A bifacial photovoltaic panel

Abstract

According to the invention, a bifacial photovoltaic panel, wherein the panel is mounted in slats, characterised in that a gap (4) is maintained between the outermost photovoltaic cells (2) of the panel (3) and the slats (1), in an area where the panel (3) is transparent, and below the panel (3) the slat (1) comprises a vertical body (1.2), from the lower part of which, on the side of the panel (3), a base wall (1.1) of rough surface extends at a distance of 1 to 2 times greater than the width of the gap (4) located above it, said base wall being parallel to the panel (3).

Description

[0001] Title

[0002] A biFacial photovoltaic panel.

[0003] Technical Field

[0004] The subject oF the invention is a biFacial photovoltaic panel. The disclosed solution relates to the structure oF a photovoltaic panel having two active sides that absorb light, mounted in slats enabling installation on supporting structures.

[0005] Background

[0006] Numerous studies have shown that under standard conditions, a panel with unrestricted light access — excluding shading caused by the panel itselF — placed in a position analogous to that oF a photovoltaic panel mounted on supporting structures, can achieve rear-side module output reaching up to 40% oF the Front side output, assuming a ground reFlectance coeFFicient oF 90%. Due to the high energy potential, there is a current trend towards maximising the use oF the rear side oF the panel by designing supporting structures that minimise rear-side shading. Since the presence oF shading structures cannot be entirely excluded For obvious reasons, solutions have been sought in which the arrangement oF photovoltaic cells relative to the supporting structure reduces the number oF shaded cells. This is particularly important For photovoltaic panels, as limited light access to a single cell aFFects the perFormance oF a larger group oF cells due to their serial connection.

[0007] From the state oF the art, a solution is known From patent application US2021359149, which optimises the arrangement oF photovoltaic cells in relation to the supporting structure by spacing apart the cells along the centreline oF the panel, beneath which runs a support beam oF the structure. The area oF the panel most shaded by the support beam contains no cells. Moreover, the created space is transparent — it transmits light rays that reach the top surFace oF the panel, and these rays are partially reflected by the support beam and redirected to the underside of the cells adjacent to the spaced area. As a result of this measure, the effect of the supporting structure limiting the access of reflected rays to the underside of the panel is minimised, while at the same time the shading elements of the supporting structure are utilised to illuminate the shaded cells with direct light rays reaching the upper surface of the panel.

[0008] Another solution disclosed in patent application PL441815, similarly to the one described above, addresses the problem of shading of central cells by the support beam. Moreover, based on a similar principle, it claims a bifacial panel construction in which the cells are offset from the outer edge by at least 2 cm. Offsetting the cells from the external edges of the panel creates space for mounting the panel frame. Commonly used panel frames are made from profiles that enclose the edge of the panel by up to 10 mm in width and extend approximately 2 cm below the panel. Offsetting the outer cells from the panel edge addresses the critical problem of direct shading of photovoltaic cells by the frame. Figure 2 shows a situation where the lower cell has its access to light partially or completely blocked by the frame. It also solves a frequently occurring problem shown in Figure 1 , where a photovoltaic cell, despite not being directly covered by the frame in the lower part, remains heavily enclosed by the frame, which results in a decrease in the performance of the lower side of the panel.

[0009] A solution known from patent application US2019319579 also involves the use of highly smooth reflective surfaces, which are positioned at various angles around the structure to illuminate the most shaded areas of the photovoltaic panel. These surfaces, described as strips or plates of polished aluminium, according to the proposed solutions, can be placed, among other locations, directly on the underside of the photovoltaic panel, between the frame and the outer cell, as shown in Figure 3 of the drawing. The purpose of this solution is to illuminate the external, lateral part of the edge cells.

[0010] Solutions known from the prior art mitigate the problem of direct shading of edge cells caused by the frame; however, the existing frame still limits access of reflected light to these cells, which continues to result in lower input power of the panel. The attempt to illuminate the edge cells using the method described in patent application US2019319579 (Figure 3) is not capable of addressing the above- mentioned issue. A light ray falling on the reflective element is largely reflected and directed mostly upwards, outside the panel. Illumination of the lateral surface affects at most 5% of the ray, which becomes scattered. Moreover, increasing the panel area in order to create a zone shaded by the frame beyond the active surface of the panel reduces access of reflected light to its central part, once again contributing to a decrease in panel power output.

[0011] Summary

[0012] The objective of the present solution is to develop a panel structure that contributes to improved uniform illumination of the surface of photovoltaic cells by illuminating with reflected light the areas of the panel that have so far been most shaded.

