WO2014174162A1

WO2014174162A1 - Method and device for optimizing the visibility of an image positioned in front of a solar collector

Info

Publication number: WO2014174162A1
Application number: PCT/FR2014/000087
Authority: WO
Inventors: Joël GILBERT
Original assignee: Sunpartner Technologies
Priority date: 2013-04-22
Filing date: 2014-04-21
Publication date: 2014-10-30
Also published as: FR3004846A1; FR3004846B1

Abstract

The invention relates to a device comprising a solar panel (1) and an image-supporting sheet (2) positioned in front of the active surface of the solar panel (1) and intended to be provided with an image (4) comprising a multitude of image zones each having its own specific visual characteristics, the image-supporting sheet (2) being provided with an array of completely or partially transparent zones in order to increase the amount of light able to reach the solar panel. The holes and the transparent zones allow the luminosity that reaches the solar panel to be increased. In order to compensate for the visual degradation of the image that results therefrom, the invention provides for the configuration of said array of holes (3) and/or said array of transparent zones to vary depending on local visual characteristics of the corresponding image zones and depending on the colour of the solar panel, so as to optimize the visual qualities of the image (4) on the device and, in the case of a photovoltaic panel, also to optimize the production of electricity by the device.

Description

METHOD AND DEVICE FOR OPTIMIZING THE VISIBILITY OF A POSITIONED IMAGE BEFORE A SOLAR SENSOR

The present invention relates to an image rendered partially transparent and positioned in front of a solar panel to visually integrate said solar panel into its environment so as to make it less visible, while minimizing the possible losses of energy production by said panel due to the absorption of solar radiation by said image. STATE OF THE ART

Most solar thermal or photovoltaic collectors are dark or even black in order to capture as much sunlight as possible. However, in order to make these sensors more aesthetic and also to allow their better visual integration in our environment, these sensors have an interest in taking appearances of colors or varied images. Techniques already exist that make it possible either to partially render transparent or invisible a photovoltaic solar collector so that it allows some of the light that it receives to pass, or to place an image in front of the solar collector, which requires to make this image partially transparent so that the solar collector receives a part of the solar radiation and produces electricity or heat.

Thus, the patent WO200785721 relates to an optical system which makes it possible to visualize an image on the surface of a solar panel without this image preventing direct solar rays. It consists of a solar panel, a lenticular surface formed of rectilinear lenses and a transparent film on which is printed an image which has been completely erased rectilinear strips parallel to the longitudinal axis of the lenses, so as to leave transparent bands. At certain viewing angles an observer will only see the image bands while at other angles of incidence the sun's rays will pass through the transparent bands and will reach the active surface of the solar collector. Also known from patent FR2955649, a perforated cover of micro holes which covers a solar thermal panel. On this cover is printed an image similar to that of its environment in order to hide said panel. An observer then sees an image more or less degraded, and the panel receives a part of the incident radiation, through the micro holes. It is obvious that with this arrangement, the larger the holes are and the higher the energy production by this device, but then we will see the dark solar panel through the holes. Conversely, if the holes are smaller, the visual performance of the device to hide the solar panel will be higher, but its energy output will be proportionally lower.

These known techniques are therefore either inefficient insofar as the visual result and / or the transparency of the image are mediocre, or difficult to implement especially when it comes to accurately aligning micro lenses and lenses. mini image bands. In addition, they greatly reduce the energy performance of the solar collectors when they are covered with a perforated image of micro holes. This deleterious effect is particularly noticeable when the solar collectors consist of photovoltaic cells electrically coupled in series mode. In fact, in the latter case, when one of the cells constituting the series is less enlightened than the others, it constitutes a weak link which forces the other cells to function with its own characteristics of tension and intensity, which decreases the production performance of the entire solar panel. PURPOSE OF THE INVENTION

The main purpose of the invention is to overcome the limitations of known techniques and to propose a method and a device capable of simultaneously optimizing the visual quality and energy performance of solar panels which are covered by a semi-transparent image.

The invention also aims to minimize the harmful optical effect holes or areas of transparency made in the image or in its support. The invention also aims, in particular for solar photovoltaic panels whose cells are electrically coupled in series mode, to standardize the amount of light that passes through each zone of the image, so as not to penalize the electrical production of the various cells connected in series.

In a particular embodiment, the invention also aims to add a device for illuminating the image to allow night vision, which is not possible with known devices. PRINCIPLE OF THE INVENTION

In its basic principle, the invention consists in modifying the visual or transparency characteristics of an image intended to be printed on a rigid plate, or on a flexible film or other support intended to be placed in front of a solar panel, so that the visual or transparency characteristics resulting from these modifications have the least possible impact, both on the visual quality of the modified image once integrated into the device, and on the energy performance of said solar panel.

It is observed that the increase in the transparency of the image makes it possible in principle to increase the energy production of the solar collector, but is in principle to the detriment of its visibility of the image when it is placed in front of the image. Solar collector typically dark in color.

The invention provides means for optimizing the transparency and visual characteristics of the image to achieve these contradictory goals.

