Lifetime power generation panels

Abstract

To provide a solar power generation panel that can reduce thermal stress in solar power generation elements. [Solution] The solar power generation panel 1 includes a stress relaxation layer 6 provided near the solar power generation element 2 to relieve thermal stress on the solar power generation element 2. The stress relaxation layer 6 has a thin plate-shaped main body member 61 with a plurality of through-holes 63 having a predetermined pattern, and a strip-shaped connecting member 62 that is larger than the thermal expansion coefficient of the main body member 61 and is provided on some of the plurality of 63, and crosses the through-holes 63 to connect the main body member 61 that is separated by the through-holes 63. The stress relaxation layer 6 is configured to contract overall when heated by utilizing the difference in the amount of thermal expansion of the main body member 61 and the connecting member 62, and to expand overall when cooled by utilizing the difference in the amount of thermal contraction of the main body member 61 and the connecting member 62.

Description

Technical Field

[0001] The present invention relates to a photovoltaic panel.

Background Art

[0002] Conventionally, as such a technical field, for example, there is what is described in Patent Document 1. The photovoltaic panel described in Patent Document 1 includes a front protection substrate, a sealing layer that seals the photovoltaic element, at least one reinforcing layer located between the front protection substrate and the sealing layer, and a back protection substrate. The front protection substrate, the reinforcing layer, the sealing layer, and the back protection substrate are each formed of different types of materials and are fixed to each other in a laminated state along the light incident direction.

Prior Art Documents

Patent Documents

[0003] <​​​​​​​​​​​​​However, in photovoltaic panels, which are multilayer laminates of dissimilar materials, when the temperature rises or falls due to changes in sunlight or ambient temperature, thermal stress is generated in each of the dissimilar materials, causing damage to the photovoltaic panel. More specifically, the surface protective substrate, reinforcing layer, sealing layer, and back protective substrate each have their own elastic modulus and thermal expansion coefficient, so when a temperature difference occurs due to a rise or fall in temperature, free expansion and contraction occur according to their respective thermal expansion coefficients. However, since the boundaries between adjacent layers (for example, the boundary between an adjacent sealing layer and the back protective substrate) are fixed, the free expansion and contraction of each layer is hindered by the adjacent layer, resulting in different axial forces being generated in each layer. As a result, this leads to damage to the photovoltaic panel. This problem is particularly pronounced when using single-crystal silicon photovoltaic elements. This is because single-crystal silicon photovoltaic elements have a larger elastic modulus and a smaller thermal expansion coefficient compared to other layers, resulting in greater thermal stress.

[0005] This invention was made to solve these technical problems, and aims to provide a photovoltaic panel that can reduce thermal stress in photovoltaic elements. [Means for solving the problem]

[0006] The photovoltaic power generation panel according to the present invention comprises a photovoltaic element, a stress-relieving layer provided near the photovoltaic element to relieve thermal stress on the photovoltaic element, and a sealing layer that seals the photovoltaic element and the stress-relieving layer. The stress-relieving layer comprises a thin plate-shaped main body member having a plurality of perforations having a predetermined pattern, and a strip-shaped connecting member that is larger than the thermal expansion coefficient of the main body member and is provided at some of the plurality of perforations to connect the main body members separated by the perforations and crosses the perforations. The stress-relieving layer is configured to contract overall when heated by utilizing the difference in the amount of thermal expansion of the main body member and the connecting member, and to expand overall when cooled by utilizing the difference in the amount of thermal contraction of the main body member and the connecting member. When the thickness of the main body member is ta, the elastic modulus of the main body member is Ea, the thickness of the connecting member is tb, and the elastic modulus of the connecting member is Eb, the main body member and the connecting member satisfy the relationship 0.1 < (Eb × tb) / (Ea × ta) < 1.0.

