Patent Application
20070277810
The present invention relates to a solar panel having a visually distinguishable feature.
Solar energy has long been considered as a renewable alternative to the energy generated from fossil fuels that is predominantly used today. Solar energy offers various advantages over more conventional power sources, and represents a clean source for generating electricity. Furthermore, solar cells do not need to be replenished with non-renewable fuels. Instead, they are powered by the effectively limitless energy from the sun.
Solar energy conversion modules that convert sunlight into electrical energy typically use photovoltaic or photoelectric cells, which convert the solar energy directly into electrical energy. The amount of energy generated by a cell is directly related to the amount of solar energy the cell absorbs; the amount of energy the cell absorbs is a function of both the size or surface area of the cell and the intensity or brightness of the sunlight that strikes the cell.
It is convenient to locate arrays of solar cells near to where the energy will be used, in order to minimise the losses associated with transmission of electricity over long distances. Most electricity is used in or near cities, towns or other human habitation, and consequently such arrays are often highly visible. A disadvantage of many solar panels is that, since they are designed to absorb the maximum amount of visible light, they appear as dark and unattractive to the eye.
There is a need for a solar panel that is aesthetically pleasing to the eye, or that may be used for purposes of marketing and advertising.
It is an object of the present invention to overcome or substantially ameliorate the above disadvantage. It is a further object to at least partially satisfy the abovementioned need.
In a first aspect of the invention there is provided a solar panel having a panel front and a panel back comprising:
Throughout the specification the expression “visually distinguishable feature” may be taken as meaning, for example, one or more of a design, a colour, a pattern, a decoration, a picture, a drawing, a sketch, an etching, a marking, a layout, a sketch, a brand, an advertisement, a notice, a sign, a name, a seal, an insignia, a portrait, a scene, a cartoon, a caricature, an icon, a signature, a photograph, an image, a logo, at least one letter, at least one number, at least one word, a calendar, a label, a trademark, a plan, a map, at least one marking or other visually distinguishable feature or a combination of two or more of these.
The nature of the visually distinguishable feature and/or the location of the element relative to the solar cells may be such that the amount of solar light incident on the array relative to the amount of solar light incident on the panel front is greater than about 50%. The amount of solar light incident on the array relative to the amount of solar light incident on the panel front may be greater than about 55, 60, 65, 70, 75, 80, 85, 90 or 95% and maybe about 50, 55, 60, 65, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.5 or 99.9%. The element may be removable from the solar panel. There may be an encapsulant between the cells, and the encapsulant may be at least partially transparent. The array may be disposed on a support panel, or between support panels, said support panel(s) being transparent. The support panel(s) may be made of glass, polymethylmethacrylate, polycarbonate, fluoropolymer (for example Tefzel or Teflon), PET, Tedlar, PE or epoxy or some other suitable transparent.
In a first embodiment, at least some of the solar cells are Sliver® cells, as described in WO02/45143, the contents of which are incorporated herein by cross-reference.
In a second embodiment the backs of at least some of the solar cells are capable of converting at least a portion of solar light incident thereon into electrical energy and either there is a reflector located between the array and the panel back or the panel back comprises a reflector. The reflector may be capable of reflecting at least part of the solar light incident on the solar panel towards the backs of at least some of the solar cells. The reflector may be, or may approximate, a Lambertian reflector, a diffuse reflector or a light scattering reflector.
In a third embodiment the visually distinguishable feature is at least partially distinguishable through the array on viewing the panel front or the panel back. The panel back may comprise the element comprising the visually distinguishable feature, or the element comprising the visually distinguishable feature may be located between the panel back and the array. The element may be a reflector and may be, or may approximate, a Lambertian reflector, a diffuse reflector or a light scattering reflector. The element may be disposed on or integral with the reflector. The element may be at least partially transparent.
In a fourth embodiment the element is located between the solar cells of the array. The element may comprise an encapsulant. The element may for example comprise transparent coloured material, optionally having different colours in different regions of the array.
In a fifth embodiment either the element is located between the array and the panel front, or the panel front comprises the element. In this embodiment the nature of the visually distinguishable feature and/or the location of the element relative to the solar cells does not completely prevent solar light incident on the panel front from being incident on at least a portion of the array.
In a sixth embodiment the element comprises at least one activatable element the appearance of which is capable of being changed by application of a stimulus, for example an electrical, thermal, optical or magnetic stimulus. The stimulus may be supplied from a source external to the solar panel, or it may be provided at least in part by the array of solar cells. For example the element may comprise one or more LEDs or LCD panels, and the visually distinguishable feature may be capable of being changed electronically.
In a seventh embodiment the solar panel additionally comprises means to change the visually distinguishable feature. The means to change the visually distinguishable feature may comprise means to change the visually distinguishable feature physically, mechanically, electrically, thermally, optically or magnetically, and may comprise, for example, at least one electrical terminal, at least one heating or cooling element or at least one magnet.