The solar collector may be a thermal or photovoltaic or mixed sensor, flat or curved, rigid or flexible. Hereinafter the solar collector may also be called "solar panel".

The support of the printed image may be indifferently a rigid plate opaque or transparent, or an opaque or transparent flexible film, it will be used in the following the term "plate" or "support", without limiting the scope of the invention. This plate is preferably of the same dimensions as the surface of the solar collector and is placed on the sensor or in front of it.

Said plate, which serves as an image carrier, can be made of various materials, such as for example paper, cardboard, an organic synthetic material such as PVC, polycarbonate or PM A or a mineral material such as glass. The plate can be self-adhesive, for example on the face that is in contact with the solar collector.

In its basic version, the device according to the invention comprises a solar panel and a plate on which an image is printed, said printed plate being positioned in front of the active surface of the solar panel and comprising a multitude of totally opaque or partly transparent image areas. or totally transparent to sunlight, with the characteristic that those image areas that are less transparent must be visually modified, before printing, preferably in their brightness, contrast and color, so as to compensate for the visual distortion they undergo because of their proximity to those image areas that are more transparent than they are.

Indeed, when the image has areas of transparency, the color of the solar panel behind it interferes with the color of said transparency area or with that of the colored areas that are nearby when the image is viewed from far enough.

Often the solar panel is a photovoltaic panel whose cells are dark blue or black, or a solar thermal panel whose surface is a very dark blue color that corresponds to the color of the titanium layer covering the sensor, the titanium allowing indeed better absorption of the spectrum of solar radiation.

The device according to the invention comprises multiple variants, only some of which will be described in more detail, without limitation.

A - According to a first version of the device according to the invention, an image is printed on a support constituted by an opaque plate, and zones of total transparency are arranged on said plate. These areas of transparency total, in this first version, are holes whose transparency is total.

These holes can be of any shape, including geometric shapes such as circles, squares, rectangles or hexagons. The overall surface of the holes relative to the total surface of the plate which is opaque defines the overall transparency of said plate. Indeed, the holes let all the sunlight that will activate the solar sensor, while the constituent material of the plate is completely opaque to sunlight. Said plate is printed on its face which is opposite to the solar collector so that an observer will visualize a color and / or an image on the surface of said plate.

For the observer, the holes are by nature completely transparent and thus take the apparent color of the surface of the solar collector which is positioned behind the plate. The observer will thus see as a result a mixture between the colors of the image printed on the plate and the apparent colors of the holes.

Preferably, the holes will be small enough so that the observer placed at a usual viewing distance from the solar collector does not individually distinguish said holes.

When the solar panel is a photovoltaic solar panel comprising cells electrically coupled in series, it is necessary that the light intensity received by each of the cells is substantially the same in order to obtain the best energy conversion performance of the panel. To obtain this equitable distribution of the solar light intensity on the cells of said photovoltaic panel, the holes of the plate are preferably chosen to have all the same geometry, the same size, and so that their positions form a regular distribution network. . We can also say, by geometric complementarity, that all the opaque zones also form an organization of ordered network type.

In order to make the printed plate as transparent as possible, i.e. with a maximum hole area, but with the least loss of brightness for the image, the invention provides that the original image is edited before being printed on the opaque plate. This modification consists of varying at least one of its fundamental visual characteristics among the following: brightness, highlight, contrast, white balance and color, hues, halftones, color saturation, percentage of gamma.

This modification of the original image is intended to compensate for the loss of brightness of the image that appears when said image is placed in partial transparency and positioned in front of a dark surface, as is generally the case with solar collectors. .

The modification of the image is first done in a computer manner on the original digital code of the image. This modification can be done using an image processing software that runs on a computer equipped with a display screen. For this purpose, the original image and the original image being modified are both displayed on a screen so that the observer can compare them visually. Under the original image being modified there is virtually the surface of the solar collector which therefore has the same visual appearance as the actual surface of the solar collector which will be used in reality. The appearance of the image being processed is then modified by this superposition which also makes it possible to make a comparison with the original image. One or more parameters of certain zones of the image being processed are then varied such as, for example, the transparency, the brightness, the contrast and / or the saturation of the colors in order to determine the most appropriate modifications for the said modified image. looks more like the original image although partially transparent and positioned in front of a dark surface. This comparison can be done visually by an operator who is at the controls of the computer, or by software and / or optical equipment that allows comparative measurements of the visual of the two images.

Ultimately, this method improves the visual rendering of an image intended to be placed in front of a dark surface such as a solar panel, when this image is partly transparent. The transparency of the image being carried out either by a network of micro-holes made in the opaque support of the image, or by areas of transparency of the image printed on a transparent support. This process is characterized by a computer processing of the original image which consists in particular in increasing the brightness of certain zones or pixels of the image before integration into the device, so that the final visual rendering is as close as possible to the rendering of the original image when the latter is observed alone without being placed in front of a dark solar panel.

This method also comprises another step subsequent to the aforementioned computer processing, which consists of a step of printing the modified image on the opaque plate and possibly the digital storage of the characteristics of the image that has been modified.