[0013] According to the invention, the bifacial photovoltaic panel mounted in slats is characterised in that a gap is maintained between the outermost photovoltaic cells of the panel and the slats, in an area where the panel is transparent. Below the panel, the slat comprises a vertical body, from the lower part of which — on the side of the panel — a base wall with a rough surface extends at a distance of 1 to 2 times greater than the width of the gap located above it, said base wall being parallel to the panel. The transparent area allows light rays to pass through to the inner side of the slat. The rays entering and directed onto the slat are reflected, so that a significant portion of the rays is redirected toward the outer photovoltaic cells. These cells remain the least illuminated area of the panel on its underside due to the slat itself limiting access to diffused light. The rough surface, which is of key importance, scatters the rays that reach it through the gap during reflection, thereby ensuring uniform illumination of the underside of the panel.

[0014] In a preferred embodiment of the invention, the gap has a width in the range from 2 to 20 millimetres. A gap within this range is optimal in terms of the resulting shading and the direction of reflected light by the slat itself. Preferably, the surface of the base wall on the side of the panel has an albedo value exceeding 80%. Such a value is achievable while maintaining a rough surface for slats made of aluminium.

[0015] Particularly preferably, the slat has an albedo value exceeding 80%. This effect can be achieved by applying reflective agents on the surface of the slat, e.g., white reflective paints.

[0016] In the most preferred embodiment of the invention, the inner surface of the slat is covered with a reflective coating. This coating may be formed by reflective paints and sprays whose albedo exceeds 90%.

[0017] In a preferred embodiment of the invention, the body of the slat is between 1 5 and 30 millimetres in height.

[0018] Most preferably, the upper surface of the base wall has a wavy structure oriented along the length of the slat. The wavy structure causes dispersion of the light rays either toward the nearest photovoltaic cells of the panel or toward the inner wall of the slat, from which the rays are reflected back onto the cells. As a result of using such a reflective surface structure, the majority of the rays are directed onto the shaded cells.

[0019] Preferably, the panel is mounted in two slats along two opposite edges, wherein the slat comprises a longitudinal channel matched to the thickness of the panel, and the side edge of the panel is glued into this channel.

[0020] Preferably, the panel is mounted in four slats forming a frame surrounding the panel, wherein on the lateral edges of the panel there are C-slats comprising C- shaped sockets matched to the thickness of the panel and enclosing the panel, and on the upper and lower edges of the panel there are L-slats comprising L-shaped sockets supporting the panel. Brief Description of the Drawings

[0021] The subject of the solution has been illustra ted by examples which do not Umi t its scope, as presented in the drawings:

[0022] • Fig. 1 - prior art-cross-section of the edge ofa panel mounted in a C-shaped profile.

[0023] • Fig. 2 - prior art - cross-section of the edge of a panel mounted in an L- shaped profile.

[0024] • Fig. 3 - prior art

[0025] • Fig. 4 - propagation of a light beam in the area of the edge connection of a panel mounted in a C-shaped profile.

[0026] • Fig. 5 - propagation of a light beam in the area of the edge connection of a panel mounted in a C-shaped profile with a wavy structure.

[0027] • Fig. 6 - propagation of a light beam in the area of the edge connection of a panel mounted in an L-shaped profile with a wavy structure.

[0028] • Fig. 7 - bifacial photovoltaic panel mounted in two slats.

[0029] • Fig. 8 - bifacial photovoltaic panel mounted in four slats forming a frame.

[0030] • Fig. 9 - brackets connecting slats into a frame.

[0031] Detailed Description

[0032] Figures 1 and 2 present solutions known from the prior art. In Figure 1 , the panel is placed in a slat. The photovoltaic cell 2 of the panel 3 is aligned with the channel of the slat 1 enclosing the panel 3, leaving no space for sunlight to pass through. In Figure 2, the panel 3 rests on the slat 1 ; direct sunlight falling on the panel 3 is limited by the non-transparent layer of the slat 1 and does not pass through the panel 3 to its underside.

[0033] Figure 4 of the drawing discloses a solution involving a bifacial photovoltaic panel 3, where the panel 3 is mounted in slats 1. A gap 4 with a width of 6 millimetres is maintained between the outermost photovoltaic cells 2 of the panel 3 and the slats 1 , in an area where the panel 3 is transparent. The profile of slat 1 has, in its lower part, a base wall 1.1 extending from the body 1 .2 of the profile by 20 millimetres on the side of the panel 3. The body 1.2 has a height of 20 mi Hi me tres. The surface of the stat 1 on the side facing the panel 3 is rough. The slat 1 is made of an atuminium attoy, and its atbedo exceeds 60%. Alternatively, the inner surface of the stat 1 may be coated with a reflective agent, for exampte, a white reflective paint providing an atbedo of 90%.

