Photovoltaic module comprising photovoltaic cells cooled by a dielectric fluid

Abstract

The photovoltaic module (1) comprises a hermetically sealed enclosure (2) defining an internal volume, a plurality of photovoltaic cells (4), which are adjacent to one another and electrically connected to one another, lying in said internal volume. The photovoltaic module further comprises at least one device (22) for making a dielectric fluid flow through the internal volume of the enclosure (2), the dielectric fluid flowing through the internal volume in such a way as to flow along at least part of each photovoltaic cell (4).

Description

[0001] DESCRIPTION

[0002] TITLE: Photovoltaic module comprising photovoltaic cells cooled by a dielectric fluid

[0003] The present invention relates to a photovoltaic module of the type comprising a hermetically sealed enclosure defining an internal volume, a plurality of photovoltaic cells, adjacent to each other and electrically connected to each other, extending in said internal volume.

[0004] The invention also relates to a method for cooling such a photovoltaic module.

[0005] In order to optimize the energy production of such a photovoltaic module, it is necessary to limit the temperature rise of the photovoltaic cells because the efficiency decreases proportionally to the heating of the photovoltaic cells. For this purpose, it is known to equip a photovoltaic module with a heat exchanger, for example on the back of the photovoltaic module, to create a heat exchange between the photovoltaic module and a coolant circulating in the heat exchanger located on the back of the photovoltaic module and thus cool the photovoltaic cells in the enclosure of the photovoltaic module.

[0006] However, such an arrangement is not optimal in terms of cell cooling. In addition, it increases the size of the photovoltaic module along the direction of its thickness, which limits the installation possibilities of the photovoltaic module.

[0007] To improve the efficiency of a photovoltaic module, it has been proposed, for example in document WO 2021 / 239286, to cool the photovoltaic cells using a dielectric fluid. However, the dielectric fluid is also arranged in a housing extending over the rear face of the photovoltaic module, which also poses a problem of space requirement for the photovoltaic module. In addition, only the rear face of each photovoltaic cell is cooled, which is not optimal in terms of efficiency.

[0008] One of the aims of the invention is to overcome these drawbacks by proposing an efficiently cooled photovoltaic module with reduced bulk.

[0009] To this end, the invention relates to a photovoltaic module of the aforementioned type, further comprising at least one device for circulating a dielectric fluid in the internal volume of the enclosure, said dielectric fluid circulating in the internal volume to flow along at least a portion of each photovoltaic cell. The dielectric fluid used to cool the photovoltaic cells being in direct contact with them, the cooling of the photovoltaic cells is optimized, which makes it possible to improve the energy efficiency of the photovoltaic module. Furthermore, since the dielectric fluid circulates directly in the enclosure of the photovoltaic module, the size of the photovoltaic module, in particular depending on its thickness, is reduced because it is not necessary to add elements on one of the faces of the photovoltaic module.

[0010] The photovoltaic module according to the invention may further comprise one or more of the following characteristics, taken in isolation or in any technically conceivable combination: the dielectric fluid flows over at least a portion of a conductive zone of each photovoltaic cell; the device for circulating the dielectric fluid comprises at least one inlet placing the internal volume of the enclosure in fluid communication with a source of dielectric fluid and at least one outlet placing said internal volume in fluid communication with a device for recovering the dielectric fluid, said dielectric fluid flowing in the internal volume from the inlet to the outlet, passing along at least a portion of each photovoltaic cell;the recovery device is in fluid communication with the source of dielectric fluid, the circulation device further comprising a device for cooling the dielectric fluid circulating between the recovery device and the source of dielectric fluid; the enclosure comprises two glasses which are substantially parallel and spaced apart from each other in a thickness direction, the photovoltaic cells extending substantially parallel and between said glasses in the thickness direction, a space extending between the photovoltaic cells and at least one of said glasses, the dielectric fluid flowing in said space along at least one of the faces of the photovoltaic cells;each photovoltaic cell is fixed to at least one of the glasses by at least one spacer element, said spacer element being arranged to maintain a space in the thickness direction between each photovoltaic cell and the glass to which said photovoltaic cell is fixed by said spacer element; a space extends between the photovoltaic cells and each of the two glasses, the dielectric fluid flowing in the two spaces along two opposite faces of the photovoltaic cells; the adjacent photovoltaic cells are spaced apart from each other in a longitudinal direction and / or a transverse direction, substantially perpendicular to the thickness direction, the dielectric fluid flowing between the photovoltaic cells in said longitudinal direction and / or said transverse direction;the enclosure comprises a frame comprising a plurality of branches surrounding the glasses and the photovoltaic cells and closing the internal volume in longitudinal and transverse directions perpendicular to the thickness direction, said internal volume extending between the glasses and the branches of the frame; the photovoltaic cells are electrically connected two by two by at least one conductive strip extending on one face of one of the photovoltaic cells and on the opposite face of the other of the photovoltaic cells; the dielectric fluid is an electrically insulating dielectric liquid having a resistivity greater than 1000 Q m at a temperature between 20°C and 130°C.;