This process may also include computer and electronic automation of changes that will need to be made to all other images that will need to be placed in front of the solar sensor. Indeed, this conversion protocol may in some cases be the same for all the images to be processed or contain adjustment parameters that will be manually entered, for example to adapt to the color characteristics of the solar sensor, or automated for example for to adapt to the optical characteristics of the ambient light.

The solar panels covered with partly transparent and modified images will be able to take place in all display devices such as pages of newspapers or books, advertising billboards, car bodies, aircraft, trains and other transport vehicles, street furniture, walls, roof tiles and roofs, and generally on the surface of any object that has a solar collector.

B - In another slightly different embodiment, when the plate is transparent, it does not need to have holes, but the image then comprises zones of total transparency, which are the functional equivalent of the holes of the plaque.

These areas of transparency, total or partial, are not arranged in a regular manner on the surface of the plate as in the previous embodiment, but are practiced in priority on areas of the original image whose color is close to the color of the surface of the solar collector, so the superimposing said transparency areas and the color of the solar collector gives a visual rendition that is closest to the initial color of the original image area, thanks to the similar color of the solar collector behind said image areas.

This priority is expressed, for example, by a number of transparency zones and / or a size of said zones which will be larger on the image areas which have a color close to that of the sensor, and a smaller number of zones of transparency on the images. image areas whose color is different from that of the solar panel.

Thus the transparency surface of the image that is due to the holes is no longer homogeneous, but will be larger on the image areas whose color is close to that of the surface of the solar panel.

As a result of these measurements, for a surface of the image having a given transparency, the resulting colors of the image placed in front of the solar panel will be less altered than if the holes or zones of transparency had been arranged in a regular manner. on the surface of the image.

For example, if the plate is opaque and the areas of transparency of the image are full transparency, as in the case of holes made in the plate, an advantageous way to proceed will be to make the surface of the holes greater than 50% the surface of the plate, which will equate to said plate to a transparency greater than 50%. This embodiment is particularly suitable for very contrasting images such as black and white images. In this example, all the image areas that are black will be able to receive a maximum of holes to obtain a maximum of transparency in these places without this characteristic degrading in this place the visual quality of the image, since behind the holes one sees the solar collector dark color.

To obtain the desired overall transparency, for example 50%, if it is not achieved by the positioning of the holes opposite the image areas whose color is close to that of the solar sensor, then a complement of holes or zones of transparency will be positioned on the rest of the image, always with this preference of positioning holes in the image areas whose color is closer to that of the solar collector. This preference or priority may be the result of a logic that is implemented by a computer program that takes into account the color of the solar panel, so the apparent color of the holes, and the color of each image area. The comparison of these two colors then determines the size of the holes and their surface densities so that the visual result obtained is closest to that of the original image zone before treatment.

C - In a slightly different variant embodiment, the plate is transparent and spaces of transparency, equivalent to holes in the plate, are practiced in the image and not in the plate itself. That is to say, a hole becomes at this point an absence of impression of the image, and no longer a localized absence of material from the plate, as before. This variant has the advantage of not requiring special equipment to make holes in an opaque plate. The distribution of the transparency areas of the image may be regular, or irregular as explained above.

D - In another embodiment, the solar panel is a photovoltaic panel comprising cells electrically coupled in series. This electrical configuration requires that the light intensity received by each of the cells is substantially the same in order to obtain the best energy conversion performance of the panel. On a transparent plate is printed a color image in which each color is partly transparent to sunlight. The term "sunlight" is defined here by the entire solar spectrum, including invisible radiation such as infrared and ultra-violet. It can be seen that the transparency of the printed colors depends on several parameters, including the nature of the ink or paint used, its thickness, any support sub-layers such as white, and the presence of metallic particles. In order to make the transparency of each of the colors substantially identical, a first method will consist in modifying the constitution and / or the thickness of the inks or paint that will be used to print the image so that each of the colors has the same transparency to sunlight.

A second method will consist in making the less transparent image areas (C1, C2) more transparent by practicing inside said zones. image areas of total transparency, or holes, so that the light that passes through all the image areas is distributed in a substantially uniform manner over the entire surface of the solar panel.

For this, each color is allocated a predefined amount of total transparency areas, so that all colors have the same overall transparency.

For example, if we want an overall transparency of the image of 60% and the black color has a transparency of 0% and the white color a transparency of 30%, to standardize the transparency of these two colors it will suffice for the black to create 60% more transparency thanks to an appropriate density of micro holes of total transparency, and for the white to create 30% additional transparency in the same way, and we obtain a transparency of 60% for the black areas and for the white areas, so an overall transparency of 60%.

It will be noticed that creating additional transparency spaces will create an alteration of the quality of the image because the color of the solar panel behind the image will be seen through these spaces of transparency. photovoltaic solar panels being generally dark and that the color transparency is lower as the color of the inks is dark, there will be less areas of total transparency in an image area than the color of the ink will be clear, so a slight alteration of this light color because of the dark color of the panel that will be seen through.

