conditions and desired effect, such as (but not limited to): size and material of the electrodes, the distances between two electrodes of a pair, the frequency and amplitude of the AC voltage, the geometry and number of electrode pairs in an array, and the dielectric material (see for exampleFIG. 3). The distance between two pairs of electrodes in an array should be larger than the inter-electrode space between a pair of electrodes. The pairs of electrodes can be parallel, as depicted inFIG. 3, or concentric. A single AC power source can be used for all the electrode pairs, or separate power sources can be provided to power arrays separately from each other or even electrodes within a pair of electrodes separately from each other. A controller can be provided to allow sequencing of the applied voltage. Alternatively, each pair of electrodes can be powered by a different voltage source. Further, the plasma generation device can be supplied as a kit and affixed to existing dielectric surfaces.

If the zone of influence of a single pair of electrodes1,2needs to be expanded, the electrodes can be spaced apart from, but still in association with, a surface of the substrate3. For example, the electrodes1,2can be positioned from 1 mm up to 10 cm (and any range there between) above the surface of the substrate3, as shown inFIG. 2. The electrodes1,2can then be surrounded by gas and the gas flow or ionic wind generated by the device can be faster and with a higher flow rate than when the electrodes are affixed on or in the surface of the substrate3. The flow produced by the ionic wind can also be canalized with the help of, for example, a housing vent8. The geometry of the electrodes can be varied, as long as the typical size of electrode1remains smaller than electrode2.

In one or more aspects the system can be placed on one or more rails and moved along the surface to be cleaned with the help of a motor, such as a step motor actuator. In order to increase the power output of a solar panel, an array of photovoltaic cells can be created and cells added to the array to increase the surface area and power output of the solar panel. Increasing the surface area of a solar panel or other dielectric surface can create a need to scale up the plasma generation device accordingly to cover the surface area of the dielectric surface area. In order to treat large surface areas, the electrodes can be organized or positioned in association with the substrate. For example as illustrated inFIG. 3pairs of the electrodes can be placed in an array. The plurality of the pairs of electrodes can be electrically connected to an AC power supply (for example, a high-voltage AC power supply) and further connected to a controller that can synchronize the voltage application between the AC power supply and plurality of electrode pairs. In this instance of an array application of the AC voltage can be sequenced in a synchronized manner in order to optimize the removal of dust or other contaminants.

EXAMPLES

Now having described the embodiments of the present disclosure, in general, the following Examples describe some additional embodiments of the present disclosure. While embodiments of the present disclosure are described in connection with the following examples and the corresponding text and figures, there is no intent to limit embodiments of the present disclosure to this description. On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of embodiments of the present disclosure.

On a dielectric flat surface (polymethylmethacrylate), that can be described following two directions, X and Y, two parallel stainless steel electrodes of 5 cm length in the X direction were affixed. The small electrode had a thickness (in the Z direction, perpendicular to the dielectric surface) of 0.85 mm, and the big electrode had a thickness of 2.5 mm (in the Z direction). The inter-electrode gap distance, in the Y direction, was 20 mm. The two electrodes were connected to a high-voltage power supply, and we applied AC voltage (a sine signal), at a repetition rate of 100 Hz, with a peak-to-peak voltage of 6 kV. An ionic wind was generated, parallel to the surface, with a velocity of 1.5 m/s along and generally parallel to the dielectric surface, measured 20 mm behind the big electrode, by a mechanical anemometer.

As another example, voltage application to the plasma discharge device can make the underlying dielectric surface more hydrophobic, repelling water. Water droplets can be forced off of the surface in this manner. The droplets can encapsulate particulate matter and remove particulate matter from the surface. Moisture in the atmosphere in the inter-electrode space can also be repelled. Voltage application to the device can be constitutive, meaning the device is always on, which can prevent deposition of moisture and particulates on the surface.

As another example, the electrodes of the plasma generation device can be positioned in association with and above the surface of the dielectric substrate, as described above (see,FIG. 2). In this example, the electrodes can then surrounded by gas upon application of a voltage from an AC voltage power supply and the gas flow generated by the device can be faster than when the electrodes are affixed to or in the substrate surface. The voltage applied to the device can be 10 kV and the frequency can be 10 Hz.

In an example, a means for canalization of the ionic wind can be coupled (such as a vent or baffle, see e.g.FIG. 2) to the present device or positioned in association with the device. This addition can cause the ionic wind generated by the plasma to be canalized, meaning the wind can be directed into a pre-designed set path with a means such as a vent or duct.