[0011] According to another aspect, the invention also relates to a method for cooling a photovoltaic module as described above, comprising a step of circulating a dielectric fluid in the internal volume of the enclosure of the photovoltaic module when said photovoltaic module is active, said dielectric fluid circulating in said internal volume along at least a portion of each voltaic cell.

[0012] Other aspects and advantages of the invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0013] [Fig. 1] - Fig. 1 is a schematic representation from above of a photovoltaic module according to the invention,

[0014] [Fig. 2] - Fig. 2 is a schematic representation of the photovoltaic module of Fig. 1 in section along the axis ll-ll of Fig. 1, and

[0015] [Fig. 3] - Fig. 3 is a schematic cross-sectional representation of part of the photovoltaic module showing in particular a photovoltaic cell.

[0016] With reference to Figs. 1 and 2, a photovoltaic module 1 is described comprising an enclosure 2 receiving a plurality of photovoltaic cells 4. Such a photovoltaic module 1 is also known as a “solar panel”.

[0017] The enclosure 2 is hermetically sealed and defines an internal volume in which the photovoltaic cells 4 extend. More particularly, the enclosure 2 comprises two glasses 6 spaced apart from each other in a thickness direction E of the photovoltaic module 1, the internal volume extending between the two glasses 6 in the thickness direction E. One of the glasses 6 forms one of the faces of the photovoltaic module intended to be exposed to light radiation, for example solar radiation, to transmit this radiation to the photovoltaic cells 4 extending opposite the glass 6 and facing it. By "facing it", it is meant that the photovoltaic cells 4 are arranged in the enclosure 2 so that the face of these cells intended to be exposed to light radiation to transform it into electricity is facing the glass 6.According to one embodiment, the two glasses 6 form faces intended to be exposed to light radiation for corresponding photovoltaic cells 4 facing each of the glasses 6. A photovoltaic module according to such an embodiment is known as a bifacial photovoltaic module.

[0018] The glasses 6 are kept apart from each other by a frame 8 comprising a plurality of branches 10, 12 surrounding the glasses 6 and the photovoltaic cells 4 and closing the internal volume in longitudinal directions L and transverse T perpendicular to the thickness direction E. For a photovoltaic module 1 having a rectangular shape as shown in Fig. 1, the longitudinal direction L corresponds for example to the length of the photovoltaic module 1 and the transverse direction T corresponds for example to the width of the photovoltaic module 1.Thus, for a rectangular photovoltaic module, the frame 8 comprises two longitudinal branches 10, extending in the longitudinal direction and spaced apart from each other in the transverse direction T to extend on either side of the glasses 6, and two transverse branches 12, extending in the transverse direction T and spaced apart from each other in the longitudinal direction L to extend on either side of the glasses 6. Thus, the internal volume of the enclosure 2 is hermetically closed by the glasses 6 on the one hand and by the branches 10, 12 of the frame 8 on the other hand. For this purpose, the branches 10, 12 are for example provided with a seal 15 ensuring the hermetic closure of the internal volume of the enclosure 2 between the frame 8 and the glasses 6, as shown in Fig. 2.

