Light transmissive panel
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-02-10
- Publication Date
- 2026-08-13
Smart Images
Figure EP2026053587_13082026_PF_FP_ABST
Abstract
Description
[0001] LIGHT TRANSMISSIVE PANEL
[0002] TECHNICAL FIELD
[0003] The present disclosure relates to a light transmissive panel for a vehicle. Aspects of the invention relate to a light transmissive panel, a light transmissive panel array, and to a vehicle comprising a light transmissive panel or a light transmissive panel array.
[0004] BACKGROUND
[0005] Photovoltaic solar cells are a renewable energy source. It is known to provide photovoltaic cells on a variety of surfaces, including surfaces on vehicles, to generate electrical energy from the solar energy of light incident on the surface. The generated electricity may be used to recharge the battery of an electric car, or to power air conditioning or other electrical accessories of the vehicle. Electric vehicles powered partially or wholly by photovoltaic cells may be cheaper to run than electric vehicles charged from the electrical grid, or vehicles powered by conventional energy sources such as diesel or petrol engines. Photovoltaic solar cells may be referred to as photovoltaic cells or solar cells, and photovoltaic modules made up of multiple photovoltaic cells may be referred to as solar panels.
[0006] Conventional solar cells may be mounted on the roof of a vehicle. However, this approach means that, if a sun roof (e.g. a sliding sun roof or a panoramic roof) is provided on the vehicle, the conventional solar cells can only be provided in the area around the sun roof to avoid obstructing light from entering the vehicle cabin. The available surface area for the solar cells is therefore reduced, and so less electricity is generated.
[0007] Sun roofs are desirable because they allow natural sunlight into the interior of the vehicle. They also enhance ventilation as the sun roof may be openable. Currently, partially transparent solar cells are available. However, this type of solar cell has reduced efficiency compared to conventional solar cells. They also are costly to manufacture, and have reduced durability compared to conventional (non-transparent) solar cells, meaning that they have to be replaced more often at increased cost.
[0008] It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.
[0009] SUMMARY OF THE INVENTION
[0010] Aspects of the invention provide a light transmissive panel, a light transmissive panel array, and a vehicle comprising a light transmissive panel or panel array, as claimed in the appended claims.
[0011] According to an aspect of the present invention there is provided a light transmissive panel for a vehicle. The light transmissive panel has an outer surface and an inner surface for defining respective outer and inner surfaces of the vehicle.
[0012] The light transmissive panel includes a photovoltaic cell comprising first and second opposed major surfaces. The first major surface of the photovoltaic cell is proximal to the outer surface of the light transmissive panel and the second major surface of the photovoltaic cell is distal to the outer surface of the light transmissivepanel. The light transmissive panel also includes a light guide layer comprising first and second opposed major surfaces. The first major surface of the light guide layer is proximal to and extends beyond the second major surface of the photovoltaic cell. The light transmissive panel also includes a reflective layer arranged between the first major surface of the light gathering layer and the photovoltaic cell for reflecting light away from the photovoltaic cell and towards the inner surface of the light transmissive panel.
[0013] The first major surface of the light guide layer comprises a light gathering region disposed around at least a portion of the periphery of the photovoltaic cell for receiving light incident on the outer surface of the light transmissive panel. The light guide layer is configured to guide light incident on the light gathering region. The guided light has a component in a plane parallel to the first and second major surfaces of the light guide layer. Accordingly, embodiments of the present invention provide a light transmissive panel which can benefit from using conventional solar cells whilst simultaneously permitting light to pass through the panel from the outer to the inner surface in such a way that the light is distributed across the inner surface by the light guide layer to areas which would otherwise be occluded by the photovoltaic cell.
[0014] In an embodiment, the light transmissive panel comprises comprising diffusing means for diffusing light prior to exiting the panel via the inner surface thereof. Diffusion means, such as diffusion particles or at least one diffusion layer, improve the homogeneity of light leaving the inner surface of the light transmissive panel and entering the interior of the vehicle. Advantageously, with this arrangement the boundary around the area where light is blocked by the photovoltaic cell is therefore less defined, which may improve the aesthetic appearance of the panel.
