NL2022796B1

NL2022796B1 - Solar energy conversion module

Info

Publication number: NL2022796B1
Application number: NL2022796A
Authority: NL
Inventors: Van Dijk Lourens
Original assignee: Soluxa B V
Priority date: 2019-03-22
Filing date: 2019-03-22
Publication date: 2020-09-28

Abstract

A solar energy conversion module, comprising: - at least one solar energy conversion device for converting solar irradiance into electric or thermal energy, the device comprising a collection surface for receiving the solar irradiance; - a transparent cover plate applied onto and covering the collection surface, wherein the cover plate has a top surface facing away from the collection surface, - an overlay applied to the top surface ofthe cover plate, wherein the overlay comprises: a substantially transparent film; and interference pigment flakes, distributed in or overthe film.

Description

Solar energy conversion module

BACKGROUND OF THE INVENTION

1. Field of the invention

[1] The present invention relates to a solar energy conversion module comprising an overlay. The invention also relates to a method for fabricating the same, to a building comprising such solar energy conversion module and to a cover plate comprising such overlay.

2. Description of the related art

[2] Fast implementation of renewable energy is essential to meet the growing energy demand. So far, the development of solar energy modules in general, and photovoltaic (PV) modules in particular, mainly focused on efficiency improvement and cost reduction while the aesthetic appearance was disregarded. Although the cost of solar energy has dropped to a very competitive level over the last decade, current PV modules still do not blend well in roofs and facades. Thus, there is a demand for aesthetic PV modules.

[3] The implementation of building integrated photovoltaics (BIPV) is expected to grow significantly in the years to come. However, the dark appearance of PV modules, or solar panels, is a major limitation for architects as this obstructs colourful integration of PV modules in facades and on terracotta-coloured roofs. In some neighbourhoods, the installation of dark PV modules on historical monuments or buildings may even violate local restrictive covenants requiring a certain appearance. Besides, it may be preferred to have PV modules resembling materials like stone and tiles to seamlessly integrate PV modules.

[4] Coloured and patterned PV modules can resolve the issues of conventional black PV modules. They give more architectural freedom to integrate PV modules on houses, office buildings, factories, and high-rise buildings. Furthermore, coloured solar panels widen the options for aesthetic integration in applications like noise barriers, fences, PV power plants in landscapes, roads, awnings, cars, and trucks. To foster mass-adoption of photovoltaics, it is thus essential that solar panels become available in a wide gamut of colours at an affordable price.

[5] In the prior art, a number of attempts have been made to create coloured PV modules to address the stated issues of black PV modules. However, these methods have various issues which hinder mass production of coloured PV modules.

[6] Currently, a few companies develop coloured PV modules. They apply a coloured layer or print containing absorbing pigments between the active PV layer and the cover plate during the production of the PV module. However, the absorption by these pigments causes a high reduction of the module efficiency. Moreover, this process requires the desired colour to be known during production. As most manufacturers are located in Asia the production and shipping to consumers in Europe or America can take multiple months. This poses a challenge if a specifically coloured PV module is wanted in a short term. Furthermore, available colouration techniques have severe shortcomings: they significantly lower the efficiency of the PV module; they are complex;

expensive; hard to customise; and/or not flexible for market changes. Moreover, they may not be suited for mass production, colouring of the frame, and creating graphics.

[7] In light of the above, it would be desirable to provide solutions which at least partially overcome some of the inconveniences of the prior art.

SUMMARY OF THE INVENTION

[8] According to the invention there is provided a solar energy conversion module, comprising: at least one solar energy conversion device for converting solar irradiance or radiation into electric or thermal energy, the device comprising a collection surface for receiving the solar irradiance; a transparent cover plate applied onto and covering the collection surface, wherein the cover plate has a top surface facing away from the collection surface, an overlay applied to the top surface of the cover plate, wherein the overlay comprises: a substantially transparent film; and interference pigment flakes, distributed in or over the film.

[9] The present invention forms a low-cost solution for mass production of high-efficiency coloured and patterned solar energy conversion modules such as PV modules. The person skilled in the art will understand that advantages related to PV modules correspondingly apply to other solar energy conversion modules such as solar thermal collectors or photovoltaic thermal hybrid solar (PVT) collectors. For the scope of this invention the ‘PV module’ can also be a ‘solar thermal collector’ or a ‘PVT collector’, unless stated otherwise.

[10] The overlay is configured to selectively reflect certain visible wavelength ranges to change the appearance of the solar energy conversion module by forming a visible image, a visible pattern or a uniform colour. Preferably, the image, pattern or colour is applied to the cover plate in front of the active solar energy conversion area of the solar energy conversion device and is not restricted to (only) the edges of the active area. The overlay may be applied as a coating on the cover plate of a PV module. In an embodiment, at least 50% of the interference pigment flakes are positioned in front of the active area of the solar energy conversion device, more preferably at least 75% or at least 90%. Alternatively or in addition, the interference pigment flakes may cover at least 30% of the active area of the solar energy conversion device and at least 80% of the inactive area of the solar energy conversion device. The cover plate may be applied directly onto the solar energy conversion device or on an encapsulant which may be part of the solar energy conversion device. ‘Applied directly’ means that no significant amounts of air or other gases are present in between.