[0019] As indicated previously, the photovoltaic cells 4 are arranged in the internal volume of the enclosure 2 so that their face intended to be exposed to light radiation is turned towards one of the glasses 6. The photovoltaic cells 4 thus extend parallel to the glasses 6. As indicated previously, the invention also applies to bifacial photovoltaic modules.

[0020] Furthermore, according to one embodiment, the photovoltaic cells 4 are spaced apart along the thickness direction E of at least one of the glasses 6, so that a space 14 extends along the thickness direction E between one face of the photovoltaic cells 4 and the face of one of the glasses 6 facing the internal volume of the enclosure, as more particularly visible in Figs. 2 and 3. According to an embodiment not shown, the photovoltaic cells 4 extend over the other glass 6, for example by being glued to it or by being fixed to it by a substrate. Preferably, however, and as shown in Figs. 2 and 3, the photovoltaic cells 4 are spaced apart from the two glasses 6 along the thickness direction E so that a space 14 extends on either side of the photovoltaic cells 4 along the thickness direction E.To maintain this space 14, each photovoltaic cell 4 is fixed to the corresponding glass 6 by at least one spacer element 16 extending between the face of the photovoltaic cell 4 spaced apart from the glass 6 and the face of the glass 6 facing the internal volume, as shown in Fig. 3. When the photovoltaic cell 4 is spaced apart from the two glasses 6, spacer elements 16 are provided between each face of the photovoltaic cell and the corresponding glass 6. The spacer element 16 is for example formed by a point of glue and / or an element made of polymer material making it possible to fix and immobilize the photovoltaic cell 4 relative to the glass 6 to which the photovoltaic cell 4 is fixed. According to one embodiment, each photovoltaic cell 4 is fixed to a glass 6 by several spacer elements 16 spaced apart from each other in the longitudinal direction L and / or in the transverse direction T.

[0021] According to one embodiment, the adjacent photovoltaic cells 4 are spaced apart from each other in the longitudinal direction L and / or in the transverse direction T so that the enclosure 2 comprises channels 18 extending in the longitudinal direction L and / or in the transverse direction T, each channel 18 extending from one branch of the frame 8 to the opposite branch between two rows of adjacent photovoltaic cells 4.

[0022] The photovoltaic cells 4 are electrically connected to each other, two by two, by at least one conductive strip 20 extending on one face of one of the photovoltaic cells 4 and on the opposite face of the other of the photovoltaic cells 4, as more particularly visible in Fig. 2. Such conductive strips 20, or conductive ribbons, make it possible to connect the photovoltaic cells in series together to conduct the electricity generated by the exposure of the photovoltaic cells 4 to light radiation to an output terminal (not shown) of the photovoltaic module 1. As shown in Fig. 3, the spacer elements 16 are for example interposed between each conductive strip 20 and the glass 6 opposite which the conductive strip 20 extends.Interposing the spacer elements 16 between each conductive strip 20 and the glass 6 makes it possible to position these spacer elements at a location where they have no impact on the efficiency of the photovoltaic cells 4. Indeed, these spacer elements 16 do not extend directly over a portion of the photovoltaic cells 4 exposed to the light radiation but rather over a portion already covered by another element, namely the conductive strip 20. Thus, the spacer elements 16 make it possible to maintain the space between the photovoltaic cells 4 and the glass 6 of the enclosure without reducing the energy efficiency of the photovoltaic module.

[0023] In order to cool the photovoltaic cells 4 extending in the enclosure 2, the photovoltaic module 1 according to the invention further comprises at least one device 22 for circulating a dielectric fluid in the internal volume of the enclosure 2. The circulation device 22 is more particularly arranged so that the dielectric fluid flows in the enclosure 2 along at least a portion of each photovoltaic cell 4 in order to cool each photovoltaic cell 4 of the photovoltaic module 1, as will be described in more detail later. By "along at least a portion of each photovoltaic cell 4", it is meant that the dielectric fluid flows over at least a portion of a conductive zone of each photovoltaic cell 4, that is to say that the dielectric fluid is directly in contact with an active portion of each photovoltaic cell 4.In other words, the photovoltaic module 1 is devoid of encapsulation of the photovoltaic cells 4 isolating them from the dielectric fluid circulating in the internal volume of the enclosure 2 so that the cooling of the photovoltaic cells 4 by the dielectric fluid is particularly effective. Such cooling makes it possible to improve the efficiency of the photovoltaic cells 4 in terms of power produced, as will be described in more detail later. In addition, the absence of encapsulation of the photovoltaic cells 4 makes recycling of the photovoltaic module easier and more efficient since it is not necessary to separate the photovoltaic cells from a material encapsulating them during recycling. Thus, when the photovoltaic module is disassembled, the dielectric fluid and the photovoltaic cells 4 can be recovered directly for recycling purposes.

