Building photovoltaic integrated wall dynamic temperature distribution calculation method

Abstract

The invention belongs to the technical field of building photovoltaic wall operation, and relates to a building photovoltaic integrated wall dynamic temperature distribution calculation method comprising the following steps: 1, building an unsteady state heat transfer mathematical model of a building photovoltaic integrated system; 2, environment parameter data are collected, and cubic spline interpolation processing is carried out on the obtained environment data; 3, substituting the fitting result into the established unsteady-state heat transfer model, and solving the temperatures of a photovoltaic module cover plate, a photovoltaic battery piece and a photovoltaic module back plate, the temperature of an air interlayer, the temperature of the outer / inner surface of a self-heat-preservation wall body and the output power of the photovoltaic module; according to the method, the dynamic temperature distribution of the building photovoltaic wall can be evaluated more accurately, the structural design of the photovoltaic wall can be optimized, the cooling and heating load of a building envelope structure is reduced, and the energy-saving effect of a building is improved.

Description

Technical Field

[0001] This invention belongs to the field of building photovoltaic wall operation technology, specifically relating to a method for calculating the dynamic temperature distribution of integrated building photovoltaic walls. Background Technology

[0002] Building-integrated photovoltaic (BIPV) walls refer to a new type of eco-friendly building that integrates photovoltaic modules into self-insulating walls, safely converting solar energy into electricity. It combines architectural decoration, photovoltaic power generation, and insulation, fully showcasing the building's multifunctionality and ecological advantages. With the rapid development of renewable energy, solar photovoltaic power generation has been widely applied and promoted globally. Fully utilizing photovoltaic technology in buildings is an effective way to achieve low-carbon or even zero-carbon buildings. Building facade integrated photovoltaic systems, as a new energy-saving technology combining photovoltaic power generation and building facades, organically combine multiple functions such as architectural decoration, photovoltaic power generation, and insulation by integrating solar photovoltaic cells onto the building's external envelope surface, offering significant potential for application and promotion.

[0003] like Figure 1 , Figure 2 As shown, the photovoltaic module consists of eight layers: a subframe, cover glass, EVA film, photovoltaic cells, POE film, PET film, EVA film, and backsheet glass. Building photovoltaic (PV) walls typically feature horizontal and vertical lightweight steel frame structures. The vertical frames are connected to the wall using steel plates and L-shaped angle steel, while the horizontal frames are secured with aluminum alloy extrusions and screws. The PV modules are fixed to the frame using aluminum alloy subframes, with structural sealant filling the gaps between the subframes to secure the modules and achieve edge sealing. When the PV modules are integrated with the self-insulating wall at a certain distance, an air gap of a certain thickness is formed between the glass backsheet and the outer surface of the self-insulating wall, allowing for internal airflow.

[0004] However, regarding the thermal performance of photovoltaic (PV) modules, only 15%–25% of the solar irradiance received by PV cells is typically converted into electrical energy, with the majority being converted into heat and dissipated into the surrounding environment. The operating temperature of PV cells is generally maintained at around 50°C, and when heat dissipation is inadequate, the temperature can rise to around 80°C. Considering the power generation performance of PV modules, the power generation efficiency test temperature for PV cells is 25°C; for every 1°C increase, the power generation efficiency decreases by approximately 0.4%. To maintain the operating efficiency of building photovoltaic (PV) walls at a high level, research on the thermoelectric performance of PV walls has become a key focus in building-integrated photovoltaics (BIPV). From a building energy conservation perspective, the presence of PV modules blocks direct solar heat gain from the building envelope, while the heat dissipation from the PV modules increases the heat gain of the building envelope, both negatively impacting the building's heating and cooling loads to varying degrees. Current research on BIPV largely focuses on the PV modules themselves, lacking methods for calculating the dynamic temperature distribution of PV walls on building facades with enclosed air gaps.

[0005] Therefore, a method is needed to calculate the temperature distribution of building photovoltaic walls through the heat transfer process of building facade photovoltaic systems in order to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention aims to analyze the heat transfer process of a building facade photovoltaic integrated system and calculate the dynamic temperature distribution of the building photovoltaic wall, taking into account the characteristics of the building facade photovoltaic wall.