[11] The interference pigment flakes allow for an optimal trade-off between the colour intensity and the module efficiency. Absorbing pigments have a certain colour due to absorption of a significant part of the spectrum. In contrast to absorbing pigments, the absorptance of a layer containing interference pigment flakes may be below 10% of the emitted power of the sun in the relevant part of the electromagnetic spectrum, preferably below 5%, more preferably close to zero. This enables coloured solar energy conversion modules having high efficiency.

[12] Preferably, at least 80% of the pigment flakes cause wavelength selective reflections 40 and transmission based on interference of light such that the amount of absorption in the overlay is minimised, in order to maximise energy conversion efficiency of the solar energy conversion module. A distinctive advantage of pigment flakes based on interference is their extremely low absorption enabling a high energy conversion efficiency as well as colour brightness of the PV module. Interference pigment flakes are available in many colours. The refractive index and layer thickness of the pigment layers determine the intensity of the reflected and transmitted light for each wavelength. Interference of light in pigment flakes is based on constructive and/or destructive thin-film interference. Contrary to absorbing pigments where the result is based on subtractive colour mixing, the result of interference pigment flakes is based on additive colour mixing. If a coating containing interference pigment flakes is applied on a white substrate the resulting colour is generally close to white: most of the light is reflected either by the pigment or by the white background. However, a more saturated colour appears when the same coating is applied on a dark or black substrate as the light being transmitted by the pigment gets absorbed by the black background and the colour is predominantly determined by the spectral selective reflection of the pigment.

[13] The interference pigment flakes may have the shape of a platelet or disk, and are preferably in the range of 1 to 100 um long, more preferably between 5 to 50 um, and about 0.05 to 4 um thick, more preferably between 0.2 to 0.5 pm.

[14] In an embodiment, the overlay comprises a flop control agent to modify the pitch (or #ilt’) characteristics of the interference pigment flakes relative to a nominal plane extending along the overlay, to optimise the angular dependent appearance of the optical radiation reflected by the overlay. Due to their large size with respect to the layer thickness of the coating, the large pigment flakes might align themselves parallel to the plane of the coating. This may result in a strongly angularly-dependent or metallic appearance. This “colour-shift effect” or “colour flop” can be modified by adjusting the orientation of the pigment flakes in the layers. A commercially available “flop control agent” or “flop corrector” may be added to control the pitch of the pigment flakes and increase the variation in the pitch of the flakes with respect to the nominal plane. This additive helps prevent the pigment flakes from aligning themselves parallel to the plane of the coating. Commercially available flop control agents are for example “Glasurit 90-M 1 Effect-additiv’ and “R-M Onyx HD HB 090 Pitch Control”.

[15] In an alternative embodiment, only relatively small pigment flakes are used having a particle size distribution of 0.5 to 25 um, to enhance the appearance at low viewing angles with respect to the plane of the PV module.

[16] The interference pigment flakes, or pearlescent pigment flakes, are generally composed of thin layers having a mutually different index of refraction. Interference pigment flakes may be composed of one or more of the following components: a high refractive oxide such as rutile titanium dioxide (TiO2), anatase TiO2, chemically grown TiO2, white TiO2, AI203, SiO2, ZrO2, BaSO4, CaCO3, Sb203, CaSO4, Pb304, MgO, MgCO3, iron oxide (such as FeO, FeO2, Fe304, Fe203), Sn02, ZnS, ZnO, mica, white lead and talc. For example, a pigment flake may consist of a natural or synthetic mica layer encapsulated by a TiO2 layer, having a layer thickness of around 40 40 to 800 nm, preferably between 40 and 200 nm. The reflection of certain wavelengths in the visible spectrum due to thin-film interference in the pigment flakes results in a certain colour as determined by the layer thickness, the composition of the pigment and some other factors. Some interference pigment flakes contain absorbing components, e.g. iron oxide, to absorb a part of the spectrum to achieve a specific colour. Overlays without such absorbing components generally result in a higher transmittance and thus better performance of the PV module. Preferably, the overlay is non-absorbing and/or free of absorbing components, although absorbing components may be present to achieve a desired appearance. Interference pigment flakes are relatively lightfast due to the inorganic composition. For additional protection, the pigment flakes may be encapsulated, e.g. by a layer of Chromium, for additional protection against ultraviolet (UV) light and other environmental factors.

