Photovoltaic power generation system

Abstract

A flexible composite strip is described that comprises a flexible printed circuit (2) with at least first and second conductor tracks (5, 6) and a group (4) of a plurality of photovoltaic cells (3) connected in parallel to the first and second tracks (5, 6) for powering them. The composite strip comprises a plurality of soldering pads (12) at which the first and second conductor tracks (5, 6) are accessible. The flexible composite strip is configured to be cut at the soldering pads (12).

Description

[Technical field]

[0001] The present invention relates to a photovoltaic module, in particular a photovoltaic module designed for a window or French window. [Background technology]

[0002] Luminescent Solar Concentrators (LSC) are devices based on sheets or films with dye molecules that are able to capture and re-emit a portion of the incident solar radiation. A portion of the radiation emitted by the dye molecules remains trapped within the film / sheet by the phenomenon of total internal reflection.

[0003] If a sheet or film has sufficiently smooth air interfaces, some of the fluorescent light trapped within said sheet or film will reach its surroundings via a process of multiple reflections from one interface to another.

[0004] The side of the sheet / film has photovoltaic cells arranged in modules called arrays, which convert a portion of the luminescent radiation trapped within the sheet / film into electrical current that can be advantageously used to power external users such as lighting, charging systems, shading or integrated lighting systems, or can be stored in a local storage system, or it can be introduced into the grid.

[0005] The photovoltaic cells located at the edges of the luminescent sheet are typically connected in series with each other to sum the potential difference generated by each cell, thus minimizing ohmic losses due to the interconnections between the cells.

[0006] The current flowing in the string of photovoltaic cells is limited by the current provided by the less illuminated cells. Unfortunately, local shading of the luminous sheet leads to non-uniform illumination of the photovoltaic array and, in the case of series connections, an overall efficiency loss associated with the current limitation induced by the less illuminated devices.

[0007] This problem can be overcome by connecting photovoltaic cells in parallel, in which case the current produced by the array is the sum of the currents produced by each photovoltaic device, and the potential difference is approximately constant regardless of the illumination level of the cells.

[0008] In the case of luminescent solar concentrators, the current density generated by the photovoltaic devices can be tens of mA / cm2, and the parallel connections can result in arrays delivering total currents of several amperes. The higher the current flowing in the circuit, the higher the ohmic losses due to the electrical resistance of the interconnects and contacts.

[0009] A common choice in the manufacture of photovoltaic arrays for luminescent concentrators is the manufacture of series-parallel circuits in which the cells are soldered onto a printed circuit that provides the electrical connections for the individual photovoltaic devices and also serves as mechanical support.

[0010] When cells are configured in an array, the potential difference generated by the series connected cells will be greater than the potential difference of a single photovoltaic device, and the current will be less than the current that would be obtained if all the photovoltaic devices were connected in parallel.

[0011] Typically, the arrays used in luminescent solar concentrators consist of 20-30 photovoltaic devices connected in series with each other. The various arrays are then connected in parallel with each other. The length of the printed circuit of a photovoltaic array usually ranges from 10 cm to 30 cm, and its width is slightly larger than the thickness of the luminescent sheet (6-15 mm).

[0012] Due to the mixed series-parallel connection, local variations in illumination of a luminous sheet do not limit the total current delivered by the entire module, but only the total current delivered by a single array.

[0013] Each photovoltaic array is connected to the next via substantially known board-to-board connectors, which allows the assembly of arrays of any length, even arrays of several meters.

[0014] The longer the length of each array, the fewer interconnects required over a given length, resulting in lower interconnect component costs.

[0015] On the other hand, the longer the length of each array, the more sensitive the module is to any unavoidable local variations in illumination, resulting in the aforementioned loss of efficiency.

[0016] The drawback of the prior art solutions stems from the fact that the printed circuit to which the photovoltaic cells are connected, i.e. the array of cells, has a given length and that in the case of sheets larger or longer than a single module, several arrays must be connected by corresponding connectors which increase the cost of the entire system formed by several modules to often unacceptable values. Moreover, since continuous sheets of glass, glass covers and windows rarely have standard dimensions, the fixed length of a single module may not be suitable to fully utilize the dimensions of the sheet, even when several arrays are combined.