In an eighth embodiment there is provided a solar panel comprising:
In a ninth embodiment there is provided a solar panel comprising:
In a tenth embodiment there is provided a solar panel comprising:
In an eleventh embodiment there is provided a solar panel comprising:
In a twelfth embodiment there is provided a solar panel comprising:
a reflector disposed so as to be capable of reflecting at least part of the solar light incident on the solar panel towards the backs of at least some of the solar cell.
The array and the reflector may be substantially parallel. The element may be at least partially transparent. The reflector may be located behind the array.
In a thirteenth embodiment there is provided a solar panel comprising:
In a fourteenth embodiment there is provided a solar panel comprising:
The array, the element and the reflector may be substantially parallel. The array may be located between the element and the array. The array may be located behind the element and the reflector may be located behind the array. The element may be at least partially transparent.
In a second aspect of the invention there is provided a solar panel comprising an array of solar cells, each of said solar cells having a front and a back, wherein at least the front is capable of converting at least a portion of solar light incident thereon into electrical energy, and wherein there are spacings between at least some of the solar cells whereby the arrangement of the solar cells in the array embodies a visually distinguishable feature.
For example, since the solar cells appear dark, there may be regions of the array in which the spacings between solar cells are relatively small, these regions appearing relatively dark, and other regions of the array in which the spacings between solar cells are relatively large, these regions appearing relatively pale. The arrangement of such regions may be such as to embody a visually distinguishable feature.
In an embodiment, the solar panel comprises a reflector located so that it is capable of reflecting at least part of the solar light incident thereon towards at least some of the solar cells of the array. The reflector may be, or may approximate, a Lambertian reflector, a diffuse reflector or a light scattering reflector. The backs of at least some of the solar cells may be capable of converting at least a portion of solar light incident thereon into electrical energy.
In another embodiment, the solar panel and a reflector are located so that the reflector is capable of reflecting at least a part of the solar light incident thereon towards at least some of the solar cells of the array. The reflector may be, or may approximate, a Lambertian reflector, a diffuse reflector or a light scattering reflector. The backs of at least some of the solar cells may be capable of converting at least a portion of solar light incident thereon into electrical energy.
In another embodiment there is provided a solar panel comprising:
In a third aspect of the invention there is provided a combination for conversion of solar energy comprising:
The nature of the visually distinguishable feature and/or the location of the element relative to the solar cells may be such that the amount of solar light incident on the array relative to the amount of solar light incident on the combination is greater than about 50%. The amount of solar light incident on the array relative to the amount of solar light incident on the combination may be greater than about 55, 60, 65, 70, 75, 80, 85, 90 or 95% and may be about 50, 55, 60, 65, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.5 or 99.9%. There may be an encapsulant between the cells, and the encapsulant may be at least partially transparent. The array may be disposed on a support panel, or between support panels, said support panel(s) being transparent. The support panel(s) may be made of glass, polymethylmethacrylate, polycarbonate, fluoropolymer (for example Tefzel or Teflon), PET, Tedlar, PE or epoxy or some other suitable transparent.
In a first embodiment, at least some of the solar cells are Sliver® cells, as described in WO02/45143, the contents of which are incorporated herein by cross-reference.
In a second embodiment the backs of at least some of the solar cells are capable of converting at least a portion of solar light incident thereon into electrical energy and there is a reflector located so that it is capable of reflecting at least part of the solar light incident on the solar panel towards the backs of at least some of the solar cells. The reflector may be, or may approximate, a Lambertian reflector, a diffuse reflector or a light scattering reflector.
In a third embodiment the visually distinguishable feature is at least partially distinguishable through the array on viewing the combination. The element comprising the visually distinguishable feature may be located either at the array back or behind the array back. The element may comprise a reflector. The element may be disposed on or integral with the reflector.
In a fourth embodiment the element comprising the visually distinguishable feature is located between the solar cells of the array. The element may comprise an encapsulant. The element may for example comprise transparent coloured material, optionally having different colours in different regions of the array.
In a fifth embodiment the element is located either at the array front or in front of the array front. In this embodiment the nature of the visually distinguishable feature and/or the location of the element relative to the solar cells does not completely prevent solar light incident on the element from being incident on at least a portion of the array.
In a sixth embodiment the element comprises at least one activatable element the appearance of which is capable of being changed by application of a stimulus, for example an electrical, thermal, optical or magnetic stimulus. The stimulus may be supplied from a source external to the solar panel, or it may be provided at least in part by the array of solar cells. For example the element may comprise one or more LEDs or LCD panels, and the visually distinguishable feature may be capable of being changed electronically.
In a seventh embodiment the combination additionally comprises means to change the visually distinguishable feature. The means to change the visually distinguishable feature may comprise means to change the visually distinguishable feature physically, mechanically, electrically, thermally, optically or magnetically, and may comprise, for example, at least one electrical terminal, at least one heating or cooling element or at least one magnet.
