CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application serial number 62/299,728 filed February 25, 2016, which is incorporated herein by reference in its entirety. BACKGROUND

[0002] Although the need to have a detailed assessment of mineral dust composition and its mineralogy in atmospheric models has been well covered in the literature, generating, collecting and measuring intrinsic aerosol dust particles deposition on surfaces with respect to their particle sizes, particle size distribution, and origin in a controlled laboratory soiling settings has not been sufficiently assessed. It is also paramount to better understand the inherent dustiness or the tendency to produce dust from different dust sources and its implications on solar modules. Comprehensive understanding of all factors that contribute to photovoltaic (PV) dust accumulation is rather challenging as so many factors contribute to it. These factors are site specific and environment dependent and at times depend on panel characteristics.

[0003] Several different dust aerosols generating devices from mineral sources have been cited in the literature. The operating principle of these devices fall into three general categories based on the method by which the aerosols are generated. One approach entails a fluidization using gas dispersion or ventilation, in which dust is suspended by direct entrainment into airflow in a tube. A second approach uses gravitation and impact method, where a source sample falls as a discrete pellet through the air into a closed chamber from which the dust is evacuated. A third approach uses mechanical dispersion or agitation using rotating drums or cylinders and is entrained into airflow. All these dust generating instruments possess some major drawbacks due to not only the lack of data standardization but also the variability of dust analysis outcome in terms of chemical composition, dust concentration, homogeneity of surface dust coverage, and the dispersion of the aerosols generated in a given sample source for different dust generating approaches.

[0004] As the dust loading in the atmosphere is highly variable especially in dust laden regions in space and time, its actual distribution is difficult to quantify. Thus, there is a need for additional apparatus and systems for the study dust aerosols, materials producing dust aerosols, and the effect of dust on various devices or objects. SUMMARY

[0005] Aspects of the invention described herein are directed to a chamber that can produce agglomerate free homogeneous dispersion of aerosols at higher production rates and concentrations than previously achieved. Described herein are the design and use of an apparatus and system for studying and assessing dust, sources of dust, and the effect of dust on devices and objects. The present disclosure describes the design of a soiling chamber or dust box, and processes of generating monodisperse aerosols from solid sands and/or dust particles inside a closed soiling system. The monodisperse aerosol or dust particles can be produced by supplying pressurized air at a constant flux rate circulating inside a chamber. The sand soil is aerosolized in the chamber enabling it to pass through a conduit (tube). The conduit can be divided into two portions, a distal portion that delivers the aerosolized dust particles to a target, e.g., a dust box, and a proximal portion located in a chamber between the gas source and the top part of the chamber. The chamber can be used to create aerosolized dust from soils of several distinct classes and sediments of different geographical locations (e.g., Kingdom of Saudi Arabia (KSA) or Arizona) under controlled laboratory conditions.

[0006] The chamber described herein can possess or demonstrate one or more of the following advantages: (1) Simplicity of chamber design and operation such that the chamber can be constructed of cost-effective, readily scalable, and interchangeable materials. Furthermore, the chamber can be operated under soiling or deposition conditions (e.g., airflow rate, mass of soil sand, time, etc.) that can be fixed or variable. (2) Uniform surface dust coverage under soiling experiments, such that potential inaccuracies due to physical, chemical heterogeneity and size in dust generating sources are drastically reduced. (3) Homogeneity of aerosol. (4) Low maintenance such that the use of the chamber for long periods of time will not result in chamber nozzle malfunction due to aerosol blockage or the formation of aerosol plumes or puffs across the surface of the entire box. (5) Versatility of use such that the generation of uniform aerosols can be useful in various industrial applications using various source materials for aerosolization and deposition (e.g., painting and coating industry).