[0015] In an embodiment, the diffusion means comprise a diffusion layer having first and second opposed major surfaces, the first major surface of the diffusion layer adjacent the second major surface of the lightguide layer for receiving light therefrom. Having a diffusion layer means that it can be added after assembly of the rest of the panel, making manufacture easier and cheaper. The homogeneity of light is also improved, as the light is diffused after being directed by the light guide layer, maximising the brightening effect in the region where light would otherwise be at least partially blocked by the photovoltaic cell.
[0016] In an embodiment, the diffusion means comprises a plurality of diffusion particles disposed within the light guide layer. Advantageously, by providing the diffusion means as particles in the light guide rather than as a separate diffusion later, this allows the light transmissive panel to be made lighter and thinner.
[0017] In an embodiment, the diffusion means comprises a coating or surface texture on the reflective layer and / or on the first major surface of the light guide layer. This may improve the ease of manufacture and reduce cost, as the light guide layer does not have to be manufactured to include diffusion means within the layer. Instead, a coating or surface texture can be added as a separate step.
[0018] In an embodiment, the light gathering region of the light transmissive panel comprises an angled boundary connecting the first and second major surfaces of the light guide layer in the light gathering region. Advantageously, the angled boundary improves the performance of the light guide layer in guiding light from the light gathering region to a light directing region that is coextensive with the photovoltaic cell and thereflective layer. In other words, the angled boundary helps to direct light such that it brightens the area of the inner surface of the panel where light would otherwise be blocked by the photovoltaic cell.
[0019] In an embodiment, the angle of the angled boundary relative to the first major surface of the light guide layer is greater than or equal to a critical angle of the light guide layer. This means that total internal reflection is achieved when light that is perpendicular to the first major surface of the light gathering layer is incident on the angled boundary. Advantageously, more light is directed from the light gathering region to the light directing region, to improve in brightening the area where light would otherwise be blocked by the photovoltaic cell. In an embodiment, the angled boundary comprises a coating that is at least partially reflective such that at least a portion of light incident on the light gathering region is reflected at the angled boundary. Advantageously, this further improves the amount of light reflected at the angled boundary, such that more light is directed into the light guide layer. The brightening of the area of the inner surface of the panel where light would otherwise be blocked by the photovoltaic cell is therefore improved.
[0020] In an embodiment, the light guide layer of the light transmissive panel comprises acrylic or glass. These materials are configured to allow light to be guided effectively from the light gathering region to the second major surface of the light guide layer while minimising light absorption.
[0021] In an embodiment, the reflective layer comprises a layer on the second major surface of the photovoltaic cell including at least one of: titanium dioxide, silver, aluminium, PVC, calcium carbonate, barium sulphate, or foamed transparent acrylic. These materials are configured to reflect light away from the second major surface of the photovoltaic cell and towards the inner surface of the light transmissive panel while minimising light absorption. It is particularly advantageous to apply a layer or coating directly to the second major surface of the photovoltaic cell, to make the light transmissive panel thinner and lighter.
[0022] In an embodiment, the diffusion means comprises at least one of: a microlens array, a textured surface, or a transparent carrier comprising reflective particles. Conveniently, these materials are configured to scatter or diffuse light, thereby improving the homogeneity of light leaving the inner surface of the light transmissive panel.
[0023] According to another aspect of the invention, there is provided a light transmissive panel array comprising a plurality of light transmissive panels arranged in a transverse plane. The light transmissive panels may be configured according to any of the embodiments described herein. Each panel within the array advantageously is able to generate electricity from light incident on the photovoltaic cell, while transmitting light incident on the light gathering region to the inner surface of the light transmissive panel. Having a plurality of light transmissive panels maximises the electricity generated, and is suitable for being installed as a large panel on a vehicle. According to another aspect of the invention, there is provided a vehicle comprising the light transmissive panel or light transmissive panel array, according to any of the embodiments described herein.
