Method for improving power generation of single-sided solar cell module based on passive temperature control

Abstract

The application provides a single-sided solar cell module power generation capacity improving method based on passive temperature control, takes phase change temperature, phase change material dosage and heat pipe number as dependent variables, performs annual dynamic simulation calculation on solar cell module power generation capacity under different dependent variable values, obtains total power generation capacity of a set time period under different dependent variable values, takes total power generation capacity as abscissa, takes cost increment as ordinate, draws a pareto graph in the form of a two-dimensional scatter diagram, obtains a pareto graph front, and takes the dependent variable value corresponding to the pareto front working condition as the optimal dependent variable parameter, and arranges the single-sided solar cell module with the optimal dependent variable parameter to realize maximum power generation capacity in the set time period, so that the application solves the problem of power generation capacity decline caused by temperature rise in the current photovoltaic panel operation process and the problem of low phase change temperature control heat storage and release rate, and improves the power generation capacity of the single-sided solar cell module.

Description

Technical Field

[0001] This invention relates to the field of solar power generation technology, and in particular to a method for increasing the power generation of a single-sided solar cell module based on passive temperature control. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Crystalline silicon cells are currently the mainstream type of solar cell power generation. Under otherwise unchanged conditions, temperature is one of the factors that leads to the degradation of power generation efficiency. Therefore, controlling the temperature of solar cell modules is of great significance to improving their working efficiency.

[0004] Currently, the main methods for increasing power generation by controlling the backsheet temperature of solar cell modules include:

[0005] (1) Active control method: heat exchange channels are arranged on the back plate, and water or refrigerant is used as working fluid. During the flow process, heat is absorbed to achieve the purpose of reducing the temperature of the back plate. This technology has good temperature control effect, but the disadvantage is that the system is complex, the processing requirements are high, and additional energy is required. It is not suitable for large-scale photovoltaic power generation.

[0006] (2) Passive temperature control method: Phase change material is arranged on the back sheet. When the temperature of the back sheet is higher than the phase change temperature, the phase change material undergoes a phase change and absorbs the heat of the back sheet in the form of latent heat, thereby reducing the temperature of the solar cell and improving the power generation efficiency.

[0007] Passive temperature control methods have the following disadvantages: 1) Phase change materials have low thermal conductivity. If they completely melt during power generation, they will act as insulation, leading to higher backplate temperatures. If they cannot dissipate heat and solidify completely at night, it will affect the temperature control effect in the next cycle. 2) Commonly used phase change materials are solid-liquid phase change materials, which are prone to leakage and require high encapsulation. During the phase change process, there is an expansion rate of about 10%, which creates cavities that affect heat transfer. 3) The design of phase change material performance parameters does not match local solar radiation and meteorological conditions, and they cannot completely melt and solidify, resulting in poor temperature control. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for improving the power generation of single-sided solar cell modules based on passive temperature control. This method solves the problem of reduced power generation caused by temperature rise during photovoltaic panel operation and the low heat storage and release rate of existing phase change temperature control systems, thereby increasing the power generation of single-sided solar cell modules.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for improving the power generation of a single-sided solar cell module based on passive temperature control includes the following processes:

[0011] Within the range of phase change temperature, phase change material usage, and number of heat pipes, the power generation of solar cell modules under different dependent variable values ​​is dynamically simulated throughout the year to obtain the total power generation for a set time period under different dependent variable values.

[0012] With total power generation as the horizontal axis and cost increment as the vertical axis, a Pareto chart is plotted in the form of a two-dimensional scatter plot to obtain the frontier of the Pareto chart. The dependent variable parameter is the value of the operating condition corresponding to the Pareto frontier.

[0013] The single-sided solar cell modules are arranged with optimal dependent variable parameters to maximize power generation within a set time period.

[0014] As an optional implementation, for any time within a set time period, the heat absorption of the heat pipe is calculated based on the assumed evaporator end temperature of the heat pipe. The difference between the heat absorption and heat transfer of the heat pipe is calculated to see if it is less than a set threshold. If so, the photovoltaic panel temperature at the current time is recorded, and the power generation efficiency and power generation at the current time are calculated. Otherwise, the assumed evaporator end temperature of the heat pipe is reset until the difference between the heat absorption and heat transfer of the heat pipe is less than the set threshold.