In a fourth aspect of the invention there is provided a process for making a solar panel having a panel front and a panel back, said process comprising locating:
In a first embodiment, at least some of the solar cells are Sliver® cells, as described in WO02/45143, the contents of which are incorporated herein by cross-reference.
In a second embodiment the backs of at least some of the solar cells are capable of converting at least a portion of solar light incident thereon into electrical energy and the process comprises locating a reflector such that the reflector is capable of reflecting at least part of the solar light incident on the solar panel towards the backs of at least some of the solar cells. The reflector may be, or may approximate, a Lambertian reflector, a diffuse reflector or a light scattering reflector.
In a third embodiment the locating is such that the visually distinguishable feature is at least partially distinguishable through the array on viewing the panel front or the panel back. The panel back may comprise the element comprising the visually distinguishable feature, or the element comprising the visually distinguishable feature may be located between the panel back and the array. The element may be a reflector, and may be, or may approximate, a Lambertian reflector, a diffuse reflector or a light scattering reflector. The element may be disposed on or integral with the reflector. The element may be at least partially transparent.
In a fourth embodiment the element is located between the solar cells of the array. The element may comprise an encapsulant. The element may for example comprise transparent coloured material, optionally having different colours in different regions of the array.
In a fifth embodiment either the element is located between the array and the panel front, or the panel front comprises the element. In this embodiment the nature of the visually distinguishable feature and/or the location of the element relative to the solar cells does not completely prevent solar light incident on the panel front from being incident on at least a portion of the array.
In a sixth embodiment the element comprises at least one activatable element the appearance of which is capable of being changed by application of a stimulus, for example an electrical, thermal, optical or magnetic stimulus. The stimulus may be supplied from a source external to the solar panel, or it may be provided at least in part by the array of solar cells. For example the element may comprise one or more LEDs or LCD panels, and the visually distinguishable feature may be capable of being changed electronically.
In a fifth aspect of the invention there is provided a process for making a solar panel comprising the step of arranging a plurality of solar cells in an array, each of said solar cells having a front and a back, wherein at least the front is capable of converting at least a portion of solar light incident thereon into electrical energy, and wherein there are spacings between at least some of the solar cells whereby the arrangement of the solar cells in the array embodies a visually distinguishable feature.
In an embodiment the process additionally comprises the step of locating the solar panel and a reflector such that the reflector is capable of reflecting at least part of the solar light incident on the solar panel towards at least some of the solar cells of the array. The backs of at least some of the solar cells may be capable of converting at least a portion of solar light incident thereon into electrical energy.
In a sixth aspect of the invention there is provided a process for making a combination for conversion of solar energy, said process comprising locating:
In a first embodiment, at least some of the solar cells are Sliver® cells, as described in WO02/45143, the contents of which are incorporated herein by cross-reference.
In a second embodiment the backs of at least some of the solar cells are capable of converting at least a portion of solar light incident thereon into electrical energy and the process comprises locating a reflector such that the reflector is capable of reflecting at least part of the solar light incident on the solar panel towards the backs of at least some of the solar cells. The reflector may be, or may approximate, a Lambertian reflector, a diffuse reflector or a light scattering reflector.
In a third embodiment the locating is such that the visually distinguishable feature is at least partially distinguishable through the array on viewing the combination. The element comprising the visually distinguishable feature may be located either at the array back or behind the array back. The element may comprise a reflector. The element may be disposed on or integral with the reflector.
In a fourth embodiment the element comprising the visually distinguishable feature is located between the solar cells of the array. The element may comprise an encapsulant. The element may for example comprise transparent coloured material, optionally having different colours in different regions of the array.
In a fifth embodiment the element is located either at the array front or in front of the array front. In this embodiment the nature of the visually distinguishable feature and/or the location of the element relative to the solar cells does not completely prevent solar light incident on the element from being incident on at least a portion of the array.
In a sixth embodiment the element comprises at least one activatable element the appearance of which is capable of being changed by application of a stimulus, for example an electrical, thermal, optical or magnetic stimulus. The stimulus may be supplied from a source external to the array, or it may be provided at least in part by the array of solar cells. For example the element may comprise one or more LEDs or LCD panels, and the visually distinguishable feature may be capable of being changed electronically.
There is also provided a solar panel, or a combination for conversion of solar energy, when made by any of the processes of the invention.
In a seventh aspect of the invention there is provided a solar cell having a front and a back, wherein at least the front is capable of converting at least a portion of solar light incident thereon into electrical energy, or an array of such solar cells, when used in a solar panel, or a combination, according to the invention.