[17] In certain embodiments, the overlay on the PV module has a matte or high gloss appearance. Due to the nature of some pigment flakes the overlay may have a high gloss and look metallic. The desired amount of sheen (or gloss units) can be realised by adding components to the overlay such that a matte, eggshell, satin, silk, semi-gloss or high gloss appearance is obtained. For example, a light-dispersing additive can be used in a most outer layer of the overlay to obtain the desired degree of gloss. A low degree of gloss can contribute to an enhanced colour appearance at low viewing angles.

[18] For the scope of this invention the PV module may comprise one or a plurality of PV cells. The cells may be based on any type of PV technology, such as monocrystalline silicon (mono ¢-Si); polycrystalline silicon (poly c-Si); dye-sensitised; hybrid organic-inorganic lead or tin halide-based perovskite; II-V materials such as indium gallium nitride and Indium gallium arsenide (InGaAs); II-VI materials such as cadmium telluride (CdTe); copper indium diselenide (CIS); and copper indium gallium selenide (CIGS). PV modules are commercially available from e.g. SunPower, Panasonic, Hanwha Q CELLS, LG Solar, First Solar and Hanergy. For photovoltaic applications, the pigment flakes preferably transmit wavelengths for which the solar cells are photovoltaically sensitive (e.g. around 300 to 1200 nm for c-Si cells), and preferably predominantly reflect a fraction of visible wavelengths that contribute to the desired colour perception. The pigment flakes can be present, for example, at a level in the range of about

0.01% to about 35% by weight of the overlay composition after curing.

[19] Interference pigment flakes of different colour can be mixed to yield the desired colour. Alternatively, layers with different types of pigment flakes can be stacked. The overlay may contain absorbing pigments such as nacreous pigments, metal flake pigments, organic pigments, composite oxide system pigments, metal complex system pigments and the like to achieve a desired appearance.

[20] In a preferred embodiment, the overlay has a layer thickness in the range from about

0.5 to 200 um, preferably between 10 and 70 um, to provide sufficient hiding power and opacity. In some embodiments, the overlay consists of one single coating to enhance the processing speed. A special adhesive may be added to improve the polar bonding to the silicon-oxygen bonds of the glass surface.

[21] In some embodiments, the interference pigment flakes may be also present in the cover plate. The interference pigment flakes may be applied on the glass cover plate after which it is fused to the glass by a calcining (or “firing”) process at a temperature of around 600 to 1400 °C. This is preferably done before the production of the PV module. Alternatively, the interference 5 pigment flakes can be applied on the glass during the production of the glass cover plate. In case of a polymer-based cover plate, the pigment flakes can be mixed through a resin before the polymerization reaction.

[22] In the prior art, the coloured layer is usually applied inside PV modules, which has the advantage that the cover plate provides good protection to the coloured layer. Therefore, manufacturers of PV modules do not prefer to apply a potentially fragile coloured layer at the front side of the glass cover plate. Moreover, it is usually complicated to apply a coloured film on top of the PV module as coatings generally do not adhere well to the fairly inert glass and often delaminate due to the impact of environmental factors. Furthermore, the anti-reflective coating on the front side of the glass cover plate may have a negative impact on the optical transmittance towards the solar cells.

[23] However, in the present invention the overlay is applied to the outside of the cover plate, facing away from the solar energy conversion device. This position of the overlay offers several advantages. For example, the overlay can be simultaneously applied to non-photovoltaic building components like tiles and filler panels which may be present around the PV module (on a roof or facade) such that a uniform appearance can be realised. The PV modules can also be patterned and/or coloured to resemble the non-photovoltaic roofing elements.

[24] The overlay is universal: it can be applied on top of every type of solar energy conversion device. Thereby, this add-on feature enables to operate more independently: the colour application is separated from the production of the PV module. This makes it possible to quickly adapt to market changes and to select PV modules that are most suited in terms of quality and price. As the preferred overlay can be applied at a site close to the client there is no long shipping time.

[25] The overlay has excellent adhesion and durability. Moreover, the overlay adheres well to glass cover plates having an anti-reflection coating. The hydrophobic properties of the overlay result in excellent anti-soiling and easy removal of graffiti. It is thus not required to apply another layer or other component to cover the overlay. Finally, the sheen and colour of the overlay are tuneable and the overlay helps to obscure the internal features of the PV module from view.

[26] It will be understood by a person skilled in the art that the solar energy conversion module may comprise a single solar energy conversion device or multiple solar energy conversion devices, for instance positioned in an array.

[27] In some embodiments, the overlay is patterned by altering the density and/or types of pigment over the area, for example in a uniform, non-uniform, random or a preselected arrangement. The overlay may comprise a monochromic or polychromic image. For example, it may show an image, logo, photo or pattern and it may contain a texture, symbols, letters, 40 geometric shapes (like stripes, circles, rectangles), or any combination thereof. The image may be designed so that the PV module has an appearance that is in harmony with its environment. For example, to optimize the integration of a PV module within a facade, roof, or landscape the module may have the appearance of coloured tiles, bricks, slates, shingles, marble, wood, metal, trees and/or grass.