The procedure for printing the image that will use the two aforementioned methods of equalizing the transparencies of the different colors, will follow a logical protocol that will begin by measuring and storing the transparency of each of the colors of the image according to the spectral receptivity of the solar cells used. Then for a desired overall transparency, we will calculate the percentage of total transparency surface to be created for each of the colors of the image. Finally, depending on the size of the transparency spaces, we will deduce the density of these transparency spaces for each of the colors. From a practical point of view, these total transparency spaces correspond to the moment of printing to areas of "no" printing on the transparent plate. The base image will be digitally transformed before printing and following the logic protocol described above.

E - In another particular embodiment of the invention, the transparency of a solar lenticular image is improved. The image support plate is then transparent and structured on its front face (the one exposed to the sun), by a network of lenses.

Image areas and areas of total transparency are positioned on the rear face of the plate so that an observer will see only the image areas and the sunlight will completely pass through the areas of total transparency and partly the image areas. A solar lenticular image therefore consists of an image positioned in front of a solar panel, said image being for example cut into strips and embedded in a rectilinear lens array. Part of the sunlight is diverted by the lenses between the image bands to reach the solar panel behind, while the observer will see the reconstructed image bands in a full image through the lenses.

In this device, the image bands are opaque to light whereas in certain positions of the sun they receive a large amount of direct solar radiation and they would have advantage to be partially transparent in order to increase the amount of global light received by the sensor solar. The particular embodiment of the invention which is described here thus proposes to apply to these image bands of the lenticular image, the image processing characteristics of the previous embodiments.

In the previous embodiments, the space between the plate and the solar panel may be an air film or consist of a transparent material whose refractive index is preferably equal to or greater than that of the plate.

F - Other variants of improving the transparency of an image are still possible which are combinations of the embodiments described in the preceding paragraphs. G - In another embodiment of the invention that requires the image to be backlit, the plate on which the image is printed according to one of the embodiments C, D, E, F above is transparent, and is used as a light guide to produce the backlight of said image.

The problem to be solved in the context of a backlit solar panel is that on the one hand known backlighting devices which use lamps to backlight the image are placed in the path of light and are not totally transparent to sunlight, which decreases the performance of the solar panel, and that on the other hand the known backlighting generally illuminate the entire image so also the spaces of total transparency present in the image, which creates a great loss of light through these areas and a glare that masks the image to the observer.

To overcome these two disadvantages, a variant of the invention provides that the plate is transparent and is used as a light guide. The light is emitted by lamps placed laterally to the plate so that light enters the thickness of said plate. The light then propagates inside the plate by successive reflections on its two flat faces. The light comes out of the plate only if it encounters a non-planar surface or a surface whose refractive index is close to that of the plate. Under these conditions the light will not emerge from the plate where the holes (or zones of total transparency) are positioned since at this point the surface of the plate has remained flat. On the other hand, the places that have been printed contain a substance, that of the ink, whose refractive index and / or roughness causes the exit of the light at this point and thus the backlighting of the image.

On the other hand, since the lamps, which are non-transparent, are placed outside the path of solar rays entering the solar panel, the performance of the panel is not diminished. Finally, if the backlight has a substantially uniform brightness over the entire surface of the plate it will be compatible with the devices D, E, F described above, the transparency of the image itself is substantially uniform. In this backlit embodiment, the space between the plate and the solar panel does not comprise an air gap, but is constituted by a transparent material whose refractive index is preferably lower than that of the plate.

In all the variants described above, the image can be either directly printed on the plate, or printed beforehand on a transparent sheet then glued or otherwise fixed on the plate. In all cases also, the printed plate can simply be positioned in front of the solar panel or be glued to its surface or replace the protective glass of the solar panel. In the latter case this plate will have three functions: that of protection of the solar panel, that of light guide for the backlighting and that of print medium for the image.

Finally, the subject of the invention is a device comprising a dark-colored solar panel and an image-support plate positioned in front of the active surface of the solar panel and intended to be provided with an image comprising a multitude of image zones having each has its own local visual characteristics, the image support plate being provided with a set of holes and / or the image being provided with a set of zones of total or partial transparency to increase the amount of light susceptible to to reach the solar panel, characterized in that the local density (that is to say at the right of a given image area) in plate holes or in zones of transparency of the image is variable, and is adapted in according to the local visual characteristics of the image (4) and / or according to the color of the solar panel, so as to optimize the visual qualities of the image (4) on the device and the energy production of the device. tif. Unlike the uniform distributions of holes as described in the known devices, locally varying the number of holes in the plate or the number of zones of transparency in function of the local characteristics of the image makes it possible to obtain a thinner and more efficient compromise both on the perceived visual quality of the image, and on the solar energy captured and transformed by the solar collector. In this way, one can choose the configuration of the network of holes or zones of transparency to obtain a substantially uniform illumination over the entire active surface of the solar panel, and / or to minimize the visual impact of the holes or zones of transparency in front of the dark solar collector. In the absence of these measures, it would degrade the appearance of the image after its transfer to the device.

The device according to the invention is not limited by the nature of the solar panel, it may be is a photovoltaic solar panel, thermal or mixed, flat or curved, rigid or flexible.

The zones of total or partial transparency of the image or the holes of the plate preferably have the form of circles or hexagons, but other forms are possible.

