WO2019186347A1

WO2019186347A1 - Solar panel waterless cleaning system and method with potential induced degradation recovery

Info

Publication number: WO2019186347A1
Application number: PCT/IB2019/052377
Authority: WO
Inventors: Moshe Meller; Eran Meller
Original assignee: Evermore United S.A.
Priority date: 2018-03-26
Filing date: 2019-03-24
Publication date: 2019-10-03

Abstract

Solar panel waterless cleaning system with potential induced degradation (PID) recovery, for cleaning a plurality of solar panels in at least one solar row and for reversing PID, the system including a body, at least two wheels, a cleaning cylinder, a plurality of cleaning fins, a power supply, including a positive terminal and a negative terminal, and a controller, the cleaning cylinder mechanically coupled with the body for moving the body over the solar panels in the solar row, the wheels being electrically isolated from the body, the body, the wheels, the cleaning cylinder and the cleaning fins being made from a conductive material, the cleaning fins rotated by the cleaning cylinder and touching an upper surface of the solar panels, the controller electrically coupling the positive terminal with a grounded connection and the negative terminal with the cleaning fins when the cleaning cylinder is rotated.

Description

SOLAR PANEL WATERLESS CLEANING SYSTEM AND METHOD

WITH POTENTIAL INDUCED DEGRADATION RECOVERY

PRIORITY CLAIM

This application claims priority from US provisional patent application serial no. 62/647,836, filed on March 26, 2018. FIELD OF THE DISCLOSED TECHNIQUE

The disclosed technique relates to solar panel cleaning systems and methods, in general, and to methods and systems for cleaning solar panels without water while simultaneously resolving the potential induced degradation effect in solar panels, in particular.

BACKGROUND OF THE DISCLOSED TECHNIQUE

The challenges of global climate change and energy circuitry demands have made the development of renewable energy alternatives vital for the future of mankind. The use of direct sun radiation on solar panels can potentially produce more than enough energy to meet the energy needs of the entire planet. As the price of solar power decreases and the pollution caused by conventional fuels is rising, the solar business has entered a new era of worldwide growth. In order to bring technologies to exploit solar energy one step closer up to par with conventional fuels, the efficiency rate of solar systems must improve. Solar panel efficiency depends amongst other things on the cleanliness of their surface. Energy losses caused by dust and soiling can reach over 40%. In desert areas, where many solar parks are located, the soiling and dust problem is significant.

A fast growing type of solar park is the solar tracker park which consists of solar panels mounted on a frame, collectively called a solar tracker. Solar trackers have the ability to follow the sun’s position continuously from morning to evening by changing their tilt angle from east (in the morning) to west (in the evening) in order to increase efficiency. Automatic cleaning solutions for solar trackers usually involve high volumes of water and/or the installation of special grids in the solar tracker park for moving automatic cleaners from solar tracker to solar tracker. Such solutions are not cost effective and require added labor for installation.

In addition, solar panels, whether in solar parks that have solar panels fixed at a specific angle or in solar tracker parks where the angle of the solar panels changes with respect to the sun’s position, can suffer from a physical phenomenon or effect known as potential induced degradation (herein abbreviated PID). Reference is now made to Figure 1A, which is a schematic illustration of a cross-section of a typical solar panel, generally referenced 10, as is known in the prior art. Figure 1A illustrates the PID phenomenon. Solar panel 10 includes a glass layer 12, an encapsulation layer 14, a foil layer 16 and a metal frame 28. Glass layer 12 is positioned above encapsulation layer 14 which is positioned above foil layer 16. Metal frame 28 houses glass layer 12, encapsulation layer 14 and foil layer 16. Encapsulation layer 14 includes a plurality of solar cells 18A, 18B, 18C and 18N, which are electrically coupled sequentially, as shown by a plurality of cables 30. Encapsulation layer 14 encapsulates plurality of solar cells 18A-18N, thus protecting them from the environment (e.g., air, water, dust and the like). Foil layer 16 is opaque and reflects sunlight to an underside 32 of plurality of solar cells 18A-18N to increase their efficiency in converting sunlight into electricity.

As shown a plurality of rays of sunlight 26 impinge upon solar panel 10. Plurality of rays of sunlight 26 pass through glass layer 12 and encapsulation layer 14 and impinge upon plurality of solar cells 18A-18N. Plurality of rays of sunlight 26 which travel between plurality of solar cells 18A-18N and impinge upon foil layer 16 are reflected to underside 32 of plurality of solar cells 18A-18N. Plurality of rays of sunlight 26 which impinge upon plurality of solar cells 18A-18N cause electrical currents to form on plurality of solar cells 18A-18N. As shown in Figure 1A, solar cell 18N is coupled with a solar inverter 22 which converts the direct current

(herein abbreviated DC) electricity generated by plurality of solar cells 18A-18N into alternating current (herein abbreviated AC) electricity which can then be used to power a utility grid or an electric grid. Power from the grid can then be used by an electric company to power homes, appliances and the like. As shown in Figure 1A, solar inverter 22 may be coupled with a single solar cell which is coupled with other cells. Alternatively, each solar cell may be coupled with an individual solar inverter (not shown). Regardless of the number of solar inverters in a solar panel, due to the flow of electricity over each solar cell, solar inverters can cause a negative voltage build-up in the solar cell or solar cells they are coupled with. The negative voltage build-up is related to the migration of positively charged ions towards the surface of each solar cell. As shown, glass layer 12 may include a plurality of positively charged ions 20, for example sodium ions, which are present in glass layer 12. Due to the negative voltage build-up on plurality of solar cells 18A-18N, plurality of positively charged ions 20 may migrate, as shown by a plurality of arrows 22 towards one of the surfaces of plurality of solar cells 18A-18N. Plurality of positively charged ions 20 may deposit themselves there upon, as shown by a plurality of V signs on one of the surfaces of plurality of solar cells 18A-18N, as shown by a plurality of arrows 24. The migration of positively charged ions to the surface of plurality of solar cells 18A-18N and the simultaneous build-up of negative voltage on plurality of solar cells 18A-18N can cause plurality of solar cells 18A-18N to short-circuit, which results in a gradual decline of performance of plurality of solar cells 18A-18N. The amount of efficiency reduction or degradation due to PID can reach up to 30% or more. As mentioned above, this phenomenon or effect is known in the art as PID, in the sense that solar cells are degraded due to an induced potential (i.e., voltage) from the migration of positively charged ions to the surface of solar cells.

Reference is now made to Figure 1 B, which is a schematic illustration of two solar panels, generally referenced 50, showing the effects of PID, as is known in the art. Figure 50 shows two solar panels, a first solar panel 52A and a second solar panel 52B. The presence of PID on a solar cell can be made visible by sending a current through a solar panel and observing the infrared light emitted from the individual solar cells in a procedure known as an electroluminescence test. Both first solar panel 52A and second solar panel 52B have been subjected to an electroluminescence test showing the resultant infrared light emitted from the solar cells of each solar panel. First solar panel 52A includes a plurality of solar cells 54 which each emits infrared light (white boxes), thus demonstrating that plurality of solar cells 54 do not exhibit any PID and therefore function properly. Second solar panel 52B includes a plurality of solar cells 56 which each emits infrared light (white boxes) however second solar panel 52B also includes a plurality of solar cells 58 which each only partially emits infrared light (single hatched boxes) as well as a plurality of solar cells 60 which each do not emit infrared light (double hatched boxes). The lack of infrared light emission indicates that a solar cell is not functioning properly and will convert sunlight into electricity at a degraded efficiency or possibly not at all. Second solar panel 52B exhibits PID as some of its solar cells do not function properly. Since PID is related to the flow of electric charge, PID can spread like a virus from solar cell to solar cell, slowly affecting all the solar cells of a given solar panel. As shown, plurality of solar cells 58 and plurality of solar cells 60 are clustered in that as one solar cell begins to degrade due to PID it can cause neighboring cells to degrade as well.

PID in general is a reversible effect and methods and systems are known in the art for preventing and resolving the issue of PID and returning solar cells in a solar panel to their full efficiency. US patent application publication no. 2017/0353155 A1 , to Hackl et al., entitled “Circuit Arrangements for Reducing Potential-Induced Degradation in Photovoltaic Modules” is directed to circuit arrangements for reducing potential-induced degradation in photovoltaic modules of a photovoltaic generator. The circuit arrangement counteracts potential-induced degradation in photovoltaic modules of a photovoltaic generator and simultaneously enables a temporally continuous insulation monitoring of the photovoltaic generator. The circuit arrangement comprises an insulation monitoring device for a temporally continuous insulation monitoring of the photovoltaic generator. A first solution involves symmetrically connecting the insulation monitoring device between a positive pole of the photovoltaic generator and ground and between a negative pole of the photovoltaic generator and ground. The circuit arrangement comprises an impulse coupling circuit, which is connected symmetrically between the positive pole of the photovoltaic generator and ground and between the negative pole of the photovoltaic generator and ground for coupling positive voltage impulses.