[0024] In an embodiment, the light transmissive panel is a roof panel of the vehicle. Advantageously, such a light transmissive roof panel allows natural light to enter the vehicle via the roof. It is also positioned on top of the vehicle for receiving the maximum amount of light incident on the vehicle while the sun is overhead.Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in anyway and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.
[0025] BRIEF DESCRIPTION OF THE DRAWINGS
[0026] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
[0027] Figure 1 shows a side view of a light transmissive panel according to an embodiment of the present invention; Figure 2 shows a side view of a light transmissive panel, including a diffusion layer, according to another embodiment of the present invention;
[0028] Figure 3 is a plan view of an outer surface of an array of light transmissive panels according to an embodiment of the present invention;
[0029] Figure 4 shows a side view of the array of light transmissive panels of Figure 3; and
[0030] Figure 5 shows a vehicle in accordance with an embodiment of the invention.
[0031] DETAILED DESCRIPTION
[0032] A light transmissive panel 100 in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figure 1.
[0033] The light transmissive panel 100 has an outer surface 102 and an inner surface 104. As shown in Figure 5, the light transmissive panel is suitable to be installed in a vehicle 500, for example as a roof panel 550. Accordingly, the outer surface 102 and the inner surface 104 of the light transmissive panel 100 may define respective outer and inner surfaces of the vehicle 500 when installed thereon.
[0034] The light transmissive panel 100 includes a photovoltaic cell 110. The light transmissive panel 100 has a first major surface 112 and is arranged such that the first major surface 112 of the photovoltaic cell 110 is proximal the outer surface 102 of the light transmissive panel 100. The photovoltaic cell 110 also has a second major surface 114 that opposes the first major surface 112. The second major surface 114 is arranged distal the outer surface 102 of the light transmissive panel 100. The second major surface 114 is parallel to the first major surface 112. Other arrangements are also useful.
[0035] In the present embodiments, the first major surface 112 of the cell 110 forms part of the outer surface 102 of the light transmissive panel 100. Region 140a is arranged between the edge of the light transmissive panel 100 and the edge of the photovoltaic cell 110 that connects the first and second major opposed surfaces 112, 114 thereof. In the present embodiment, region 140a comprises a substantially transparent material for transmitting light incident on the outer surface 102. In some embodiments, region 140a comprises glass, whichis advantageous due to its rigidity. In other embodiments, it may comprise at least one of glass, acrylic, polyvinyl butyral (PVB), polycarbonate (PC), or another suitable substantially transparent material.
[0036] The photovoltaic cell 110 is configured to convert solar energy into electrical energy. Light incident on the first surface 112 from outside the vehicle can therefore be converted into electricity by the photovoltaic effect. The photovoltaic cell 110 may be a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, a multijunction solar cell, an organic solar cell, a perovskite solar cell, a dye sensitized solar cell, or a tandem solar cell combining different solar cell technologies. The photovoltaic cell 110 is opaque, and therefore absorbs all or most of the light incident on the first major surface 112 of the photovoltaic cell. The absorbed light is therefore prevented from being transmitted to the inner surface 104 of the light transmissive panel 100.
[0037] The light transmissive panel 100 also includes a reflective layer 120 arranged between a light gathering layer 130 and the photovoltaic cell 110. Reflective layer 120 is configured to reflect light away from the photovoltaic cell and towards the inner surface 104 of the light transmissive panel 100. In the present embodiments, the reflective layer 120 comprises titanium dioxide. In other embodiments, the reflective layer 120 may alternatively be at least one of silver, aluminium, gold, mylar, barium sulphate, or another suitable reflective material. The reflective layer 120 has a first major surface 122 and a second major surface 124 which are opposed to one another, and preferably are parallel to one another.
[0038] In the present embodiment, the reflective layer 120 comprises a backing or a reflective surface treatment on the photovoltaic cell 110, such that the first major surface 122 of reflective layer 120 is adjacent the second major surface 114 of the photovoltaic cell 110. Advantageously, when the reflective layer 120 is substantially the same size and shape as the photovoltaic cell 110, it is able to reduce or substantially prevent light from being absorbed by the second major surface 114 of the photovoltaic cell 110. It also does not block any additional light from reaching the light guide layer 130 around the periphery of the photovoltaic cell 110. Accordingly, in some embodiments the reflective layer 120 is co-extensive with the second major surface 114 of the photovoltaic cell 110.