[28] In some embodiments, the interference pigment flakes are applied in a raster image such that the image, pattern or colour is formed by small dots (in the range of 3.01 to 10 mm in size) which are spaced 0.01 to 15 mm apart. The size and position of the dots can be optimised to realise higher transmittance than a closed layer and thus higher solar energy conversion performance. For example, the area coverage of the coloured dots may be higher on top of inactive areas of the PV module, such as the electrical contact points and the area between the cells. Also, structures in the PV device (e.g. metallic busbars, electrical contacts, and cells) can be fully or partially concealed using patterns and/or raster images. For this purpose, the position of the dots (or any other geometry) of the coloured overlay may be in substantial registration with the structural features of the solar cells and the PV module.

[29] In certain embodiments, the pigment flakes are provided in one or more sublayers of the overlay. Each layer of the overlay may be applied as a coating, lacquer, or varnish on the surface of the cover plate. In a preferred embodiment, various coating (or paint) formulations are consecutively applied on top of the cover plate of the PV module.

[30] In an embodiment, the interference pigment flakes have a content of between 0.01% and 35% based on the total weight of the overlay, and the overlay further comprises a binder with a content of between 5% and 99.9% based on the total weight of the overlay after curing.

[31] The binder {or film-forming component) is preferably substantially transparent and is, for example, epoxy, alkyd, {poly)urethane, acrylic resin, vinyl acetate/ethylene, polyesters, melamine resins, polysilazane, silanes, siloxanes, or any combination of the like. In case of a two- component resin, a hardener is added. Optionally, the formulation can have OH-functionalities and a reactive polyurethane or melamine crosslinker. Specific thinners and binders may be added to improve the processability of the coating and to improve the durability of the coating. The overlay may comprise a primer applied to the cover plate to improve the adhesion of the overlay to the cover plate. The primer may contain components like acetic acid, ethyl ester, or modified silane that chemically alter the glass surface, increase the surface energy and/or make the surface more receptive to adhesive bonding. The top coating may contain additional components like butyl acetate, xylene, ethyl 3-ethoxypropionate and/or 2-methoxy-1-methylethyl acetate. The coating formulation may contain one or more components for faster curing of the coating. The final strength of the coating is reached in hours to days after application depending on the formulation and drying conditions. In some embodiments, the coating is hydrophobic, which is beneficial against soiling and graffiti.

[32] In certain embodiments, a fraction of the pigment flakes may be optimised to reflect infrared wavelengths for which the solar cells are not photovoltaically sensitive. This may help to lower the module temperature which has a positive effect on the efficiency of the PV module.

[33] Examples of interference pigment flakes include those available from Fujian Kuncai Material Technology Co. Ltd (Kuncai), People's Republic of China and pigments from Merck KGaA, Darmstadt, Germany. Merck provides various types of interference pigment flakes including the Iriodin®, ColourStream®, Meoxal® and Xirallic® series. Some types of interference pigment flakes such as ChromaFlair and “Chameleon” pigments of Kuncai show a strongly angular dependent colour, which may be desired for some applications. Alternatively, mixtures containing interference pigment flakes may be obtained from e.g. Valspar Corporation and PPG Industries.

[34] In some embodiments, the solar energy conversion device is a photovoltaic cell array or a dark absorber plate, or the solar energy conversion module is a photovoltaic thermal hybrid solar collector. In this case, the overlay is applied on the front side of the cover plate, or collector glazing, of a solar thermal collector or a photovoltaic thermal hybrid solar collector (PVT). A solar thermal collector consists of an enclosure containing a dark absorber plate with fluid circulation passageways, and a transparent cover to allow transmission of solar energy into the enclosure. A solar thermal collector may be a flat plate collector or an evacuated tube collector. In case of an evacuated tube collector the cover plate actually has the form of a tube. A PVT collector converts solar radiation into both electric and usable thermal energy. A PVT collector comprises one or more solar cells to convert sunlight to electricity and fluid circulation passageways to collect the generated heat in the solar cells which may be transferred to a heat exchanger.

[35] In some embodiments, the solar energy conversion device further comprises a secondary cover plate placed in front of the cover plate, wherein the overlay is applied to an outer or inner surface of the secondary cover plate, wherein the secondary cover plate is substantially transparent, wherein said secondary cover plate has a geometric structure to enhance the transmittance towards the solar energy conversion device and/or the visual appearance. Said secondary cover plate may be positioned on top of the first cover plate and there may be an air gap between both. The geometric structure of said secondary cover plate may resemble a wave, a louver, a corrugated sheet, or 3D sinusoidal surface to enhance the optical performance and visual appearance.

[36] In an embodiment, a total power transmitted through the overlay is 60% to 99.5% of a total incident power of sunlight. The total incident power of sunlight refers to the relevant part of the solar spectrum, for a c-Si PV module this is the range between 300-1200 nm.