The present invention relates to a solar panel, or a combination for conversion of solar energy, having a visually distinguishable feature. As described herein, it has been found that a solar panel, or combination, comprising solar cells having a front and a back, wherein at least the front is capable of converting a portion of solar light incident thereon into electrical energy, may be constructed with substantial spacings between the solar cells while retaining adequate light capture efficiency. The spacings between the solar cells may thus be utilised in order to provide the solar panel or combination with a visually distinguishable feature in order to provide decoration, identification, advertising, information, or for any other suitable purpose. The element of the panel or combination to which the visually distinguishable feature is capable of being applied may be located either between the solar cells of the array or behind the array of the solar cells or in front of the array of the solar cells, or it may be manifested in the arrangement of the solar cells in the array, these alternatives being described in several of the aspects and embodiments of this specification. The visually distinguishable feature is at least partially distinguishable when viewing the front of the solar panel or the combination.
In this specification, when an element of the solar panel or combination is referred to as “comprising a visually distinguishable feature”, the element either comprises a visually distinguishable feature or is capable of comprising a visually distinguishable feature when an appropriate stimulus is applied to that element. The stimulus may be for example electrical, thermal, optical or magnetic, and may be either provided by an external source or provided at least in part by the solar array. An example is a solar panel with a reflector comprising one or more LEDs or LCD or video display panels, wherein the visually distinguishable feature may be created or changed electronically. Alternatively the element comprising the visually distinguishable feature may be separate from the reflector, as described elsewhere herein. If the element comprising the visually distinguishable feature comprises a plurality of panels, each of which is changeable electronically, the panels may be connected to a control unit, which converts an input signal to a plurality of output signals, each of which is fed to one of the panels so that the images on the panels provide a single visually distinguishable feature. The control unit may comprise a computer or some other signal processing device, and may also comprise means to output the output signals to the panels, for example an output manifold. The control unit may be a multi-screen processor, for example ComputerWall® from RGB Spectrum or VN-2400 Networked Processor from Visionetwork™. The control unit may use appropriate software for multi-screen processing, for example C-THROUGH™ for Windows® (which supports Imagestar™ and PICBLOC™ videowall processors) or Commander™ control software from Electrosonic Ltd. (Hawley Mill, Hawley Mill Road, Dartford, Kent DA27SY, United Kingdom). It may be a video matrix processor, for sending different images to the different panels, or it may be a video wall controller/server/video server for controlling an array of screens to show different parts of the same image (i.e. make a single composite image). For example the input signal may be multiplexed using a multiplexer, for example in order to create a single visually distinguishable feature over the panels. In another example the reflector comprises thermally sensitive components and the visually distinguishable feature may depend on the temperature in different regions of the solar panel.
The element may be a component or a part of the solar panel. It may be integral with the solar panel. The element may be for example the panel back or the panel front or the array or some other element of the solar panel. The element may be located between the panel back and the panel front, on the panel front, on the panel back, at the panel front, or at the panel back. Thus the element may be attached to (i.e. “on”) the panel back or the panel front, or it may be at a location which represents the panel front or panel back (i.e. it may be “at” the panel front or panel back). Alternatively it may be at a location intermediate (i.e. “between”) the panel front and the panel back.
The visually distinguishable feature may be reflective and/or absorbing towards light. Part of the visually distinguishable feature may be reflective and part may be absorbing. In particular the visually distinguishable feature or a part thereof may reflect light which is absorbable by the solar cells.
In this specification, the term “transparent” refers to a material that is substantially transparent to light at a wavelength to which the solar cells are responsive (for silicon about 350 nm to about 1200 nm). “Substantially” in this context refers to transmission of greater than about 80% of incident light at a wavelength to which the solar cells are responsive. The transmission may be greater than about 85%, 90%, 95% or 98%, and may be about 80, 85, 90, 95, 96, 97, 98, 99, 99.5 or 99.9%.
A Lambertian reflector is a diffuse reflector which obeys Lambert's Law. Lambert's Law states, that for such a reflector, the radiance of the reflected light is directly proportional to the cosine of the angle, with respect to the direction of maximum radiance, from which the reflector is viewed. A diffuse reflector is a reflecting surface that scatters radiation that is incident on it, thus producing diffuse reflection.
It is theorised that in a solar panel, or a combination. according to this invention wherein the solar panel or combination comprises a reflector, incident light that passes through spaces between the cells may be reflected by the reflector. It may then be absorbed by the rear (backs) of the cells, or may reflect from the front support panel onto the cells, and only a portion of the light will escape. In a representative solar panel or combination, when about 50% of the area of the array is occupied by solar cells, about 84% of light incident on the array may be captured, and when about 33% of the area of the array is occupied by solar cell, about 74% of light incident on the array may be captured. A portion of light that is not captured may be used to transmit a visually distinguishable feature to an observer.