[0039] The light transmissive panel 100 also includes the light guide layer 130. The light guide layer 130 has a first major surface 132 comprising a light gathering region 131. The light guide layer 130 also has a second major surface 134 that opposes the first major surface 132. The first and second major surfaces 132, 134 of the light guide layer 130 are preferably parallel to one another, and parallel to the first and second major surfaces 112 and 114 of the photovoltaic cell 110. The first major surface 132 of the light guide layer 130 is proximal the photovoltaic cell 110 and the outer surface 102 of the light transmissive panel 100. The second major surface 134 is distal the photovoltaic cell 110 and proximal the inner surface 104 of the light transmissive panel 100.
[0040] The light gathering region 131 is disposed around at least a portion of the periphery of the photovoltaic cell 110 for receiving light incident on the outer surface 102 of the light transmissive panel 100. In the present embodiment, the surface area of the first major surface 132 of the light guide layer 130 is greater than the surface area of the first major surface 112 of the photovoltaic cell 110 to allow the light gathering region 131 to extend beyond the area defined by the outline of the photovoltaic cell 110. A portion of light incident on theouter surface 102 of the light transmissive panel 100 will therefore be received at the light gathering region 131 of the light guide layer 130, as it will not be blocked by the photovoltaic cell 110. It will be understood that the amount of light incident on the light gathering region 131 varies depending on the source of light, for example with the angle of the sun in the sky at different times of day or in artificial light.
[0041] In the present embodiment, the first major surface 132 of the light guide layer 130 is adjacent the second major surface 124 of the reflective layer 120. The light gathering region 131 of the first major surface 132 is in the same plane as the remainder of the first major surface 132. In other embodiments, the photovoltaic cell 110 and I or the reflective layer 130 is embedded in the light guide layer 130 such that the light gathering region 131 is in a different plane to the remainder of the first major surface 132. In this alternative embodiment, the light gathering region 131 will be closer to the outer surface 102 of the light transmissive panel 100 than the remainder of the first major surface 132.
[0042] In the present embodiment, the second major surface 134 of the light guide layer 130 forms part of the inner surface 104 of the light transmissive panel 100. In other embodiments, a diffusion layer may be provided, as will be discussed elsewhere in this disclosure. A region 140b is defined between the edge of the light transmissive panel 100 and boundary 135 of the light guide layer 130 that connects the first and second major opposed surfaces 132, 134 thereof. In the present embodiment, region 140b comprises a substantially transparent material for transmitting light. In some embodiments, region 140a comprises glass, which is advantageous due to its rigidity. In other embodiments, it may comprise at least one of glass, acrylic, polyvinyl butyral (PVB), or polycarbonate (PC). In alternative embodiments, in which boundary 135 is not angled but instead perpendicular to the first and second major opposed surfaces 132, 134, region 140b of Figure 1 will instead form part of the light guide layer 130.
[0043] The light guide layer 130 is configured to guide light incident on the light gathering region 131. Advantageously, light from the light gathering region 131 is directed to the second major surface 132 of the light guide layer 130 such that, when the inner surface 104 of the light transmissive panel 100 is viewed, portions of the inner surface 104 that would otherwise be dark appear brighter. In some embodiments, the light guide layer 130 comprises acrylic or glass. The guided light has a component in a plane parallel to first and second major opposed surfaces 131 , 134 of the light guide layer 130. The area of the light guide layer 130 between the dashed vertical lines may be referred to as the light directing region 133. Light is therefore directed from the light gathering region 131 around the periphery of the photovoltaic cell 110 to regions of the light guide layer 130 that are coextensive with the photovoltaic cell 110. Light is therefore directed towards the regions that would otherwise be dark or in shadow from the photovoltaic cell 110 as viewed from the inner surface 104, i.e. by an occupant of the vehicle 500.
[0044] In the present embodiment, the edge or boundary 135 that connects the first and second major opposed surfaces 132, 134 of the light guide layer 130 is angled. Boundary 135 forms an angle 136 to the first major surface 132 of the light guide layer 130. Angle 136 is an acute angle. This is particularly advantageous because light incident on boundary 135 of the light guide layer 130 is at least partially reflected. This causes the reflected light to be directed within the light guide layer 130. In some embodiments, the angle is the critical angle of thelight guide layer 130. In an example, vertical light incident on angled boundary 135 forming a critical angle 136 to the first major surface 132 is totally internally reflected within the lightguide layer 130. In some embodiments, the angle 136 may be around 45 degrees. The light reflected at boundary 135 has a horizontal component, and in some embodiments is horizontal.
[0045] The light directing region 133 is configured to direct light through the light guide layer 130 such that it exits via the second major surface 134. The reflective layer 120 also reduces or substantially prevents light from being absorbed by the second major surface 114 of the photovoltaic cell 110 by reflecting light back into the light guide layer 130. It is particularly advantageous for the light directing region 133 to be coextensive with the photovoltaic cell 110 and I or the reflective layer 120. In the present embodiment, the second major surface 134 has the same surface area and / or shape as the photovoltaic cell 110. This allows the region of the inner surface 104 which would otherwise be in shadow due to the opaque photovoltaic cell 110 to be brightened by the light exiting the light guide layer 130 via the second major surface 134.
[0046] In some embodiments, the angled boundary 135 has a reflective or partially reflective coating applied to it. The coating forms a layer between the angled boundary 135 of the light guide layer 130 and region 140b. In an example, titanium dioxide may be applied to at least a portion of boundary 135. In alternative embodiments, silver, aluminium, gold, mylar, barium sulphate, or another suitable reflective material is used as a reflective or partially reflective coating. The coating is configured to increase the amount of light that is reflected when incident on the angled boundary 135, rather than being transmitted through the light gathering region 131 to region 140b. The partially reflective coating further improves homogeneity of light transmitted from the inner surface 104 of the light transmissive panel 100. This is particularly advantageous when the acute angle between the boundary 135 and the first major surface 132 of the light guide layer 130 is less than the critical angle of the light guide layer 130. The light gathering region 131 can be made larger without increasing the thickness of the light transmissive panel 100. However, light transmission can be maintained by the reflective or partially reflective coating which aids in directing light from the light gathering region 131 to the light directing region 133.
[0047] A light transmissive panel 200 in accordance with another embodiment of the present invention is described herein with reference to the accompanying Figure 2.
[0048] Figure 2 includes the features described with reference to Figure 1 and light transmissive panel 100. The light transmissive panel 200 of Figure 2 includes a diffusion layer 250 having a first major surface 252 and a second major surface 254. In the present embodiment, the first and second major surfaces 252, 254 are opposed to each other, and parallel to one another. They are also parallel to the first and second major surfaces 112, 114 of the photovoltaic cell 110, and the first and second major surfaces 122, 124 of the reflective layer 120, and the first and second major surfaces 132, 134 of the light guide layer 130. The first major surface 252 of the diffusion layer 250 is adjacent the second major surface 134 of the light guide layer 130 for receiving light therefrom.It is advantageous that light is further scattered so that the light exiting the inner surface 104 of the light transmissive panel 200 is diffuse rather than directional. When the inner surface 104 of the light transmissive panel 200 is viewed, the boundary around the area blocked by photovoltaic cell 110 is diffused. The homogeneity of light leaving the inner surface 104 of the light transmissive panel 200 is therefore improved. The diffusion layer 250 comprises at least one of a microlens array, a textured surface, or a transparent carrier comprising reflective particles. In some alternative embodiments, the diffusion layer 250 forms part of the light guide layer 130, and be additionally treated, for example by applying a texture to the surface or the inclusion of diffusion particles to form a diffusion layer 250.
[0049] It is particularly advantageous for the diffusion layer 250 to extend across the majority of the inner surface 104 of the light transmissive panel 200. At least a portion of the diffusion layer 250 therefore extends beyond the periphery of the photovoltaic cell 110, for receiving light incident on the light gathering region 131 that is not directed into the light guide layer 130. For example, light that is not reflected at the angled boundary 135, but is instead transmitted through region 140b. Similarly, at least a portion of the diffusion layer 250 is provided to receive light from the second major surface 134 of the light guide layer 130. Accordingly, light that both has and has not exited via the light guide layer 130 is scattered by the diffusion layer 250, improving the homogeneity of light leaving the light transmissive panel200 via the inner surface 104.
[0050] In other embodiments, alternative or additional diffusion means may also be provided. In some embodiments, the light guide layer 130 comprises diffusion particles. The diffusion particles may be reflective particles configured to scatter light within the light guide layer 130. In some embodiments, the diffusion particles are evenly distributed throughout the light guide layer 130. Alternatively, they are concentrated in one region, for example to form a layer within the light guide layer 130. Advantageously, the use of diffusion particles within another layer of the light transmissive panel 100 leads to a more compact design, so that the light transmissive panel can be thinner and lighter. Diffusion particles may alternatively or additionally be provided in region 140b to scatter light that is not reflected at angled boundary 135. Likewise, in some embodiments, diffusion particles are provided in region 140a and / or within any layers between the photovoltaic cell 110 and the outer surface 102 of the light transmissive panel 100, to scatter incident light.
[0051] In some embodiments, the alternative or additional diffusion means comprise an additional or alternative diffusion layer provided between the reflective layer 120 and the light guide layer 130. The diffusion layer may be provided as a coating on the second major surface 124 of the reflective layer 120 and / or on the first major surface 132 of the light guide layer 130. Alternatively, the reflective layer 120 is configured to both reflect and scatter light, such that the reflected light is diffuse.
[0052] An array 300 of light transmissive panels 350, 360, 370, 380 in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figure 3.
[0053] Figure 3 depicts a view from the outer surface of the vehicle. For example, the array of light transmissive panels 300 is suitable to be installed in a vehicle 500, for example as a roof panel 550 as shown in Figure 5. The view of Figure 3 depicts the areas that light from outside a vehicle 500 is incident on. Light transmissivepanels 350, 360, 370 and 380 are exemplary light transmissive panels according to Figure 1 . However, it will be understood that an array may comprise a plurality of light transmissive panels according to any of the embodiments described herein.
[0054] Light transmissive panel 350 comprises a photovoltaic cell 250 depicted in dark grey, and a light guide layer 130 having a light gathering region 131 depicted in light grey. Similarly, light transmissive panel 360 has a photovoltaic cell 210, and a light gathering region 231 of a light guide layer 230. Light transmissive panel 370 has a photovoltaic cell 310, and a light gathering region 331 of a light guide layer 330. Light transmissive panel 380 has a photovoltaic cell 410, and a light gathering region 431 of a light guide layer 430. Light from outside the vehicle will be incident on the first major surface of each of photovoltaic cells 110, 210, 310, 410 and the light gathering regions 131 , 231 , 331 , 431 of the light guide layers 130, 230, 330, 430.
[0055] In the present embodiment, the light gathering region is depicted as one continuous region disposed around the periphery of the photovoltaic cell 110. The photovoltaic cell is substantially square in shape, and has cropped corners. The corresponding light guide layer is substantially the same shape as the photovoltaic cell, but without cropped corners and having a larger surface area. The light gathering region 131 is therefore provided around the edges of the photovoltaic cell 110, and the width of the light gathering region 131 is largest at the four corners of the light guide layer 130.
[0056] In some alternative embodiments, the light gathering region 131 comprises one or more discrete regions, each surrounding a portion of the periphery of the photovoltaic cell 110. In an example, the photovoltaic cell 110 having chamfered or cropped corners may be substantially the same shape and size as the light guide layer 130, howeverthe lightguide layer 130 does not have cropped or chamfered corners. For a square photovoltaic cell, four discrete light gathering regions are therefore provided in this alternative embodiment, one in each corner of the first major surface 132 of the light guide layer 130.