[0017] There is a need felt in the art for improved versatility in the manufacture of arrays of photovoltaic cells, and therefore LSC devices of any size, to facilitate the penetration of this technology into the housing and construction sector in general.

[0018] This need must be combined with the constraint of minimizing both the number of connectors present and the currents circulating in the photovoltaic array, in order to reduce ohmic losses, the cross-sectional area of ​​the conductors and, consequently, their cost.

[0019] In this context, the object is to provide a photovoltaic module for a luminescent solar concentrator, which is able to overcome at least some of the drawbacks of the prior art and meet the above-mentioned needs. Summary of the Invention

[0020] In particular, it is an object of the present invention to provide a photovoltaic module for a photovoltaic concentrator that is easy to use, practical, versatile and relatively inexpensive.

[0021] This object is achieved by a photovoltaic module having the technical features recited in one or more of the appended claims. The dependent claims correspond to possible various embodiments of the invention.

[0022] According to a first aspect, the invention relates to a composite strip comprising a flexible printed circuit, the flexible printed circuit comprising at least first and second conductor tracks and a plurality of groups of photovoltaic cells connected in series, the plurality of groups of photovoltaic cells supplying the conductor tracks.

[0023] The thickness of the flexible printed circuit is preferably 0.2 to 2 mm, and the flexible printed circuit is formed on, for example, a Kapton® support.

[0024] Groups of multiple cells are placed one after the other along the strip with solder pads between successive groups.

[0025] The conductor tracks are accessible from the soldering pads.

[0026] The strip is configured to be cut at the solder pads.

[0027] Preferably, the flexible composite strip comprises a pair of tracks which are not electrically connected to the track which is connected to the photovoltaic cell.

[0028] Preferably, the flexible composite strip includes graphical indicia, such as dashed lines, to identify corresponding cut lines with respect to the electrical connections of the photovoltaic cells and the electrical connections of groups of photovoltaic cells.

[0029] Preferably, the flexible composite strip is provided with an adhesive for bonding to the edges of the corresponding luminescent sheets, for example an adhesive in the form of a double-sided adhesive tape.

[0030] Preferably, the flexible composite strip comprises at least one electronic component for protecting the photovoltaic cells.

[0031] The electronic protection components are preferably mounted on the flexible printed circuit on the opposite side of the photovoltaic cell.

[0032] According to one aspect, the invention relates to a photovoltaic module comprising a piece of flexible composite strip as described above.

[0033] The photovoltaic module includes a conversion circuit soldered to the strip.

[0034] The conversion circuit has an input connected to the track powered by the photovoltaic cell, and an output at a predetermined voltage.

[0035] The conversion circuit is configured to convert an input voltage to a predetermined output voltage, the predetermined output voltage being an output voltage of the photovoltaic power generation module.

[0036] Preferably, the flexible composite strip comprises a pair of tracks which are not electrically connected to the tracks powered by the photovoltaic device, and the output of the conversion circuit is connected to the tracks.

[0037] Further features and advantages of the above-mentioned aspects and other aspects will become more apparent in the following non-limiting description of preferred embodiments of a photovoltaic module for a luminescent solar concentrator. [Brief description of the drawings]

[0038] The following description refers to the accompanying drawings, which are provided for illustrative purposes only, without limiting the scope of the invention. [Figure 1] FIG. 1 is a schematic side view of a luminescent solar concentrator including a photovoltaic module according to the present invention. [Diagram 2] FIG. 1 is a schematic side view of a luminescent solar concentrator including a photovoltaic module according to the present invention. [Diagram 3] 1 is a schematic plan view of a photovoltaic power generation module according to the present invention; [Figure 4] 1 is a schematic plan view of a photovoltaic power generation module according to the present invention; [Diagram 5] 1 is a schematic plan view of a composite strip according to the present invention; [Figure 6] FIG. 1 is a schematic perspective view of a luminescent solar concentrator including a photovoltaic module according to the present invention; [Figure 7] FIG. 1 is a schematic perspective view of a luminescent solar concentrator including a photovoltaic module according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] With reference to the accompanying drawings, the numeral 100 designates a luminescent solar concentrator.