[0024] The dielectric fluid is a fluid arranged to promote heat exchanges between the photovoltaic cells 4 and the dielectric fluid so that the heat generated by the photovoltaic cells 4 is transmitted to the dielectric fluid to be evacuated from the photovoltaic cells 4 and cool them. For this purpose, the dielectric fluid is for example an electrically insulating dielectric liquid having a resistivity greater than 1000 μm at a temperature between 20°C and 130°C. More particularly, the dielectric liquid has for example a resistivity substantially between 20,000 μm to 5000 μm at a temperature between 20°C and 130°C. According to other parameters of the dielectric liquid, it has for example at least one of the following characteristics: a kinematic viscosity less than or equal to 25 mm 2 / s at 40°C, for example less than 10 mm 2 / s at 40°C; a thermal conductivity substantially between 105 mW / mk and 180 mW / mk at 25°C; a thermal capacity substantially between 1500 J / gK and 3000 J / gK, for example close to 2000 J / gK; a density substantially between 700 kg / m 3 and 1100 kg / m 3 at 25°C; and a transmittance greater than 70%, preferably greater than 90%.

[0025] The dielectric fluid is a water-based or oil-based liquid. When the dielectric fluid is water-based, the water is, for example, deionized and / or demineralized, comprising, for example, a compound of the alkylene glycol derivative type, which may have a thickening and / or antifreeze function. When the dielectric fluid is oil-based, the oil comprises one or more of the following compounds, considered alone or in combination: paraffin oil (n- or iso-paraffins) containing hydrocarbons and / or naphthenes, aromatic molecules, ester, polyalkylene glycol, estolide esters, silicones. These oils may comprise additives such as antioxidants, corrosion inhibitors, antifoaming agents, demulsifying agents, pour point depressants or other. The dielectric fluid may be bio-sourced or biodegradable.

[0026] The circulation device 22 comprises at least one inlet 24 placing the internal volume of the enclosure 2 and a source of dielectric fluid 26 in fluid communication. Thus, the inlet 24 makes it possible to inject and circulate the dielectric fluid from the source of dielectric fluid 26 in the internal volume of the enclosure 2 so that the dielectric fluid flows along at least a portion of each voltaic cell 4 present in the enclosure 2. The fluid communication between the source of dielectric fluid 26 and the internal volume of the enclosure 2 is sealed and can, for example, be authorized or prevented by means of a valve (not shown). The inlet 24 is located in one of the branches 10, 12 of the frame 8, for example in a transverse branch 12 according to the embodiment shown in Fig. 1.According to one embodiment, several inlets 24 in fluid communication with the source of dielectric fluid 26 are distributed along a branch 10, 12 of the frame 8 so that the dielectric fluid enters the internal volume of the enclosure 2 along the entire branch 10, 12 comprising the inlets 24. Alternatively, a single inlet 24 is provided in one of the branches of the frame 8. The temperature of the dielectric fluid at the inlet 24 of the circulation device 22 is arranged so that the dielectric fluid cools the photovoltaic cells 4 when the dielectric fluid is in direct contact with these photovoltaic cells. The temperature of the dielectric fluid at the inlet 24 of the circulation device 22 is thus, for example, between 5°C and 40°C.The circulation device 22 further comprises at least one outlet 28 placing the internal volume of the enclosure 2 in fluid communication with a device 30 for recovering the dielectric fluid. Thus, the outlet 28 makes it possible to evacuate the dielectric fluid from the internal volume of the enclosure 2 after it has cooled the photovoltaic cells 4 by having circulated throughout the enclosure 2. The fluid communication between the internal volume of the enclosure 2 and the recovery device 30 is sealed and can, for example, be authorized or prevented by means of a valve (not shown). In order to ensure that the dielectric fluid has circulated throughout the internal volume of the enclosure before being evacuated therefrom, the outlet 28 is for example arranged in the branch of the frame 8 opposite that receiving the inlet(s) 24. Thus, according to the embodiment of FIG.1, the outlet extends in the transverse branch 12 opposite the transverse branch receiving the inlet 24 and the dielectric fluid flows into the enclosure in the longitudinal direction L. A single outlet 28 is for example provided at one end of the branch so that the dielectric fluid is forced to fill the internal volume of the enclosure 2 before reaching the outlet 28. Alternatively, several outlets 28 may be provided in one of the branches of the frame 8. The temperature of the dielectric fluid at the outlet 28 is higher than the temperature of the dielectric fluid at the inlet 24 because the dielectric fluid has been heated in contact with the photovoltaic cells 4. Thus the temperature at the outlet 28 is for example between 40°C and 90°C while being higher than the temperature of the dielectric fluid at the inlet 24.

[0027] In the enclosure, the dielectric fluid circulates in the spaces around the photovoltaic cells 4 and flows along at least a portion of each photovoltaic cell 4 directly in contact therewith in order to create a heat exchange between each photovoltaic cell 4 and the dielectric fluid and cool the photovoltaic cells 4. Thus, the dielectric fluid flows at least in one space 14 extending between the photovoltaic cells 4 and one of the glasses 6 in the thickness direction E, preferably in the two spaces 14 extending on either side of the photovoltaic cells 4 so that the photovoltaic cells are completely immersed in the dielectric fluid.If necessary, the dielectric fluid also flows in the channels 18 between the photovoltaic cells 4 so as to flow on the sides of the photovoltaic cells 4 and increase the contact surface between each photovoltaic cell 4 and the dielectric fluid. Thus, the circulation device 22 makes it possible to effectively cool the photovoltaic cells 4 and improve the energy efficiency of the photovoltaic module 1. This efficient cooling is made possible in particular by the direct contact between the photovoltaic cells 4 and the dielectric fluid and by the large contact surface between each photovoltaic cell 4 and the dielectric fluid. It has thus been observed that a non-encapsulated photovoltaic cell 4 completely immersed in a dielectric fluid produces a power of the order of 2.0 to 2.5 Watts, while a non-encapsulated but non-immersed cell and an encapsulated cell produce a power of the order of 1.8 to 2.0 Watts.

[0028] According to an embodiment shown in Fig. 1, the circulation device 22 is a closed circuit comprising a supply pipe 32 for the dielectric fluid to the inlet(s) 24 forming the dielectric fluid source 26 and a discharge pipe 34 for the dielectric fluid in fluid communication with the outlet 28 and forming the recovery device 30 for the dielectric fluid. The supply pipe 32 and the outlet pipe 34 are connected to a cooling device 36 for the dielectric fluid. The cooling device 36 is for example formed by a heat exchanger 36 in which the heated dielectric fluid from the discharge pipe 34 is cooled by heat exchange with a cooling fluid pipe 38, the cooled dielectric fluid then being injected into the supply pipe 32 for the dielectric fluid.A pump 40 makes it possible to circulate the dielectric fluid in the supply pipe 32, the enclosure 2 and the discharge pipe 34. Thus, the photovoltaic module 1 consumes little dielectric fluid, the heated dielectric fluid being reused to cool the photovoltaic cells 4 after passing through the heat exchanger 36.

[0029] The photovoltaic module 1 can also have a thermal function, by recovering the heat generated in particular by the photovoltaic cells. Such a photovoltaic module is known as a hybrid module.

[0030] It should be noted that several photovoltaic modules 4 can be connected together in series or in parallel to form a matrix of photovoltaic modules 1, making it possible to manage the temperature and the flow rate of the dielectric fluid according to the applications of the matrix. By connected, it is meant that the photovoltaic modules are electrically and fluidically connected to each other. Thus, according to one embodiment, a device for circulating a dielectric fluid can be provided to cool several photovoltaic modules in order to recover the heat generated in particular by the photovoltaic cells in order to confer a thermal function to the matrix of photovoltaic modules.