The effects of potential-induced degradation are accelerated by increasing a negative voltage amplitude to ground, thus it is presumed that increasing the voltage amplitude comprising opposite polarity subdues the PID effect in an amplified manner. According to the first solution short voltage impulses comprising high amplitude (larger than 50 volts) are applied to ground to the photovoltaic generator in order to terminate or even reverse a movement of the charge carrier in the cells of the photovoltaic module. The pulse-duty factor and the voltage amplitude are to be adjusted specifically to the photovoltaic module in order to prevent the effect of degradation for the cell type in use as effectively as possible. Units of a few seconds are used as an impulse duration.

US patent application publication no. 2016/0233374 A1 , to

Knight et al., entitled“Methods, Apparatus, and Systems for Passivation of Solar Cells and Other Semiconductor Devices” is directed to a method of passivating semiconductor devices using existing tools of junction isolation and phosphosilicate glass (PSG)/borosilicate glass (BSG) etching via room temperature wet chemical growth processes (RTWCG). Back side processing of the semiconductor device achieves passivation and junction isolation in a single step, while front side processing achieves passivation, PSG/BSG etch, anti-reflection coating and potential induced degradation (PID) mitigation simultaneously. A modified solar cell fabrication method is then provided by integrating the passivation formation method into conventional solar cell manufacturing systems. The front surface is coated with a silicon oxide (SiOx) layer less than 50 nm thick, over which a silicon nitride (SiNx) layer is deposited. On the back surface, another SiOx layer is coated.

The method described utilizes a junction isolation and PSG/BSG etch solar cell processing tool to facilitate fabrication of a passivated emitter and rear solar cell via a RTWCG process. In this method, the back side of a semiconductor substrate is exposed to a first RTWCG solution, contained in a junction isolation process tank of the processing tool, to form a back side oxide layer to passivate the back surface of the substrate. During the same step, the RTWCG solution can also etch away a diffused layer on the substrate edge to achieve junction isolation, and etch away any BSG on the surface. Following the back side processing, the front side of the semiconductor substrate is exposed to a second RTWCG solution, contained in a PSG/BSG etch process tank of the processing tool, to form a front side oxide layer less than 50 nm to passivate the front surface of the substrate. Any PSG/BSG impurity on the front surface of the substrate can also be cleaned by the second RTWCG solution before the formation of the back side oxide layer. After each RTWCG step, the substrate is rinsed using de-ionized water to remove excessive chemicals on the substrate. The method can further comprise a step to deposit a layer of SiNx on the front side oxide layer such that the combination of SiOx and SiNx layers can improve the anti-reflection property and mitigate the PID of the semiconductor device.

US patent application publication no. 2015/0096613 A1 , to Tjahjono et al., entitled“Photovoltaic Device and Method of Manufacturing the Same” is directed to a photovoltaic device and method of manufacturing. The photovoltaic device includes a semiconductor structure assembly and a protection layer. The semiconductor structure assembly has a plurality of side surfaces and includes a p-n junction, an n-p junction, a p-i-n junction, an n-i-p junction, a tandem junction or a multi-junction. In particular, the protection layer is formed to overlay the sides of the semiconductor structure assembly to inhibit the potential-induced degradation effect of the photovoltaic device. The photovoltaic device also comprises a second protection layer formed to overlay the first protection layer. The method of manufacturing the photovoltaic device comprises the steps of preparing a semiconductor structure assembly and forming a first protection layer to overlay the side surfaces. The semiconductor structure assembly has a plurality of side surfaces and includes a junction being a p-n junction, n-p junction, p-i-n junction, n-i-p junction, double junction or a multiple junction.

US patent application publication no. 2014/0283904 A1 , to Huang et al., entitled“Solar Cell of Anti Potential Induced Degradation and Manufacturing Method Thereof” is directed to a solar cell having anti-potential induced degradation and a manufacturing method thereof. The method includes the steps of performing plasma cleaning on a silicon wafer by using an oxidizing gas, so as to form a first silicon oxide film on the surface of the silicon wafer and forming an anti-reflection film on the surface of the first silicon oxide film, where the anti-reflection film includes at least a silicon oxide film. The silicon oxide film has an electrical insulation property and an anti-reflection effect thus giving the solar cell manufactured a good electrical insulation property with the packaging material and the glass substrate. The corresponding photovoltaic module thus has an anti-potential induced degradation effect.

Besides the described the patent applications listed above, the following companies manufacture products which prevent PID and can reverse its effect: Vigdu Technologies, iLumen, Pidbull, SMA Solar Technology AG and PADCON GmbH. For example, Pidbull manufactures different units, such as a string inverter unit and a central inverter unit for reversing the effects of PID in a solar panel depending on the type of inverter used with the solar panel to generate AC electricity. Inverter units are coupled with each solar panel and require an external power source. Each inverter unit generates an electric potential at night over the solar panel it is attached to in order to invert the polarizing effect of the migration of positively charged ions as well as the build-up of negative voltage on the surface of the solar cells of the solar panel. The prior art describes solutions for preventing or reversing PID either by using specially prepared and manufactured solar cells or photovoltaic modules which prevent PID or by installing an external system on each solar panel for reversing the effects of PID. What is needed is a system and method for preventing PID and reversing its effects that does not require the installation of an external system and which can reverse and prevent PID on all types of solar cells and photovoltaic modules, even those not prepared with special coatings for preventing PID.

SUMMARY OF THE PRESENT DISCLOSED TECHNIQUE

It is an object of the disclosed technique to provide a novel method and system for cleaning the surface of solar panels of at least one solar row without water while simultaneously removing potential induced degradation in the solar row. In accordance with the disclosed technique, there is thus provided a solar panel waterless cleaning system with potential induced degradation (PID) recovery, for cleaning a plurality of solar panels in at least one solar row and for reversing PID. The solar panel waterless cleaning system with PID recovery includes a body, at least two wheels, a cleaning cylinder, a plurality of cleaning fins, a power supply and a controller. The wheels are mechanically coupled with the body, the cleaning cylinder is housed in the body, the cleaning fins are coupled with the cleaning cylinder, and the controller is coupled with the wheels, the cleaning cylinder and the power supply. The wheels are for moving the body over the solar panels in the solar row and the wheels are electrically isolated from the body. The power supply includes a positive terminal and a negative terminal. The body, the wheels, the cleaning cylinder and the cleaning fins are made from a conductive material. The cleaning fins are rotated by the cleaning cylinder and touch an upper surface of the solar panels thereby generating a directional air flow for waterlessly cleaning the solar panels. When the cleaning cylinder is rotated, the controller electrically couples the positive terminal with a grounded connection and electrically couples the negative terminal with the cleaning fins. The cleaning fins apply a negative voltage to the upper surface of the solar panels, thereby reversing PID while simultaneously cleaning the upper surface of the solar panels waterlessly.

In accordance with another aspect of the disclosed technique there is thus provided a solar panel waterless cleaning system with potential induced degradation (PID) recovery, for cleaning a plurality of solar panels in at least one solar row and for reversing PID. The solar panel waterless cleaning system with PID recovery includes a cleaning cylinder, a plurality of brushing elements, a conductive cover, a power supply, a controller and a wheel assembly. The brushing elements are coupled with the cleaning cylinder and the power supply is coupled with the cleaning cylinder and the controller. The wheel assembly is mechanically coupled with the conductive cover, the power supply and the controller. The cleaning cylinder rotates and the brushing elements rotate as the cleaning cylinder rotates. The conductive cover is for covering the cleaning cylinder and the brushing elements. The power supply includes a positive terminal and a negative terminal. The wheel assembly includes a plurality of wheels for enabling the solar panel waterless cleaning system with PID recovery to move along a length of the solar row. The wheel assembly is electrically isolated from the conductive cover. The conductive cover, the cleaning cylinder and the brushing elements span a width of the solar row. The conductive cover, the cleaning cylinder and the brushing elements are made from a conductive material. When the cleaning cylinder rotates, the brushing elements brush an upper surface of the solar row. When the cleaning cylinder is rotated, the controller electrically couples the positive terminal with a grounded connection and electrically couples the negative terminal with the brushing elements. The brushing elements apply a negative voltage to the upper surface of the solar row, thereby reversing PID while simultaneously cleaning the upper surface of the solar row waterlessly.

