Aerogel coating

Abstract

The invention relates to an anti-reflection aerogel coating on glass that provides water harvesting and self-cleaning properties in solar panel applications.

Description

[0001] AEROGEL COATING

[0002] Technical Field

[0003] The invention relates to an anti -refl ection aerogel coating on glass that provides water harvesting and self-cleaning properties in solar panel applications.

[0004] State of the Art

[0005] Agrophotovoltaics(AgriPV) systems are a set of applications that enable electricity production from solar energy and agricultural activities together on the same land. These systems offer a suitable area for agriculture under the solar panels.

[0006] One of the most common methods to decrease reflection on solar panels is texturing the silicon surface. Anti-reflection coatings used in solar panels also play a critical role in increasing panel efficiency. These coatings minimize the reflection of light that the solar cell can use from the panel glass, allowing more light to reach the solar cells, thus producing more energy. However, the accumulation of particles that cause dust and dirt to accumulate on the panel surface over time also reduces the transmission of light reaching the surface to the solar cell, reducing the efficiency of the solar panels. This requires regular cleaning of the panels, which leads to water and time consumption.

[0007] The use of anti-reflection coating has become widespread in the current system in order to eliminate the mentioned disadvantages and to minimize reflection. These materials, which are coated on the glass in solar panels, should have a low refractive index. For this, porous materials are recommended. Aerogels are suitable materials for this. The air environment trapped in the porous structure of the aerogels ensures that the aerogel has a refractive index value close to the refractive index of air. In addition to this type of anti -refl ection coatings, multi-layer, gradient refractive index, or textured surface coatings are also included in the literature [1], In addition to these coatings, texturing the solar panel glass also leads to reduced reflection. An example is the final application of prism patterned glass produced by a company. In case of coating on the front glass surface, the refractive index of the coating material should be lower than that of the glass and at the same time it should be resistant to external factors such as wind, rain, and hail. In addition, hydrophilic or hydrophobichydrophobic coatings are offered to remove dust and dirt from the solar panel surfaces. Hydrophobic coatings shift dirt and dust from the surface when in contact with water due to low sliding angles and high contact angles. Both physical and chemical modification are required for such high contact angles in coatings. Low contact angles of hydrophilic coatings allow water to spread completely on the surface and take dust particles with water as it flows [2],

[0008] Hygroscopic salt-based materials, hydrophilic / hydrophobic patterned coatings, metalorganic frames (MOFs), polymeric gels are materials used for water harvesting [3], The materials to be used in panel glasses must be optically permeable at the glass level.

[0009] In the current system, there are patent / utility model applications and articles related to the subject. US7393515B2 relates to obtaining hydrophilic patterns using ultraviolet light after coating the fluorinated compounds in the form of a hydrophobic thin film on glass or another substrate. When the hydrophobic thin film is exposed to ultraviolet light, a hydrophobic / hydrophilic pattern is obtained by forming hydrophilic parts by decomposing the fluorinated compound in the irradiated parts. However, there is no mention of water collection, self-cleaning or anti -refl ection properties.

[0010] US8298622B2 relates to low diffraction index silica aerogel, anti -refl ection coating that repels water. Aerogel obtained by the sol-gel method can be coated with methods such as spray coating, spin coating, dip coating, flow coating, and bar coating. Organic modifiers were used to obtain hydrophobic organic groups.

[0011] WO1999057185A1 discloses a polymeric matrix containing hydrophilic and hydrophobic surface regions. The polymer used is a hydrophobic material with a low inorganic oxide concentration. The polymer surface is removed from some regions by a high-energy process. In these regions, hydrophilic high-concentration silica particles are formed. Thus, a hydrophilic / hydrophobic pattern is obtained. This material can be used in areas requiring light transmission.

[0012] W02003046062A1 aims to create hydrophilic regions with high energy activation methods (plasma activation, electron beam discharge, corona discharge, ultraviolet radiation). The mask with the desired pattern makes it hydrophilic by exposing only certain regions, while the remaining regions remain hydrophobic. In the article titled "Desert beetle-inspired superwettable patterned surfaces for water harvesting" aerogel was used for water collection. In this study, certain regions were exposed to platinum using a stainless-steel mask. These areas became hydrophilic, while other regions continued to be hydrophobic aerogels. However, in this study, two different materials with different contact angles were used to obtain a hydrophilic / hydrophobic pattern.