[0031] The photovoltaic module 1 described above has a high energy efficiency thanks to the efficient cooling of the photovoltaic cells 4. In addition, it has a reduced size, particularly in the thickness direction E, which facilitates its installation.

Claims

CLAIMS 1. Photovoltaic module (1) comprising a hermetically sealed enclosure (2) defining an internal volume, a plurality of photovoltaic cells (4), adjacent to each other and electrically connected to each other, extending in said internal volume, said photovoltaic module being characterized in that it further comprises at least one device (22) for circulating a dielectric fluid in the internal volume of the enclosure (2), said dielectric fluid circulating in the internal volume to flow along at least a portion of each photovoltaic cell (4).

2. Photovoltaic module according to claim 1, wherein the dielectric fluid flows over at least part of a conductive area of ​​each photovoltaic cell (4).

3. Photovoltaic module according to claim 1 or 2, in which the device (22) for circulating the dielectric fluid comprises at least one inlet (24) placing the internal volume of the enclosure in fluid communication with a source of dielectric fluid (26) and at least one outlet (28) placing said internal volume in fluid communication with a device (30) for recovering the dielectric fluid, said dielectric fluid flowing in the internal volume from the inlet (24) to the outlet (28) passing along at least a portion of each photovoltaic cell (4).

4. Photovoltaic module according to claim 3, in which the recovery device (30) is in fluid communication with the source of dielectric fluid (26), the circulation device (22) further comprising a cooling device (36) for the dielectric fluid circulating between the recovery device (30) and the source of dielectric fluid (26).

5. Photovoltaic module according to any one of claims 1 to 4, in which the enclosure (2) comprises two glasses (6) substantially parallel and spaced from each other in a thickness direction (E), the photovoltaic cells (4) extending substantially parallel and between said glasses (6) in the thickness direction (E), a space (14) extending between the photovoltaic cells (4) and at least one of said glasses (6), the dielectric fluid flowing in said space (14) along at least one of the faces of the photovoltaic cells (4).

6. Photovoltaic module according to claim 5, wherein each photovoltaic cell (4) is fixed to at least one of the glasses (6) by at least one spacer element (16), said spacer element (16) being arranged to maintain a space (14) in the thickness direction (E) between each photovoltaic cell (4) and the glass (6) to which said photovoltaic cell (4) is fixed by said spacer element (16).

7. Photovoltaic module according to claim 5 or 6, in which a space (14) extends between the photovoltaic cells (4) and each of the two glasses (6), the dielectric fluid flowing in the two spaces (14) along two opposite faces of the photovoltaic cells (4).

8. Photovoltaic module according to any one of claims 5 to 7, in which the adjacent photovoltaic cells (4) are spaced from each other in a longitudinal direction (L) and / or a transverse direction (T), substantially perpendicular to the thickness direction (E), the dielectric fluid circulating between the photovoltaic cells (4) in said longitudinal direction (L) and / or said transverse direction (T).

9. Photovoltaic module according to any one of claims 5 to 8, in which the enclosure (2) comprises a frame (8) comprising a plurality of branches (10, 12) surrounding the glasses (6) and the photovoltaic cells (4) and closing the internal volume in longitudinal (L) and transverse (T) directions perpendicular to the thickness direction (E), said internal volume extending between the glasses (6) and the branches (10, 12) of the frame (8).

10. Photovoltaic module according to any one of claims 1 to 9, in which the photovoltaic cells (4) are electrically connected two by two by at least one conductive strip (20) extending on one face of one of the photovoltaic cells (4) and on the opposite face of the other of the photovoltaic cells (4).

11. Photovoltaic module according to any one of claims 1 to 10, in which the dielectric fluid is an electrically insulating dielectric liquid having a resistivity greater than 1000 Q m at a temperature between 20°C and 130°C.

12. Method for cooling a photovoltaic module (1) according to any one of claims 1 to 11, comprising a step of circulating a dielectric fluid in the internal volume of the enclosure (2) of the photovoltaic module when said photovoltaic module is active, said dielectric fluid circulating in said internal volume along at least a part of each photovoltaic cell (4).

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