[0007] This invention provides the following technical solution: a method for calculating the dynamic temperature distribution of a building photovoltaic integrated wall, comprising the following steps: step S 1. Establish an unsteady-state heat transfer model for building photovoltaic walls; step S 2. Collect environmental data and perform cubic spline interpolation on the collected environmental data; step S 3. Substitute the fitting results into the steps. S In the unsteady-state heat transfer model established in section 1, the temperatures of the photovoltaic module cover plate / cell / backsheet, the air interlayer temperature, the output power of the photovoltaic module, and the internal / external surface temperatures of the self-insulating wall are solved.

[0008] Preferably, in step 1, the unsteady heat transfer model includes: Unsteady-state energy balance equation for photovoltaic module cover plate: (1) Unsteady-state energy balance equation of photovoltaic cells: (2) Unsteady-state energy balance equation for photovoltaic module backsheet: (3) Unsteady energy balance equation of air gap: (4) Unsteady energy balance equation for the outer surface of a self-insulating wall: (5) Unsteady energy balance equation for the inner surface of a self-insulating wall: (6) In equations (1) to (6), d For thickness, For density, c For specific heat capacity, T For temperature, R For thermal resistance, Solar radiation energy absorbed by photovoltaic modules The output power of the photovoltaic module; where, d、 c, T, R The subscripts are as follows: cover Represents the cover plate for photovoltaic modules, subscript pv Represents photovoltaic cells, subscript backer Represents the backsheet of a photovoltaic module, subscript fluid Represents a closed air gap, subscript wall,out Represents the outer surface of a self-insulating wall, subscript wall,in Represents the inner surface of a self-insulating wall, subscript amb Represents outdoor air temperature, subscript sky Represents sky temperature, subscript in Represents indoor temperature, subscript cover-pv Represents the thermal resistance from the photovoltaic module cover plate to the photovoltaic cell, subscript pv-backer Represents the thermal resistance from the photovoltaic cell to the backsheet of the photovoltaic module, subscript wall This represents the thermal resistance of a self-insulating wall. The convective heat transfer coefficient between the photovoltaic module cover plate and the outdoor environment. The radiative heat transfer coefficient between the photovoltaic module cover plate and the outdoor environment. The convective heat transfer coefficient between the inner surface of the self-insulating wall and the indoor environment. The radiative heat transfer coefficient between the inner surface of the self-insulating wall and the indoor environment. The convective heat transfer coefficient of the air gap. The radiative heat transfer coefficient is the coefficient between the backsheet of the photovoltaic module and the outer surface of the self-insulating wall.

[0009] More preferably, the steps SIn 2, the aforementioned The formula for calculation is:

[0010] in, Let be the solar radiation absorption coefficient of the photovoltaic cell, and E be the solar radiation intensity projected onto the surface of the photovoltaic module. Transmittance of the cover plate for photovoltaic modules.

[0011] More preferably, the steps S In 2, the aforementioned The formula for calculation is: (7) In equation (7), Outdoor air thermal conductivity, The vertical height of the photovoltaic wall on the building facade. Nu for Nu number.

[0012] More preferably, the aforementioned The formula for calculation is: (8) In equation (8), For the emissivity of the cover plate of the photovoltaic module, The viewing angle factor between the photovoltaic module cover plate and the sky. is the Stefan-Boltzmann constant.

[0013] More preferably, the aforementioned The formula for calculation is: (9) In equation (9), The thermal conductivity of the air in the air gap. The thickness of the air gap.

[0014] More preferably, the aforementioned The formula for calculation is: (10) In equation (10), The emissivity of the photovoltaic module backsheet. The emissivity of the outer surface of the self-insulating wall.

[0015] More preferably, the aforementioned The formula for calculation is: (11) In equation (11), The thermal conductivity of indoor air.

[0016] More preferably, the aforementioned The formula for calculation is: (12) In equation (12), The emissivity of the inner surface of the self-insulating wall. The perspective factor between the inner surface of the self-insulating wall and the indoor air. is the Stefan-Boltzmann constant.