In accordance with a further aspect of the disclosed technique there is thus provided a solar panel waterless cleaning system with potential induced degradation (PID) recovery, for cleaning a plurality of solar panels in at least one solar row and for reversing PID. The solar row has a length direction and a width direction. The solar panel waterless cleaning system with PID recovery includes a main frame, a secondary frame, at least one waterless cleaning apparatus, a controller, a first drive mechanism, a second drive mechanism, a plurality of conductive plates and a power supply. The secondary frame is mounted on the main frame. The waterless cleaning apparatus is mounted on the secondary frame. The controller is coupled with the waterless cleaning apparatus, the main frame and the secondary frame. The first drive mechanism is coupled with the main frame and the second drive mechanism is coupled with the secondary frame. The conductive plates are coupled with the secondary frame. The power supply is coupled with the first drive mechanism, the second drive mechanism and the waterless cleaning apparatus. The power supply includes a positive terminal and a negative terminal. The main frame is moveable in the length direction and the secondary frame is moveable in the width direction. The waterless cleaning apparatus is operable to clean a solar panel surface of a solar row to be cleaned without using water. The controller is for selectively moving the waterless cleaning apparatus in the length direction and for selectively moving the waterless cleaning apparatus up and down in the width direction of the solar row. The first drive mechanism is for driving the main frame along the length direction of the solar row and the second drive mechanism is for driving the secondary frame along the width direction of the solar row. The waterless cleaning apparatus includes a cleaning cylinder and a plurality of cleaning fins. The cleaning fins are coupled with the cleaning cylinder. The cleaning cylinder rotates and the cleaning fins touch the solar panel surface. When the cleaning cylinder rotates, the cleaning fins generate a directional air flow in the width direction of the solar row, thereby pushing debris on the solar panel surface off the solar panel surface without using water. The cleaning fins are made from a conductive material. The conductive plates electrically couple the cleaning fins with the negative terminal. When the cleaning cylinder rotates, the controller electrically couples the positive terminal with a grounded connection and electrically couples the negative terminal with the cleaning fins. The cleaning fins apply a negative voltage to the solar panel surface, thereby reversing PID while simultaneously cleaning the solar panel surface waterlessly.

In accordance with another aspect of the disclosed technique there is thus provided a method for simultaneously cleaning at least one solar row waterlessly and reversing potential induced degradation (PID) on the solar row. The method utilizes a solar panel waterless cleaning apparatus which includes a cleaning cylinder and a plurality of electrically conductive cleaning fins. The electrically conductive cleaning fins are coupled with the cleaning cylinder for generating a directional air flow when the cleaning cylinder rotates. The method includes the procedure of coupling the electrically conductive cleaning fins with a negative terminal of a power supply and coupling a positive terminal of the power supply with a grounded connection. The method also includes the procedure of moving the solar panel waterless cleaning apparatus over the solar row such that the electrically conductive cleaning fins touch an upper surface of the solar row. The electrically conductive cleaning fins clean the upper surface waterlessly via the directional air flow and simultaneously apply a negative voltage to the upper surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technique will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:

Figure 1A is a schematic illustration of a cross-section of a typical solar panel, as is known in the prior art;

Figure 1 B is a schematic illustration of two solar panels showing the effects of PID, as is known in the art;

Figure 2A is a schematic illustration of a waterless solar panel cleaning and PID recovery system of the disclosed technique reversing the effects of PID, constructed and operative in accordance with an embodiment of the disclosed technique;

Figure 2B is a schematic illustration of a solar panel after use of the waterless solar panel cleaning and PID recovery system of Figure 2A, constructed and operative in accordance with another embodiment of the disclosed technique;

Figure 3 is a top view schematic illustration of a first embodiment of the waterless solar panel cleaning and PID recovery system of the disclosed technique, constructed and operative in accordance with a further embodiment of the disclosed technique;

Figure 4 is a cross-sectional view of the first embodiment of the waterless solar panel cleaning and PID recovery system of Figure 3 along a line A-A, constructed and operative in accordance with another embodiment of the disclosed technique;

Figure 5 is a top view schematic illustration of a second embodiment of the waterless solar panel cleaning and PID recovery system of the disclosed technique, constructed and operative in accordance with a further embodiment of the disclosed technique; and

Figure 6 is a cross-sectional view of the second embodiment of the waterless solar panel cleaning and PID recovery system of Figure 5 along a line B-B, constructed and operative in accordance with another embodiment of the disclosed technique.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The disclosed technique overcomes the disadvantages of the prior art by providing a novel method and system for reversing and eliminating the effects of PID in a solar park while also not requiring the installation of a separate external system for PID elimination. In addition, the disclosed technique works with existing solar cells that may not have special anti-PID coatings. According to the disclosed technique, a potential difference is generated between the solar cells of a solar park and a waterless solar panel cleaning apparatus equipped with conductive cleaning fins. The solar cells are grounded thus having a potential of zero volts relative to ground. The waterless solar panel cleaning apparatus is given a negative voltage. As the waterless solar panel cleaning apparatus cleans the glass surface of the solar panel with conductive fins, due to the potential difference between the waterless solar panel cleaning apparatus and the solar cells, positively charged ions residing on the solar cells which cause the PID effect are attracted to the negative voltage of the waterless solar panel cleaning apparatus which is applied to the glass surface of the solar panel. As the waterless solar panel cleaning apparatus moves over the glass surface of the solar panel, a negative voltage is applied through the glass surface which attracts the positively charged ions residing on the solar cells back to the glass surface. This action reverses the effects of PID and returns the positively charged ions on the solar cells back to the glass layer of the solar panel. As the waterless solar panel cleaning apparatus may be used each night to clean the glass surface of the solar panels of a solar park, the disclosed technique enables the effects of PID which may have built up during the day on a solar panel to be reversed and eliminated on a daily basis. In addition, the disclosed technique will work on any type of solar panel, even those without anti-PID coatings, for removing the effects of PID.

According to the disclosed technique, the novel system and method for removing and eliminating the effects of PID is integrated into an existing waterless solar panel cleaning system and method thereby obviating the need to install an external system for PID removal. The disclosed technique thus does not require any external power source for generating a negative voltage or for powering an external PID removal system. According to the disclosed technique the power source of an existing waterless solar panel cleaning system is used with the PID removal system and method of the disclosed technique, thus enabling PID elimination to occur simultaneously as solar panel cleaning occurs. As mentioned above, PID reduces the efficiency of solar cells and thus reduces the electricity production potential of a solar park. In addition, electricity production of a solar park is also affected by dirty, dusty and soiled solar panels. According to the disclosed technique, the effects of PID can eliminated simultaneously as the glass surface of a solar panel is cleaned of dirt, dust and debris, thereby maintaining electricity producing of a solar park at its maximum. Reference is now made to Figure 2A, which is a schematic illustration of a waterless solar panel cleaning and PID recovery system of the disclosed technique reversing the effects of PID, generally referenced 100, constructed and operative in accordance with an embodiment of the disclosed technique. Waterless cleaning and PID recovery system 100 is schematic in nature and shows the components of the disclosed technique and how a solar panel can be simultaneously cleaned of dirt, dust and debris while also having the effects of PID removed. Specific embodiments of the waterless cleaning and PID recovery system of the disclosed technique are described below in Figures 3, 4, 5 and 6 as are other embodiments of the disclosed technique.

Waterless cleaning and PID recovery system 100 includes a waterless cleaning apparatus 104 which is used to clean the glass surface of a solar panel 102. As shown, solar panel 102 includes a glass layer 108, a plurality of solar cells 1 14A, 1 14B, 1 14C and 1 14N, which are each coupled to one another via a plurality of electrical cables 1 16. Plurality of solar cells 1 14A-1 14N are encased in an encapsulation layer 1 10 which is just below glass layer 108. Encapsulation layer 1 10 is backed with a foil layer 1 12 and all three layers (glass layer 108, encapsulation layer 1 10 and foil layer 1 12) are housed in a metal frame 106. Plurality of solar cells 1 14A-1 14N may be electrically grouped together in rows or strings of solar cells. Each row or string of solar cells is coupled to a solar inverter for converting the DC electricity generated by the solar cells into AC electricity to be stored and used to power a utility grid or electric grid. Power from the grid can then be used to power buildings, houses, infrastructure and appliances. As shown, a solar inverter 1 18 is coupled with solar cell 1 14N and converts all the DC electricity generated by plurality of solar cells 1 14-1 14N into AC electricity. Solar inverter 1 18 is also electrically grounded, shown by a grounding arrow 120. Part of the function of solar inverter 1 18 is to synchronize the generation of electricity from solar panel 102 with the utility grid or electric grid it is attached to. For example, solar inverter 1 18 functions to guarantee that the phase, frequency and amplitude of the electricity produced by solar panel 102, once converted to AC electricity, matches the phase, frequency and amplitude of the utility grid. Solar inverter 1 18 collects all the DC electricity of the solar panels coupled with it, inverts the DC electricity to AC electricity and also performs a complete correspondence of the inverted AC electricity to the requirements of the utility grid. Solar inverter 1 18 thus synchronizes what it outputs to the input of the utility grid.