[0015] As an optional implementation method, heat pipe heat transfer... ,include:

[0016]

[0017] in, and These represent the heat transfer on the four sides of the input heat pipe.

[0018] As a further limitation,

[0019] ; ;

[0020] ; ;

[0021] in, and This represents the thickness and width of the heat pipe. represent i The temperature of the node, The thermal conductivity of photovoltaic modules, The thermal conductivity of the phase change material, and These represent the thickness and width directions of the heat pipe, respectively. This refers to the wall temperature of the heat pipe.

[0022] As a further limitation, the heat pipe wall temperature ,include:

[0023] ;

[0024] ;

[0025] in, and These are the density, specific heat capacity, and volume of the heat pipe, respectively. and These are the density, specific heat capacity, and volume of the heat pipe wall, respectively. and These are the density, specific heat capacity, and volume of the heat pipe wick, respectively. The convective heat transfer coefficient of the condenser section of the heat pipe. The area of ​​the heat pipe's condenser section. This refers to the air temperature.

[0026] As an optional implementation method, the phase change material is an expanded graphite-paraffin shaped phase change material.

[0027] As an alternative implementation, the phase change material is bonded to the backsheet of the solar cell.

[0028] As an optional implementation, multiple heat pipes are arranged side by side, with the evaporation section of each heat pipe extending into the phase change material. One side surface of each heat pipe is attached to the backsheet of the solar cell, while the condensation section of each heat pipe is located outside the phase change material and the solar cell.

[0029] As an optional implementation method, the heat pipe is a U-shaped heat pipe.

[0030] As an optional implementation, both the evaporation and condensation sections of the heat pipe are parallel to the back plate.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. The passive temperature control-based method for improving the power generation of single-sided solar cell modules described in this invention solves the problem of power generation reduction caused by temperature rise during photovoltaic panel operation and the low heat storage and release rate of existing phase change temperature control, thereby improving the power generation of single-sided solar cell modules. It can solve the design and calculation problems of phase change / heat pipe coupled temperature control devices for different climate and irradiation conditions, improve the accuracy of power generation optimization of single-sided solar cell modules, and meet the temperature control requirements of solar cell modules under different meteorological conditions.

[0033] 2. The method for improving the power generation of a single-sided solar cell module based on passive temperature control described in this invention achieves the following: During the day, when the solar cell is working, the phase change material absorbs heat in the form of latent heat, and the heat pipe transfers the heat to the air, enhancing the temperature control effect and extending the phase change temperature control time. At night, when the solar cell is not working, the heat inside the phase change material is released through the heat pipe and natural convection around the phase change material, shortening the recovery time of the phase change material and improving the reliability of phase change temperature control, thereby achieving a bidirectional enhanced heat transfer effect.

[0034] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0035] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0036] Figure 1 A flowchart illustrating the method for improving the power generation of a single-sided solar cell module based on passive temperature control, provided in an embodiment of the present invention.

[0037] Figure 2 A front view of the power boosting device combined with a photovoltaic panel according to an embodiment of the present invention;

[0038] Figure 3 A side view of the power boosting device combined with a photovoltaic panel according to an embodiment of the present invention;

[0039] Figure 4 A rear view of the power boosting device combined with a photovoltaic panel according to an embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of heat transfer between the power enhancement device and the photovoltaic panel provided in an embodiment of the present invention;

[0041] Among them, 1-solar photovoltaic module; 2-crystalline silicon cell; 3-heat pipe; 3a-evaporation section; 3b-condensation section; 4-phase change material; 5-frame; 6-backsheet. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0044] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0045] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0046] Example 1:

[0047] like Figure 1 As shown, this embodiment provides a method for improving the power generation of a single-sided solar cell module based on passive temperature control, including the following processes:

[0048] Within the range of phase change temperature, phase change material usage, and number of heat pipes, the power generation of solar cell modules under different dependent variable values ​​is dynamically simulated throughout the year to obtain the total power generation for a set time period under different dependent variable values.