[0040] For example, according to the embodiment shown in FIG. 1, light concentrator 100 comprises a sheet 101 of fluorescent material, ie, having a pigment (not shown) dispersed therein.

[0041] These dyes emit light or fluorescent radiation FL which, in use, propagates isotropically when the sheeting is exposed to solar radiation SR.

[0042] A portion of the fluorescent radiation FL remains trapped inside the sheet 101 by total internal reflection and is transmitted towards the edge 102 of the sheet 101 .

[0043] According to the invention, the concentrator 100 comprises a photovoltaic module, generally designated by the numeral 1 .

[0044] The photovoltaic power generation module 1 is attached to an edge 102 of the sheet 101 along said edge 102 .

[0045] For example, according to the embodiment shown in FIG. 2, the concentrator 100 comprises a glass sheet 103, a glass sheet 104, and a film 105 disposed between the glass sheets 103 and 104 to form a layered sheet 106.

[0046] A plurality of dyes are dispersed in the film 105, causing the film 105 to emit light.

[0047] A portion of the fluorescent radiation FL remains trapped within the film 105 by total internal reflection and is transmitted towards the edge 107 of the sheet 106 .

[0048] The concentrator 100 comprises a photovoltaic module 1 attached to an edge 107 of a sheet 101 along said edge 107 .

[0049] The sheet 101 and / or the plate 106 may be coated, preferably at their respective edges 102 , 107 , with a reflective material 108 to minimize light loss near the module 1 .

[0050] The photovoltaic module 1 defines a photovoltaic receiver for a concentrator 100 .

[0051] The module 1 comprises a flexible printed circuit 2 .

[0052] The thickness of the flexible printed circuit 2 is preferably 0.2 to 2 mm. For example, the flexible printed circuit 2 is formed on a Kapton® support.

[0053] The module 1 comprises a number of photovoltaic or solar cells 3 soldered onto a printed circuit 2 .

[0054] According to one embodiment, the cells 3, shown diagrammatically in the accompanying drawings as diodes representing an equivalent circuit, are divided into groups 4, for example of five cells 3 connected in series.

[0055] According to alternative embodiments, group 4 comprises four batteries 3 or six batteries or any other number based on the desired performance.

[0056] Groups 4 of modules 1 are identical to one another and are connected in parallel to provide as output a predetermined voltage determined by the number and type of associated batteries 3 .

[0057] The photovoltaic module 1 comprises several groups 4 of photovoltaic cells 3 connected in series with each other. The groups 4 of cells are connected in parallel to provide a voltage equal to the voltage of a single group, thus increasing the current.

[0058] Preferably, the dimensions of a single solar cell 3 are less than or equal to 20x20 mm, preferably less than or equal to 10x10 mm.

[0059] The length of the group 4 of batteries 3 is preferably less than 10 cm, more preferably less than 5 cm.

[0060] Preferably, the photovoltaic module 1 comprises electronic components for protecting the photovoltaic cells 3 mounted on the printed circuit 2 on the side opposite the cells 3 .

[0061] The protection components may include, for example, bypass diodes or varistors. For example, Figures 3, 4 and 5 show bypass diodes labeled 15, each connected in anti-parallel to a corresponding group 4 of photovoltaic cells 3.

[0062] The printed circuit 2 comprises a first track 5 and a second track 6 for connecting the groups 4 in parallel. The groups 4 are connected in parallel to the tracks 5, 6.

[0063] Tracks 5, 6 define the DC output provided by the group 4 itself depending on the number of groups 4 connected in parallel.

[0064] According to one embodiment, the printed circuit 2 comprises a third track 8 and a fourth track 9 which are not directly connected to the photovoltaic cell 3, as will be explained in more detail below.

[0065] With reference to the module 1, the printed circuit 2, together with the groups 4 of photovoltaic cells 3 connected in parallel on tracks 5 and 6 and, if necessary, protection devices, is preferably a piece 20 of a flexible composite strip 200, which comprises a flexible printed circuit 2 in the form of a strip, with tracks 5, 6, 8 and 9 (if provided), to which a series of groups 4 are soldered.