Waterless cleaning apparatus 104 includes a body 122, at least two wheels 124, a cleaning cylinder (not shown), a plurality of cleaning fins 126, a power supply (not shown), such as a rechargeable battery and a processor (not shown). The processor can also be referred to as a controller. Plurality of cleaning fins 126 are coupled with the cleaning cylinder which rotates in the direction of an arrow 128. The cleaning fins make physical contact with the surface of glass layer 108 when they rotate around, as shown by an arrow 130. Described below in greater detail, waterless cleaning apparatus 104 cleans the surface of glass layer 108 by rotating plurality of cleaning fins 126 outwards, thereby generating a directional air flow that pushes dirt, dust and debris off the surface of glass layer 108. The touch of plurality of cleaning fins 126 on the surface of glass layer 108 along with the directional air flow generated by the rotation of the cleaning fins cleans the surface of glass layer 108 without water. Waterless cleaning apparatus 104 is generally used at night when solar panel 102 is not generating any electricity from the sun. At least two wheels 124 enable body 122 to move over the surface of glass layer 108 and are electrically isolated from said plurality of cleaning fins 126.

Each of plurality of cleaning fins 126 is made from a soft, fabric material that is also conductive. For example, plurality of cleaning fins 126 may be made from a microfiber having small threads of a conductive material, such as a conductive metal, such as silver, gold, brass, zinc, copper and the like, woven into the microfiber. According to the disclosed technique, the power supply of waterless cleaning apparatus 104 is electrically coupled such that the positive terminal of the power supply is coupled to ground whereas the negative terminal of the power supply is coupled with plurality of cleaning fins 126. For example, in the case of a rechargeable battery, the positive terminal of the battery is electrically coupled to ground and the negative terminal of the battery is electrically coupled to plurality of cleaning fins 126. A battery provides energy by having a potential difference between its positive and negative terminals. The positive terminal may have a voltage of +12 volts and the negative terminal may have a voltage of 0 volts, thus having a potential difference which can be used to provide electricity. According to the disclosed technique by coupling the positive terminal of the power supply to ground, the voltage of the positive terminal is thus 0 volts. Depending on the power supply used, this will cause the negative terminal of the power supply to have a negative voltage, such as -12 volts, -24 volts, -48 volts and the like. At night, when waterless cleaning apparatus 104 is to clean the glass surface of glass layer 108, solar inverter 1 18 is coupled to ground (as shown by grounding arrow 120), thereby giving each one of plurality of solar cells 1 14A-1 14N a voltage of 0 volts. This is schematically shown by an arrow 134 pointing to ‘V=0’. Plurality of cleaning fins 126 is coupled with the negative terminal of the power supply, thus giving plurality of cleaning fins 126 a negative voltage, depending on the potential difference of the power supply. This is shown schematically by an arrow 138 pointing to‘V=-X’ where‘X’ is the potential difference of the power supply.

As shown in Figure 2A, solar panel 102 exhibits the PID effect as a plurality of positively charged ions 132 reside on the surface of plurality of solar cells 1 14A-1 14N. As waterless cleaning apparatus 104 cleans the surface of glass layer 108 via the rotation of plurality of cleaning fins 126 in the direction of arrow 128, plurality of cleaning fins 126 applies a negative charge, shown by an arrow 136, to the surface of glass layer 108. As plurality of solar cells 1 14A-1 14N is coupled with solar inverter 1 18 which is grounded, plurality of cleaning fins 126 generates a negative charge on the surface of glass layer 108. Plurality of positively charged ions 132 is electrically attracted to negative charge 136 and causes plurality of positively charged ions 132 to migrate off the surface of plurality of solar cells 1 14A-1 14N back to glass layer 108, shown schematically by a plurality of arrows 140. As waterless cleaning apparatus 104 traverses over the entire surface of solar panel 102, not only cleaning the surface of glass layer 108 from dust, dirt and debris waterlessly but applying a negative charge to the surface of glass layer 108, waterless cleaning apparatus 104 also reverses the effects of PID and recovers the energy producing potential of solar panel 102 by causing plurality of positively charged ions 132 to return to glass layer 108 and leave the surface of plurality of solar cells 1 14A-114N. It is noted that any charge drawn from the surface of plurality of solar cells 1 14A-1 14N into plurality of cleaning fins 126 is transferred via the negative terminal of the power supply to the power supply. In the disclosed technique, the power supply has sufficient capacitance for holding the charge drawn from the surface of plurality of solar cells 1 14A-1 14N. In another embodiment of the disclosed technique, waterless cleaning apparatus 104 includes a capacitor (not shown), which is also electrically coupled with plurality of cleaning fins 126, for absorbing and storing charge drawn from the surface of plurality of solar cells 1 14A-1 14N. In a further embodiment, since the positively charged ions resting on the surface of solar cells 1 14A-1 14N are supposed to reside in glass layer 108, the negative charge applied by plurality of cleaning fins 126 to the surface of glass layer 108 merely attracts the positively charged ions on the surface of the solar cells back to glass layer 108 and no excess charge needs to be stored in the power supply.

Once waterless cleaning apparatus 104 has finished cleaning solar panel 102 and reversing the effects of PID, waterless cleaning apparatus 104 may couple with a ground connection (not shown), either on solar panel 102 or on a docking station (not shown) for waterless cleaning apparatus 104, where any excess charge collected by waterless cleaning apparatus 104 is discharged to the ground connection. Depending on the amount of charge collected from solar panel 102 due to the effects of PID, the collected charge may be discharged more than once a cleaning cycle. In another embodiment of the disclosed technique, no charge may need to be discharged from the power supply. As mentioned above, the cleaning cycle of waterless cleaning apparatus 104 along with the removal of excess positive charge on the solar cells which causes PID is executed at night when solar panel 102 is not generating electricity. The disclosed technique thus does not require an external system for PID recovery or removal and can fully integrate into a waterless cleaning apparatus. Reference is now made to Figure 2B, which is a schematic illustration of a solar panel after use of the waterless solar panel cleaning and PID recovery system of Figure 2A, generally referenced 160, constructed and operative in accordance with another embodiment of the disclosed technique. Identical elements in Figures 2A and 2B are referenced using identical reference numbers. As shown, solar panel 102 has been cleaned of dirt and debris along with removing the effects of PID. A plurality of positively charge ions 162, which cause PID, such as sodium ions, are now shown being located in glass layer 108 and are not on the surface of plurality of solar cells 1 14A-1 14N, shown schematically by an arrow 164. The effects of PID are similar to dust, dirt and debris which collects on the surface of glass layer 108 and are substantially always present. The waterless cleaning apparatus of the disclosed technique thus constantly cleans the surface of glass layer 108 of dust, dirt and debris and also constantly cleans the surface of plurality of solar cells 1 14A-1 14N by the removal of excess buildup of positively charged ions. The cleaning cycle of the waterless cleaning apparatus may be executed once daily, once weekly or on any other time schedule during non-electricity producing hours of solar panel 102, which is usually at night.

Reference is now made to Figure 3, which is a top view schematic illustration of a first embodiment of the waterless solar panel cleaning and PID recovery system of the disclosed technique, generally referenced 180, constructed and operative in accordance with a further embodiment of the disclosed technique. Waterless solar panel cleaning and PID recovery system 180 (herein simply referred to as cleaning and PID system 180) is shown in combination with a row of solar panel assemblies 182 (herein referred to as a solar row). Solar row 182 comprises a plurality of solar panels of any type and construction known to the worker skilled in the art. A length of solar row 182 can vary between a few meters to a few kilometers. A width of solar row 182 ranges from about one meter to about several meters. As mentioned above, each solar row 182 or each solar panel (not labeled) in solar row 182 is coupled with a solar inverter (not shown), which electrically grounds each solar panel and each solar row. In general, solar cells in a solar panel are coupled in series and solar panels are coupled in series in a solar row. Each solar row is housed in a construction or frame, with the construction or frame being grounded, either via a specific grounding connection or physically grounded by conductive poles coupled with the construction or frame that are inserted deep enough into the ground. Thus, each solar row is coupled to the ground just like a building is grounded by a coupling to the ground. This is shown schematically by an arrow 238. Thus solar row 182 has a voltage of 0 volts. Whereas it may be unclear from Figure 3, solar row 182 is constructed in an angular or inclined position toward the sun, which creates a lower edge and a higher edge of solar row 182. A pair of parallel rails 184 and 186 is coupled with the upper edge and the lower edge of solar row 182, with parallel rail 184 being at the upper edge and parallel rail 186 being at the lower edge. Parallel rails 184 and 186 are electrically grounded, as shown by a grounding arrow 242, thus giving the parallel rails a voltage of 0 volts.