[37] In an embodiment, the solar energy conversion device is a bifacial solar energy conversion device, preferably a bifacial photovoltaic module, and wherein the overlay is applied to a front side and/or a backside outer transparent surface of the solar energy conversion device.

Bifacial modules with an overlay at both sides are particularly advantageous for use in garden fences, or noise barriers along highways.

[38] In an embodiment, the solar energy conversion module comprises a frame surrounding the solar energy conversion device, and wherein the overlay is applied on the cover plate and on the frame, preferably wherein the frame is made of metal. This will further improve the visual 40 appearance of the module.

[39] In an embodiment, the overlay comprises openings of 1 to 30 mm through which the incident light is fully transmitted. The opening can be spaced 1 to 30 mm apart. The openings may be formed directly after the paint application, e.g. when the surface tension of the glass and the paint do not match. The openings have the advantage that more light reaches the solar energy conversion device.

[40] In an embodiment, the film is made of material which adheres to the cover plate, or the film may be an adhesive foil.

[41] In an embodiment, the interference pigment flakes are encapsulated with a UV absorbing layer, for enhanced environmental protection.

[42] In an embodiment, a substantially transparent top coating is applied as a top layer of the overlay for scratch and colour protection; preferably wherein the top coating comprises light dispersing additives to obtain a matte appearance, and/or wherein the top coating comprises polysilizanes for anti-soiling and/or anti-reflection properties.

[43] In an embodiment, the interference pigment flakes cover at least 30% of the active area of the solar energy conversion device and at least 80% of the inactive area of the solar energy conversion device.

[44] In an embodiment, the interference pigment reflects at least 30% of infrared light for which the solar energy conversion device is not photovoltaically responsive such to reduce the temperature of the solar energy conversion module and improve its efficiency. If the device is a c-Si PV cell, only the infrared range above 1200 nm is meant, since such cell is photovoltaically responsive until 1200 nm.

[45] According to an aspect of the invention, and in accordance with the effects and advantages described hereinabove, there is provided a building comprising an outside surface, such as a facade or a roof, wherein the outside surface comprises at least one solar energy conversion module as described hereinabove.

[46] The dimensions of a facade or roof often do not allow the area to be completely filled by an integer number of PV modules. Generally, PV modules cannot be cut into pieces. Therefore, tiles, filler or dummy panels from other materials (such as ceramic, polymer, and metal) are used for the uncovered edge area. These non-active panels and mounting components, like clamps, can be coloured using the described coating process for the modules. To achieve a uniform roof or facade appearance, the mounting component preferably has a dark appearance before applying the overlay. The modules can also be applied to vehicles, fences or other constructions.

[47] In an embodiment, the outside surface of the building further comprises at least one filler panel or mounting component, such as a rail or a clamp, located adjacent to the solar energy conversion module, wherein the filler panel or mounting component comprises an overlay corresponding to the overlay of the solar energy conversion module.

[48] According to an aspect of the invention, and in accordance with the effects and advantages described hereinabove, there is provided a coloured cover plate for use in solar energy conversion modules as described hereinabove, comprising a cover plate made of glass or a polymer-based transparent material; and interference pigment flakes dispersed close to the surface of the cover plate or through the entire volume of the cover plate.

[49] According to an aspect of the invention, and in accordance with the effects and advantages described hereinabove, there is provided a method for fabricating a solar energy conversion module, comprising: providing a solar energy conversion device; providing a cover plate which is configured to cover the solar energy conversion device; applying an overlay to the cover plate, wherein the overlay comprises a substantially transparent film and interference pigment flakes dispersed in or over the film; mounting the cover plate in front of the solar energy conversion device, either before or after applying the overlay to the cover plate, such that the overlay faces away from the solar energy conversion device.

[50] The overlay may be applied onto the cover plate by various methods including using a paint application tool, a brush, an aerosol paint can, by printing, and/or using a mask. More specifically, using a paint application tool refers to spray painting, powder coating, stencilling, dip coating, slot coating, spin coating, supersonic atomization; printing refers to inkjet printing, screen printing, tampon printing, roller printing, digital image printing, laser printing, or gravure printing. Also, any other suitable painting, printing or coating process may be conceived by a person skilled in the art. The desired image may be realised by lithography or by masking parts of the area that are not intended to be coated. Alternatively, the coating application device can move over a specific path such that a patterned overlay is realised. Some patterns, such as stone or marble, may be realised using a special calligraphic nozzle and an adapted paint composition.

[51] In an embodiment, the solar energy conversion module comprises a frame surrounding the solar energy conversion device, and wherein applying the overlay comprises: applying the overlay to the cover plate and to the frame in a single production step.

[52] The method may further comprise modifying a top surface of the cover plate using abrasive chemical or mechanical methods, such as sanding, abrasive blasting or acidic treatments, to enhance the surface adhesion and/or to create a textured interface.