If the solar cells are small, the visually distinguishable feature may appear to be unobscured when the solar panel or combination is viewed from a distance. The distance may depend on the spacings between the solar cells, on the dimensions of the solar cells and on the nature of the visually distinguishable feature, and may be greater than about 1 meter, or it may be greater than about 2, 3, 4, 5, 10, 20, 50, 100, 200, 500 or 1000 meters, and may be between about 1 and 1000 meters, or between about 2 and 500 meters or between about 5 and 100 meters or between about 10 and 50 meters, and may be about 1, 2, 3, 4, 5, 10, 20, 50, 100, 200, 500 or 1000 meters, or it may be less than about 1 meter. The spacings between solar cells may be the same or they may be different. The mean ratio between the spacing between solar cells and the width of a solar cell may be between about 0.5 and 5, or between about 1 and 4 or between about 1 and 3, and may be about 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5. The spacing between solar cells may be between about 0.1 and 20 mm, and may be between about 0.1 and 10, 0.1 and 5, 0.1 and 2, 0.1 and 1, 0.5 and 5, 0.5 and 2, 0.8 and 2, 0.8 and 1.5, 0.5 and 20, 1 and 20, 5 and 20, 10 and 20, 0.5 and 10, 1 and 10 or 2 and 5 mm, and may be about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.5 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 mm, or may be greater than 20 mm. The spacings may be all the same, or may be different, or some may be the same and some may be different. The ratio of the area of an array to the area of a single solar cell within said array may be greater than about 100, 200, 500, 1000, 2000, 5000 or 10000, and may be between about 100 and about 100000, or between about 200 and about 50000 or between about 500 and about 10000 or between about 1000 and about 5000, and may be about 100, 200, 500, 1000, 2000, 5000, 10000, 20000, 50000 or 100000. There may be more than about 50 solar cells in an array, or more than about 100, 200, 500, 1000, 2000, 5000 or 10000, and may be between about 50 and 100000, or between about 100 and about 100000, or between about 200 and about 50000 or between about 500 and about 10000 or between about 1000 and about 5000, and may be about 50, 100, 200, 500, 1000, 2000, 5000, 10000, 20000, 50000 or 100000.
The solar cells in the array may be electrically interconnected in series, in parallel, or in a combination of series and parallel. The electrical connections may be small in cross-section so as to absorb only a small amount of light. The electrical connections may be made of a transparent electrically conductive material, for example indium-tin-oxide or other oxide materials based on cadmium, gallium, copper, zinc, indium and/or tin, or may be based on a conductive polymer such as polyaniline.
The solar cells may be rectangular, square, round, elliptical, oval, parallelogram, polygonal, triangular or some other shape, and may be a mixture of shapes. They may be all the same size or they may be different sizes, or some may be the same size and some may be different sizes. The arrangement of different shapes and/or of different sizes of solar cells may embody a visually distinguishable feature according to the present invention.
Sliver® cells, described in WO02/45143, are particularly suitable for use as solar cells in the solar panels or combinations of the present invention. Sliver® cells are long and narrow (commonly about 0.75-1.5 mm wide, about 50-150 mm long and about 0.03-0.1 mm thick), and light incident on either the front or the back thereof may be converted into electrical energy. Due to their dimensions, the cells commonly do not obscure any entire aspect of a visually distinguishable feature viewed through an array of such cells, and consequently a visually distinguishable feature is commonly distinguishable through such an array. When viewed from a distance, the visually distinguishable feature commonly appears unobscured. A feature of Sliver® cells is that they may be assembled into an array with substantial spaces between individual cells, and still display an acceptable level of solar collection efficiency. This feature renders Sliver® cells particularly suitable for use in the present invention, since in several embodiments of the invention the visually distinguishable feature may be readily distinguished through the spaces between cells or between the cells. The width of the solar cells of the invention may be between about 0.2 and 10 mm, or between about 0.3 and 5 mm or between about 0.4 and 4 mm or between about 0.5 and 3 mm or between about 0.5 and 2 mm, and may be about 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9 or 10 mm. The length of the solar cells of the invention may be between about 10 and 300 mm, or between about 20 and 250 mm or between about 30 and 200 mm or between about 40 and 150 mm or between about 50 and 150 mm, and may be about 10, 20, 30, 40,50, 60, 70, 80, 90, 100, 110, 120, 140, 160, 180, 200, 250 or 300 mm. The thickness of the solar cells of the invention may be between about 0.025 and 0.25 mm, or between about 0.025 and 1 mm, 0.025 and 0.05 mm, 0.05 and 0.25 mm, 0.1 and 0.25 mm, or 0.05 and 0.1 mm, and may be about 0.025, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.21, 0.22, 0.23, 0.24 or 0.25 mm. The thickness of the solar cells may be such that they are at least partially transparent, that is, at least a portion of light incident on the front of the cell passes through the solar cell. The proportion of light incident on the front of the cell that passes through the solar cell may be between about 0 and 80%, or between about 0 and 70, 0 and 60, 0 and 50, 0 and 40, 0 and 30, 0 and 20, 0 and 10, 0 and 5, 10 and 80, 20 and 80, 50 and 80, 10 and 60, 20 and 50 or 30 and 50%, and may be about 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 or 80%. Commonly Sliver® cells are about 1 mm wide and about 100 mm long. A solar cell that may be used in the present invention may have a p-n junction on the front and/or on the back thereof, and may have p-n junctions on both the front and the back thereof. When a solar cell is in an array as described in the present invention, it may have an electrical contact on at least one side thereof. It may have no electrical contact on the front or on the back thereof.