Cleaning and PID system 180 includes a main frame 188 and a secondary frame 226, which together enables bi-directional movement of a waterless cleaning apparatus 202, as described below. This bi-directional movement enables waterless cleaning apparatus 202 to move along a solar row in two directions, either along the length of solar row 182 and in the width direction of solar row 182. Main frame 188 is configured to be movable along the length of solar row 182 and can be made from aluminum constructive profiles, steel and the like, or any other conductive material. Supporting elements 190 are connected to main frame 188 for support, four of which are shown in Figure 3. Main frame 188 is coupled with parallel rails 184 and 186 via a plurality of wheels 206,

218 and 220 which enable main frame 188 to move along the length of solar row 182. Wheels 206, 218 and 220 serve different functions and number six in total as shown in Figure 3 however other numbers of wheels, particular placement on main frame 188 and functions are possible and can vary as is known to the worker skilled in the art. Wheels 206, which number three, support main frame 188 in a perpendicular direction relative to the surface of the solar panels in solar row 182. Wheels 206 are made from a conductive material such as brass, bronze, galvanized steel or other conductive materials. Wheels 206 are electrically coupled with parallel rails 184 and 186 and also with main frame 188. As shown, wheels 206 are electrically grounded, as shown by a grounding arrow 240, and thus wheels 206, supporting elements 190 and main frame 188 have a voltage of 0 volts as does parallel rails 184 and 186 and solar row 182.

Wheels 220, which number two, support main frame 188 in a parallel direction relative to the surface of the solar panels in solar row 182. As mentioned above, other amounts of wheels 220 may be used, such as three, four and the like. A drive wheel 218 is arranged in the same orientation as wheels 206, i.e. in a perpendicular direction relative to the surface of the solar panels in solar row 182 and is driven by a drive system 194, such as a motor, in forward and reverse directions along the length of solar row 182. Drive wheel 218 functions to drive main frame 188 along solar row 182 in the length direction of the solar row. The motor in drive system 194 may be any type of motor or other system capable of generating a motive force, such as a DC motor. When a motor is present in drive system 194, an encoder may be connected to the motor and reads the angular position of the motor. The angular position is converted by a processor or a controller into a determination of the location of the cleaning and PID system along solar row 182. Drive wheel 218 can drive main frame 188 along the solar row in two directions. A movement limiting sensor 192 is located on the upper edge of main frame 188 and may be embodied as a limit switch or a limit sensor.

Secondary frame 226 is configured to be movable along main frame 188. Whereas main frame 188 has a longitudinal axis as shown in Figure 3, secondary frame 226 may be considered to move longitudinal or in the longitudinal or length direction along main frame 188. Secondary frame 226 can be made from aluminum profiles or other materials as mentioned above regarding main frame 188. Secondary frame 226 supports at least one waterless cleaning apparatus 202. Figure 3 shows secondary frame 226 supporting two waterless cleaning apparatuses. Each waterless cleaning apparatus 202 is coupled to secondary frame 226 through a respective central shaft 234 and bearings (not shown) to enable the waterless cleaning apparatuses to rotate on secondary frame 226. The rotational axis of each waterless cleaning apparatus is shown as two broken lines 236 in Figure 3.

A drive system 204 is provided to drive the waterless cleaning apparatuses. Drive system 204 may comprise a DC motor or another type of motor or motive power source as is known in the art. A power transfer system is provided to convey the motive power from drive system 204 to waterless cleaning apparatuses 202 and convert the motive power into rotational force to rotate waterless cleaning apparatuses 202. For example, a pulley 210 may be coupled with drive system 204 and a plurality of belts 208 which are each wound around pulley 210 and each waterless cleaning apparatus 202. Drive system 204 causes pulley 210 to rotate and the rotation of pulley 210 causes plurality of belts 208 to move, which in turn causes a shaft of each waterless cleaning apparatus to rotate. Plurality of belts 208 may be made of polyurethane and be round however other types of belt shapes, such as V-belts or timing-belts, and other materials may be used.

Coupled with main frame 188 is also a winch cylinder 214 having at least one or more cables or ropes 216 attached thereto and partly wound thereon. Rotation of winch cylinder 214 controls the winding and unwinding of cables 216. This controlled winding and unwinding drives secondary frame 226 upward and downward along the angular slope of main frame 188, i.e. longitudinally along main frame 188. As illustrated, the winding of cables 216 by winch cylinder 214 causes the upward movement of secondary frame 226 along the solar panels in solar row 182, while the unwinding of cables 216 by winch cylinder 214 causes the downward movement of secondary frame 226 along the solar panels in solar row 182, which is also aided by the gravitational pull of secondary frame 226 downward. Winch cylinder 214 is driven by a drive system 196 which may include a DC motor. Cables 216 are made from a conductive metal such that charge can be carried over them.

A power source 198 is provided to power the cleaning and PID system of the disclosed technique. Power source 198 may be batteries that are rechargeable, replaceable and the like and include a positive terminal (not labeled) and a negative terminal (not labeled). In addition, power source 198 may provide power to a programmable controller 200 that controls the operation of the cleaning and PID system, including the operation and movement of the various motors of cleaning and PID system 180, such as drive system 194, drive system 196 and drive system 204. Power source 198 may itself include a set of solar panels 232 attached to main frame 188. Solar panels 232 are designed to charge any batteries of power source 198 during daylight hours and when sunlight is received by solar panels 232. Power source 198 and solar panels 232 are attached to main frame 188 to be movable therewith and thereby allow the cleaning and PID system to operate independently while cleaning the solar row without connection to any other source of electricity (other than that provided by solar panels 232 and the onboard power source 198). Cleaning and PID system 180 might include a docking station (not shown) at the edge of a solar row where main frame 188 is docked at the end of a cleaning cycle. The docking station might include a dynamic electrical connector for charging power source 198.

Several sensing devices or sensors are provided in cleaning and PID system 180, such as a sensor 212, positioned on parallel rail 184, to detect a maximum leftward movement of main frame 188 on parallel rails 184 and 186, as well as a sensor 224, also positioned on parallel rail 184 to detect a maximum rightward movement of main frame 188 on parallel rails 184 and 186. Sensors 212 and 224 may alternatively be positioned on parallel rail 186. Limiting sensor 192 is positioned on main frame 188 to detect a maximum upward movement of secondary frame 226 on main frame 188, whereas a sensor 222 is positioned on main frame 188 to detect a maximum downward movement of secondary frame 226 on main frame 188. An encoder on the motor of drive system 194, when present, transmits limit signals and position signals to programmable controller 200, which allows for an effective operation of cleaning and PID system 180. In some cases, an encoder can replace sensors 212 and 224 by feeding a position of the waterless cleaning apparatus corresponding to the positions of sensors 212 and 224.

Programmable controller 200 is known in the industry and will not be described in detail herein.

Secondary frame 226 is mounted on main frame 188 via a plurality of wheels 228 that rotate perpendicularly to the solar panel surface. Plurality of wheels 228 is mechanically coupled with secondary frame 226 yet is electrically isolated from secondary frame 226. The axis of rotation of plurality of wheels 228 is perpendicular to the normal of the surface of the solar panels in solar row 182. As shown, secondary frame 226 is mounted on main frame 188 via four wheels 228, however other numbers of wheels are possible. In addition, one or more additional wheels 230 are mounted on secondary frame 226 to rotate parallel to the solar panel surface, i.e. their axis of rotation is parallel to the normal of the surface of the solar panels in solar row 182. Plurality of wheels 228 and 230 are coupled through bearings (not shown) to secondary frame 226 and roll against the surface of the profiles that make up main frame 188. Plurality of wheels 228 and 230 therefore enable secondary frame 226 to move upward and downward along main frame 188. This movement of secondary frame 226 relative to main frame 188 and solar row 182 is independent of the movement of main frame 188 along the length of solar row 182. A cross-sectional view of secondary frame 226 and waterless cleaning apparatus 202 along a line A-A is provided below in Figure 4. Additional details of waterless cleaning apparatus 202 can be found in U.S. patent no. 8,500,918 B1.