Preferably, the zones of total transparency of the image and / or the holes of the image support plate are sufficiently small for an observer placed at a usual viewing distance from the solar panel not to distinguish individually said zones of total transparency and / or said holes.

According to a first variant of the device, the plate is made of an opaque material, the solar collector is of a dark color, and the said set of holes has relatively more holes compared with the darker areas of the image and fewer holes with regard to the images. brighter areas of the image, so as to reveal the dark solar panel mainly in the dark areas of the image, which has the advantage of increasing the output of the solar panel without distorting the visual perception of the image . According to an advantageous sub-variant of this first variant, said solar panel is a photovoltaic panel composed of electrically connected cells in series mode, and said set of holes is then configured in the form of a regular network capable of conferring on the plate a degree of transparency substantially uniform over the entire surface of the plate In this way, the brightness received by each of said photovoltaic cells located behind the plate is substantially identical from one cell to another. According to another variant of the device, said plate is made of a transparent material and the image then comprises a set of zones of total or partial transparency to increase the amount of light likely to reach the solar panel. According to the invention, said set of transparency zones is then configured according to the visual characteristics of the corresponding image zones and according to the color of the solar panel, so as to optimize the visual qualities of the image on the device. Said areas of total or partial transparency of the image are obtained in particular by digital image processing before printing it on the image support plate. Ideally, the density in areas of total transparency of a given part of the image is modified according to the initial transparency of this part of the image and / or according to its color cast, it being understood that the parts of the image initially dark images are less transparent than the clear parts and allow a density in zones of total transparency higher than the initially clear parts. More specifically, the invention provides that areas of total or partial transparency of the image are arranged primarily on areas of the image whose original color is close to the color of the surface of the solar panel, so that superimposing said transparency areas of the image and the color of the solar panel gives a visual rendering close to the color of the original image area.

For example, rather than making more transparent areas in a dark yellow area, we take a lighter yellow, because more transparent. Once put in front of the dark solar panel, it will appear darker again. So to increase the transparency, either we make holes in dark areas, or we take a lighter color on a dark area because in front of the dark panel the image resumes its darker color.

In a sub-variant of the transparent plate embodiments, the plate is structured on its front face by a lens array, and image areas and zones of total transparency are positioned on the rear face of the plate, so that an observer will only see the image areas and the sunlight will completely traverse the areas of total transparency and in part the image areas. In the previous variants, the space between the plate and the solar panel is constituted by a transparent material whose refractive index is preferably equal to or greater than that of the plate, so as to avoid parasitic reflections and losses of light.

In another sub-variant of the transparent plate embodiments, the plate is traversed in its thickness by a light emitted in its periphery and that this light guided in the thickness of the plate only comes out of the plate through the partly transparent image areas, and not through completely transparent areas, so as to enhance the visibility of the image. In this case, the space between the plate and the solar panel is constituted by a transparent material whose refractive index is preferably lower than that of the plate, so that the plate acts as a light guide.

The subject of the invention is also a method for producing a device as described above, in which a solar panel, a plate and an image intended to be attached or printed on said plate are supplied, said plate being either opaque and pierced with a multitude of holes for passing ambient light, being transparent to ambient light, said image comprising image zones that are more or less transparent to ambient light, characterized in that it comprises a step for treating the ambient light, image prior to its integration into said device, to form a modified image of which certain visual and / or transparency characteristics are treated either to compensate for the optical effect of the hole pattern on the image, or to create a degree of uniform transparency for the assembly formed by the plate and the modified image so that the solar panel is illuminated by a brightness substantially a asleep on its surface.

According to one embodiment of the method, said processing consists in rendering the zones of the less transparent original image more transparent, by modifying the nature and / or the transparency of the inks which are used in the modified image, so that the light passing through the printed plate is distributed in a substantially uniform manner over the entire surface of the solar panel. According to another embodiment of the method, said treatment consists in making the less transparent image areas more transparent by practicing, within said image zones, zones of total transparency arranged so that the light that passes through all the image zones is distributed. in a substantially uniform manner over the entire surface of the solar panel.

In its most complete version, the method according to the invention comprises the following steps:

- We start by making the initial image more transparent by providing holes or areas of total transparency in its dark areas and / or by increasing the transparency of the inks used;

- Then digital image processing is applied to increase the contrast, and / or brightness of the image to increase the perceived quality;

if the solar sensor is a photovoltaic sensor composed of cells connected in series mode, the areas of transparency of the image are modified by creating holes or zones of total transparency with a density capable of creating a degree of substantially uniform transparency. between the different image areas.

DETAILED DESCRIPTION

The invention is now described in more detail by the eight indexed figures.

Figure 1 is an exploded diagram showing the four main components of the device according to the invention, in particular an image plate with a network of holes whose distribution is regular.

Figure 2 is a diagram similar to Figure 2, showing the four main components of the device when said components are superimposed.

Figure 3 is a diagram showing the four main components of the device of Figure 2, including a modified image including brightness and contrast.