As depicted inFIG. 3, the electrodes of the plasma generation device can be affixed into a system300including one or more rails312positioned about a plurality of devices, such as solar cells314, to be cleaned (of dust humidity, etc.) and coupled (mechanically or otherwise) to motive means, such as one or more step actuator motors (not shown). Activation of the motive means (motor(s)) can move the electrodes along the one or more rails312, and can maintain a distance between the electrodes and an inter-electrode space therein. A controller316is provided for controlling the motive means and/or actuating the electrodes. The controller can be any conventionally available motive controller. The controller316can be coupled to a power supply318.

In a further example, the device of the present disclosure can be used for the cleaning of surfaces for visualization devices, and housings of visualization devices, such as CCTV cameras, safety cameras, or optical sensors. For example, the electrodes can be printed directly on the glass surface of the lens of the camera, or alternatively on the protective covering of the housing of the camera. The surfaces can be any mineral glass as well as organic glass material. These surfaces can be flat or parabolic, or spherical, or any shape. The electrodes can be transparent, or not, as long as they can allow efficient cleaning of the visualization surface, without altering the field of view. The applied voltage can be either DC or AC, with a frequency in the range of 10 to 10 000 Hz.

FIG. 4presents an example of use of a device400for cleaning the field of view of a CCTV camera411with a flat housing415. One pair of electrodes401,402can be printed on the protective glass of the CCTV camera411, spaced by a distance of about 10 mm. The large electrode402is a line of 2 mm large and 0.1 mm thickness, connected to the ground, while the second electrode401consists of an array of parallel lines of 2 mm length, 0.5 mm large and 0.1 mm thickness, spaced by 2 mm, and connected together and to an AC high voltage power supply418. The frequency of the applied high voltage can be 1 kHz, and the maximum amplitude of the voltage can be 15 kV.

FIGS. 5 and 6present an example of the present device installed on the spherical surface513,613of the housing of a CCTV camera511,611. Three pairs of transparent electrodes520,620are printed on the spherical surface and arranged such as they allow cleaning of the entire surface of the field of view by generating ionic wind at the proximity of the surface, removing dust accumulation and organic material such as spider webs. The high voltage can be applied in sequence between each pair of electrodes by a power supply518,618. The applied voltage can be DC or AC, with a frequency in the range 10 Hz to 10 kHz. The applied voltage can be in the range of 500 V to 20 kV.

In another example, the device can be used for cleaning the front andior back windshields as well as the door windows of a vehicle. The electrodes720can be printed either directly on a side of the glass703or under a thin transparent flexible coating material. The electrodes can be printed from transparent or non-transparent materials as long as they do not affect the visualization of the driver and the passengers. The electrical circuitry717can either be placed inside of the door chassis or close to the electrical circuitry of the vehicle.

The electrode configuration on the interior side of the door700window703presented inFIG. 7can be applied on the interior glass surface of the vehicles to remove the organic particles such as fingerprints or the dust accumulated. Based on the purpose of the application, ionic wind or plasma is generated between the electrodes by applying a DC or AC voltage in the range of 100 V to 20 kV with the frequency range of 10 Hz to 10 kHz. The car battery or an external power supply can be used to generate the power with the desired specifications. The cleaning procedure can be applied either on a programmed schedule by controller716connected to a power supply718such as after the driver and the passengers get out of the vehicle or on demand of the user.

As another example, the electrodes of the present plasma generation device can be positioned on any type of display (e.g., liquid crystal display (LCD), thin-film-transistor liquid crystal display (TFT-LCD), light emitting diode display (LED), plasma display (PDP), any touchscreen, tablet or any device with an integrated display of any type. Due to generation of plasma during operation of the plasma generation device it can be used for removing dirt, dust, oils, fingerprints, germs and other contaminants from the touchscreens of automated teller machines (ATM) and a wide range devices with an integrated display of any type and any shape. The combination of the plasma generation device with a heating unit of any type can be used as a de-dusting, germs removing and de-icing device for cleaning of the displays of ATMs. The plasma generation device can be also positioned on biometric scanner of any design and shape.

As another example, the electrodes of the plasma generation device can be positioned on any type of manned or unmanned aeronautical vehicle, such as an airplane. The operation of such a device can prevent dirt, dust, oil and ice formation on the plane.