[0007] In the photovoltaic power generation panel according to the present invention, the stress relaxation layer has a main body member and a connecting member whose thermal expansion coefficient is greater than that of the main body member. It is configured to contract overall when heated by utilizing the difference in the amount of thermal expansion between the main body member and the connecting member, and to expand overall when cooled by utilizing the difference in the amount of thermal contraction between the main body member and the connecting member. In this way, the stress relaxation layer contracts in response to the expansion of the photovoltaic power generation element when heated, and expands in response to the contraction of the photovoltaic power generation element when cooled, thereby relieving the thermal stress of the photovoltaic power generation element. In other words, in the photovoltaic power generation panel according to the present invention, thermal stress of the photovoltaic power generation element can be relieved by using a stress relaxation layer that undergoes deformation different from the expansion and contraction of the photovoltaic power generation element in response to temperature changes.

[0008] In addition, the main body member and the connecting member satisfy the relationship 0.1 < (Eb × tb) / (Ea × ta) < 1.0. Therefore, by adjusting the material and thickness of the main body member and the connecting member to satisfy this relationship, it becomes possible to control the thermal expansion coefficient of the entire stress relaxation layer (in other words, the apparent thermal expansion coefficient of the stress relaxation layer). As a result, the thermal stress of the photovoltaic element can be appropriately relieved, thereby reducing the thermal stress of the photovoltaic element.

[0009] In the photovoltaic power generation panel according to the present invention, the connecting member comprises a first connecting member and a second connecting member, and it is preferable that the first connecting member and the second connecting member are provided in different through-ports of the main body member so as to be substantially perpendicular to each other in the in-plane direction. In this way, the apparent thermal expansion coefficient of the stress relaxation layer can be made isotropic.

[0010] In the photovoltaic power generation panel according to the present invention, it is preferable that the first connecting member and the second connecting member are made of the same material. This ensures that the apparent thermal expansion coefficient of the stress relaxation layer is reliably isotropic.

[0011] In the photovoltaic power generation panel according to the present invention, it is preferable that the first connecting member and the second connecting member are made of different materials. This makes it possible to introduce anisotropy to the apparent thermal expansion coefficient of the stress relaxation layer. [Effects of the Invention]

[0012] According to the present invention, thermal stress in photovoltaic power generation elements can be reduced. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view showing a solar power generation panel according to an embodiment. [Figure 2] This is a schematic plan view showing the stress relaxation layer. [Figure 3]This is a schematic plan view illustrating the deformation of the stress relaxation layer during heating. [Figure 4] This is an enlarged view of portion A in Figure 3. [Figure 5] This figure shows the thermal stress distribution of the example (invention). [Figure 6] (a) is a schematic cross-sectional view showing a photovoltaic panel relating to a comparative example (conventional product), and (b) is a diagram showing the thermal stress distribution of the comparative example (conventional product). [Modes for carrying out the invention]

[0014] Hereinafter, embodiments of the photovoltaic power generation panel according to the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. In addition, in the following description, unless otherwise specified, "side surface" refers to the end surface along the direction of light incidence (in other words, the end surface parallel to the direction of light incidence) assuming that sunlight is incident perpendicularly on the photovoltaic power generation panel, and "thickness" refers to the distance along the direction of light incidence.

[0015] Figure 1 is a schematic cross-sectional view showing a photovoltaic power generation panel according to an embodiment. As shown in Figure 1, the photovoltaic power generation panel 1 of this embodiment is flat and comprises a photovoltaic element 2, a sealing layer 3 that seals the photovoltaic element 2, a surface protection layer 4 disposed on the light incidence side relative to the sealing layer 3, a back surface protection layer 5 disposed on the side opposite to the light incidence side relative to the sealing layer 3, and a thin plate-shaped stress relaxation layer 6 disposed below the photovoltaic element 2 in the light incidence direction and sealed together with the photovoltaic element 2 in the sealing layer 3. The surface protection layer 4, the sealing layer 3 in which the photovoltaic element 2 and the stress relaxation layer 6 are disposed, and the back surface protection layer 5 are sequentially laminated along one direction (in this case, the direction of sunlight incidence).

[0016] The solar power generation element 2 is not particularly limited, and may be a crystalline silicon-based solar power generation element or a perovskite-type solar power generation element. In this embodiment, the solar power generation element 2 is a single crystal silicon-based one. This solar power generation element 2 may be one or a plurality of electrically connected ones.

[0017] The encapsulation layer 3 serves to prevent the deterioration of the solar power generation element 2 due to moisture or the like and protect the solar power generation element 2 from impact, and is provided so as to surround the entire solar power generation element 2. This encapsulation layer 3 is formed in a flat plate shape by a resin material having transparency to transmit sunlight (for example, a light transmittance of 90% or more) and chemical stability. Examples of such a resin material include EVA (ethylene vinyl acetate copolymer resin), polyolefin, PVB (polyvinyl butyral), and the like.

[0018] The front surface protection layer 4 is a member that protects the front surface side of the solar power generation element 2 and has a flat plate shape. The front surface protection layer 4 is formed of a material that has, for example, barrier properties and scratch resistance against water and gas and is transparent to transmit sunlight (for example, a light transmittance of 90% or more). For this front surface protection layer 4, a glass plate, polycarbonate, polyethylene terephthalate, polyamide, polyimide, a resin sheet such as polytetrafluoroethylene, or the like can be used.

[0019] The back surface protection layer 5, also referred to as a support layer, is a member that protects the back surface side of the solar power generation element 2 and has a flat plate shape. The back surface protection layer 5 may be a material having barrier properties and scratch resistance against water and gas, and is formed of a transparent or non-transparent material. For this back surface protection layer 5, a glass plate, polycarbonate, polyethylene terephthalate, polyamide, polyimide, a resin sheet such as polytetrafluoroethylene, a metal plate, or the like can be used. Note that the back surface protection layer 5 is preferably formed of a material that reflects light in order to increase the amount of light incident on the solar power generation element 2.

[0020] The stress relaxation layer 6 is provided in the vicinity of the photovoltaic element 2 and is a layer that relaxes the thermal stress of the photovoltaic element 2. This stress relaxation layer 6 has a main body member 61 and a connecting member 62 having a coefficient of thermal expansion larger than that of the main body member 61. The stress relaxation layer 6 is configured to contract as a whole by utilizing the difference in the amount of thermal expansion of the main body member 61 and the connecting member 62 during heating, and to expand as a whole by utilizing the difference in the amount of thermal contraction of the main body member 61 and the connecting member 62 during cooling. Hereinafter, the stress relaxation layer 6 will be described in detail based on FIGS. 2 to 4.

[0021] FIG. 2 is a schematic plan view showing the stress relaxation layer. The stress relaxation layer 6 of the present embodiment has substantially the same structure as a thin panel that autonomously undergoes out-of-plane deformation (see Japanese Patent No. 7074092) invented by the inventor of the present application.

[0022] As shown in FIG. 2, the stress relaxation layer 6 has a unit structure 60 having a structure in which a part is partially hollowed out in a symmetric figure such as a square, and a main body member 61 formed by regularly arranging and connecting a plurality of the unit structures 60 in the diagonal direction or the plane direction, and a connecting member 62 disposed in a part of the hollowed-out region so as to expand and contract a part thereof. In the main body member 61, the material exists only in the region indicated by the hatching, and the material is removed (hollowed out) in the region indicated by the plain surface. The portion where the material is removed constitutes the through-hole 63. As shown in FIG. 2, there are a plurality of through-holes 63, which have a predetermined pattern and are regularly arranged around a first square region 611 (described later) that forms a symmetric figure.

[0023] In other words, as described in Japanese Patent Publication No. 7074092 (for example, paragraphs 0012, 0023 and Figure 2), the main body member 61 has material in the entirety of the first square (first square region 611 in Figure 2) and in a band-shaped region (leg-shaped region 612 in Figure 2) along the sides of the second squares, which are inside the third squares formed by the diagonals and extensions of the second squares that do not overlap the first square, with the material in the entire first square (first square region 611 in Figure 2) and in the areas other than these, the material is removed in a shape (penetration portion 63 in Figure 2), and a plurality of these unit structures 60 are connected in the planar direction. Furthermore, a strip-shaped connecting member 62 that can expand and contract in the diagonal direction is positioned at the diagonal of the second square on the side of the third square.

[0024] As shown in Figure 2, the unit structure 60 is formed by arranging multiple segments along a predetermined direction, each segment having a first square region 611 positioned in the center and two leg-shaped regions 612 projecting outward from each side of the first square region 611. The leg-shaped regions 612 of segments adjacent to each other diagonally in the direction of the first square region 611 are connected in such a way that their cross-section is "V" shaped. Both the first square region 611 and the leg-shaped regions 612 exist in the in-plane direction of the main body member 61. Furthermore, the area of ​​the first square region 611 is larger than the area of ​​the leg-shaped regions 612.

[0025] The main body member 61 having the above structure is formed from any elastic material that has rigidity to maintain the planar structure and is bendable in the out-of-plane direction. For example, the main body member 61 is formed from an inorganic material such as CFRP (Carbon Fiber Reinforced Plastics), GFRP (Glass Fiber Reinforced Plastics), or glass. Preferably, the main body member 61 has a thermal expansion coefficient of 10 × 10-6 (K) It is formed from the following materials. More preferably, the main body member 61 is made of carbon fiber reinforced epoxy resin (CFRP) or single crystal silicon with a thermal expansion coefficient of 0 to 3 × 10 -6 It is made of material (K).

[0026] The thickness of the main body member 61 is 0.5 mm or less. Furthermore, as shown in Figure 2, the stress relaxation layer 6 has a peripheral edge 64 surrounding the main body member 61 and the connecting member 62. The peripheral edge 64 is formed from, for example, the same material as the main body member 61.

[0027] The connecting member 62 is provided in accordance with a predetermined rule to connect the main body members 61 that are separated by the through-holes 63 in a portion of the multiple through-holes 63. More specifically, the connecting member 62 is positioned across the through-holes 63 to connect the leg-shaped regions 612 that are separated by the through-holes 63 and face each other.

[0028] The connecting member 62 is made of a material with a thermal expansion coefficient greater than that of the main body member 61. This connecting member 62 is made of a resin material such as polyolefin resin, polyurethane, polyethylene, or polyester, and has a thermal expansion coefficient of 100 × 10⁻⁶ -6 It is preferable that it be formed from a resin material of (K) or higher. Furthermore, the connecting member 62 is formed to be thicker than the main body member 61.

[0029] In this embodiment, the connecting member 62 further comprises a first connecting member 621 and a second connecting member 622. The first connecting member 621 and the second connecting member 622 are provided in different through-holes 63 such that they are substantially perpendicular to each other in the in-plane direction of the main body member 61. Here, "subtly perpendicular" means that the first connecting member 621 and the second connecting member 622 are at an angle of 85° to 95°.

[0030] More specifically, for example, if the vertical direction is defined as the up-down direction and the horizontal direction as the left-right direction on the plane of the paper in Figure 2, the first connecting member 621 is positioned within the through-holes 63 on both the left and right sides of the first square region 611 so as to extend along the vertical direction. On the other hand, the second connecting member 622 is positioned within the through-holes 63 on both the top and bottom sides of the first square region 611 so as to extend along the horizontal direction. The first connecting member 621 is connected and fixed to the main body member 61 by adhesive bonding of both of its vertical ends to the connection points of adjacent leg-shaped regions 612. As described above, since the leg-shaped regions 612 of adjacent segments are connected in a "V" shape in cross-section, the first connecting member 621 is connected to the leg-shaped region 612 by adhesive bonding with both of its vertical ends abutting against the inside of the vertices of the "V" shape.