[0066] Strip 200 is referred to as a composite because it comprises multiple parts.

[0067] As will be explained in more detail below, the pieces 20 are preferably cut into strips 200 .

[0068] Group 4 supplies strip 200 as well as strip 20 with tracks 5,6 which define the DC output supplied by group 4.

[0069] Preferably, the dimensions of the cells 3 are small enough to allow the strip 200, and therefore the module 1, to have a longitudinal radius of curvature of less than 10 cm, more preferably less than 5 cm.

[0070] The module 1 comprises a conversion circuit 7 configured to convert an input voltage to a predetermined value, ie to an output voltage of a predetermined voltage, for example 18V.

[0071] According to one embodiment, circuit 7 has inputs connected to tracks 5 , 6 and outputs connected to tracks 8 and 9 .

[0072] According to one embodiment, the output of the circuit 7 may be used directly or to power a further device.

[0073] According to one embodiment, the output of circuit 7 can be used directly or to power further devices and is connected to tracks 8 and 9 to transmit a predetermined voltage to the opposite end of module 1 as well.

[0074] In this way, the output of the photovoltaic module 1 has standard electrical characteristics regardless of the length of the module 1 , i.e. the length of the segments 20 .

[0075] Typically, a DC-DC type output of the conversion circuit 7 has an output of the predetermined voltage mentioned above.

[0076] In practice, the converter circuit 7 is powered by tracks 5, 6 and provides as an output a predetermined voltage, for example 18 V, which can be used directly or by means of tracks 8 and 9.

[0077] According to one embodiment, the conversion circuit 7 is formed on a flexible printed circuit.

[0078] The conversion circuit 7 comprises, for example, a DC-DC step-up converter 7 a of substantially known type, which increases the potential difference provided by the group 4 of cells 3 of the strip 20 .

[0079] According to one embodiment, the flexible conversion circuit 7 is configured to perform maximum power point tracking, i.e. to modify the operating point of the photovoltaic devices present in the strips 20 in order to optimize the electrical efficiency of the module 1.

[0080] According to one embodiment, the module 1 comprises two tracks 8, 9 connected to the output of a conversion circuit 7, i.e. powered with a given voltage.

[0081] According to a simpler embodiment, the module 1 , i.e. the flexible printed circuit on which it is formed, does not have the two tracks 8 , 9 and a predetermined output voltage is available at the conversion circuit 7 .

[0082] In the following, without limiting the scope of the invention, reference will be made to four tracks.

[0083] As shown in FIG. 7, according to one embodiment, the module 1 comprises a pair of conductors 10, 11 soldered to tracks 8, 9 to which, for example, a connector for a photovoltaic system may be connected, if required.

[0084] In practice, tracks or conductors 5, 6 carry the current supplied by each group 4 of batteries 3 to a DC-DC conversion circuit which increases the voltage supplied by each group 4 of batteries 3 to a value that can be matched by an external DC-DC converter or a low voltage user (<50V).

[0085] Substantially at both ends of each group 4 along the strip 200, the strip 200 comprises soldering pads 12 by means of which the conversion circuit 7 can be soldered to a printed circuit.

[0086] In fact, the tracks 5 , 6 , 8 and 9 are accessible at the soldering pad 12 .

[0087] Advantageously, the strip 200 is cut to a desired length at one of the pads 12 to obtain the pieces 20 .

[0088] The conversion circuit 7 may then be soldered to the tracks 5, 6, 8, 9 at one of the pads 12 of the strip 20, preferably at one end thereof.

[0089] The conversion circuit is connected to a pad that is directly connected to a group of photovoltaic devices and two further pads that are electrically connected to a bus, which allows for a constant voltage line and is optimized for the entire length of the photovoltaic module 1.

[0090] This solution makes it possible to obtain the positive and negative poles of the module 1 at one end or the other of the module 1 .

[0091] According to one embodiment, it is possible to carry a positive electrode at one end and a negative electrode at the opposite end, depending on the interconnection requirements.

[0092] According to one embodiment, the tracks 5 , 6 , 8 , 9 are thinned at the pad 12 to facilitate cutting of the strip 200 .