[53] In some embodiments, the interference pigment flakes may be embedded in a paint in an aerosol paint (or paint can). This may facilitate the application of the paint in situations where other options are undesired. The invention also extends to paint cans comprising interference pigment flakes specifically made to provide an overlay to PV modules. The paint can comprises a propellant and a lacquer containing interference pigment flakes as described hereinabove.

[54] According to an aspect of the invention, and in accordance with the effects and advantages described hereinabove, there is provided a method of retrofitting a solar energy conversion module, comprising: providing a solar energy conversion module including a solar energy conversion device and a cover plate covering or configured to cover the solar energy conversion device; applying an overlay to the cover plate, wherein the overlay comprises a substantially transparent film and interference pigment flakes dispersed or distributed in or over the film.

[55] In the retrofitting method, the coloured overlay is applied on top of the cover plate of an 40 already manufactured PV module without an expensive module production line. The method may thus be applied at a different location as the module production, e.g. after shipping to an installer or distributor. Both the glass cover plate and the frame of the PV module may be coloured in one process while other colouring methods would require multiple processes. Moreover, the overlay can also be applied on fitting panels, mounting components, and other solar energy conversion modules. Furthermore, PV modules and solar thermal collectors, which are often placed next to each other on roofs, can be coloured in the same low-cost and flexible process.

[56] In some embodiments, the surface of the cover plate can be pre-treated to improve the adhesion and wetting of the coating. Moreover, the cover plate generally has an anti- reflective (AR) and/or anti-soiling coating which can have a negative impact on the coating application as well as the optical properties. For enhanced adhesion, the AR coating can be removed by abrasive methods such as sanding, chemically etching, and/or flame arc cleaning. The anodised aluminium frame of a PV module can be sanded for improved adhesion.

BRIEF DESCRIPTION OF THE DRAWINGS

[57] The features and advantages of the invention will be further appreciated upon reference to the following schematic drawings of a number of exemplary embodiments, in which corresponding reference symbols indicate corresponding parts.

[58] FIG. 1 shows an exemplary front view of a 80 cells PV module according to an embodiment.

[59] FIG. 2 is a schematic representation of a PV module with an overlay.

[60] FIG. 3 is a schematic illustration of a part of the edge of a PV module having a metal frame. There is an overlay on both the PV assembly and the frame.

[61] FIG. 4 is a graph of the power output of a yellow coloured PV module and a black reference PV module.

[62] FIG. 5 shows an example of the transmittance and reflectance of a red coloured PV module.

[63] FIG. 6 shows an example of the relative performance of various coloured PV module.

[64] FIG. 7 is a schematic illustration of a front view of a facade of a building according to an embodiment.

[65] The figures are for illustrative purposes only, and do not serve as a restriction on the scope or the protection as laid down by the claims.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[66] FIG. 1 schematically shows an exemplary front view of a 60-cells PV module 100. The outer edge of the PV module 100 is a metallic frame 102, which may be omitted in some module configurations. The back sheet 104 may be white, black or transparent. The visible busbars 108 are used to electrically interconnect the solar cells 106. A person skilled in the art will understand that other components, such as a junction box and wiring, may be present for connection of the module 100 to the grid.

[67] In this example, the PV module 100 consists of an array of 60 (interconnected) c-Si solar cells 106. The size and number of the cells 106 and dimensions of the PV module 100 can be different than illustrated.

[68] FIG. 2A is a schematic representation of a PV module 218 including an overlay 220. The coloured PV module 218 comprises consecutively: - a transparent or a non-transparent substrate 202 such as glass or a foil made from e.g. ethylene-vinyl acetate (EVA), polyolefin, a Tedlar® composite or polyethylene terephthalate (PET); - a photovoltaic device 206 comprising a plurality of photovoltaic cells of any type of PV technology, bushars, reflectors and the like encapsulated between the top encapsulation sheet 208 and the cover plate 210, including a bottom encapsulant layer 204, made from e.g. ethylene- vinyl acetate (EVA), polyolefin or polyethylene terephthalate (PET), and a transparent top encapsulant layer 208; and - a substantially transparent cover plate 210, such as textured, toughed glass, low-iron glass, solar roll glass, polycarbonate, polymethylmethacrylate, of a thickness sufficient to protect the PV module 218, which may have an anti-reflective layer or coating (not shown) on the top side. The photovoltaic device 206 defines a collection surface 207 for receiving the solar radiation on which the cover plate 210 is applied. The photovoltaic device 206 as shown may be replaced by a dark absorber plate with fluid circulation passageways to form a solar thermal device instead of a PV device.

[69] The overlay 220 is applied on top of the cover plate 210 and comprises in this embodiment one or more of the following layers: - a primer layer 212, which adheres well to the material of the cover plate 210; - a colour coating 214 composed of one or multi-component coating containing a colourant, e.g. interference pigment flakes, to cause wavelength selective reflections of the incident light; and - a top coating 216 for environmental protection. The top coating 216 and primer 212 are not required.