[0031] On the other hand, the second connecting member 622 is connected and fixed to the main body member 61 by bonding its upper lateral ends to the connection points of adjacent leg-shaped regions 612. Since the leg-shaped regions 612 of adjacent segments are connected in a "V" shape in cross-section, the second connecting member 622 is connected to the leg-shaped regions 612 by bonding with its upper lateral ends abutting against the inside of the vertices of the "V" shape.

[0032] The stress relaxation layer 6, constructed as described above, deforms when heated, for example, as shown in Figures 3 and 4. In Figures 3 and 4, the dashed line shows the stress relaxation layer 6 before deformation, and the solid line shows the stress relaxation layer 6 after deformation.

[0033] When the stress relaxation layer 6 is heated, the main body member 61 and the connecting members 62 (first connecting member 621 and second connecting member 622) expand according to their respective coefficients of thermal expansion as the temperature rises. At this time, the connecting members 62 have a larger coefficient of thermal expansion than the main body member 61 and are formed to be thicker than the main body member 61, so the amount of expansion of the connecting members 62 is greater than the amount of expansion of the main body member 61. As a result, the main body member 61 is pressed down by the connecting members 62.

[0034] Specifically, as shown in Figure 4, upon heating, the first square region 611 and the leg-shaped region 612, as well as the first connecting member 621 and the second connecting member 622, expand according to their respective coefficients of thermal expansion. The first connecting member 621, which is positioned within the through-hole 63 surrounding the first square region 611 and extends vertically, expands along the vertical direction. Since its vertical expansion is greater than that of the first square region 611 and the leg-shaped region 612, it pushes its end and the fixed leg-shaped regions 612 apart vertically. Consequently, the through-hole 63 in which the first connecting member 621 is positioned expands vertically.

[0035] At this time, as shown in Figure 4, near the peripheral edge 64 of the stress relaxation layer 6, the expansion of the penetration portion 63 is inhibited by the peripheral edge 64. Therefore, the expansion of the penetration portion 63 toward the peripheral edge 64 is relatively small, while the expansion toward the opposite side of the peripheral edge 64 is relatively large. In the interior of the stress relaxation layer 6, away from the peripheral edge 64, there is no inhibition by the peripheral edge 64, so the penetration portion 63 expands almost evenly on both sides in the vertical direction.

[0036] Similarly, the second connecting member 622, which is positioned within the through-hole 63 surrounding the first square region 611 and extends laterally, expands laterally. Since its laterally expanding amount is greater than the expansion amounts of the first square region 611 and the leg-shaped region 612, it pushes its end and the fixed leg-shaped regions 612 apart laterally. Consequently, the through-hole 63 in which the second connecting member 622 is positioned expands laterally.

[0037] As a result of being expanded vertically by the first connecting member 621 and horizontally by the second connecting member 622, the first square region 611 shrinks. Therefore, the stress relaxation layer 6 undergoes apparent contraction. In other words, when heated, the stress relaxation layer 6 can achieve overall contraction of the stress relaxation layer 6 by utilizing the difference in thermal expansion between the main body member 61 and the connecting member 62.

[0038] On the other hand, when the stress relaxation layer 6 is cooled, the main body member 61 and the connecting members 62 (first connecting member 621 and second connecting member 622) contract according to their respective coefficients of thermal expansion as the temperature decreases. However, since the amount of contraction of the connecting members 62 is greater than that of the main body member 61, the stress relaxation layer 6 will appear to expand. In other words, when cooled, the stress relaxation layer 6 can achieve overall expansion of the stress relaxation layer 6 by utilizing the difference in the amount of thermal contraction of the main body member 61 and the connecting members 62.

[0039] Furthermore, in this embodiment, when the thickness of the main body member 61 is ta, the elastic modulus of the main body member 61 is Ea, the thickness of the connecting member 62 is tb, and the elastic modulus of the connecting member 62 is Eb, the main body member 61 and the connecting member 62 are configured to satisfy the relationship 0.1 < (Eb × tb) / (Ea × ta) < 1.0.

[0040] Therefore, for example, using the main body member 61 as a reference (i.e., using the elastic modulus Ea and thickness ta of the main body member 61 as a reference), it becomes possible to set the thickness of the connecting member 62 according to the elastic modulus Eb of the connecting member 62 based on the above-mentioned relational expression. In this embodiment, the elastic modulus of the connecting member 62 is smaller than that of the main body member 61, and the thickness is larger than that of the main body member 61.

[0041] The condition 0.1 < (Eb × tb) / (Ea × ta) < 1.0 is determined based on the analysis results and practicality of the stress relaxation layer 6. In other words, since the elastic modulus of the connecting member 62 is set to be smaller than that of the main member 61, if (Eb × tb) / (Ea × ta) is 0.1 or less, the thickness of the connecting member 62 becomes thinner. In that case, the amount of expansion of the connecting member 62 cannot counteract the rigidity of the main member 61, leading to the problem that the overall contraction of the stress relaxation layer 6 cannot be achieved.

[0042] On the other hand, when (Eb×tb) / (Ea×ta) is 1.0 or greater, the connecting member 62 becomes relatively thick, and the unevenness caused by the relatively thin main body member 61 becomes more pronounced. To eliminate this unevenness, one could consider increasing the thickness of the sealing layer 3 that seals the stress relaxation layer 6. However, this not only increases the amount of sealant used in the sealing layer 3, but also creates a new problem: the entire solar power generation panel 1 becomes thicker.

[0043] To avoid the above problems, the range of (Eb×tb) / (Ea×ta) was defined as described above.

[0044] In the photovoltaic power generation panel 1 according to this embodiment, the stress relaxation layer 6 has a main body member 61 and a connecting member 62 whose thermal expansion coefficient is greater than that of the main body member 61. The stress relaxation layer 6 is configured to contract overall when heated by utilizing the difference in the amount of thermal expansion of the main body member 61 and the connecting member 62, and to expand overall when cooled by utilizing the difference in the amount of thermal contraction of the main body member 61 and the connecting member 62. In this way, the stress relaxation layer 6 contracts in response to the expansion of the photovoltaic power generation element 2 when heated, and expands in response to the contraction of the photovoltaic power generation element 2 when cooled, thereby easing the thermal stress of the photovoltaic power generation element. In other words, in the photovoltaic power generation panel 1 of this embodiment, by using a stress relaxation layer 6 that behaves differently (more specifically, deforms differently) from the expansion and contraction of the photovoltaic power generation element 2 in response to temperature changes, it is possible to achieve thermal stress relief of the photovoltaic power generation element 2.

[0045] Generally, when a temperature difference occurs in a solar power generation panel, different axial forces are generated in each layer that makes up the panel. However, since the boundaries between adjacent layers are fixed, no slippage occurs between layers. Therefore, the axial forces of each layer are balanced as a whole (i.e., the sum of the individual axial forces is zero). In particular, adjacent layers exhibit a strong balancing effect between different axial forces. Furthermore, solar power generation elements with a relatively large elastic modulus and a relatively small coefficient of thermal expansion experience large axial forces as a proportional burden, resulting in high thermal stress.

[0046] In this embodiment, a stress relaxation layer 6 capable of controlling the apparent coefficient of thermal expansion is provided near the photovoltaic element 2. By utilizing this stress relaxation layer 6, an axial force opposite to the axial force acting on the photovoltaic element 2 is generated, thereby maintaining equilibrium with the axial force of the photovoltaic element 2 while bearing a proportionate share of its axial force. As a result, the axial force of the photovoltaic element 2 can be reduced.

[0047] Furthermore, in the photovoltaic power generation panel 1 of this embodiment, the main body member 61 and the connecting member 62 satisfy the relationship 0.1 < (Eb × tb) / (Ea × ta) < 1.0. Therefore, by adjusting the material and thickness of the main body member 61 and the connecting member 62 so as to satisfy this relationship, it becomes possible to control the apparent thermal expansion coefficient of the stress relaxation layer 6. Consequently, the thermal stress of the photovoltaic power generation element 2 can be appropriately relaxed, thereby reducing the thermal stress of the photovoltaic power generation element 2.

[0048] Furthermore, the connecting member 62 has a first connecting member 621 and a second connecting member 622, and the first connecting member 621 and the second connecting member 622 are provided in different penetration portions 63 such that they are substantially perpendicular to each other in the in-plane direction of the main body member 61, so that the apparent thermal expansion coefficient of the stress relaxation layer 6 can be made isotropic.

[0049] The first connecting member 621 and the second connecting member 622 may be formed from the same material or from different materials. When the first connecting member 621 and the second connecting member 622 are formed from the same material, the apparent thermal expansion coefficient of the stress relaxation layer 6 can be reliably made isotropic. On the other hand, when the first connecting member 621 and the second connecting member 622 are formed from different materials, the apparent thermal expansion coefficient of the stress relaxation layer 6 can be made anisotropic. For example, if it is desired to ensure a large amount of thermal expansion in a specific direction (for example, the vertical or horizontal direction mentioned above), the first connecting member 621 and the second connecting member 622 can be made from different materials.

[0050] In this embodiment, an example was described in which the stress relaxation layer 6 is placed below the photovoltaic element 2. However, the stress relaxation layer 6 does not necessarily have to be placed below the photovoltaic element 2. If it is made of a material with excellent light transmission properties, it may be placed above the photovoltaic element 2. Furthermore, one stress relaxation layer 6 may be placed above and one below the photovoltaic element 2.

[0051] The present invention will be described below with reference to examples, but the present invention is not limited to the scope of these examples.

[0052] [Examples] In the embodiment, the photovoltaic power generation panel 1 (inventive product) described in the above embodiment was manufactured. In this case, polycarbonate was used for both the surface protective layer 4 and the back protective layer 5, ethylene vinyl acetate copolymer resin was used for the sealing layer 3, and single crystal silicon was used for the photovoltaic power generation element 2. Furthermore, CFRP (0.1 mm thick) with a carbon fiber plain weave as the reinforcing base material and epoxy as the matrix resin was used for the main body member 61 of the stress relaxation layer 6. For the first connecting member 621 and the second connecting member, epoxy resin veneer with a thickness of 2 mm was used for both.

[0053] The elastic modulus, thermal expansion coefficient, and thickness of each layer of the materials used are summarized in Table 1 below. In Table 1, the first, second, and third sealing layers are all the sealing layer 3 described above, but the first sealing layer is the portion between the surface protection layer 4 and the photovoltaic element 2 of the sealing layer 3, the second sealing layer is the portion between the photovoltaic element 2 and the stress relaxation layer 6, and the third sealing layer is the portion between the stress relaxation layer 6 and the back surface protection layer 5.

[0054] Then, the thermal stress of the fabricated invention was calculated when it was heated from room temperature of 25°C to 90°C. The thermal stress distribution of each layer was calculated using multilayer beam theory. In multilayer beam theory, the axial force, bending moment, and radius of curvature of each layer were unknown variables, and the calculation was performed based on the boundary condition that no slip occurs at the joint surfaces of each layer, as well as the condition that the sum of the axial forces and the sum of the moments are both 0 (i.e., in equilibrium).

[0055] Furthermore, the apparent modulus of elasticity and apparent coefficient of thermal expansion in stress relaxation layer 6 were calculated from the average value of the displacement obtained by FEM analysis. As shown in Table 1, the apparent coefficient of thermal expansion of stress relaxation layer 6 was negative.

[0056] [Table 1]

[0057] The thermal stress distribution of each layer of the photovoltaic panel according to the example is shown in Figure 5.

[0058] [Comparative Example] As a comparative example, a conventional photovoltaic panel (conventional product) without a stress relaxation layer was also fabricated. As shown in Figure 6(a), the conventional photovoltaic panel 1A comprises a photovoltaic element 2, a sealing layer 3 that seals the photovoltaic element 2, a surface protection layer 4 positioned on the light incidence side relative to the sealing layer 3, and a back surface protection layer 5 positioned on the side opposite to the light incidence side relative to the sealing layer 3. In other words, the conventional photovoltaic panel 1A differs from the photovoltaic panel 1 according to the embodiment in that it does not have a stress relaxation layer, but other structures are the same as those of the photovoltaic panel 1.

[0059] Furthermore, the materials used in each layer of conventional photovoltaic panels were the same as those in the invention described in the examples. In addition, the elastic modulus and thermal expansion coefficient of each material were the same as those in the invention described in the examples (see Table 1). Also, as shown in Figure 5 and Figure 6(b) described later, the total thickness of the invention and the conventional product were the same, and the thickness of the surface protective layer, photovoltaic element, and back protective layer were also the same.

[0060] In the comparative example, the thermal stress distribution of each layer was calculated for a conventional product having the structure described above, using the same conditions and methods as the inventive product. The results are shown in Figure 6(b).

[0061] In Figures 5 and 6(b), the horizontal axis represents thermal stress σ (unit: MPa), and the vertical axis represents the thickness h of each layer (unit: mm). The number "0" on the vertical axis is based on the top surface of solar power generation panel 1,1A, i.e., the top surface of surface protective layer 4.

[0062] As can be seen by comparing Figure 5 and Figure 6(b), the thermal stress of the photovoltaic element in the conventional product was approximately 90 MPa, while the thermal stress of the photovoltaic element in the invention was approximately 60 MPa. Therefore, the photovoltaic panel of the present invention demonstrates the effect of reducing the thermal stress of the photovoltaic element by providing a stress relaxation layer.

[0063] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various design modifications can be made without departing from the spirit of the invention as described in the claims. [Explanation of Symbols]

[0064] 1: Photovoltaic panel, 2: Photovoltaic element, 3: Sealing layer, 4: Surface protection layer, 5: Back surface protection layer, 6: Stress relaxation layer, 60: Unit structure, 61: Main body component, 62: Connecting component, 63: Through-hole, 611: First square region, 612: Leg-shaped region, 621: First connecting component, 622: Second connecting component

Claims

1. Photovoltaic power generation element, A stress relaxation layer provided near the photovoltaic element to relieve thermal stress on the photovoltaic element, A sealing layer that seals the photovoltaic element and the stress relaxation layer, Equipped with, The stress-relieving layer comprises a thin plate-shaped main body member having a plurality of perforations having a predetermined pattern, and a strip-shaped connecting member that is larger than the thermal expansion coefficient of the main body member and is provided in some of the plurality of perforations, connecting the main body members separated by the perforations and traversing the perforations. The stress-relieving layer is configured to contract overall when heated by utilizing the difference in the amount of thermal expansion of the main body member and the connecting member, and to expand overall when cooled by utilizing the difference in the amount of thermal contraction of the main body member and the connecting member. A solar power generation panel characterized in that, when the thickness of the main body member is ta, the elastic modulus of the main body member is Ea, the thickness of the connecting member is tb, and the elastic modulus of the connecting member is Eb, the main body member and the connecting member satisfy the relationship 0.1 < (Eb × tb) / (Ea × ta) < 1.

0.

2. The connecting member comprises a first connecting member and a second connecting member. The photovoltaic panel according to claim 1, wherein the first connecting member and the second connecting member are provided in different through-ports of the main body member so as to be substantially perpendicular to each other in the in-plane direction.

3. The photovoltaic power generation panel according to claim 2, wherein the first connecting member and the second connecting member are formed of the same material.

4. The photovoltaic panel according to claim 2, wherein the first connecting member and the second connecting member are formed of different materials.

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