[0049] With total power generation as the horizontal axis and cost increment as the vertical axis, a Pareto chart is plotted in the form of a two-dimensional scatter plot to obtain the frontier of the Pareto chart. The dependent variable parameter is the value of the operating condition corresponding to the Pareto frontier.

[0050] The single-sided solar cell modules are arranged with optimal dependent variable parameters to maximize power generation within a set time period.

[0051] In this embodiment, a combination of phase change material and heat pipe is used at the back sheet of the single-sided solar cell module to increase the heat transfer path of the photovoltaic panel. By combining phase change heat storage and heat pipe heat dissipation, the purpose of temporarily storing and removing the heat generated by the photovoltaic panel to the greatest extent can be achieved.

[0052] Meanwhile, in the absence of solar radiation at night, the heat pipe will accelerate the rate at which the phase change material dissipates the heat stored during the day into the air, helping to ensure the performance of the phase change material in the next heat storage cycle and enabling the entire device to operate continuously and efficiently.

[0053] In this embodiment, parameters such as the phase change material phase change temperature, the amount of phase change material used, and the number of heat pipes need to be optimized, including:

[0054] S1: Establish a coupled heat transfer model and a power generation calculation model. Based on the coupled heat transfer model, calculate the photovoltaic panel temperature under dynamic radiometer meteorological conditions. Based on the photovoltaic panel temperature and temperature decay coefficient, calculate the real-time power generation of the photovoltaic panel.

[0055] For the PV (photovoltaic panel) and PCM (phase change material) regions, a two-dimensional PV-PCM model is selected, and the following assumptions are made:

[0056] (1) Expanded graphite is used to enhance the thermal conductivity of paraffin. Due to the shaping effect of expanded graphite + paraffin material, the natural flow inside PCM is ignored.

[0057] (2) The thermal properties of PCM are constant;

[0058] (3) Ignore the contact thermal resistance between the PCM and the PV backsheet.

[0059] Based on the above assumptions, the governing equations are as follows:

[0060]

[0061] in, For the density of each part, The specific heat capacity of each part, Representing the temperature of each node, These are the thermal conductivity coefficients of each part. Represents the time item. Represents the source term;

[0062] The source term S is defined as follows:

[0063] For PV-PCM internal nodes:

[0064] ;

[0065] For PV-PCM front surface nodes:

[0066] ;

[0067] For the surface nodes after PV-PCM:

[0068] ;

[0069] For nodes adjacent to heat pipes inside the PV-PCM:

[0070] ;

[0071] in, This refers to the absorptivity of the encapsulating glass on the front surface of the photovoltaic module, set at 0.9. It is the total amount of solar radiation reaching the front surface of the photovoltaic module; It refers to the photoelectric conversion efficiency of photovoltaic modules; and These are the emissivity of glass and PCM, respectively; Represents the Stefan-Boltzmann constant. These are the temperatures of the front surface of the photovoltaic module, the back surface of the PCM, the sky, the ground, the surface of the HP (heat pipe), the air, and the PV and PCM nodes adjacent to the HP. and The convective heat transfer coefficients of the front and rear surfaces are given. and Thermal conductivity of photovoltaic modules and PCM.

[0072] To simulate the changes in thermophysical properties of PCM during phase transition, the effective heat capacity method is used, as defined below:

[0073]

[0074] in, , and These are the specific heat capacities of PCM, solid PCM, and liquid PCM, respectively. , and These are the current temperature of the PCM, the phase transition temperature, and the phase transition radius of the PCM, respectively. LH is the enthalpy of phase transition. Used in governing equations.

[0075] For any node in the PCM region, its liquid fraction is defined as follows:

[0076]

[0077] The liquid phase fraction is used to monitor the melting of PCM.

[0078] In this embodiment, the sky temperature :

[0079] .

[0080] Front surface convective heat transfer coefficient:

[0081]

[0082] in, For ambient wind speed.

[0083] Back surface convective heat transfer coefficient:

[0084]

[0085] Increased PV temperature leads to a decrease in photoelectric conversion efficiency, as shown in the following correlation:

[0086]

[0087] PV output power:

[0088]

[0089] in, This refers to the actual photoelectric conversion efficiency of the photovoltaic module. This is the reference efficiency of photovoltaic modules; It is the temperature coefficient of the photoelectric conversion efficiency of a photovoltaic module. and These are the actual operating temperatures of photovoltaic modules under standard test conditions and the reference operating temperatures under standard conditions. This represents the actual output power of the photovoltaic module. The calculation here represents the simulated photovoltaic module's photoelectric conversion efficiency and output power, which is one of the output results.

[0090] For the HP region, due to its excellent thermal conductivity, the internal temperature of the object can be considered independent of its position in unsteady-state heat conduction problems. Furthermore, this embodiment does not concern itself with the temperature of individual components within the HP region. Therefore, a one-dimensional lumped model is chosen, and the following assumptions are made:

[0091] (1) The thermal resistance of the HP wall, liquid core and working fluid is negligible;

[0092] (2) Ignore the advection effect of the working fluid flowing back from the condenser to the evaporator;

[0093] (3) Ignore the thermal resistance generated by the evaporation and condensation of the working fluid inside the HP.

[0094] Based on the foregoing, the HP input power is:

[0095]

[0096]

[0097]

[0098]

[0099]

[0100] in, This represents the net heat input to HP, which is determined by the heat transfer from the four sides of the input HP. and , and This represents the thickness and width of HP, therefore and These represent the number of nodes in the PV / PCM region in the thickness and width directions, respectively.

[0101] In this embodiment, Fourier's law is applied to each PV / PCM node adjacent to HP, and the results are added together to obtain the heat input of each HP.

[0102] The temperature of the PV and PCM in contact with the heat pipe changes over time, as does the heat pipe wall temperature. The energy balance equation is as follows:

[0103]

[0104]

[0105] in, and These are the density, specific heat capacity, and volume of HP, respectively. and These are the density, specific heat capacity, and volume of the HP wall, respectively. and These are the density, specific heat capacity, and volume of the HP liquid core, respectively. The convective heat transfer coefficient of the HP condenser section; Let be the area of ​​the HP condenser section.

[0106] Based on the above mathematical model, PV&PCM calculation modules and HP calculation modules were developed respectively. The two regions are coupled through the temperature and heat absorption at the evaporator end of the heat pipe. Figure 5 As shown.

[0107] S2: Annual Optimization Analysis

[0108] Phase change temperature, phase change material usage, and number of heat pipes were selected as influencing factors. The parameter range was determined in combination with the actual engineering situation. The above calculation method was used to perform dynamic calculations on the solar cell module throughout the year to obtain the hourly temperature distribution and power generation of the PV panel. The installation space of the temperature control device was used as a constraint, and the total annual power generation and cost increment were used as constraints to perform dual-objective optimization to obtain the optimal design calculation parameters.

[0109] The specific implementation steps are as follows:

[0110] Determine the value ranges of variables dpcm, nhp, and tm. Calculate the optional amount or thickness of the phase change material (dpcm) based on the available installation space of the temperature control device as the upper limit, ensuring the thickness does not exceed the frame (generally 3cm), with a 15cm installation space reserved on all four sides. Set the heat pipe spacing within a range of 4cm-10cm to determine the optional heat transfer quantity (nhp). Determine the optional phase change temperature (tm) of the phase change material based on a temperature greater than the local daytime average temperature. Calculate the cost of the passive temperature control device based on the selected amount of phase change material and the number of heat pipes.

[0111] Using the S1 calculation method, the annual dynamic simulation calculation of the power generation of solar cell modules under different parameter values ​​is performed to obtain the total annual power generation.

[0112] Plot all the calculation results into a Pareto chart in the form of a two-dimensional scatter plot with power generation and cost increment as the horizontal and vertical axes, find the Pareto front, and the optimal parameter design is the parameter value of the operating condition corresponding to the Pareto front.

[0113] In this embodiment, the passive temperature control device includes a solar cell module 1 (with crystalline silicon solar cells 2 on it), an expanded graphite-paraffin-shaped phase change material 4, multiple heat pipes 3, and a frame 5. The phase change material 4 is attached to the backsheet 6 of the solar cell. Multiple heat pipes 3 are arranged side-by-side, with their evaporation sections 3a extending into the phase change material and one surface attached to the backsheet of the solar cell. The condensation sections 3b of the heat pipes 3 are located outside the phase change material 4 and the solar photovoltaic module 1. Figure 2 , Figure 3 and Figure 4 As shown.