[0007] Certain embodiments are directed to a dust aerosol generating apparatus comprising an aerosol generating chamber coupled to a particle introduction cone forming a dust aerosol generating apparatus. The aerosol generating chamber can have (i) a sealed top cover; (ii) a bottom opening in fluid communication with the particle introduction cone; (iii) a sidewall; and (iv) a flow tube. The flow tube enters the chamber sidewall from a first direction forming an inlet and exits the chamber sidewall on the opposite side of the chamber forming an outlet. The portion of the flow tube connected to the chamber has (a) a first inlet portion entering the chamber from a first direction, (b) a chamber portion being positioned between the inlet and the outlet, and (c) an outlet portion exiting the chamber through the sidewall on the opposite side of the chamber relative to the inlet portion. Other embodiments are directed to an venturi apparatus for dust aerosol generation comprising: (a) an aerosol tube having an inlet, an outlet, and at least one particle receiving opening in the wall of the tube, the inlet being connected to a nozzle configured to provide airflow through the aerosol tube producing an acceleration of airflow and decreased pressure in the aerosol tube; and (b) a chamber through which the aerosol tube passes, the chamber having a cone shaped bottom portion with a second inlet in the apex portion of the cone providing airflow into the cone; wherein the airflow through the first and second inlet provides a venturi effect in the aerosol tube for drawing a dust aerosol into the aerosol tube with the dust aerosol exiting the apparatus through the aerosol tube outlet. The inlet portion of the flow tube can comprise a nozzle that is inserted or formed inside the inlet portion of the tube. The nozzle can, but need not taper from the sidewall towards the center of the chamber and is configured so that a pressurized fluid entering the chamber is accelerated through tube. The inlet portion of the flow tube is configured to allow a first fluid stream to move through the aerosol generating chamber. The chamber portion of the flow tube is positioned between the inlet and the outlet. The chamber portion has an opening on two sides of the tube that are positioned within the chamber and are configured to allow the contents of the chamber to enter the tube and mix with fluid moving through the tube. The outlet portion exiting the chamber through the sidewall on the opposite side of the chamber relative to the inlet portion is configured to deliver a dust aerosol formed in the chamber. The particle introduction cone has (i) a top portion that opens into and is in fluid communication with the aerosol generating chamber; and (ii) tapered sidewalls forming a cone that tapers to a second inlet that is configured to allow a second fluid stream to enter the apparatus. In certain aspects the sidewall taper can be about 10, 20, 30, 40 to about 50, 60, 70, 80 degrees. In particular aspects the particle introduction cone has a taper of about 45 degrees. The second fluid stream containing particles to be aerosolized and mixed with the first fluid stream. The dust aerosol generating apparatus can further comprise a first valve connected to the first inlet and a second valve connected to the second inlet. In certain aspects the apparatus can further comprise a target material reservoir coupled to the second inlet and configured to supply target material to be aerosolized. In a further aspect the target material reservoir contains a sand soil. In certain aspects the sand soil has a silicate component of 20 to 95% by weight of the sand soil. The target material reservoir can contain a dust generating material that is representative of a geographic location, for example a Kingdom of Saudi Arabia (KSA), Arizona, or a KSA+Arizona sediment. The dust aerosol generating apparatus can further comprise a carrier fluid source coupled to the first, second, or first and second inlet. The carrier fluid can be a gas or gas mixture. In certain aspects the gas is N ₂ , 0 ₂ , H ₂ , or a mixture thereof. The carrier fluid can be introduced under pressure. In certain aspects the carrier fluid is introduced at a pressure of about 2, 5, 10, 20 bar or more. In certain aspects the carrier fluid is introduced at a pressure of about 2, 3, 4, 5, 6, 7, 8, 9, or 10 bar, including all values and ranges there between.

[0008] The source material can be a sand soil, which comprises sand - a naturally occurring granular material composed of finely divided rock and mineral particles. The source material can be defined by its composition, geographic location, and size - sand being finer than gravel and coarser than silt. Sand soil is a textural class of soil or soil type; i.e. a soil containing more than 85% sand-sized particles (by mass). The composition of source material varies, depending on the local rock sources and conditions. One the most common constituent of sand in inland continental settings and non-tropical coastal settings is silica (silicon dioxide, or Si0 ₂ ), usually in the form of quartz. Another common type of sand is calcium carbonate, for example aragonite, which has mostly been created, over the past half billion years, by various forms of life, like coral and shellfish.