[0013] As can be seen from the current system and the above-mentioned patent applications, various methods and materials are used to obtain hydrophobic and hydrophilic patterns. Hydrophobic / hydrophilic patterns can be created by using fluorinated compounds, but these methods do not mention water collection, self-cleaning or anti -refl ection properties. Anti-reflection coatings are made by using aerogels and organic groups with low diffraction index, and in some studies, hydrophilic and repellent regions are created in polymer structures with high energy processes. While patterns are created with high- energy activation methods, in some applications, aerogels are used for water collection and hydrophilic / hydrophobic patterns are obtained with materials with different contact angles.

[0014] As a result, due to the negativities described above and the inadequacy of the current solutions on the subject, there is a need for the anti -refl ection coating to increase the performance of the solar panels.

[0015] Brief Description and Objects of the Invention

[0016] The invention relates to an anti-reflection aerogel coating on glass that meets all the above- mentioned requirements and provides water harvesting and self-cleaning properties in solar panel applications that eliminate negativities and disadvantages in the existing system.

[0017] With the invention, a coating that can collect water from humid air, self-cleaning, and has anti -reflection properties in the visible, near-infrared, and ultraviolet regions has been developed to meet the water needs of the plants in the region. The object of this coating is to increase the electrical energy efficiency produced by using solar energy while at the same time reducing the water consumption required for the agricultural region. Thus, a sustainable agricultural activity is ensured by optimizing not only energy production but also water use.

[0018] Said invention provides a more functional coating than the existing methods by combining reflection reduction, surface cleaning and water harvesting. The developed multifunctional coating offers a wide range of performance compared to the single function anti-reflection or hydrophobic coatings in the literature. [4,5]

[0019] An anti-reflection coating has been developed with the invention in order to increase the performance of the solar panels. In order to make the solar panels more sustainable, these coatings are ensured to be self-cleaning. The need for irrigation of plants in AgriPV systems made it necessary to focus on coatings that can harvest water. An ultrasonic homogenizer (sonicator), an ultrasonic spray coating device and a rotational coating device are used for the synthesis and coating of the coating material. Scanning electron microscopy, spectroscopic ellipsometry, ultraviolet-visible region spectroscopy, contact angle meter (goniometer), surface profilometer, Fourier-transform Infrared Spectroscopy (FTIR) and optical microscopy were used for characterization.

[0020] Descriptions of the Figures

[0021] Figure 1 : a) A view of immediately before the water drop falls, b) A view of immediately after the water drop falls.

[0022] Figure 2: A view of the surface profile that allows the aerogel to be superhydrophobic.

[0023] Figure 3: A view of the porous structure of the aerogel.

[0024] Figure 4: A view of the method of applying hydrophobic and hydrophilic patterned aerogel.

[0025] Detailed Description of the Invention

[0026] The invention relates to an anti -reflection aerogel coating on glass that provides water harvesting and self-cleaning properties in solar panel applications. Aerogel coating increases the performance of solar panels. This coating combines the properties of antireflection in the visible and ultraviolet region, self-cleaning effect and water harvesting by accumulating moisture. In this way, solar panels that are highly efficient and can harvest water can be developed. Water harvesting in the solar panel refers to the collection of condensation or rainwater formed on the surface of the solar panels and the use of this water for various purposes.

[0027] Said coating material contains 9.22% by weight of methyltrimethoxysilane, 85.58% by weight of methanol, 0.0006% by weight of oxalic acid and 2.2% by weight of ammonium hydroxide. Alternatively, it may comprise 3% by weight of tetraethyl orthosilicate or 16.99% by weight of hexamethyldisilazane. The aerogel material for the coating mentioned in the invention was synthesized by the solgel method. Methyltrimethoxysilane (MTMS) and tetraethyl orthosilicate (TEOS) were used as silica precursors, and methanol was used as a solvent. The solution obtained becomes a gel under atmospheric pressure and is called aerogel. After the aerogel was diluted with methanol, it was coated on the glass substrate using an ultrasonic spray device. References in the literature on turning aerogel into a solution ready for coating have been used.