FIG. 4 is a block diagram for showing an embodiment of the device according to the invention, in which the holes ensuring the transparency of the image plate have been positioned in priority in image areas whose color is close to that of the solar panel.

Figure 5 is a cross-sectional diagram, which shows a solar panel known per se and covered with image areas of different colors and receiving at the panel, solar radiation that is not equal over its entire surface.

FIG. 6 is a sectional diagram similar to that of FIG. 5, in which, in accordance with the principle of the invention, the image zones contain spaces of transparency which restore the homogeneity of the irradiation reaching the surface of the solar panel.

Fig. 7 is a diagram illustrating the variable density of the holes formed in the image areas to uniformize for the different colors of an image, the solar radiation reaching the solar collector.

FIG. 8 is a cross-sectional diagram of a variant of the device according to the invention, in which the image support plate is structured by a lens array on its front face exposed to the sun, and the image is printed at back of the plate in parallel bands spaced by bands of transparency.

Fig. 9 is a cross-sectional block diagram of the device according to the invention when the image is backlit by a light which propagates in the thickness of the transparent image support plate.

The device according to the invention (FIG. 1) is composed of a solar panel (1), an opaque or transparent plate (2) serving as image support, on which is affixed, for example by printing, an image (4). In the plate (2) provided with the image (4) are formed "holes" (3), namely orifices when the plate is opaque, or zones of total transparency of the image, when the support plate is transparent.

The plate (2) provided with the image (4) is arranged in front of the solar panel (Figure 2) so that a portion of the light which illuminates the image (4) passes through the holes (3) or the total transparency and also illuminates the solar panel (1). An advantageous characteristic of the invention is, for photovoltaic solar panels whose cells are coupled in series mode, to arrange on the plate (2) holes of identical shape according to an ordered network so that the luminous intensity which is received by each of the photovoltaic cells is substantially identical, which maximizes the electrical production of the solar panel.

Another feature of the invention is to propose means for increasing the transparency of said plate (2) and / or for increasing the visual quality of the image (4) printed when said image is perforated and placed in front of the solar panel ( 1). To obtain this result (FIG. 3), the original image (4) is modified beforehand (4M), before it is printed on the plate (2), in its characteristics of brightness, contrast, hue, colors, so as to compensate at least in part for the loss of brightness and contrast that occurs as soon as transparency spaces or holes (3) are formed in said image or said plate, respectively. Indeed, these spaces of transparency or holes (3) reveal the color of the solar panel (1) which is placed behind the image (4). The observer then sees a combination between the colors of the image (4) and the color of the solar panel (1). When the solar panel (1) is dark, for example, the image (4) will be modified into an image (4M) before printing, to increase its brightness and contrast, which will restore at least in part the brightness and the contrast of the original image (4) when it is positioned in front of the solar panel (1).

FIG. 4 shows that it is possible to further increase the visual quality of the image (4) (but this time to the detriment of the uniformity of the light received by the sensor when the holes (3) or Transparency spaces (6) are preferably located opposite areas of the image which have a color close to the color of the solar panel (1), so the visual appearance of the resulting image (4M) will be little modified by compared to that of the original image (4), because the image areas (6) which have become transparent will retain substantially their original color after positioning in front of the solar collector. In a slightly different embodiment, the plate (2) is transparent and the image is composed of image zones (FIG. 5, C 1, C 2, C 3) that are more or less transparent, in particular as a function of the color and the thickness. and / or the composition of the ink that is used for printing the image. The incident light (7) which is homogeneous in its intensity therefore passes more or less well the image areas (C1, C2, C3) which causes a disparity in the light intensity of the light (ZI, Z2, Z3) which at crossed the image areas (C1, C2, C3) and which ultimately illuminates the surface of the solar panel (1). When the solar panel (1) is composed of photovoltaic cells electrically mounted in series mode this disparity of light intensity received by the cells causes a significant drop in the power of the solar panel (1). To remedy this drawback, the device according to the present invention (FIG. 6) comprises image zones (C1, C2, C3) in which transparency spaces (T1, T2, T3) have been made in such a way that these zones transparency (T1, T2, T3) increase the overall transparency of the image areas (C1, C2, C3) in a proportion that will make substantially the same overall transparency of said image areas (C1, C2, C3). It follows from this device that the light intensities (Z11, Z21, Z31) which pass through all the image areas (C1, C2, C3) are substantially identical and uniformly illuminate the surface of the solar panel (1), thus the cells photovoltaic systems.

FIG. 7 is a diagram complementary to FIGS. 5 and 6 which shows the surface of the three image zones (C1, C2, C3) having different transparency Tr, respectively of 15, 30 and 35%, which means that the luminosities (Z1 , Z2, Z3) received by the photovoltaic cells in these three image areas are themselves different. To establish the equilibrium, spaces of total transparency, possibly holes in the case of an opaque plate, are practiced on each of the image areas (C1, C2, C3), in a proportion such that they increase the overall transparency. and make identical the brightness (Z11, Z21, Z31) received respectively by each of the photovoltaic cells. Thus, in the example shown, the transparency Tr of all image areas (C1, C2, C3) has become equal to 50%. In another particular embodiment of the device according to the invention, (FIG. 8), the plate (2) is transparent and structured on its front face by an array of rectilinear and convergent lenses (9) and the image is printed in parallel strips (C4) spaced by bands of transparency (T4) on the back of the plate (2). The space (11) between the plate (2) and the solar panel (1) can be filled by a transparent substance, such as a film of glue, in order to avoid possible parasitic reflections.