As explained above, according to the disclosed technique, a negative electric potential, i.e., a negative voltage, is induced on the glass surface of the solar cells of solar row 182 to attract positive ions resting on the solar cells, which are mainly migrated sodium ions from the glass layer (not labeled) of the solar panels towards the solar cells, back to the glass layer of the solar cells. As described and shown in greater detail below in Figure 4, waterless cleaning apparatus 202 includes a plurality of conductive fins (not shown in Figure 3) which are made of conductive microfiber. The conductive fins touch the surface of solar row 182 as they clean the surface of the solar panels of dirt and debris and also generate a continuous electrical conductivity line between the solar cell surfaces and a power source having a negative potential relative to the ground potential. The conductivity is created automatically while the conductive fins execute a cleaning process of the solar panels. As shown via grounding arrows 238, 240 and 242, the main construction of the cleaning and PID system is grounded. As mentioned above, power source 198 has a positive terminal and a negative terminal (both not shown). According to the disclosed technique, the positive terminal of power source 198 is electrically coupled with wheels 206. Secondary frame 226 might be coupled with the positive terminal of power source 198 via cable 248A. The negative terminal of power source 198 is coupled with waterless cleaning apparatus 202 via one of cables 216, such as cable 248B. It is noted that cables 248A and 248B might only receive voltage once waterless cleaning apparatus 202 starts a cleaning cycle, with cable 248A being coupled with the positive terminal and cable 248B being coupled with the negative terminal of power source 198. Thus, if drive system 196 is not functioning, then cables 248A and 248B can be shorted such that no voltage is provided via cables 216. In one embodiment, one of cables 248A or 248B may remain coupled to a voltage source (e.g., power source 198) whereas the other might be connected and disconnected depending on whether drive system 196 is operating or not. Since the positive terminal of power source 198 is grounded, the electrical potential provided by the negative terminal of power source 198 is a negative voltage relative to the ground potential of 0 volts. For example, in Figure 3, waterless cleaning apparatus 202 is provided with a negative voltage of -24 volts, as shown by reference number 246. Waterless cleaning apparatus 202 is coupled with the negative terminal of power source 198 via a plurality of conductive plates (not shown in Figure 3) and conducting wires (also not shown in Figure 3). Waterless cleaning apparatus 202 includes a plurality of conductive fins (not shown in Figure 3) which are provided with a negative voltage of -24 volts. Secondary frame 226 is electrically coupled with the positive terminal of power source 198 via one of cables 216, thereby being provided with a voltage of 0 volts. As the conductive fins touch the glass surface of the solar panels of solar row 182, the plurality of conductive fins provide a negative electrical potential to the glass surface of the solar panels. It is noted that waterless cleaning apparatus 202 is electrically isolated from main frame 188 and from secondary frame 226. As mentioned above, during nighttime hours when electricity production of solar row 182 is stopped, all the solar cells of solar row 182 are grounded via at least one solar inverter (not shown). During nighttime hours, the negative terminal of power source 198 is also electrically coupled with the plurality of conductive fins. Power source 198 has a very high capacitance. As the plurality of conductive fins touch the surface of solar row 182, the conductive fins apply a negative voltage to the glass of the solar panels of solar row 182, therefore attracting the positively charged ions resting on the surface of the solar cells of each solar panel. The charge generated by the migration of the positively charged ions back to the glass surface of the solar panels can be stored in power source 198 due to its high capacitance. If a higher capacitance is required, then an additional capacitor can be coupled in parallel to power source 198 for storing the charge generated. In some embodiments, no charge may need to be stored in power source 198. Programmable controller 200 may monitor the amount of charge stored in power source 198 accumulated from the surface of solar row 182, if applicable. Once a predetermined amount of charge from the surface of solar row 182 has been accumulated on power source 198, programmable controller 200 may provide a signal to disconnect the negative terminal of power source 198 from secondary frame 226 and to couple the negative terminal with a ground source, such as wheels 206, in order to discharge the accumulated charge. Once power source 198 has been discharged, its negative terminal may once again be coupled with secondary frame 226.

Reference is now made to Figure 4, which is a cross-sectional view of the first embodiment of the waterless solar panel cleaning and PID recovery system of Figure 3 along a line A-A, generally referenced 270, constructed and operative in accordance with another embodiment of the disclosed technique. Identical elements between Figures 3 and 4 are labeled using identical reference numbers. Figure 4 shows details of secondary frame 226 that is movable upward and downward along main frame 188 in the width direction of solar row 182. To provide solar row 182 with its angularity relative to a ground level 278, an angular construction 272 supports the solar row and has a longer vertical riser construction proximate to the upper edge of solar row 182 and a shorter vertical riser construction proximate to the lower edge of solar row 182. Secondary frame 226 has mounted thereon plurality of wheels 228 that each rotate perpendicularly to the solar panel surface. One or more additional wheels 230 are mounted on secondary frame 226 to rotate parallel to the solar panel surface. Plurality of wheels 228 and 230 are connected through bearings (not shown) to secondary frame 226 and roll against the surface of the profiles that make up main frame 188. Plurality of wheels 228 and 230 therefore enable secondary frame 226 to move upward and downward along main frame 188. This movement of secondary frame 226 relative to main frame 188 and solar row 182 is independent of the movement of mainframe 188 along the length of solar row 182.

As shown in Figure 4, waterless cleaning apparatuses 202 rotate in the same direction, counterclockwise as indicated by an arrow 276. This direction of rotation occurs as secondary frame 226 moves downward along main frame 188. Waterless cleaning apparatuses 202 are driven by drive system 204 through pulley 210 and plurality of belts 208. Plurality of belts 208 drive the two waterless cleaning apparatuses through two additional pulleys (not shown) that are attached to each waterless cleaning apparatus 202. Each waterless cleaning apparatus 202 includes four conductive fins 274 that, through a control scheme originating in drive system 204, rotate at approximately 170 rotations per minute (herein abbreviated RPM). It is noted that other rotational speeds are feasible. While conductive fins 274 rotate and secondary frame 226 moves downward, an outer part of conductive fins 274 touches, sweeps and wipes the surface of the solar panels in solar row 182. Rotation of conductive fins 274 creates an air blowing effect or directional air flow which helps to push dirt, debris and dust on the surface of the solar panels downward as a result of the slope of solar row 182.

Figure 4 also shows a connection between cables 216 that wind and unwind about the shaft coupled to winch cylinder 214 (Figure 3) and an upper edge of secondary frame 226 which is close to a center region of an upper profile that is part of secondary frame 226. Each one of cable 216, such as cable 248B, may be similarly connected to the shaft and secondary frame 226. The rotation of winch cylinder 214 extends (unwinding) or retracts (winding) the amount of cables 216 thereby lowering or raising secondary frame 226 along main frame 188. Secondary frame 226 also includes two conductive plates 280 that are coupled with it at a fixed position. The number of conductive plates used corresponds to the number of waterless cleaning apparatuses, thus one conductive plate per waterless cleaning apparatus. Conductive plates 280 can be made from stainless steel, galvanized steel, copper covered with zinc or other conductive materials. Conductive plates 280 are electrically coupled to each other via a conductive wire 282. Conductive plates 280 are electrically isolated from secondary frame 226. As mentioned above, one of cables 216 may be coupled with the negative terminal (not shown) of the power supply of the cleaning and PID system of the disclosed technique. Cable 248B, as shown, is coupled with the negative terminal of the power supply. Another conductive wire 284 couples conductive plates 280 to cable 248B. The rotating cylinder (not labeled) of waterless cleaning apparatus 202 to which conductive fins 274 are coupled with is also conductive, and can be made from an aluminum alloy that is brass coated, bronze coated or coated with another conductive material. As mentioned above, conductive fins 274 are made from a conductive fabric, such as a conductive microfiber woven with silver thread, gold thread, copper thread, zinc thread, brass thread and the like. For example, microfibers infused with silver are commercially available such as the UberGreen® microfiber cleaning cloth, which can be used to embody conductive fins 274. It is noted that conductive fins 274 can be made from other conductive cloths and fabrics. Conductive fins 274 are thus electrically coupled with the negative terminal of the power supply via conductive plates 280, conductive wires 282 and 284 and cable 248B. As shown, when cable 248B is coupled with the negative terminal of the power supply, it exhibits a negative voltage of -24 volts, for example. Thus conductive fins 274 also exhibit a negative voltage of -24 volts which is applied to the surface of solar row 182 as conductive fins 274 rotate as they brush the surface of solar row 182 and create a directional air flow. As mentioned above, both solar row 182 and main frame 188 are grounded at nighttime, shown by grounding arrows 238 and 240 and thus exhibit a voltage of 0 volts.

According to the PID phenomenon described above, the solar cells of the solar panels of solar row 182 will be effected by positively charged ions that migrated from the glass layer (not shown) of the solar panels toward the solar cells in the encapsulation layer (not shown). This migration causes the electrical potential of the solar cells to be lower than the electrical potential of the ground and will interfere with the electrical current that should be produced by the solar cells thereby lowering the overall efficiency of the solar panels in solar row 182. According to the disclosed technique, waterless cleaning apparatuses 202 are used during nighttime hours to clean the surfaces of the solar panels of solar row 182. During nighttime hours, no electricity is produced by solar row 182 and the solar cells are given a ground voltage of 0 volts via the solar inverters they are coupled with. Main frame 188 and secondary frame 226 are also provided with a ground voltage of 0 volts whereas conductive fins 274 are provided with a negative voltage of, for example, -24 volts. During a cleaning cycle, waterless cleaning apparatuses 202 are lowered down along the slope of the solar panels, with the downward movement being controlled by cables 216. The programmable controller (not shown) of the cleaning and PID system 180 couples drive system 204 (Figure 3) to the power supply (not shown) through cables 216, with one of the cables, such as cable 248B as shown in Figure 4 being coupled with the negative terminal of the power supply. The other cable, such as cable 248A (Figure 3) may be coupled with the positive terminal of the power supply. Drive system 204 rotates the rotating cylinder of waterless cleaning apparatus 202 thus also rotating conductive fins 274 as cables 216 unwind and lower secondary frame 226 down the slope of a solar panel of solar row 182. As conductive fins 274 rotate and clean the surface of the solar panel, at any given moment, at least one of conductive fins 274 touches the surface of the solar panels whereas at least another one of conductive fins 274 touches conductive plates 280. Thus while cleaning the surface of the solar panels, according to the disclosed technique a conductive line is generated from the surface of the solar panels through conductive fins 274 through the rotating cylinder (which is conductive) through conductive plates 280 through conductive wires 282 and 284 and finally through cable 248B to the negative terminal of the power supply of the cleaning and PID system. As the electric potential of the solar cells is zero relative to the ground via the at least one solar inverter coupled with the solar cells and the electric potential of conductive fins 274 is -24 volts, positively charged ions that migrated from the glass layer of the solar panels onto the solar cells will now will be attracted by the -24 volts potential difference being applied to the glass surface of the solar panels and will be migrated back to the glass layer of the solar panels from the solar cells. Once this recovery process of the solar cells from the effects of PID is completed, the power supply may have an excess amount of charge stored. The excess charge can be discharged by coupling the negative terminal of the power supply to ground. As mentioned above, since the amount of charge drawn from the solar cells affected by PID can be quite large, an additional large capacitor (not shown) can be coupled in parallel to the power supply to storing the drawn charge from the solar cells. As mentioned above, the positive terminal of the power supply can be grounded through wheels 206 (Figure 3) which are also conductive.

Reference is now made to Figure 5, which is a top view schematic illustration of a second embodiment of the waterless solar panel cleaning and PID recovery system of the disclosed technique, generally referenced 310, constructed and operative in accordance with a further embodiment of the disclosed technique. Cleaning and PID system 310 is similar to cleaning and PID system 180 (Figure 3) however its construction is slightly different. As shown in Figure 5, a solar row 312 includes a plurality of solar panels (not shown) which each include a plurality of solar cells (not shown). Cleaning and PID system 310 includes a cleaning cylinder 316 which rotates. A plurality of brushing elements 318 is coupled with cleaning cylinder 316. As cleaning cylinder 316 rotates, plurality of brushing elements 318 brushes the surface of solar row 312, similar to conductive fins 274 (Figure 4). Cleaning cylinder 316 and plurality of brushing elements 318 are covered by a conductive cover 314 which may span the width of solar row 312. Cleaning cylinder 316 and plurality of brushing elements 318 may also span the width of solar row 312. Cleaning and PID system 310 also includes a power supply 322, such as a rechargeable battery, and may also include a programmer (not shown), similar to programmable controller 200 (Figure 3). The programmer can also be referred to as a processor or controller. Cleaning and PID system 310 further includes a wheel assembly 324, comprising a plurality of wheels which enables cleaning and PID system 310 to move along the length of solar row 312. As shown, wheel assembly 324 includes four wheels although other arrangements are possible. An arrow 328 indicates a direction of movement of cleaning and PID system 310. A cross-sectional view of conductive cover 314, cleaning cylinder 316 and plurality of brushing elements 318 is provided along line B-B below in Figure 6. Wheel assembly 324 is mechanically coupled with conductive cover 314 yet electrically isolated from conductive cover 314.

As shown, the cleaning process of cleaning and PID system 310 is performed and executed by a cylindrical brush (cleaning cylinder 316 and plurality of brushing elements 318) that is supported in the width direction of solar row 312. As cleaning cylinder 316 rotates with plurality of brushing elements 318, conductive cover 314 moves the whole system along the length of solar row 312 in the direction of arrow 328, thereby cleaning a strip of solar row 312. According to the disclosed technique, plurality of brushing elements 318 are electrically conductive and may be made from a conductive microfiber woven with either silver, gold, zinc, copper, brass or another conductive material. Cleaning cylinder 706 is conductive as well as is conductive cover 314. A conductive wire 320 electrically couples conductive cover 314 to power supply 322. As shown, conductive wire 320 couples conductive cover 314 to the negative terminal of power supply 322, thereby electrically coupling plurality of brushing elements 318 to the negative terminal of power supply 322. It is noted that as plurality of brushing elements rotates, they make contact with the surface of solar row 312 as well as with conductive cover 314. Wheel assembly 324 is made from a conductive material such as brass, bronze and the like. As shown schematically in parentheses, wheel assembly 324 is coupled with the positive terminal of power supply 322, which is itself coupled to the ground potential, shown as grounding arrows 330. As described above in Figures 3 and 4, wheel assembly 324 is electrically isolated from conductive cover 314, cleaning cylinder 316 and plurality of brushing elements 318. Wheel assembly 324 moves along rails (not shown) that are coupled with the solar row construction (not labeled). Since the solar row is grounded, for example via a solar inverter (not shown), the solar row construction is also grounded. Wheel assembly 324 is thus grounded and exhibits a voltage of 0 volts, whereas conductive cover 314, cleaning cylinder 316 and plurality of brushing elements 318 each exhibit a negative voltage, depending on the size and strength of power supply 322. The negative voltage might be -24 volts.

Reference is now made to Figure 6, which is a cross-sectional view of the second embodiment of the waterless solar panel cleaning and PID recovery system of Figure 5 along a line B-B, generally referenced 350, constructed and operative in accordance with another embodiment of the disclosed technique. As seen in Figure 6, an arrow 326 indicates the direction of rotation of cleaning cylinder 316 and plurality of brushing elements 318. It is also clearly seen how the rotation of cleaning cylinder 316 causes plurality of brushing elements 318 to both touch the surface of solar row 312 and simultaneously conductive cover 314. Also shown in Figure 6 is how during a cleaning cycle, wheel assembly 324 along with solar row 312 have a voltage of 0 volts, shown via an arrow 352, whereas cleaning cylinder 316 and thus plurality of brushing elements 318 is provided with a negative voltage of -24 volts, shown via an arrow 354.

The operation of cleaning and PID system 350 is similar to the operation of cleaning and PID system 180 (Figure 3). Plurality of brushing elements 318 are electrically coupled with conductive cover 314 which are functionally similar to conductive fins 274 (Figure 4) and conductive plates 280 (Figure 4). While plurality of brushing elements 318 brush and clean the surface of solar row 312 as conductive cover 314 moves in the direction of arrow 328 over the surface of solar row 312, plurality of brushing elements 318 also apply a negative voltage to the surface of solar row 312 which attracts positively charged ions resting on the surface of the solar cells in the solar panels of solar row 312 which cause PID. The negative voltage applied by plurality of brushing elements 318 causes the positively charged ions on the solar cells to migrate back to the glass layer (not labeled) of solar row 312 thereby reversing the effects of PID. As mentioned above, the cleaning of solar row 312 occurs at night when no electricity production occurs. Power supply 322 may store any built-up charge transferred form plurality of brushing elements 318 to its negative terminal during a cleaning cycle, if applicable. The negative terminal might then be coupled with a ground terminal for discharging power supply 322 of any excess charge. In addition, a capacitor coupled in parallel with power supply 322 might also be included for storing excess charge drawn from the surface of solar row 312 during a cleaning and PID removal cycle. Cleaning and PID system 350 is similar to cleaning and PID system 180 (Figure 3) except that plurality of brushing elements 318 do not create a directional air flow for removing dirt and debris off the solar panel surface. Plurality of brushing elements 318 brushes dirt and debris off the surface of a solar panel much in the same way that a street sweeper brushes dirt, dust and debris off the street, however unlike a street sweeper, plurality of brushing elements 318 does not brush dirt and debris into a container but brushes dirt and debris forward in the direction of arrow 328, eventually off the solar panel surface.

The disclosed technique has been described above in two embodiments using the examples of a fixed angle solar row which is part of a solar array wherein the cleaning and PID system moves over a plurality of parallel rails. The disclosed technique however is not limited to such types of solar rows. The disclosed technique can be used with solar trackers which have a variable angle. In such solar rows and arrays, the solar trackers may be brought to a predetermined cleaning angle at nighttime during a cleaning cycle wherein the cleaning and PID system of the disclosed technique is moved from solar row to solar row. The disclosed technique is also not limited to the waterless cleaning apparatuses as described above which use a winch cylinder for lowering and raising a waterless cleaning apparatus over the surface of a solar row. The disclosed technique can also be used with waterless robotic cleaners, for example as described in WIPO patent application no. PCT/US2018/015221 , which can waterlessly clean a solar tracker when placed at a horizontal angle. In each of these embodiments, the waterless robotic cleaner or the waterless cleaning apparatus is to be equipped with conductive fins or conductive brushes which can apply a negative voltage to the surface of the solar row for removing the effects of PID while simultaneously cleaning the solar row surface without water. In such an embodiment, the conductive fins are coupled with the negative terminal of the power source whereas the positive terminal of the power source is to be coupled to ground. This can be achieved via a tether coupling the positive terminal to the power source to the metal frame of the solar row. In the case of a waterless robotic cleaner, a charge or docking station of the waterless robotic cleaner may be equipped with a discharge connector where the power supply and/or capacitor which stores the excess charge drawn from the glass surface of the solar row to reverse the effects of PID can electrically couple with and can discharge the excess charge.

It will be appreciated by persons skilled in the art that the disclosed technique is not limited to what has been particularly shown and described hereinabove. Rather the scope of the disclosed technique is defined only by the claims, which follow.

Claims

1. A solar panel waterless cleaning system with potential induced degradation (PID) recovery (100), for cleaning a plurality of solar panels (102) in at least one solar row and for reversing said PID, said solar panel waterless cleaning system with PID recovery (100) comprising:

a body (122);

a cleaning cylinder, housed in said body;

a power supply, coupled with said cleaning cylinder, comprising a positive terminal and a negative terminal; and

a controller, coupled with said cleaning cylinder and said power supply,

wherein said solar panel waterless cleaning system with PID recovery (100) comprising: at least two wheels (124), mechanically coupled with said body, for moving said body over said plurality of solar panels in said at least one solar row wherein said at least two wheels are electrically isolated from said body; and

a plurality of cleaning fins (126), coupled with said cleaning cylinder,

wherein said controller is also coupled with said at least two wheels characterized in that said body, said at least two wheels (124), said cleaning cylinder and said plurality of cleaning fins (126) are made from a conductive material;

wherein said plurality of cleaning fins (126) are rotated by said cleaning cylinder and touch an upper surface of said plurality of solar panels thereby generating a directional air flow for waterlessly cleaning said plurality of solar panels;

wherein when said cleaning cylinder is rotated and said plurality of cleaning fins (126) touch said upper surface, said controller electrically couples said positive terminal with a grounded connection (120) and electrically couples said negative terminal with said plurality of cleaning fins (126); and

wherein said plurality of cleaning fins (126) applies a negative voltage to said upper surface of said plurality of solar panels, thereby reversing said PID while simultaneously cleaning said upper surface of said plurality of solar panels waterlessly.

2. A solar panel waterless cleaning system with potential induced degradation (PID) recovery (180), for cleaning a plurality of solar panels in at least one solar row (182) and for reversing said PID, said at least one solar row (182) having a length direction and a width direction, said solar panel waterless cleaning system with PID recovery (180) comprising: a main frame (188), moveable in said length direction;

a secondary frame (226), mounted on said main frame (188), moveable in said width direction;

at least one waterless cleaning apparatus (202) mounted on said secondary frame (226) and being operable to clean a solar panel surface of a solar row (182) to be cleaned without using water;

a controller (200), coupled with said at least one waterless cleaning apparatus (202), said main frame (188) and said secondary frame (226), for selectively moving said at least one waterless cleaning apparatus (202) in said length direction and for selectively moving said at least one waterless cleaning apparatus (202) up and down in said width direction of said at least one solar row (182);

a first drive mechanism (194), coupled with said main frame

(188), for driving said main frame (188) along said length direction of said at least one solar row (182);

a second drive mechanism (196), coupled with said secondary frame (226), for driving said secondary frame (226) along said width direction of said at least one solar row (182); and a power supply (198), coupled with said first drive mechanism (194), said second drive mechanism (196) and said at least one waterless cleaning apparatus (202), said power supply (198) comprising a positive terminal and a negative terminal,

wherein said at least one waterless cleaning apparatus (202) comprises a cleaning cylinder, which rotates; and

wherein said solar panel waterless cleaning system with PID recovery (180) comprising a plurality of conductive plates (280), coupled with said secondary frame (226) and said at least one waterless cleaning apparatus (202) comprising a plurality of cleaning fins (274) coupled with said cleaning cylinder, said plurality of cleaning fins (274) touching said solar panel surface,

characterized in that when said cleaning cylinder rotates, said plurality of cleaning fins (274) generates a directional air flow in said width direction of said at least one solar row (182), thereby pushing debris on said solar panel surface off said solar panel surface without using water;

wherein said plurality of cleaning fins (274) are made from a conductive material;

wherein said plurality of conductive plates (280) electrically couples said plurality of cleaning fins (274) with said negative terminal;

wherein when said cleaning cylinder rotates and said plurality of cleaning fins (274) touch said solar panel surface, said controller (200) electrically couples said positive terminal with a grounded connection (240) and electrically couples said negative terminal with said plurality of cleaning fins (274); and

wherein said plurality of cleaning fins (274) applies a negative voltage to said solar panel surface, thereby reversing said PID while simultaneously cleaning said solar panel surface waterlessly.

3. The solar panel waterless cleaning system with PID recovery as claimed in any one of claims 1 and 2, wherein said plurality of cleaning fins is made from a conductive microfiber.

4. The solar panel waterless cleaning system with PID recovery as claimed in claim 3, wherein said conductive microfiber is infused with a conductive material. 5. The solar panel waterless cleaning system with PID recovery as claimed in claim 4, wherein said conductive material is selected from the list consisting of:

silver;

zinc;

gold;

brass; and

copper.

6. The solar panel waterless cleaning system with PID recovery as claimed in any one of claims 1 and 2, wherein said power supply is a rechargeable battery. 7. The solar panel waterless cleaning system with PID recovery as claimed in any one of claims 1 and 2, wherein said at least one solar row is a fixed angle solar row.

8. The solar panel waterless cleaning system with PID recovery as claimed in any one of claims 1 and 2, wherein said at least one solar row is a solar tracker row having a variable angle.

9. The solar panel waterless cleaning system with PID recovery as claimed in any one of claims 1 and 2, wherein said grounded connection is a ground connection of said at least one solar row.

10. A method for simultaneously cleaning at least one solar row (182) waterlessly and reversing potential induced degradation (PID) on said at least one solar row, utilizing a solar panel waterless cleaning apparatus (202) comprising a cleaning cylinder, a plurality of electrically conductive cleaning fins (274), coupled with said cleaning cylinder, for generating a directional air flow when said cleaning cylinder rotates and a controller (200), coupled with said solar panel waterless cleaning apparatus (202), said method comprising the step of:

coupling, via said controller (200), said plurality of electrically conductive cleaning fins (274) with a negative terminal of a power supply (198) and coupling a positive terminal of said power supply

(198) with a grounded connection (240); and

moving said solar panel waterless cleaning apparatus (202) over said at least one solar row such that said plurality of electrically conductive cleaning fins (274) touches an upper surface of said at least one solar row (182), thereby cleaning said upper surface waterlessly via said directional air flow and simultaneously applying a negative voltage to said upper surface.

1 1. The method for simultaneously cleaning at least one solar row waterlessly and reversing PID as claimed claim 10, wherein said grounded connection (240) is a ground connection of said at least one solar row (182).