[0028] The process steps for the production of the aerogel are as follows. a. Preparation of a mixture of methyltrimethoxy silane and tetraethyl orthosilicate,

[0029] First, a mixture of methyltrimethoxysilane (MTMS) (0.66% by volume in the solution just before coating) and tetraethyl orthosilicate (TEOS) (0.22% by volume in the solution just before coating) is prepared in a beaker. Methyltrimethoxysilane contributes to the hydrophobic property of aerogel. Tetraethyl orthosilicate provides the silica-based skeleton of the structure. b. Adding methanol to the mixture,

[0030] Methanol acts as a solvent and regulates the hydrolysis reaction. The volume ratio of methanol in the solution just before coating is 6.14%. c. Accelerating the hydrolysis process by adding acid catalyst to the mixture,

[0031] The hydrolysis process is started by adding an acid catalyst to the mixture. At this stage, a few drops of hydrochloric acid, oxalic acid or acetic acid are usually used. The volume ratio of the acid catalyst in the solution just before coating is 0.44%. d. Allowing the mixture to hydrolyze at room temperature for 24 hours after mixing, The mixture is mixed slowly and then left to react. At this stage, silica structures are formed as a result of the reaction of metal alkoxides with water. The mixture is mixed for 30 minutes at this stage. e. Accelerating the gelation process by adding base catalyst to the mixture,

[0032] Ammonium hydroxide is used as the base catalyst. The ratio of the base catalyst is 0.54% by volume in the solution just before coating. f. Mixing the mixture,

[0033] The mixture is mixed for 15 minutes at this stage. g. Gelation of the mixture, h. Adding methanol to the mixture, i. Adding hexamethyldisilazane to the mixture. During the gelation stage of the mixture, some of the methanol evaporates and the remaining materials become a solid gel. As mentioned in the process step h, methanol is added to the mixture (72% by volume in the solution just before coating) and reconstituted. Hexamethyldisilazane (20% by volume in the solution just before coating), which increases the hydrophobicity of the mixture, is also added to this solution.

[0034] Hexamethyldisilazane affects the porous structure of the aerogel and makes the surface hydrophobic in contact with water. This process helps the aerogel to gain hydrophobic properties and then ensures that the structure remains stable during the drying phase. Hexamethyldisilazane provides a hydrophobic coating on the surface even after the aerogel has dried and prevents the reaction of the aerogel with water.

[0035] Thanks to the high porosity structure of the aerogel produced by the sol-gel method, it provides the intended anti-reflection effects. The sol-gel method offers easy, fast, and cost- effective production. The aerogel in the invention is one of the aerogels that is dried at atmospheric pressure without requiring supercritical CO2 extraction. Thus, it is among the methods with a low cost compared to CO2 extraction. Thin film is quickly obtained on the glass surface by aerogel spray coating method. It is cost-effective, fast, and scalable compared to the methods including spin coating and vacuum required methods.

[0036] Hydrophobic coatings obtained by hexamethyldisilazane (HMDS) modification have contact angles up to -160 degrees and a high stability that lasts for months in the indoor area. The modified hydrophobic surface aims to clean the dirt by sliding the rainwater drops falling on it.

[0037] This coating has also been developed to reduce the reflected light on the surface, allowing more light to be transmitted to the solar cells. The porous structure of the aerogel reduces the reflection of the incident rays coming from the air to the glass by ensuring that it has a low refractive index.

[0038] For the self-cleaning feature of solar panels, the coating is made hydrophobic. Hexamethyldisilazane (HMDS) is used to increase the hydrophobic property of the film. This material is added to the solution which is diluted with methanol before the spray coating step. However, both physical and chemical modifications are required to achieve high contact angles. It has been observed that the surface profile created by optimizing the spray parameters contributes to such high contact angles and the cleaning of the dust and dirt on the surface. Hydrophilic areas on the surface absorb moisture and water from the air, while hydrophobic areas remove moisture and water, and slide water drops on the coating surface.

[0039] For the water collection feature, hydrophilic / hydrophobic patterns are created on the surface by using a UV-ozone device and a mask that can block ultraviolet light. At this stage, lithography or inkjet printer is not needed. The hydrophobic coating becomes hydrophilic when exposed to UV-ozone. Using a UV-ozone-impermeable polycrystalline silicon mask, only certain regions are exposed. The mask used creates a surface where certain regions of the coating have hydrophilic and hydrophobic properties. In this way, hydrophilic regions attract water from the air and direct the water they collect by sliding on the pattern created to the targeted regions. In addition, cost and time are reduced by obtaining two different surface features, which are hydrophobic and hydrophilic, with a single film type. It is not necessary to make two different types of films or to recoat them with different wettability values. The surface covered with a single film type is patterned in a single step. Aerogel coating, which maintains its hydrophobic feature even after the hydrophilic pattern is obtained on the surface, continues its self-cleaning and water-sliding properties.