In some embodiments of the invention, solar cells for use in the present invention may have electrical contacts on the front and on the back, wherein the electrical contact on the front and/or on the back is capable of permitting at least a portion of the light incident thereon to pass to the solar cell. Thus for example the electrical contact may be at least partially transparent, and/or may comprise holes or spaces to permit passage of light. It may for example comprise a conductive grid or mesh.
A solar cell which may be used in the present invention may comprise:
A suitable solar cell may for example comprise:
The semiconductor strip may be of lightly doped p-type conductivity, wherein the first diffusion layer is of heavily doped n-type conductivity, wherein a second diffusion layer of heavily doped p-type conductivity has been formed by diffusion, using a p-type dopant, into at least a portion of the second side surface and wherein the second electrical contact is in electrical contact with the second diffusion layer.
The first diffusion layer of n-type conductivity may have, in addition to the front and first side surface, also been formed into at least a portion of the back.
Another suitable solar cell may comprise:
The semiconductor strip may be of lightly doped n-type conductivity, wherein the first diffusion layer is of heavily doped p-type conductivity, wherein a second diffusion layer of heavily doped n-type conductivity has been formed by diffusion, using an n-type dopant, into at least a portion of the second side surface and wherein the second electrical contact is in electrical contact with the second diffusion layer. The first diffusion layer of n-type conductivity may have, in addition to the front and first side surfaces, also been formed into at least a portion of the back.
In a solar cell suitable for use in the present invention, the semiconductor may be for example silicon, the p-dopant may be for example boron and the n-dopant may be for example phosphorus. The solar cell may comprise a textured surface provided on at least one of the front and back to reduce reflectance of light incident thereon. It may comprise an anti-reflective layer provided on at least one of the front and back to reduce reflectance of light incident thereon. It may comprise a textured surface provided on at least one of the front and back to reduce reflectance of light incident thereon and an anti-reflective layer provided on the or each textured surface to further reduce reflectance of light incident on the solar cell.
A solar panel according to the present invention may comprise a solar concentrator comprising an array of solar cells as described above and a support substrate adapted to support each of the array of solar cells in an orientation allowing at least one of is the front and the back of each of the solar cells to be exposed to solar radiation, in use, the first and second metal contacts of each of the array of solar cells being electrically interconnected. In the solar collector, the solar cells may be electrically interconnected in series, in parallel, or in a combination of series and parallel. The array of solar cells may be oriented on the support substrate such that gaps exist between adjacent solar cells. The distance of the gap between any two adjacent solar cells may be from 0.5 up to about 5 times the width of one of the solar cells. The concentrator may comprise a rear reflector spaced from the rear surfaces of the array of solar cells, the rear reflector being oriented relative to the rear surfaces of the solar cells such that, in use, incident light passing through the gaps between adjacent solar cells is reflected by the rear reflector toward the back of at least one of the solar cells. The solar concentrator may comprise a transparent superstructure having an optically reflective surface spaced from the fronts of the array of solar cells and oriented relative to the fronts of the solar cells such that, in use, incident light reflected from the solar cells or from the rear reflector and passing through the gaps between adjacent solar cells, is reflected toward the front of at least one of the solar cells. The solar concentrator may comprise a transparent superstructure located in front of the array of solar cells, a transparent substructure located on the rear side of the array of solar cells and a pottant (encapsulant) filling a space between the substructure, the array of solar cells and the superstructure.
Thus the solar concentrator may comprise:
In use, light reflected from one or more of the solar cells of the solar concentrator and the rear reflector may be reflected to a front of at least one of the solar cells by the front surface of the superstructure. The solar concentrator may further comprise a light transparent substrate on the rear side of the array of solar cells, and a polymeric or a silicone pottant material to fill a space between the superstructure, the array of solar cells and the substructure. The rear reflector may be a layer of reflective material extending through at least a portion of the rear light-transparent substrate or applied to at least a portion of a rear surface of the rear light-transparent substrate. The layer of reflective material may have a lambertian surface facing the array of cells.
The solar cells described earlier herein may be manufactured using a semiconductor wafer. The semiconductor wafer may have an upper surface, a lower surface and a plurality of slots extending from the upper surface to the lower surface and defining a plurality of semiconductor strips disposed between adjacent slots, each semiconductor strip having a front surface extending from the upper surface of the wafer to the bottom surface of the wafer, a rear surface extending from the upper surface of the wafer to the bottom surface of the wafer, a first side surface located in the same plane as and forming part of the upper surface of the wafer and a second side surface located in the same plane as and forming part of the lower surface of the wafer, wherein corresponding ends of the semiconductor strips are interconnected and form part of a portion of the wafer which surrounds the plurality of slots so as to form a protective frame.