[0114] In this embodiment, the heat pipe 3 is a U-shaped heat pipe. The evaporation section 3a and the condensation section 3b of the heat pipe 3 are parallel to and arranged opposite to the back plate 6. Each heat pipe 3 is evenly distributed on the back plate 6 of the solar cell.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving the power generation of a single-sided solar cell module based on passive temperature control, characterized by, The method comprises the following steps: S1: a coupled heat transfer model and a power generation calculation model are established, the temperature of the photovoltaic panel under dynamic radiometer meteorological conditions is calculated based on the coupled heat transfer model, and the real-time power generation of the photovoltaic panel is calculated based on the temperature of the photovoltaic panel and a temperature attenuation coefficient S2: within the value range of the phase change temperature, the amount of phase change material and the number of heat pipes, the phase change temperature, the amount of phase change material and the number of heat pipes are taken as dependent variables, the method of S1 is used to perform dynamic calculation on the operation of the solar cell module throughout the year, the hourly temperature distribution and power generation of the PV panel are obtained, the installable space of the temperature control device is taken as a limiting condition, the total power generation and the cost increment are taken as constraints, and a double-objective optimization is performed, the total power generation is taken as the abscissa, the cost increment is taken as the ordinate, a pareto diagram is drawn in the form of a two-dimensional scatter plot, the front of the pareto diagram is obtained, the optimal dependent variable parameters corresponding to the working conditions of the pareto front are obtained, and the single-sided solar cell module is arranged with the optimal dependent variable parameters to maximize the power generation in the set time period; The phase change material is attached to the back plate of the solar cell, a plurality of heat pipes are arranged side by side, the evaporation section of the heat pipe extends into the phase change material, one side surface of the heat pipe is attached to the back plate of the solar cell, and the condensation section of the heat pipe is located outside the phase change material and the solar cell. For any time in the set time period, the heat absorption amount of the heat pipe is calculated based on the assumed evaporation end temperature of the heat pipe, the difference between the heat absorption amount of the heat pipe and the heat transfer amount of the heat pipe is calculated, and the difference is less than the set threshold value. If yes, the current photovoltaic panel temperature is recorded, and the power generation efficiency and power generation at the current time are calculated; otherwise, the assumed evaporation end temperature of the heat pipe is reset until the difference between the heat absorption amount of the heat pipe and the heat transfer amount of the heat pipe is less than the set threshold value.

2. The passive temperature control based single-sided solar cell module power generation improvement method of claim 1, wherein Heat pipe heat transfer comprising: ； wherein, and are the heat transfer rates of the four faces of the heat pipe, respectively.

3. The passive temperature control based single-sided solar cell module power generation improvement method of claim 2, wherein ； ； ； ； wherein, and represents the thickness and the width of the heat pipe, represents i the temperature of the node, is the thermal conductivity of the photovoltaic module, is the thermal conductivity of the phase change material, and respectively represent the thickness direction and the width direction of the heat pipe, is the heat pipe wall surface temperature.

4. The passive temperature control based single-sided solar cell module power generation improvement method of claim 3, wherein Heat pipe wall surface temperature comprising: ； ； wherein, and are the density, specific heat capacity and volume of the heat pipe, respectively, and are the density, specific heat capacity and volume of the heat pipe wall, respectively, and are the density, specific heat capacity and volume of the heat pipe liquid core, respectively, is the convective heat transfer coefficient of the condenser section of the heat pipe, is the area of the condenser section of the heat pipe, is the air temperature.

5. The passive temperature control based single-sided solar cell module power generation improvement method of claim 1, wherein The phase change material is an expanded graphite-paraffin shaped phase change material.

6. The passive temperature control based single-sided solar cell module power generation improvement method of claim 1, wherein The heat pipe is a U-shaped heat pipe.

7. The passive temperature control based single-sided solar cell module power generation improvement method of claim 1, wherein The evaporation section and the condensation section of the heat pipe are parallel to the back plate.

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