This arrangement allows an observer (10) to see the reconstituted full image without seeing the transparency bands (T4) so without seeing the color of the solar panel (1), while the light (7) of the sun is deflected by the lenses (9) and passes through the zones of transparency (T4) and / or illuminates the image bands (C4). The image bands (C4) are then semi transparent and the characteristics of their transparencies are those described in the previous paragraphs, that is to say (A) opaque image bands modified at least in their brightness and contrast with a network. areas of transparency homogeneously distributed over the entire surface of the image bands, (B) opaque image bands comprising areas of transparency positioned in priority on the image areas of the same color as the solar panel (1), (D) ) Image bands in which all the colors have the same degree of transparency, this characteristic being achieved either by modifying the nature and the thickness of the inks used, or by practicing a multitude of zones of transparency on each of the colors so that the transparency overall of each of said colors is substantially identical for all colors.

The partial transparency of the image bands will therefore increase the amount of light received by the solar panel (1) and distribute this surplus of light in a homogeneous manner on all photovoltaic cells mounted in series mode, which will not affect the smooth operation said solar panel (1).

In addition, the device of the invention allows in a simple manner the retro ^¬ lighting of the image (Figure 9). The backlighting requires that the ink that has been used to print the image (4) is partly transparent and that the backlighting light (L) does not pass through the areas of total transparency (6) in order to avoid the glare of the observer (10). In addition the components that allow the backlighting shall not obstruct the passage of sunlight (7) to the solar panel (1). At least one lamp (L) is thus disposed at the periphery of the plate (2) so as to introduce a light in the thickness of said plate (2). The plate (2) then behaves as a light guide which transmits this light in all its thickness and the light is only visible from its front face at the places (C1, C2, C3) where ink has been applied. The space (11) between the plate (4) and the solar panel (1) may be air or a glue whose refractive index will be sufficiently small for the plate (4) to be able to play its role. waveguide.

EXEMPLARY EMBODIMENT

An advertising billboard is rectangular and its dimensions are 1 x 2 m. It consists on the one hand of a photovoltaic solar panel of the same dimensions whose cells are electrically mounted in series mode and whose peak power is 300 Watt, and on the other hand of a PMMA (Polymethyl Methacrylate) plate transparent 5 mm thick, the same dimensions as the solar panel, placed in front of it, and on which was printed the image of an advertisement with opaque ink.

The image is printed on the inner face of the plate so the side of the photovoltaic panel. This printed image has been modified and optimized before printing so as, on the one hand, to increase its brightness and contrast and on the other hand to reveal an ordered network of zones of total transparency, circular 3 mm in diameter, forming a rectilinear grid where all the areas of total transparency are spaced 0.75 mm, so as to create a global surface of transparency of 50% of the surface of the image.

A bar of LED lamps (Electro Luminescent Diodes) disposed at the periphery of the plate injects a white light into the thickness of said plate so as to illuminate the front face of the printed image, facing the observer. The light flowing through the plate illuminates the printed areas of the image but does not emerge through the unprinted areas that are the areas of total transparency, which makes the lighting mode all the more effective. In the daytime, an observer placed more than 3 meters from the advertising poster will not distinguish the network of transparency zones in the image because of their smallness, this network of transparency zones will be black in appearance and will not have on the other hand, it has little impact on the brightness of the original image because said brightness of the image has been raised before printing to compensate for the optical effect of the black-appearing transparency zone network which has superimposed on the image. By day, the solar panel will produce a power of 150 Watts peak which corresponds to the transformation of 50% of the light received by the device. At night, the LED lamps are lit and effectively illuminate the front of the image.

ADVANTAGES OF THE INVENTION

Ultimately, the invention fulfills the objectives set by improving the visual quality and / or the transparency of an image (4) printed or placed on the surface of a solar panel (1), even when it is a photovoltaic panel whose cells are mounted in series mode. In addition, the invention allows the backlighting of said image (4) without hindering the ambient light (7) which illuminates the solar panel (1).

Claims

1 - Device comprising a dark-colored solar panel (1) and an image-support plate (2) positioned in front of the active surface of the solar panel (1) and intended to be provided with an image (4) comprising a multitude image areas each having its own local visual characteristics, the image-supporting plate (2) being provided with a set of holes (3) and / or the image (4) being provided with a set of transparency (T1, T2, T3) total or partial to increase the amount of light likely to reach the solar panel, characterized in that the local density holes (3) of the plate (2) or areas of transparency (T1 , T2, T3) of the image (4) is variable and is adapted according to the local visual characteristics of the image (4) and / or depending on the color of the solar panel, so as to optimize the visual qualities of the image. the image (4) on the device and the power generation of the device.