The solar cells may be manufactured using a method which comprises the steps of:
The method of manufacturing a solar cell may comprise the steps of:
The first metal contact to the first diffusion layer may be an ohmic contact. The second metal contact to the second side surface may be an ohmic contact.
The semiconductor strip may be of lightly doped p-type conductivity, wherein, in the step in which the first diffusion layer is provided, sufficient dopant is diffused into the first diffusion layer to yield a heavily doped n-type conductivity, the method comprising a further step wherein a second diffusion layer of heavily doped p-type conductivity is provided by diffusion, using a p-type dopant, into at least a portion of the second side surface, so that the second metal contact is in electrical contact with the second diffusion layer. The first diffusion layer of n-type conductivity may be, in addition to the front and first side surfaces, also formed into at least a portion of the rear surface.
A suitable method of manufacturing a solar cell for use in the present invention may comprise the steps of:
The first metal contact to the first diffusion layer may be an ohmic contact. The second metal contact to the second side surface may be an ohmic contact.
The semiconductor strip may be of lightly doped n-type conductivity, wherein, in the step in which the first diffusion layer is provided, sufficient dopant is diffused into the first diffusion layer to yield a heavily doped p-type conductivity, the method comprising a further step wherein a second diffusion layer of heavily doped n-type conductivity is formed by diffusion, using an n-type dopant, into at least a portion of the second side surface and so that the second metal contact is in electrical contact with the second diffusion layer. The first diffusion layer of heavily doped p-type conductivity may be, in addition to the front and first side surfaces, is also formed into at least a portion of the rear surface.
In order to manufacture the solar cell, a groove may be etched into a semiconductor waver. The method of etching the groove into a semiconductor wafer may include the steps of repeatedly inserting the wafer into an alkaline solution so as to expose a groove area in the surface of the wafer to the alkaline solution whilst another area on the surface of the wafer is not so exposed, and removing the wafer from the alkaline solution so as to allow the alkaline solution to drain from the wafer. The groove may be from about 5 to about 20 micrometers wide and from about 50 to about 250 micrometers deep. The semiconductor strip may be polycrystalline silicon or single crystal silicon.
The semiconductor wafer may be processed so as to form an intermediate product useful for subsequent manufacture of a solar cell, the semiconductor wafer having a substantially planar surface and a thickness dimension at right angles to said substantially planar surface. The method for processing the wafer may comprise the steps of:
The method of processing the semiconductor wafer having a substantially planar surface may include the steps of:
Thus a method for producing silicon solar cells for use in the present invention may comprise the steps of:
A laser may be used to form said slots in said wafer. Wet anisotropic etching of (110) oriented wafers may be used to form said slots. Alternatively a dicing saw may be used to form said slots in said wafer. See for example WO02/45143, the contents of which are incorporated herein by cross-reference.
A solar cell suitable for use in the present invention may comprise a semiconductor strip having a front provided with a p-n junction and a back provided with a p-n junction, the thickness of the semiconductor strip being from 50 to 250 micrometers, whereby, in use, at least a portion of light having a wavelength shorter than 1100 nm that enters the semiconductor strip from the front is absorbed in the semiconductor strip. The thickness of the semiconductor strip may be less than 100 micrometers. At least another portion of the light having a wavelength shorter than 1100 nm that enters the semiconductor strip from the front may exit the semiconductor strip at its back. The semiconductor strip may be polycrystalline silicon. The semiconductor strip may be single crystal silicon. The solar cell may comprise a first metal contact in electrical contact with the p-n junction of the front surface; and a second metal contact in electrical contact with the p-n junction of the rear surface.
The solar panel of the present invention may comprise an array of solar cells as described above and a support substrate adapted to support each of the array of solar cells in an orientation allowing at least one of the front and the back of each of the solar cells to be exposed to solar radiation, in use, the first and second metal contacts of each of the array of solar cells being electrically interconnected.
A solar cell for use in the present invention may comprise a semiconductor strip having a front, a back, a first side surface and a second side surface, wherein a p-n junction is provided on each of the front and the back, a first metal contact in electrical contact with the p-n junction of the front surface, and a second metal contact in electrical contact with the p-n junction of the rear surface. The semiconductor strip may be polycrystalline silicon. The semiconductor strip may be single crystal silicon.
A solar panel, or combination, displaying a visually distinguishable feature according to the invention may have a solar energy conversion efficiency that is not substantially lower than that of a solar panel or combination that differs from it only in that no visually distinguishable feature is displayed. The ratio of the solar energy conversion efficiency of a solar panel, or combination, displaying a visually distinguishable feature according to the invention to the solar energy conversion efficiency of a solar panel or combination that differs from it only in that no visually distinguishable feature is displayed may be between about 0.7 and 1.0 or about 0.8 and 1.0 or between about 0.85 and 1.0 or between about 0.9 and 1.0 or between about 0.95 and 1.0 or between about 0.97 and 1.0, and may be about 0.7, 0.8, 0.85, 0.9, 0.95, 0.96, 0.97, 0.98, 0.99 or 1.0. The array may be planar or curved or may be some other shape.