[0093] Preferably, at the pads 12, i.e. between the groups 4 of batteries 3 along the strip 200, the strip 200 has graphical indicia 13, e.g. dashed lines, to identify where to cut the strip 200 to obtain pieces 20 that respect the series-parallel connections of the batteries 3 and the series-parallel connections of the groups 4.

[0094] Each group 4 is separated from the next group 4 by a separation line along the printed circuit of the strip 200, which allows the strip 200 to be cut without adversely affecting the electrical function of the module 1.

[0095] According to one embodiment, the strip 200 is provided with an adhesive 14, for example in the form of a double-sided adhesive tape, which is applied to the battery 3 side of the strip 200 so as to facilitate bonding of the module 1 to corresponding sheets, for example sheets 101 and 106.

[0096] The adhesive 14 is transparent to allow optical coupling between the photovoltaic device and the material of the sheet.

[0097] The edges 102,107 may advantageously be coated with a reflective material 108 to minimize light loss resulting from the use of the adhesive 14 used to adhere the photovoltaic cells 3 to the sheets 101,106.

[0098] The described solution offers important advantages especially in the production of luminescent solar concentrators.

[0099] The strip 200 with the batteries 3 and tracks 5, 6, 8 and 9 may be formed in indefinite lengths and packaged, for example, in a practical roll.

[0100] Depending on the dimensions of the sheet to which the module 1 is to be applied, it is possible to cut pieces 20 of the strip 200 at the pad 12 and / or at the dashed line 13 to the appropriate length.

[0101] The conversion circuit 7 is then soldered to the strip 20, in particular to the tracks 5, 6, 8 and 9.

[0102] The module 1 thus obtained may be attached to the corresponding edge of the sheet, for example by means of an adhesive 14 .

[0103] In effect, the conversion circuit converts the direct current supplied by each of the groups into a direct current of a larger voltage, independent of the length of the module 1 .

[0104] The conversion circuit makes the output voltage of the luminescent solar concentrator constant regardless of the size of the luminescent sheet.

[0105] Generally, once the photovoltaic module is attached to the sheet, the assembly may undergo other processes, such as sealing with silicone and / or encapsulation of the edges of a dedicated profile, or other processes not important here, with the aim of producing a luminescent solar concentrator.

[0106] The proposed solution makes it possible to create flexible photovoltaic receivers of any length with a constant voltage output suitable for optical coupling to solar concentrators of various sizes.

[0107] The lack of connecting elements makes the strip very thin and flexible, which makes it possible to supply it in the form of long reels which can be cut according to requirements.

[0108] In general, LSC devices offer a number of important advantages over conventional concentrating planar photovoltaic systems. The main advantages are: a) A significant reduction in the amount of semiconductor material used. b) Collection of the direct and diffuse components of solar radiation, which are converted with identical efficiency regardless of the arrangement of the panels, resulting in the possibility of use both on facades directly exposed to the sun and on facades exposed only to the diffuse component, regardless of the inclination of the capture surface. c) Good heat dissipation due to the large area of ​​the collector panel placed in contact with the external environment, which makes it possible to work the photovoltaic devices bonded to the edges of the sheet under reduced temperature conditions (indeed, the effectiveness of commercial semiconductors decreases with increasing temperature), giving them a high conversion efficiency. d) The absence of a solar tracking system, i.e. this feature which makes LSC photovoltaic panels unique compared to conventional CPV panels, on the one hand significantly improves the architectural integration of the device and on the other hand significantly reduces costs, weight and maintenance activities. e) The possibility of identifying dyes that allow a good overlap between the emission spectrum of the dye itself and the spectral response curve of the photovoltaic cell, which makes it possible to operate the cell with maximum conversion efficiency and with minimal heating and damage to the cell.

Claims

1. A flexible composite strip with a flexible printed circuit (2), said flexible printed circuit (2) comprising at least first and second conductor tracks (5, 6); The composite strip comprises a group (4) of photovoltaic cells (3), the plurality of groups (4) are connected in parallel to the first and second tracks (5, 6) for supplying power to the first and second tracks (5, 6) and are arranged consecutively along the flexible printed circuit (2); Each group (4) of photovoltaic cells (3) comprises a plurality of photovoltaic cells (3) connected in series; the composite strip comprises a plurality of soldering pads (12) at which the first and second conductor tracks (5, 6) are accessible, Each soldering pad (12) is disposed along said flexible printed circuit (2) between first and second groups (4) of consecutive photovoltaic cells (3); The flexible composite strip is configured to be cut at the soldering pads (12).