2 - Device according to claim 1, characterized in that said plate (2) is an opaque material, the solar collector (1) is dark in color, and in that said set of holes (3) has more holes ( 3) with regard to the darker areas of the image (4) and fewer holes (3) with respect to the brighter areas of the image (4), so as to reveal the solar panel (1) dark mainly in the dark areas of the image (4). 3 - Device according to one of the preceding claims, characterized in that the zones of total or partial transparency of the image (4) or the holes (3) of the plate (2) have the shape of circles or hexagons .

4 - Device according to any one of the preceding claims, characterized in that said visual characteristics of the image areas are taken in the set including their brightness, contrast and / or color. 5 - Device according to any one of the preceding claims, characterized in that the areas of total transparency of the image (4) and / or the holes (3) of the plate (2) image support are sufficiently small for an observer placed at a usual viewing distance from the solar panel does not individually distinguish said areas of total transparency and / or said holes (3).

6 - Device according to any one of the preceding claims, characterized in that the solar panel (1) is a photovoltaic solar panel, thermal or mixed, flat or curved, rigid or flexible.

7 - Device according to any one of claims 1 to 6, wherein said plate (2) is an opaque material and said solar panel is a photovoltaic panel composed of cells electrically connected in series mode, characterized in that said set of holes (3) is configured as a regular network capable of imparting to the plate (2) a degree of substantially uniform transparency over the entire surface of the plate (2), so that the brightness received by each of said photovoltaic cells behind the plate (2) is substantially identical from one cell to another.

9 - Device according to any one of the preceding claims, characterized in that said areas of total or partial transparency of the image are obtained by digital image processing before printing thereof on the plate (2) of support of 'picture.

10- Device according to claim 8 or claim 9, characterized in that the density in areas of total transparency of a given portion of the image is changed according to the initial transparency of this part of the image and / or depending on its color cast, with the understanding that the initially dark image portions are less transparent than the light portions and allow a density in zones of total transparency higher than the initially clear portions.

11 - Device according to claim 8 or claim 9, characterized in that areas of total or partial transparency of the image are arranged primarily on areas (5) of the image (4) whose original color is close to the color of the surface of the solar panel (1), so that the superposition of said areas of transparency of the image and the color of the solar panel (1) gives a visual rendering close to the color of the image area. origin (4).

12 - Device according to one of claims 8 to 11, wherein said plate (2) is a transparent material, characterized in that the plate (2) is structured on its front face by a lens array (9), and that image areas (C4) and areas of total transparency (T4) are positioned on the back side of the plate (2), so that an observer (10) will only see the image areas (C4) and that the sunlight (7) will completely traverse the areas of total transparency (T4) and in part (8) the image areas (C4).

13 - Device according to one of claims 8 to 12, characterized in that the space (11) between the plate (2) and the solar panel (1) is constituted by a transparent material whose refractive index is preferably equal to or greater than that of the plate (2), so as to avoid parasitic reflections and losses of light. 14 - Device according to one of claims 8 to 13, characterized in that the plate (2) is traversed in its thickness by a light (L) emitted in its periphery and that this light (L) guided in the thickness of the plate (2) only comes out of the plate (2) through the partly transparent image areas (C1, C2, C3), and not through the totally transparent zones, so as to enhance the visibility of the image . 15- Device according to claim 14, characterized in that the space (11) between the plate (2) and the solar panel (1) is constituted by a transparent material whose refractive index is preferably lower than that of the plate (2), so that the plate acts as a light guide.

16 - Device according to one of the preceding claims, characterized in that the inks and the support which are used for printing said image areas are transparent at least for part of the solar spectrum, for example for infrared and the ultraviolet ones.

17 - Device according to any one of the preceding claims, characterized in that the image (4; 4M) is either directly printed on the plate (2) support, or printed on a transparent intermediate support intended to be positioned against the plate (2).

18 - A method of producing a device according to any one of the preceding claims, wherein a solar panel (1), a plate (2) and an image (4) intended to be attached or printed on said plate are supplied ( 2), said plate being either opaque and pierced with a multitude of holes (3) for passing ambient light, or transparent to ambient light, said image having image zones more or less transparent to ambient light, characterized in it comprises a step of processing the image (4) before its integration into said device, to form a modified image (4M) of which certain visual characteristics and / or transparency are treated so as to compensate for the effect hole array (3) in the image (4), so as to create a uniform degree of transparency for the assembly formed by the plate (2) and the modified image (4M), so that the solar panel be illuminated by a substantially uniform brightness on its surface. 19 - Method according to claim 18, characterized in that said processing consists in making more transparent the zones of the image (4) of origin the less transparent, by modifying the nature and / or the transparency of the inks which are used in the modified image (4M), so that the light passing through the printed plate (2) is distributed in a substantially uniform manner over the entire solar panel surface (1).

20 - Process according to claim 18, characterized in that said treatment consists in rendering more transparent the less transparent image areas (C1, C2) by practicing inside said image zones zones of total transparency arranged so that the light which passes through all the image areas is distributed in a substantially uniform manner over the entire surface of the solar panel (1).

21 - Method according to one of claims 18 to 20, characterized in that it comprises the following steps: