Heat dissipation structure of high-power photovoltaic module

Abstract

The invention discloses a heat dissipation structure of a high-power photovoltaic module. The heat dissipation structure is a heat management module mounted on the back of the photovoltaic module and comprises a sealed box body and a composite phase change material filled in the sealed box body. In order to perform differentiated management on uneven heat on the back of the assembly, the composite phase change material is divided into at least two areas: a first heat management area corresponding to a junction box serving as a core hot area and a second heat management area covering other conventional hot areas. The first thermal management area is filled with a first composite phase change material composed of gradient pore foam metal and a paraffin-based phase change material; the second thermal management area is filled with a second composite phase change material composed of expanded graphite and a paraffin-based phase change material. The box body part containing the first heat management area is of a surrounding structure to adapt to the protruding junction box, and cooling fins are arranged on the outer surface of the box body. According to the invention, high-efficiency passive thermal management is realized, the working temperature of the module can be obviously reduced, and the cost is controllable.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic thermal management technology, and more specifically, to a passive heat dissipation structure for high-power photovoltaic modules and a photovoltaic power generation device including the structure. Background Technology

[0002] In recent years, with the rapid development of high-efficiency cell technologies such as PERC, TOPCon, and HJT, the output power and conversion efficiency of photovoltaic modules have been greatly improved. However, the sharp increase in power density has also made the heat dissipation problem of the modules increasingly serious. When photovoltaic cells are working, only about 20-23% of solar energy is converted into electrical energy, while the majority of the rest is converted into heat energy, resulting in a significant increase in module temperature. According to the physical characteristics of photovoltaic cells, their output power has a negative temperature coefficient; for every 1°C increase in temperature, the power generation efficiency will decrease by about 0.3% to 0.5%. In summer or in areas with high radiation, the module operating temperature can easily exceed 80°C. This not only causes a 5%-15% loss in instantaneous power generation, but the long-term high-temperature stress also accelerates the aging of module encapsulation materials (such as EVA and backsheet), induces hot spot effects, and thus exacerbates the long-term power degradation (LID, PID) of the modules, seriously affecting the return on investment of photovoltaic power plants over their 25-year life cycle.

[0003] To address this issue, the industry has proposed various heat dissipation solutions, but all of them have significant drawbacks: 1. Traditional passive cooling solutions: The most common method is to add aluminum heat sink fins to the back panel of the module. Although this solution is simple in structure and low in cost, its heat dissipation efficiency is heavily dependent on the temperature difference (ΔT) between the module surface and the ambient air, as well as the air velocity (wind speed). In the sweltering heat of summer and windless weather when heat dissipation is most needed, the ambient temperature is already very high, resulting in a very small ΔT, weak air convection, and a sharp drop in heat dissipation capacity, which cannot meet the high heat flux density heat dissipation requirements of modern high-power modules.

[0004] 2. Active cooling solutions: such as forced air cooling (adding fans) or forced liquid cooling (adding water pumps and cooling circulation pipes). While these solutions offer significant cooling effects, they suffer from fundamental contradictions. First, they consume additional electrical energy (parasitic losses), reducing the net power generation of the photovoltaic power plant. Second, the introduction of moving parts such as fans and water pumps significantly increases system complexity, initial investment cost (CAPEX), and subsequent operation and maintenance cost (OPEX). Most importantly, the failure rate of mechanical components is far higher than that of the photovoltaic modules themselves, failing to meet the stringent requirements of large-scale photovoltaic power plants for 25 years of high reliability and maintenance-free operation, thus lacking practicality for large-scale promotion.

[0005] 3. Single Phase Change Material (PCM) Heat Dissipation Solution: Some research attempts to utilize the property of phase change materials (PCMs) to absorb a large amount of latent heat during phase change while maintaining a constant temperature for component temperature control. This approach is highly promising, but simple, pure phase change materials face three long-standing inherent contradictions in practical applications: (1) Poor thermal conductivity: The thermal conductivity of common paraffin-based and other organic PCMs is extremely low (about 0.2 W / m·K), which is similar to that of insulation materials. This means that heat cannot be quickly conducted from the back sheet of the module to the interior of the PCM, nor can it be quickly released from the interior of the PCM at night, so that the heat storage capacity of the PCM is far from being fully utilized.

[0006] (2) Dramatic volume change: PCM undergoes a volume change of about 10-15% during solid-liquid phase transition. The melting expansion during the day will generate huge stress on the package shell, which may cause cracking; the solidification and contraction at night will form air voids with extremely poor thermal conductivity between the PCM and the heat transfer interface, which will seriously degrade the heat transfer efficiency of the next working cycle.

[0007] (3) Poor stability and safety: During long-term hot and cold cycles, some PCMs may experience phase separation or performance degradation; at the same time, the risk of leakage in the liquid state also poses a threat to the long-term safety of the system.

[0008] In summary, existing technologies cannot perfectly balance the four core requirements of heat dissipation efficiency, passive reliability, total lifecycle cost, and long-term stability. Therefore, the industry urgently needs a new heat dissipation structure for high-power photovoltaic modules that can overcome all the aforementioned shortcomings. Summary of the Invention

[0009] The main objective of this invention is to address the shortcomings of existing heat dissipation solutions in the background art by providing a high-efficiency, passive, highly reliable, long-life, and cost-controllable heat dissipation structure for high-power photovoltaic modules. This structure aims to effectively suppress the peak temperature of photovoltaic modules during operation, reduce temperature fluctuations, thereby improving their power generation efficiency and delaying their long-term performance degradation.

[0010] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a heat dissipation structure for a high-power photovoltaic module, which is a thermal management module. The thermal management module is installed on the back of the photovoltaic module and includes a sealed box and a composite phase change material. The composite phase change material is filled in the box and includes a phase change material and a highly thermally conductive porous skeleton for supporting the phase change material and enhancing thermal conductivity.

[0011] Furthermore, in order to perform differentiated thermal management on the core hot zone and the conventional hot zone formed on the back of the photovoltaic module due to uneven heat distribution, the composite phase change material is divided into at least two regions within the housing, including a first thermal management region, the location of which corresponds to the junction box area of ​​the photovoltaic module, which is the core hot zone; and a second thermal management region, which covers the area other than the first thermal management region, which is the conventional hot zone.

[0012] Furthermore, the first thermal management area is filled with a first composite phase change material, and the highly thermally conductive porous skeleton of the first composite phase change material is foam metal.

[0013] Furthermore, the foam metal is a gradient porosity foam metal, whose pore density varies in a gradient along its thickness direction, with the pore density on the side closer to the photovoltaic module being higher than that on the side farther away from the photovoltaic module.

[0014] Furthermore, the second thermal management region is filled with a second composite phase change material, wherein the highly thermally conductive porous framework of the second composite phase change material is expanded graphite.

[0015] Furthermore, the phase change material is a paraffin-based phase change material.

[0016] Furthermore, the housing portion accommodating the first thermal management area has an enclosing structure, which is used to accommodate and surround the protruding photovoltaic module junction box during installation.

[0017] Furthermore, the outer surface of the box is provided with several heat dissipation fins for enhancing heat dissipation.

[0018] Furthermore, the box body is made of aluminum alloy and its outer surface has a fluorocarbon coating.

[0019] Furthermore, the edge of the housing is provided with mounting ears for fixing it to the photovoltaic module or its mounting bracket.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention employs a zoned design, enabling targeted thermal management based on the uneven heat distribution on the backsheet of photovoltaic modules. For the junction box area, which is the core hot zone, a high-performance first composite phase change material is configured; for the conventional hot zones, a cost-effective second composite phase change material is configured, thereby improving material utilization efficiency and optimizing the overall system cost.

[0021] 2. The gradient porosity foam metal used in this invention is designed to accommodate multiple functions: First, it achieves an optimal balance between performance, weight, and cost: its dense structure near the heat source ensures efficient heat absorption and conduction, while the sparse structure away from the heat source effectively reduces material usage and the overall weight of the module.

[0022] Secondly, this gradient structure cleverly solves the problem of volume expansion during the phase transition process. When the dense PCM region near the heat source melts and expands, its liquid phase can flow smoothly along the porous framework to the sparse region with larger pores, farther from the heat source. This sparse region acts like an internally integrated "expansion buffer cavity," effectively accommodating and mitigating expansion stress, further improving the long-term structural reliability of the module.

[0023] 3. By filling the phase change material into a highly thermally conductive porous framework, the thermally conductive network constructed by the framework improves the overall thermal conductivity of the composite material. At the same time, the "shape stability" effect of the framework inhibits the formation of macroscopic voids that affect heat transfer during the solidification and shrinkage of the phase change material, and reduces the risk of leakage in the liquid state, thereby improving the long-term heat transfer stability.

[0024] 4. The heat dissipation structure of this invention has no moving parts and requires no external energy supply during operation, achieving passive operation. This reduces system complexity and potential failure points, helping to improve operational stability throughout the 25-year lifespan of the photovoltaic power plant. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of a high-power photovoltaic module in the prior art; Figure 2 This is a schematic diagram of a photovoltaic module with a thermal management module installed on a support according to an embodiment of the present invention. Figure 3 This is a three-dimensional structural diagram of the thermal management module of the present invention (top view, showing the side that is attached to the photovoltaic panel); Figure 4 This is a three-dimensional structural diagram of the thermal management module of the present invention (viewed from below, showing the side with heat dissipation fins). Figure 5 This is a schematic diagram of the hollow shell of the thermal management module of the present invention, used to illustrate the cavity layout of the first thermal management area and the second thermal management area; Figure 6 For along Figure 5 The diagram shows the internal structure of the empty shell after it has been filled with the corresponding composite phase change material, illustrating the filling state and distribution of the first and second composite phase change materials. Figure 7 This is a schematic diagram of the microstructure of the first composite phase change material of the present invention, showing its gradient pore distribution.

[0026] The diagram includes the following components: 100. Photovoltaic module; 200. Junction box; 300. Mounting bracket; 400. Thermal management module; 401. First thermal management area; 4011. First composite phase change material; 402. Second thermal management area; 4021. Second composite phase change material; 403. Heat sink fins; 404. Mounting lugs. Detailed Implementation

[0027] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0028] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0030] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] This embodiment provides a heat dissipation structure for a high-power photovoltaic module, specifically a thermal management module 400. This thermal management module 400 is designed for integration with a high-power N-type TOPCon photovoltaic module 100 deployed on a large scale in the high-irradiance region of Northwest China. (Refer to...) Figure 1 and Figure 2The photovoltaic module 100 is supported by a mounting bracket 300. A single junction box 200 is located at the midpoint of the long side of its back, serving as the main concentrated heat source during module operation. The purpose of this invention is to address the issues of reduced power generation efficiency and long-term reliability caused by overheating in such modules under local conditions of high summer radiation, high ambient temperature, large diurnal temperature range, and sandstorms.

[0032] The main body of the thermal management module 400 is a flat, sealed box made of 6061-T6 aluminum alloy sheet of predetermined thickness through precision stamping and laser welding processes to ensure its structural strength and airtightness. To ensure the thermal management module 400 has a long outdoor service life matching that of the photovoltaic module 100, the outer surface of the box is coated with a sufficiently thick PVDF (fluorocarbon) coating to resist ultraviolet radiation, humidity corrosion, and wind and sand abrasion. On the outer surface of this box (such as...) Figure 4 As shown in the bottom view, the photovoltaic module 100 has several parallel heat dissipation fins 403 integrally formed. The principle of this structural design is to increase the contact area with ambient air and utilize the "chimney effect" generated when the photovoltaic module 100 is installed at an angle to enhance natural air convection, thereby increasing the rate at which the module releases heat at night or during periods of low irradiance. Several mounting ears 404 are also integrally stamped on the edge of the housing for fixing the thermal management module 400 to the frame of the photovoltaic module 100 or its mounting bracket 300.

[0033] Reference Figure 5 and Figure 6 The sealed enclosure of the thermal management module 400 is divided into two independent regions: a first thermal management region 401 and a second thermal management region 402. The core principle of this partitioned design lies in the precise matching of the asymmetric heat load on the backsheet of the photovoltaic module 100. This involves using different thermal management strategies to address the junction box 200 area as a "point / line heat source" and the conventional battery area as a "surface heat source," thereby achieving an optimal balance between performance and cost. The first thermal management region 401 is a roughly C-shaped open enclosure structure, positioned corresponding to the core heat zone formed by the junction box 200. Its opening provides necessary routing space for cables extending from the junction box 200. The second thermal management region 402 covers all other conventional heat zones except for the first region.

[0034] Both regions are filled with a paraffin-based phase change material with high latent heat value using a vacuum impregnation process. The phase change temperature of this material is set at a preset temperature point (e.g., between 55℃ and 65℃). The "peak shaving and valley filling" principle of the thermal management module 400 lies in the complete thermal cycle of its internal phase change material within a solar cycle. During the morning heating phase, as sunlight intensifies, the temperature of the photovoltaic module 100 begins to rise. The solid phase change material inside the module heats up synchronously with the module by absorbing sensible heat. At this time, the role of the highly thermally conductive porous framework is to ensure that heat can be quickly and evenly transferred to the entire bulk phase of the phase change material. When the midday irradiance is strongest, the phase change "peak shaving" phase begins. At this time, the temperature of the backsheet of the photovoltaic module 100 rises to the preset phase change temperature point, triggering the solid-liquid phase change (melting) process of the phase change material. During this stage, the massive excess heat generated by the modules due to sunlight is stored in large quantities by the phase change material through latent heat absorption. Physically, this manifests as an extremely gradual temperature rise rate in the entire thermal management module 400 before the phase change material completely melts, thus preventing the module temperature from continuing to spike into inefficient and high-risk ranges, achieving "peak shaving" of the temperature curve. Entering the evening and nighttime cooling phase, the "valley filling" energy release and heat regeneration stage begins. As the ambient temperature decreases, when the module temperature drops below the phase change temperature point, the liquid phase change material begins to solidify and release all its stored latent heat. At this time, the heat dissipation fins 403 on the module casing play a crucial role, efficiently dissipating this released heat into the surrounding environment. Because this heat is released during the "temperature trough" period when the photovoltaic modules have stopped or are operating inefficiently, it does not negatively impact power generation; hence the term "valley filling." This process continues until all phase change materials have completely solidified, fully preparing for the "peak shaving" work of the next solar cycle.

[0035] The first thermal management region 401 is filled with a first composite phase change material 4011, whose high thermal conductivity porous framework is gradient-porous aluminum foam. The technical principle lies in using a gradient structure to simultaneously solve the three major problems of thermal conductivity, cost, and volume expansion. (Refer to...) Figure 7The porosity of this gradient porous aluminum foam smoothly transitions from a lower value (dense structure) on the side in contact with the photovoltaic backsheet to a higher value (sparse structure) on the side away from the backsheet. The principle of the dense side is to maximize the density of the thermally conductive network to achieve instantaneous absorption and rapid conduction of high heat flux in the core hot zone; the principle of the sparse side is that, on the one hand, it reduces the amount of material used and the weight of the module, and on the other hand, it cleverly acts as an internally integrated "expansion buffer cavity" to dissipate the volume expansion stress generated when the phase change material melts. Filling the second thermal management region 402 is the second composite phase change material 4021, whose highly thermally conductive porous framework is expanded graphite. The technical principle is to utilize the excellent lateral thermal conductivity and cost advantages of expanded graphite to achieve economical and efficient thermal management in conventional areas with low heat load. The C-shaped enclosed structure of the first thermal management area 401 is designed based on the principle of "physical avoidance and maximizing effective contact". That is, it bypasses the plastic shell of the junction box 200, which is a physical obstacle, so that the heat-conducting surface of the module can achieve the largest area of ​​close contact with the component back plate around the junction box, which is the main path of heat conduction, thereby ensuring that heat can be "extracted" from its source in the most efficient way.

[0036] To verify the actual effects of the embodiments of the present invention, a comparative experimental platform was built.

[0037] The experimental subjects included a "control group" and an "experimental group." The "control group" consisted of a high-power N-type TOPCon photovoltaic module of the same model as mentioned in this embodiment, installed using a standard mounting bracket 300 without any additional heat dissipation structure. The "experimental group" consisted of another photovoltaic module of the same model, with the thermal management module 400 described in this embodiment mounted on its back. The experiment was conducted in Yinchuan, Ningxia, on a clear, windless day in July, with a peak solar irradiance of no less than 1000 W / m². 2 K-type thermocouples are used and are attached to the same location (right next to the edge of the junction box) on the back plates of the two components using high thermal conductivity adhesive. Real-time temperature acquisition and recording are performed using a multi-channel data logger.

[0038] The following table shows an example of the recorded experimental data:

[0039] As can be seen from the experimental data in the table above, the heat dissipation structure of this embodiment exhibits significant and effective temperature control capabilities. In the initial stage of the experiment (9:00 AM to 11:00 AM), as the solar radiation intensity increased, the core hot zone temperatures of the components in both the control group and the experimental group rose rapidly and synchronously, with little temperature difference between them. This indicates that the heat storage effect of the thermal management module 400 has not yet been activated below the phase change threshold temperature.