[0057] In other alternative embodiments, the photovoltaic cell 110 and the light guide layer 130 are different shapes and I or sizes. In an example, the photovoltaic cell 110 may be circular and the light guide layer 130 may be square. This embodiment is particularly advantageous as it means that the photovoltaic cells do not need to be shaped after being produced by sliced a cylinder of silicon, making them cheaper and quicker to manufacture.
[0058] The relative surface area of the first major surface 112 of the photovoltaic cell 110 and the light gathering region 131 of the first major surface 132 of the light guide layer 130 affects the amount of light transmitted by the light transmissive panel. In some embodiments, light transmission is between 2% and 20%. Increasing the relative surface area of the photovoltaic cell 110 allows more energy to be generated by the light transmissive panel. It will also decrease the light transmission which can be advantageous in that it prevents the interior of the vehicle from overheating.In some embodiments, at least one light transmissive panel according to any of the embodiments described herein forms a panel array with one or more transparent photovoltaic cells. For example, light transmissive panels 350 and 380 of Figure 3 may be replaced with transparent photovoltaic cells or panels comprising transparent photovoltaic cells. In some embodiments, transparent photovoltaic cells are arranged such that they cover some or all of a light gathering region of a light transmissive panel or panels. For example, transparent photovoltaic cells may be arranged such that they cover a portion of regions 131, 231 , 331 , 431 of Figure 3.
[0059] Turning to Figure 4, a side view of a light transmissive panel array 400 comprising a plurality of light transmissive panels 350, 360 is depicted.
[0060] Although Figure 4 depicts the side view of light transmissive panels according to Figure 1 , and does not depict a diffusion layer, it would be understood that any of the embodiments described herein are suitable for joining to form an array of light transmissive panels.
[0061] The light transmissive panels 350, 360, 370, 380 are joined to one another to form a larger light transmissive panel comprising a plurality of photovoltaic cells. The photovoltaic cells may be connected in series, in parallel, or in a mixed-mode comprising both series and parallel connections.
[0062] The edge of each light transmissive panel 350, 360 may be defined by the widest part of their respective light guide layers 130, 230. In the present embodiment, the right edge of light transmissive panel 350 is joined to the left edge of light transmissive panel 360. Likewise, with reference to array 300 depicted in Figure 3, the lower edge of light transmissive panel 350 is joined to the upper edge of light transmissive panel 370, the lower edge of light transmissive panel 360 is joined to the upper edge of light transmissive panel 380, and the right edge of light transmissive panel 370 is joined to the left edge of light transmissive panel 380. In some embodiments, a single continuous light guide layer and I or diffusion layer may be provided that is coextensive with a plurality of light transmissive panels 350, 360.
[0063] In alternative embodiments, any of the embodiments described herein further comprise one or more layers between the photovoltaic cell 110 and the outer surface 102 of the light transmissive panel. Additionally or alternatively, any of the embodiments described herein may further comprise one or more layers between the light guide layer 130 or the diffusion layer 250 and the inner surface 104 of the light transmissive panel. These additional layers between the photovoltaic cell 110 and the outer surface 102 provide advantageous properties such as protecting the photovoltaic cell 110 from environmental stresses like moisture, mechanical stresses, and I or UV degradation. In an example, the light transmissive panel may be laminated in glass, which is particularly advantageous due to its rigidity. Alternatively or additionally, the light transmissive panel may comprise layers including one or more of polyvinyl butyral (PVB), polycarbonate (PC), ethylene-vinyl-acetate (EVA), thermoplastic polyolefins (TPO) and polyolefin elastomers (POE). Advantageously, this materials are light, which reduces the overall weight of the panel or panel array.In embodiments where there is an array of light transmissive panels, at least one continuous layer may be provided that is coextensive with a plurality of the light transmissive panels in the array. For example, a continuous glass lamination layer may be provided proximal an outer surface and I or an inner surface of the light transmissive panel. Such a layer provides rigidity across the array of light transmissive panels, and reduces the risk of cracks and breaks.