[70] In some embodiments, the overlay 220 is applied to a bifacial PV module 222. A bifacial PV module has two light-incident surfaces and can collect light from both sides. FIG. 2B shows such bifacial module having two overlays 224, in which the same components as Fig. 2A are referred to by the same reference numerals as in Fig. 2A. For a bifacial module the substrate 202 is transparent. The overlay 220 may be applied on the cover plate 210 and at the transparent substrate 202 at the backside of the PV module 224. In the shown embodiment the overlays 220 applied to the cover plate 210 and the substrate 202 are identical, but this is not necessarily the case. Such coloured bifacial panels are suited for applications such as landscape integration and fences. Bifacial PV modules may be obtained from e.g. Trina and DMEGC.

[71] Both in FIG. 2A and in FIG. 2B, the primer layer 212 is applied on the front side of the cover plate to obtain good adhesion to the surface of the cover plate 210. The formulation of the primer may be optimised for adhesion to the anti-reflection coating present on the glass of the PV 40 module. The glass is preferably properly cleaned and degreased before applying the primer 212.

[72] The colour coating 214 is designed for reflecting certain wavelengths. Colourants, such as pigment flakes, in this colour coating 214 can be used to generate the desired visual properties like colour, patterns, and effects. The colour coating 214 may be applied in multiple layers. The first layer can have a first colouration, and the second layer can have a second colouration different from the first colouration.

[73] The top coating 216 is applied to seal the overlay 220 and to give additional protection against environmental factors and scratches. The top coating 216 may also provide additional colour protection by absorbing or reflecting certain wavelengths such as ultraviolet light. Layer 216 is preferably substantially transparent and may contain colourants.

[74] FIG. 3 is a schematic illustration of the edge of a PV module 300 where both the glass cover plate 302 of the PV module 300 and the frame 304 are coloured by an overlay with a pigmented coating 306. The frame 304 is generally made of black anodised aluminium. The overlay 306 can be applied both on the cover plate of the PV module 302 and the frame 304 in a single production step. In some embodiments, the PV module 300 does not have a frame.

[75] FIG. 4 is a graph of the power output (in arbitrary units) of a yellow coloured PV module 402 and a black reference module 404, on a sunny day in Nijmegen, The Netherlands. The efficiency of a coloured solar panel depends among others on the type of pigment (which determines the colour) and the pigment surface coverage (e.g. in gram/m?). In this example, a relatively high amount of pigment was applied resulting in a bright yellow to a golden appearance of the PV module.

[76] FIG. 5 shows an example of the transmittance 502 and reflectance 504 of a red coloured overlay at normal incidence containing interference pigment flakes. In this particular measurement the module included an air gap between the cell and the cover plate which caused some parasitic light trapping lowering the measured transmittance. The majority of the light is transmitted towards the solar cell, not only in the infrared (wavelength longer than 700 nm), but also in the visible range (typically 380 to 700 nm). The overall low absorption of less than a few percents will be appreciated by someone skilled in the art as this gives optimal efficiency of the PV module. In the wavelength range of 510 to 810 nm up to 40% of the light is reflected resulting in a red colour. Overall, the absorption by the overlay is rather low. The optical absorption losses by the coating are thus kept to a minimum: most of the sunlight is either being transmitted to the solar cells or reflected. The intensity of the reflected light, or brightness, can be enhanced by applying more pigment flakes on a given surface area.

[77] FIG. 6 shows an example of the relative performance of a blue, green, yellow, orange, and red PV module measured over a period of one month in outdoor conditions in Nijmegen, The Netherlands. The relative performance is given by the generated electrical energy of each coloured PV module divided by the generated electrical energy of a black reference PV module. The relative performance of the coloured PV modules is around 85 to 99% with respect to a black reference PV module. The performance of coloured PV modules depends on the irradiance conditions, the type of pigment and the colour intensity.

[78] FIG. 7 is a schematic illustration of a front view of a facade of a building 700. An array of PV modules 702 is mounted on the facade 700. Filler panels 704 are mounted next to the PV modules 702 at the edges of the facade 700. The PV modules 702 may be mounted using visible clamps 706 (shown in only a part of the facade). The PV modules 702, filler panels 704 and clamps 706 may have the same overlay such that all elements have the same appearance.

Naturally, filler panels 704 can be applied on the roof of a building in a similar fashion next to PV modules 702.

[79] The invention has been described by reference to certain embodiments discussed above. It will be recognised that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art.

[80] Many modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.

Claims

PE076941EN 14 CONCLUSIONS

A solar energy conversion module, comprising: - at least one solar energy conversion device for converting solar radiation to electrical or thermal energy, the device comprising a collecting surface for receiving the solar radiation, - a transparent cover plate which is disposed on the collection surface and covering the collection surface, the cover plate having a top surface facing away from the collection surface, a cover applied to the top surface of the cover plate, the cover comprising: e a substantially transparent film; and + interference pigment flakes, distributed in or over the film.

The solar energy conversion module according to claim 1, further comprising a frame around the solar energy conversion device, and wherein the cover is disposed on the cover plate and on the frame, preferably wherein the frame is made of metal.

The solar energy conversion module according to any one of the preceding claims, wherein the solar energy conversion device is a two-sided solar energy conversion device, preferably a two-sided photovoltaic module, and the cover is disposed on a transparent outer surface on a solar panel. front and / or a rear of the solar energy conversion module.

The solar power conversion module according to any of the preceding claims, wherein a total transmitted power through the cover is 60% to 99.5% of the total incoming sunlight power.

The solar energy conversion module according to any of the preceding claims, - wherein the solar energy conversion device is a grid of photovoltaic cells for converting solar energy to electrical energy; or - wherein the solar energy conversion device is a dark absorbent sheet for converting solar energy into usable thermal energy; or - wherein the solar energy conversion device is a photovoltaic hybrid solar collector for converting solar energy to both electrical and thermal energy.

The solar energy conversion module according to any of the preceding claims, wherein the interference pigment flakes have a content size between 0.01% and 35%, based on the total weight of the coating, and the coating further comprises a binder with a content size between 5 % and 99.9%

based on the total weight of the cover.

The solar power conversion module according to any one of the preceding claims, wherein the cover comprises openings 1 to 30 mm spaced 1 to 30 mm apart, through which the light is fully transmitted.

The solar power conversion module according to any of the preceding claims, wherein the film is made of a material that adheres to the cover plate, or the film of the cover is a self-adhesive film.

The solar energy conversion module according to any of the preceding claims, wherein the interference pigment flakes are coated with a UV absorbing layer.

The solar power conversion module according to any of the preceding claims, wherein the cover comprises a flop control means for adjusting the angular or slope characteristic of the interference pigment flakes with respect to a nominal plane extending along the cover, to optimize the angular appearance of the optical radiation reflected from the cover.

The solar energy conversion module according to any of the preceding claims, wherein a substantially transparent cover layer is applied as a top layer of the cover for scratch and color protection; preferably wherein the cover layer comprises light-diffusing additives to obtain a matte appearance, and / or wherein the cover layer comprises polysilizanes for anti-fouling and / or anti-reflection properties.

The solar energy conversion module of any preceding claim, wherein the interference pigment flakes cover at least 30% of the active area of the solar energy conversion device and at least 80% of the inactive portion of the solar energy conversion device. .

The solar energy conversion module according to any of the preceding claims, wherein the cover reflects at least 30% of the infrared light.

The solar power conversion module according to any one of the preceding claims, wherein the cover comprises an image, pattern or color formed by dots ranging from 0.01 to 10mm in size spaced 0.01 to 15mm apart.

15. The solar power conversion module according to any of the preceding claims, further comprising a secondary cover plate disposed in front of the cover plate, the cover being disposed on an outer or inner surface of the secondary cover plate,

e wherein the secondary cover plate is substantially transparent, + wherein the secondary cover plate has a geometric structure to improve the optical transmission to the solar energy conversion device and / or the visual appearance.

A building comprising an exterior surface, such as a facade or a roof, wherein the exterior surface comprises at least one solar energy conversion module according to any preceding claim.

A building according to claim 16, wherein the outer surface further comprises at least one fitting panel or mounting element, such as a rail or a clip, located adjacent to the solar power conversion module, the fitting panel or mounting element comprising a cover corresponding to the cover of the solar energy conversion module.

A colored cover plate for use in solar energy conversion modules according to any one of the preceding claims, comprising: - a cover plate made of glass or a polymer-based transparent material; and - interference pigment flakes scattered near the surface of the cover plate or throughout the volume of the cover plate.

19. A method of retrofitting a solar energy conversion module, comprising: - providing a solar energy conversion module including a solar energy conversion device and a cover plate covering the solar energy conversion device; - applying a cover to the cover plate, the cover comprising a substantially transparent film and interference pigment flakes dispersed in or on the film.

A method of manufacturing a solar energy conversion module, comprising: - providing a solar energy conversion device; - providing a cover plate configured to cover the solar energy conversion device; - applying a cover to the cover plate, the cover comprising a substantially transparent film and interference pigment flakes dispersed in or on the film; - attaching the cover plate for the solar energy conversion device, prior to or after applying the cover to the cover plate, so that the cover faces away from the solar energy conversion device.

40

The method of claim 19 or 20, wherein the coating is applied with a paint application tool, a brush, an aerosol spray can, a printer, and / or with a mask.

The method according to any of claims 19-21, wherein the solar energy conversion device comprises a frame around the solar energy conversion device, and wherein applying the cover comprises: - applying the cover to the cover plate and on the frame in a single production step.

The method according to any one of claims 19-22, further comprising: - modifying a surface of the cover plate by means of chemical etching or mechanical methods such as abrasion, shot blasting or acid treatments, to improve the surface adhesion and / or to obtain a structured surface.