2. 2. The flexible composite strip according to claim 1, comprising a third conductor track (8) and a fourth conductor track (9) which are not electrically connected to the first and second conductor tracks (5, 6).

3. 3. The flexible composite strip according to claim 1 or 2, wherein the sealing pads (12) are provided with graphical indications (13), such as dashed lines, for identifying corresponding cutting lines with respect to the electrical connections of the photovoltaic cells (3) and the electrical connections of the groups (4) of the plurality of photovoltaic cells (3).

4. 3. The flexible composite strip according to claim 1 or 2, further comprising an adhesive (14), for example an adhesive (14) in the form of a double-sided adhesive tape, applied to the flexible printed circuit (2) above the photovoltaic cells (3) in order to bond the flexible composite strip to the edges (102, 107) of the corresponding luminescent sheets (101, 106).

5. 5. The flexible composite strip of claim 4, wherein the adhesive (14) is transparent.

6. A flexible composite strip according to claim 1 or 2, wherein the dimensions of the photovoltaic cells (3) are less than or equal to 20x20 mm, preferably less than or equal to 10x10 mm.

7. 3. A flexible composite strip according to claim 1 or 2, wherein the length of said group (4) of photovoltaic cells, measured along said flexible printed circuit (2), is not more than 10 cm, preferably not more than 5 cm.

8. 3. The flexible composite strip according to claim 1 or 2, comprising at least one electronic component for protecting the photovoltaic cells (3), the electronic protection component being mounted on the flexible printed circuit on the opposite side of the photovoltaic cells (3) relative to the flexible printed circuit.

9. 3. The flexible composite strip according to claim 1 or 2, wherein the thickness of the flexible printed circuit (2) is between 0.2 and 2 mm.

10. A photovoltaic module comprising a piece (20) of the flexible composite strip (200) according to claim 1 or 2 and at least one conversion circuit (7) soldered to said piece (20), The conversion circuit (7) has inputs connected to the first and second tracks (5, 6) and an output at a predetermined voltage; The conversion circuit (7) is configured to convert the voltage of the input to the predetermined output voltage, The predetermined output voltage is an output voltage of the solar power generation module.

11. 11. The photovoltaic module of claim 10, wherein the flexible composite strip (200) comprises a third conductor track (8) and a fourth conductor track (9) that are not electrically connected to the first and second conductor tracks (5, 6), and the output of a predetermined voltage is connected to the third and fourth tracks (8, 9).

12. 11. A photovoltaic module according to claim 10, wherein the conversion circuit (7) is soldered to the strip (20) at a first soldering pad (12) at one end of the strip (20).

13. 11. The photovoltaic module according to claim 10, wherein the conversion circuit (7) is formed on a second flexible printed circuit.

14. 11. The photovoltaic module according to claim 10, wherein the conversion circuit (7) is configured to modify the operating point of the photovoltaic cells (3) present on the strip (20) to optimize the electrical efficiency of the photovoltaic module.

15. A kit for manufacturing at least one photovoltaic module (1) according to claim 10, comprising: A flexible composite strip (200) according to claim 1 or 2; and at least one conversion circuit (7) solderable to said flexible composite strip (200) or to a piece (20) of said flexible composite strip (200), the conversion circuit (7) has inputs connectable to the first and second tracks (5, 6) and an output at a predetermined voltage; The conversion circuit (7) is configured to convert the voltage of the input to the predetermined output voltage, The predetermined output voltage is the output voltage of the solar power generation module (1).

16. the flexible composite strip (200) comprises a third conductor track (8) and a fourth conductor track (9) which are not electrically connected to the first and second conductor tracks (5, 6); 16. A kit according to claim 15, wherein the outputs of the converter circuit (7) at predetermined voltages are connectable to the third and fourth tracks (8, 9).

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