The visually distinguishable feature of the present invention may be suitable for the purposes of advertising or marketing or for identifying the solar panel in case of theft, or it may be decorative, or it may be capable of conveying information. It will be understood that a plurality of solar panels or combinations according to the invention may be located together, and that each may have a portion of a visually distinguishable feature in such a manner that, when viewed together, an entire visually distinguishable feature may be distinguished. The solar panel, or combination, of the present invention may have slightly lower solar conversion efficiency than a comparable solar panel, or combination, with no visually distinguishable feature. However use of a visually distinguishable feature provides substantial aesthetic benefits.
A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings wherein:
a is an illustration of the plan view of a solar panel according to the invention, having a feature which is visually distinguishable through an array of solar cells;
b is an illustration of the cross-section of a solar panel according to the invention, having a feature which is visually distinguishable through an array of solar cells;
c is an illustration of the plan view of a combination for conversion of solar energy according to the invention, having a feature which is visually distinguishable through an array of solar cells;
d is an illustration of the cross-section of a combination for conversion of solar energy according to the invention, having a feature which is visually distinguishable through an array of solar cells;
a is a diagrammatic representation of a combination for conversion of solar energy according to the present invention wherein the element is a reflector comprising a visually distinguishable feature;
a is a diagrammatic representation of a solar panel according to the present invention wherein the element comprising the visually distinguishable feature is located between a reflector and the array;
b is a diagrammatic representation of a solar panel according to the present invention wherein the element located between a reflector and the array comprises LEDs which may be used to display a visually distinguishable feature;
c is a diagrammatic representation of a combination for conversion of solar energy according to the present invention wherein the element comprising the visually distinguishable feature is located between a reflector and the array;
d is a diagrammatic representation of a combination for conversion of solar energy according to the present invention wherein the element located between a reflector and the array comprises LEDs which may be used to display a visually distinguishable feature;
a is a diagrammatic representation of a combination for conversion of solar energy according to the present invention wherein the element comprising the visually distinguishable feature is located between the cells of the array;
a is a diagrammatic representation of a combination for conversion of solar energy according to the present invention wherein the array is located between the element which comprises a visually distinguishable feature and a reflector;
a is a diagrammatic representation of a solar panel according to the present invention wherein a visually distinguishable feature is embodied in the arrangement of the solar cells in an array;
b is a diagrammatic representation of a combination for conversion of solar energy according to the present invention wherein a visually distinguishable feature is embodied in the arrangement of the solar cells in an array, and wherein the combination incorporates a reflector;
When light impinges on solar panel 100, incoming light beam 150 is reflected in multiple directions by element 135. Several representative beams are shown in
a is an illustration of the plan view of solar panel 200 having feature 230 (an “X”) which is visually distinguishable through array 220 of solar cells, and
c is an illustration of the plan view of combination 200c for conversion of solar energy, having feature 230c (an “X”) which is visually distinguishable through array 220c of solar cells, and
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A solar panel was constructed with the following specifications: Aperture area 1185 cm22×6 strings of 88 series-connected Sliver® solar cells.
Each Sliver® cell was 1 mm×57 mm and about 65 micron thick. The Sliver® cells were bi-facial (i.e. capable of collecting light on either side).
Surface coverage of solar cells was 50%, ie there was a 1 mm gap between each solar cell.
The solar cells were mounted between two panes of glass, the front pane being about 1 mm thick and the back pane being about 3 mm thick. The cells were encapsulated in an EVA encapsulant. Behind the back pane of glass was located a reflector of coloured paper (“Reflex” copy paper) as specified in Table 1. The logo was a reasonably bright pale poster. There was an air gap between the glass and the paper of about 0.1 mm.
Results for solar light collection are shown in Table 1.
In Table 1, abbreviations used are:
Values should be taken as relative values and need to be referenced to the numbers for the “Parallel White” (with White paper). Since the experiment deals with relative light intensity on the solar cells, the significant parameters are “Nisc” and “Eff”. Even with Red paper (which should be the worst case after Black paper), the short-circuit current was still more than 90% of the short-circuit current with the white paper. The Black paper gave a short-circuit current of 70% of the short-circuit current with the white paper. All the other colours gave a nlsc greater than 90% of the nIsc of the white paper.
The back surface of the back pane of glass of the solar panel of the above example was then painted with white paint to form a Lambertian reflector optically coupled to the panel. Results are shown in Table 2.
The same abbreviations are used for Table 2 as for Table 1, as well as the following:
It should be noted that the current for the pp case is approximately double that of the lp and rp cases, since the area is approximately double, however the voltages are about the same, since the intensity of incident light is about the same. The efficiency of the solar panel of the comparative example is slightly higher than that of the example of Table 1, since the reflector is optically coupled to the back panel.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004900329 | Jan 2004 | AU | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/AU05/00069 | 1/21/2005 | WO | 5/22/2007 |