[0009] In terms of particle size, sand particles range in diameter from 0.0625 mm (or 1/16 mm) to 2 mm. An individual particle in this size range is termed a sand grain. Sand grains are between gravel (with particles ranging from 2 mm up to 64 mm) and silt (particles smaller than 0.0625 mm down to 0.004 mm).

[0010] The composition of sand soils is highly variable and depends on the local rock sources and conditions. Sand soils can comprise various amounts of coral and shell fragments, organic or organically derived material, gypsum, feldspar, magnetite, chlorite, glauconite, iron, garnet and/or other resistant minerals. [0011] The article, object, device, or surface targeted for aerosol deposition may be almost any solid material and preferably is composed of materials typically subjected to aerosols or dust. Examples include: wood, brick, stone, metal, glass, cloth, vegetation, skin, hair, fur, plastic, paper etc. The target surface may be porous or non-porous. The target surface may be macroporous or microporous to allow movement of gasses but not aerosol particles and thereby act as a filter.

[0012] Certain embodiments are directed to a soiling system comprising at least one dust aerosol generating apparatus as described herein coupled to a dust chamber by a dust aerosol delivery tube. The dust aerosol delivery tube can be a distal portion of the flow tube, which has a proximal portion as described above. The dust chamber configured to house a test article to be exposed to a dust aerosol generated by the dust generating apparatus and delivered to the dust chamber by the dust aerosol delivery tube. The dust delivery tube can have a plurality of openings with a predetermined size. In certain aspects the dust delivery tube comprises a screen through which the dust aerosol passes before entering the dust chamber. The soling system can further comprise a monitor configured to determine the amount of dust in the chamber or in the dust aerosol delivered from the dust aerosol generating apparatus, or both. The soiling system can also include a sensor configured to monitor properties of the test article. The sensor can be an optical sensor configured to determine the amount of dust retained on a test article, and/or a functional sensor configured to quantitate the functionality of the test article. The soiling system can further comprise an evacuation port configured to evacuate the chamber when desired.

[0013] Further embodiments are directed to methods of assessing an article comprising placing the article in a dust chamber of the system described herein, exposing the article to a dust aerosol for a period of time, and monitoring various parameters and characteristics of the article before, during, and/or after exposure to the dust aerosol. In certain aspects the dust aerosol comprises 0.1 to 10 grams of dust per meter squared (g/m ² ). In a further aspect the dust aerosol is generated from a sand soil. The sand soil can have a silicate component of 20 to 95% by weight of the sand soil. In certain aspects the dust aerosol is representative of a geographic location, for example KSA or Arizona sediment.

[0014] Certain embodiments are directed to coating an article or a target with a non-sand soil source material by using the apparatus, system, and method as described herein. The article or target can be assessed for cleaning, decontamination, weathering, disinfecting, wearing, or abrading in the presence of sand soils or materials other than sand soils. In certain aspects the source material is representative of a contaminant, such as a biological, chemical, or radiological contaminant. A contaminant can include viruses; bacteria; fungi; toxins; spores; agricultural chemical sprays (e.g., pesticides, etc.); air pollutants; irritating, hazardous and caustic agents; radioactive materials; white phosphorous; poisonous liquids; industrial chemicals; and almost anything which forms or can be formed as an aerosol. Furthermore, substances, including those not normally forming or considered to be an aerosol, are included when they are adhered to or bound to carrier particles, which can form an aerosol and/or carry various chemicals or biologicals in order to deliver them to the target surface. The source material only needs to be representative of the contaminant properties and need not actually be the contaminant itself. [0015] In another aspect the source material can be used as a coating, thus producing coated articles or target materials. The source material can be paint, nanoparticles, polymers, disinfectants, or any other material that can be aerosolized and deposited on a surface forming a permanent or temporary coating on the target surface. The coating material can be any suitable material capable of being applied to the article, object, or surface. Suitable materials include, but are not limited to, thermal barrier coating (TBC) materials, bond coating material, environmental barrier coating (EBC) materials, crystallized coating materials, abrasion resistance coating materials, or a combination thereof. The coating material can be applied at a thickness of between about 0.5, 1, 10, 20, 30, 40, 50, 100 mil and about 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, to about 2000 mils, including all values and ranges there between.