[0040] After 11:00 AM, the temperature difference between the two groups began to widen significantly. The temperature in the control group continued to rise rapidly, while the rate of temperature rise in the experimental group slowed significantly as the phase change material began to absorb latent heat. Especially during the peak solar radiation and heat generation period from 12:00 PM to 2:00 PM, the core hot zone temperature of the experimental group was successfully "pinched" within a very narrow range of 58.5℃ to 61.3℃, forming a clear "phase change plateau." This clearly demonstrates that the phase change material inside the thermal management module 400 underwent a sufficient solid-liquid phase change during this period, effectively "devouring" the excess heat energy that the component could not dissipate through conventional means by absorbing a large amount of latent heat, thus achieving strong suppression of temperature peaks.

[0041] At the peak time of 13:00, when the temperature of the control group reached 81.5℃, which is extremely detrimental to the performance and lifespan of the modules, the temperature of the experimental group was only 60.0℃, achieving a peak temperature difference of up to 21.5℃. Furthermore, during the critical power generation period of three hours (12:00-15:00), the temperature of the experimental group was consistently more than 13℃ lower than that of the control group. This significant temperature drop, based on the negative temperature coefficient of photovoltaic cells (typically around -0.3% / ℃), can be directly translated into an increase of several percentage points in instantaneous power generation during that period.

[0042] More importantly, reducing the peak operating temperature of the module from the "high-risk zone" of over 80°C to the "safe zone" of around 60°C can significantly slow down the yellowing and cracking of encapsulation materials such as EVA, as well as the long-term thermally induced power decay rate of the solar cells. Therefore, the experimental data, both qualitatively and quantitatively, powerfully verify the significant beneficial effects of this invention, through passive phase-change thermal storage, in improving the thermal operating environment of photovoltaic modules, enhancing instantaneous power generation performance, and ensuring long-term operational reliability.

[0043] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A heat dissipation structure for a high-power photovoltaic module, comprising a thermal management module (400), wherein the thermal management module (400) is mounted on the back of the photovoltaic module (100), characterized in that, include: A sealed box; and A composite phase change material is filled in the housing, the composite phase change material comprising a phase change material and a highly thermally conductive porous framework for supporting the phase change material and enhancing thermal conductivity.

2. The heat dissipation structure according to claim 1, characterized in that, To differentiate the thermal management of the core hot zone and the conventional hot zone formed on the back of the photovoltaic module (100) due to uneven heat distribution, the composite phase change material is divided into at least two regions within the housing, including: The first thermal management area (401) is located corresponding to the junction box (200) area of ​​the photovoltaic module (100), which is the core thermal zone; and The second thermal management zone (402) covers the area other than the first thermal management zone (401), which is the conventional thermal zone.

3. The heat dissipation structure according to claim 2, characterized in that, The first thermal management region (401) is filled with a first composite phase change material (4011), and the highly thermally conductive porous skeleton of the first composite phase change material (4011) is foam metal.

4. The heat dissipation structure according to claim 3, characterized in that, The foam metal is a gradient porous foam metal, and its pore density varies in a gradient along its thickness direction. The pore density on the side closer to the photovoltaic module (100) is higher than that on the side farther away from the photovoltaic module (100).

5. The heat dissipation structure according to claim 2, characterized in that, The second thermal management region (402) is filled with a second composite phase change material (4021), and the highly thermally conductive porous skeleton of the second composite phase change material (4021) is expanded graphite.

6. The heat dissipation structure according to claim 1, characterized in that, The phase change material is a paraffin-based phase change material.

7. The heat dissipation structure according to claim 2, characterized in that, The housing portion accommodating the first thermal management area (401) has an enclosing structure for accommodating and surrounding the raised photovoltaic module junction box (200) during installation.

8. The heat dissipation structure according to claim 1, characterized in that, The outer surface of the box is provided with several heat dissipation fins (403) for enhancing heat dissipation.

9. The heat dissipation structure according to claim 1, characterized in that, The box is made of aluminum alloy and has a fluorocarbon coating on its outer surface.

10. The heat dissipation structure according to claim 1, characterized in that, The edge of the housing is provided with mounting ears (404) for fixing it to the photovoltaic module (100) or its mounting bracket (300).

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