[0034] Figure 5 presents an embodiment of the bifaciat photovottaic panet 3, in which the upper surface of the base watt 1.1 has a wavy structure oriented atong the Length of the stat 1 . The base watt 1.1 has an atbedo of approximateLy 85% due to surface polishing treatments. In this way, a Light beam fatting on the base watt 1.1 becomes dispersed within the ptane of the profile.

[0035] Figure 6 illustrates an example of a slat 1 containing an L-shaped socket 1.3L supporting the panel 3. A gap 4 with a width of 3 millimetres is maintained between the outermost photovoltaic cells 2 of the panel 3 and the slats 1 , in an area where the panel 3 is transparent. The profile of the slat 1 includes, in its lower part, a base wall 1.1 extending from the body 1 .2 of the profile by 3 millimetres on the side of the panel 3. The body 1.2 has a height of 20 millimetres.

[0036] In all the above-described cases, the proportion of the length of the base wall 1.1 to the gap 4 and the height of the slat body 1.2 may vary. The dimensional examples given above should be treated as optimal for use in the panels 3 shown in Figures 7, 8, and 9.

[0037] Figure 7 presents a panel 3 mounted in two slats 1 along two opposite edges. The slats 1 comprise a longitudinal channel 1.3 matched to the thickness of the panel 3, and the side edge 3.1 of the panel 3 is joined to the channel 1.3 with an adhesive agent, for example, mounting silicone.

[0038] Figure 8 shows a panel 3 mounted in four slats 1 forming a frame 5 surrounding the panel 3, connected by means of a bracket 5 as presented in Figure 9. On the lateral edges of the panel 3 there are C-slats 1 C comprising C-shaped sockets 1 ,3C matched to the thickness of the panel 3 and enclosing the panel 3. On the upper and lower edges of the panel 3 there are L-slats 1 L comprising L-shaped sockets 1 ,3L supporting the panel 3. The side edges 3.1 of the panel 3 are joined to the slats using adhesive agents.

Claims

Claims1. A biFacial photovoltaic panel, wherein the panel is mounted in slats, characterised in that a gap (4) is maintained between the outermost photovoltaic cells (2) oF the panel (3) and the slats (1 ), in an area where the panel (3) is transparent, and below the panel (3) the slat (1 ) comprises a vertical body (1 .2), From the lower part oF which, on the side oF the panel (3), a base wall (1 .1 ) oF rough surFace extends at a distance oF 1 to 2 times greater than the width oF the gap (4) located above it, said base wall being parallel to the panel (3).

2. The panel according to claim 1 , wherein the gap (4) has a width in the range From 2 to 20 millimetres.

3. The panel according to claim 1 or 2, wherein the surFace oF the base wall (1.1 ) on the side oF the panel (3) has an albedo value exceeding 80%.

4. The panel according to claim 1 , 2 or 3, wherein the inner surFace oF the slat (1 ) is covered with a reFlective coating.

5. The panel according to claim 1 , 2, 3 or 4, wherein the body (1.2) oF the slat (1 ) measures From 1 5 to 30 millimetres in height.

6. The panel according to claim 1 , 2, 3, 4 or 5, wherein the upper surFace oF the base wall (1.1 ) has a wavy structure oriented along the length oF the slat (1 ).

7. The panel according to claim 1 , 2, 3, 4, 5 or 6, wherein the panel (3) is mounted in two slats (1 ) along two opposite edges, wherein each slat (1 ) comprises a longitudinal channel (1.3) matched to the thickness oF the panel (3), and the side edge (3.1 ) oF the panel (3) is glued into said channel (1.3).

8. The panel according to claim 1 , 2, 3, 4, 5, 6 or 7, wherein it is mounted in Four slats (1 ) Forming a Frame (5) surrounding the panel (3), wherein on the lateral edges oF the panel (3) there are C-slats (1 C) comprising C-shaped sockets (1 ,3C) matched to the thickness oF the panel (3) and enclosing the panel (3), and on the upper and lower edges oF the panel (3) there are L-slats (1 L) comprising L-shaped sockets (1 .3 L) supporting the panel (3).

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