[0040] The mask is made of polycrystalline silicon. Patterns were cut out using infrared lasers.

[0041] This coating ensured that the panel is cleaned by the flow of water drops formed as a result of the water collection of the panel with moisture as well as the flow of rainwater droplets and thus generates more electricity. Anti-reflection, self-cleaning and waterharvestingfeatures are integrated to provide a more effective and sustainable use in solar energy systems.

[0042] Thanks to the thin aerogel film coating used in the invention, the panels have higher light transmission (-95%) and lower reflection values (-5%) than bare glass panels in the visible and ultraviolet region.

[0043] The panels mentioned in the invention have a self-cleaning feature and aim to reduce the amount of water consumption. The surface, which can slide rainwater thanks to its hydrophobic feature, cleans the dust and dirt on it.

[0044] In the invention, aerogel coatings are made to harvest water without compromising their anti -reflection feature.

[0045] References [1] Chattopadhyay, S., Huang, Y. F., Jen, Y. J., Ganguly, A., Chen, K. H., & Chen, L. C. (2010). Anti-reflecting and photonic nanostructures. Materials Science and Engineering: R: Reports, 69(1-3), 1-35. https: / / doi.Org / 10.1016 / j.mser.2010.04.001

[0046] [2] Mozumder, M. S., Mourad, A.-H. I., Pervez, H., & Surkatti, R. (2019). Recent developments in multifunctional coatings for solar panel applications: A Review. Solar

[0047] Energy Materials and Solar Cells, 189, 75-102. https: / / doi.Org / 10.1016 / j.solmat.2018.09.015

[0048] [3] Lu, H., Shi, W., Guo, Y., Guan, W., Lei, C., & Yu, G. (2022). Materials engineering for Atmospheric Water Harvesting: Progress and perspectives. Advanced Materials, 34(12). https: / / doi.org / 10.1002 / adma.202110079

[0049] [4] Zhang, Q., Wang, J., Wu, G., Shen, J., & Buddhudu, S. (2001). Interference coating by hydrophobic aerogel-like SiO2 thin films. Materials Chemistry and Physics, 72(1), 56-59. https: / / doi.org / 10.1016 / s0254-0584(01)00322-4

[0050] [5] Budunoglu, H. (2012). Organically Modified Silica Based Nanomaterials for Functional Surfaces.

Claims

CLAIMS1. An anti -refl ection coating material on the solar panel, characterized in comprising;• 9.22% by weight of methyltrimethoxysilane,• 85.58% by weight of methanol,• 0.0006% by weight of oxalic acid,• 2.2% by weight of ammonium hydroxide.

2. A coating material according to claim 1, characterized in comprising 3% by weight of tetraethyl orthosilicate.

3. A coating material according to claim 1, characterized in comprising 16.99% by weight of hexamethyldisilazane.

4. A coating material according claim 2 or 3, wherein said coating material is in aerogel form.

5. A production method of the coating material according to claim 4, characterized in comprising; a. Preparation of a mixture of methyltrimethoxy silane and tetraethyl orthosilicate, b. Adding methanol to the mixture, c. Accelerating the hydrolysis process by adding acid catalyst to the mixture, d. Allowing the mixture to hydrolyze at room temperature for 24 hours after mixing, e. Accelerating the gelation process by adding base catalyst to the mixture, f. Mixing the mixture, g. Gelation of the mixture, h. Making a solution by adding methanol to the mixture i. Adding hexamethyldisilazane to the mixture.

6. A production method of the coating material according to claim 5, wherein said acid catalyst is hydrochloric acid, oxalic acid, or acetic acid.

7. A production method of the coating material according to claim 5, wherein said base catalyst is ammonium hydroxide.

8. A production method of the coating material according to claim 5, wherein said the mixture is mixed for 30 minutes in the process step d).

9. A production method of the coating material according to claim 5, wherein said the mixture is mixed for 15 minutes in the process step f).

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