[0064] Figure 5 illustrates a vehicle 500 according to an embodiment of the present invention. The vehicle 500 comprises a roof panel 550.
[0065] The light transmissive panel 550 comprises light transmissive panels according to any of Figures 1 to 4, or any of the embodiments described herein. In an example, an array of light transmissive panels may be joined together, and laminated in glass to form roof panel 550. It is particularly advantageous for a light transmissive panel to be installed on the roof of a vehicle, as it will receive large amounts of incident natural light as the vehicle is driven during the day and the amount of electricity generated is maximised. The light transmissive panels described herein also allow natural light to enter the interior of the vehicle. The light that reaches the interior is partially blocked by the opaque photovoltaic cells, such that light transmission is less than 100%, preventing the interior from overheating.
[0066] It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.
Claims
CLAIMS1. A light transmissive panel for a vehicle, the light transmissive panel having an outer surface and an inner surface for defining respective outer and inner surfaces of the vehicle, the light transmissive panel comprising:a photovoltaic cell comprising first and second opposed major surfaces, the first major surface of the photovoltaic cell being proximal to the outer surface of the light transmissive panel and the second major surface of the photovoltaic cell being distal to the outer surface of the light transmissive panel;a light guide layer comprising first and second opposed major surfaces, the first major surface of the light guide layer being proximal to and extending beyond the second major surface of the photovoltaic cell;a reflective layer arranged between the first major surface of the light gathering layer and the photovoltaic cell for reflecting light away from the photovoltaic cell and towards the inner surface of the light transmissive panel;wherein the first major surface of the light guide layer comprises a light gathering region disposed around at least a portion of the periphery of the photovoltaic cell for receiving light incident on the outer surface of the light transmissive panel; andwherein the light guide layer is configured to guide light incident on the light gathering region, the guided light having a component in a plane parallel to the first and second major surfaces of the light guide layer.
2. A light transmissive panel according to claim 1 , comprising diffusing means for diffusing light prior to exiting the light transmissive panel via the inner surface thereof.
3. A light transmissive panel according to claim 2, wherein the diffusion means comprise a diffusion layer having first and second opposed major surfaces, the first major surface of the diffusion layer adjacent the second major surface of the light guide layer for receiving light therefrom.
4. A light transmissive panel according to claim 2 or 3, wherein the diffusion means comprises a plurality of diffusion particles disposed within the light guide layer.
5. A light transmissive panel according to any of claims 2 to 4, wherein the diffusion means comprises a coating or surface texture on the reflective layer and / or on the first major surface of the light guide layer.
6. A light transmissive panel according to any preceding claim, wherein the light gathering region comprises an angled boundary connecting the first and second major surfaces of the light guide layer in the light gathering region.
7. A light transmissive panel according to claim 6, wherein the angle of the angled boundary relative to the first major surface of the light guide layer is greater than or equal to a critical angle of the light guide layer.
8. A light transmissive panel according to claim 6 or 7, wherein the angled boundary comprises a coating that is at least partially reflective such that at least a portion of light incident on the light gathering region is reflected at the angled boundary.
9. A light transmissive panel according to any preceding claim, wherein the light guide layer comprises acrylic or glass.
10. A light transmissive panel according to any preceding claim, wherein the reflective layer comprises a layer on the second major surface of the photovoltaic cell including at least one of: titanium dioxide, silver, aluminium, PVC, calcium carbonate, barium sulphate, or foamed transparent acrylic.
11. A light transmissive panel according to any one of claims 2 to 10, wherein the diffusion means comprises at least one of: a microlens array, a textured surface, or a transparent carrier comprising reflective particles.
12. A light transmissive panel array comprising a plurality of light transmissive panels according to any of claims 1 to 11 arranged in a transverse plane.
13. A vehicle comprising the light transmissive panel or light transmissive panel array of any of claims 1 to 12.
14. A vehicle according to claim 13, wherein the light transmissive panel or light transmissive panel array is a roof panel of the vehicle.