[0016] Other embodiments of the invention are discussed throughout this application. Any embodiment discussed with respect to one aspect of the invention applies to other aspects of the invention as well and vice versa. Each embodiment described herein is understood to be embodiments of the invention that are applicable to all aspects of the invention. It is contemplated that any embodiment discussed herein can be implemented with respect to any method or composition of the invention, and vice versa. Furthermore, compositions and kits of the invention can be used to achieve methods of the invention.

[0017] The use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims and/or the specification may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one." [0018] Throughout this application, the term "about" is used to indicate that a value includes the standard deviation of error for the device or method being employed to determine the value.

[0019] The use of the term "or" in the claims is used to mean "and/or" unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and "and/or."

[0020] As used in this specification and claim(s), the words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0021] Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating specific embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

DESCRIPTION OF THE DRAWINGS

[0022] The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of the specification embodiments presented herein.

[0023] FIG. 1. Chamber design and main parts.

[0024] FIG. 2. Soiling device for homogeneous dust deposition experiments used for large amounts of dust.

[0025] FIG. 3. Homogeneity of accumulated amount of dust on glass surfaces in (3) different runs.

[0026] FIG. 4. Reproducibility of accumulated amount of dust on glass surfaces in (8) different runs. [0027] FIG. 5. Illustrates a side view of one embodiment of an exploded dust generating apparatus.

[0028] FIG. 6. Illustrates a perspective view of one embodiment of an exploded dust generating apparatus. [0029] FIG. 7. Illustrates a perspective view of one embodiment of an assembled dust generating apparatus.

[0030] FIG. 8. Illustrates a perspective view of an dust box incorporating a dust generating apparatus.

DESCRIPTION

[0031] Certain embodiments described herein are directed to the design of a simple and efficient dust aerosols generating chamber, and the processes of delivering homogeneous dust deposition to a target article. In certain aspects the target article can be bare conventional glasses or glasses coated with different functional dirt repellent materials, in strictly controlled soiling laboratory environment. Aerosols of different particle sizes and particle size distribution have different effects on solar photovoltaic (PV) modules and hence the use of dusts from different geographical locations, and hence of different chemical compositions.

[0032] The air circulating flow inside the venturi operating component of the chamber as shown in FIG. 1 is established by controlling the air flux inside the chamber using air valves 104 and 105, creating dust turbulences inside the chamber based on the "venturi principle." The nozzle 107 has a smaller diameter than the tube 106. In certain aspects the nozzle to tube diameter ratio is about 0.01, 0.05, 0.1, 0.25, to 0.5, including all values and ranges there between. By virtue of a pressure gradient between the two nozzles, an air flow from the dust circling chamber into the tube 106 is created with high accuracy of air suck. With this type of design an area of lower static air pressure is created with concomitant migration of homogeneous aerosols into tube 106 regardless of dust aerosol source properties.

[0033] FIG. 1 illustrates one embodiment of a dust generating device. The device comprising main body or chamber 101 having an open bottom that is fluidly connected to particle introduction cone 102. The particle introduction cone can have a taper defined by angle 109. Chamber 101 has a top cover 103 opposite the particle introduction cone 102. A first air pressure inlet 105 enters a sidewall of chamber 101. The first pressure inlet is configured to include a nozzle 107. The particle introduction cone has a second air pressure inlet 104. The chamber has a main outlet or dust delivery tube 106 that is configured to deliver a dust generated within the dust generating device.

[0034] FIG. 2 illustrates one embodiment of a soling device or dusting box incorporating a dust generation device described herein. Soiling device of FIG. 2 can be used for homogeneous dust deposition experiments. The soiling device can include dust generating device or turbulence chamber 220 connected to a dust feeder tube 221. In certain aspects the dust feeder tube 221 can be made of conventional polymers. The dust feeder tube 221 fluidly connects turbulence chamber 220 to dust chamber 224: The chamber and other components are constructed to be dust tight with clear and light weight design out of polymeric materials. Sample holder 226 can be located in the chamber and can be designed for manipulating a large number of samples.

[0035] FIG. 5 illustrates an exploded two dimensional side view of an embodiment of a dust generation apparatus. Dust delivery tube or aerosol tube 506 traverses chamber 508 positioning particle receiving opening 510 with in the chamber. Nozzle 507 can be inserted into the inlet portion of aerosol tube 506, the nozzle comprising an inlet 505. Chamber 508 has a top cover 503 and a bottom introduction cone 502. Introduction cone 502 has inlet 504 for introduction of airflow to the introduction cone 502.

[0036] FIG. 6 illustrates a perspective view of the exploded device of FIG. 5. Dust delivery tube or aerosol tube 606 traverses chamber 608 positioning particle receiving opening 610 in the chamber. Nozzle 607 can be inserted into the inlet portion of aerosol tube 606, the nozzle comprising an inlet 605. Chamber 608 has a top cover 603 and a bottom introduction cone 602. Introduction cone 602 has inlet 604 for introduction of airflow to the introduction cone 602. [0037] The components when assembled form a dust aerosol generating chamber, as illustrated in FIG. 7. FIG. 7 shows top cover 703 sealing chamber 708. Chamber 708 having aerosol tube 706 position in and passing through chamber 708. The aerosol tube 706 having nozzle 707 positioned with the inlet of aerosol tube 706 with inlet 705 configured to receive an source of air or gas. Chamber 708 tapers into an introduction cone 702, that has inlet 704 in the apex portion of introduction cone 702. [0038] FIG. 8 illustrates one embodiment of a soiling device or dust box incorporating a dust generating apparatus or device 830. In this particular embodiment the box comprises four walls, a top and a bottom. The dust box can contain one or more adjustable platform 826 for presentation of a test item at varying degrees of incline. One wall can be configure as door 832 to provide access to the interior of the box. Door 832 can be sealed during use of the dust box. A dust box can be configured to receive dust generating apparatus 830 in a variety of positions. In one embodiment the dust generating apparatus can be fluidly connected with the dust box by box inlet 831. Inlet 831 can be position in a box wall towards the top portion of the box wall. In other embodiments dust generating apparatus 830 can be fluidly connected to a delivery tube that spans the width of the box with the delivery tube having openings to deliver the dust aerosol at a variety of positions with in the dust box. In other embodiments inlet 831 can be offset to one top side of a box wall, or positioned at the top middle of a box wall, or any other position in the wall to provide an appropriate dust delivery for particular studies or conditions, as needed. [0039] As one example, soiling tests were run with the following non-limiting soiling box parameters: The air pressure flow was set to 2 bar and the two air valves were fully opened to allow constant air flow inside the chamber for 5 minutes. 10-15 grams of dust was introduced inside the chamber for every experiment. Eight numbered glass substrates (10 x 10 cm ² ) were positioned inside the chamber to collect the amount of dust accumulated onto with respect to amount of solid particles blown in different soiling conditions. It can be concluded from these soiling studies that the chamber can be used to simulate the outdoor soiling of semi-arid weathering conditions and reliable homogeneous and reproducible different aerosols particle sizes in a closed laboratory environment.