[0017] Preferably, the steps S In section 3, the Runge-Kutta fourth-order model algorithm is used to solve the differential equations.

[0018] The beneficial effects of this invention are: 1. This invention establishes an unsteady-state energy balance equation and constructs a heat transfer theoretical model for a building-integrated photovoltaic (BIPV) system, enabling a holistic analysis of the dynamic temperature distribution of the photovoltaic system. The model comprehensively considers the influence of external environmental factors (such as solar irradiance, ambient temperature, and outdoor wind speed) on the system's dynamic temperature distribution, as well as the moderating effects of air gaps, self-insulating wall structures, and the indoor environment on the thermal behavior of photovoltaic modules. This allows for a more accurate acquisition of the dynamic temperature distribution of the building's photovoltaic walls, facilitating the optimization of photovoltaic wall design and reducing the heating and cooling loads on the building envelope.

[0019] 2. The method of the present invention is applicable to a variety of photovoltaic systems, especially to photovoltaic integrated systems on building facades with enclosed air gaps, thus the present invention has a wide range of applications.

[0020] 3. In solving the differential equations of the heat transfer model, this invention employs a highly accurate fourth-order Runge-Kutta numerical algorithm, which improves the stability and accuracy of the calculation. Therefore, the method of this invention is accurate, precise, and the calculation results are stable. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a photovoltaic module structure based on existing technology. Figure 2 A structural schematic diagram of existing building photovoltaic walls; Figure 3 This invention provides a method for calculating the dynamic temperature distribution of a building photovoltaic integrated wall system, which is illustrated in the heat transfer network diagram of the building photovoltaic wall system. Figure 4 This is a flowchart of the method for calculating the dynamic temperature distribution of building photovoltaic walls according to the present invention.

[0022] Figure 1 In the diagram, a represents the photovoltaic module subframe; b represents the cover glass; c represents the EVA film; d represents the photovoltaic cell; e represents the POE film; f represents the PET film; g represents the EVA film; and h represents the backsheet glass. Figure 2In the diagram, A represents the photovoltaic module; B represents the subframe; C represents the horizontal keel; D represents the vertical keel; E represents the steel plate; F represents the L-shaped angle steel; and G represents the self-insulating wall. Figure 3 In the diagram, 1 is the first node; 2 is the second node; 3 is the third node; 4 is the fourth node; 5 is the fifth node; and 6 is the sixth node. Detailed Implementation

[0023] The related technologies of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figures 1-4 As shown in this embodiment, a method for calculating the dynamic temperature distribution of a building photovoltaic integrated wall is provided. The building photovoltaic wall includes photovoltaic modules, an air gap, and a self-insulating wall. An air gap exists between the photovoltaic modules and the self-insulating wall. The calculation method includes the following steps: S 1. Establish an unsteady-state heat transfer model for building photovoltaic walls, including: Unsteady-state energy balance equation for photovoltaic module cover plate: (1) Unsteady-state energy balance equation of photovoltaic cells: (2) Unsteady-state energy balance equation for photovoltaic module backsheet: (3) Unsteady energy balance equation of air gap: (4) Unsteady energy balance equation for the outer surface of a self-insulating wall: (5) Unsteady energy balance equation for the inner surface of a self-insulating wall: (6) In the formula, d For thickness, For density, c For specific heat capacity, T For temperature, R For thermal resistance, Solar radiation energy absorbed by photovoltaic modules The output power of the photovoltaic module, subscript cover Represents the cover plate for photovoltaic modules, subscript pvRepresents photovoltaic cells, subscript backer Represents the backsheet of a photovoltaic module, subscript fluid Represents a closed air gap, subscript wall,out Represents the outer surface of a self-insulating wall, subscript wall,in Represents the inner surface of a self-insulating wall, subscript amb Represents outdoor air temperature, subscript sky Represents sky temperature, subscript in Represents indoor temperature, subscript cover-pv Represents the thermal resistance from the photovoltaic module cover plate to the photovoltaic cell, subscript pv-backer Represents the thermal resistance from the photovoltaic cell to the backsheet of the photovoltaic module, subscript wall This represents the thermal resistance of a self-insulating wall. The convective heat transfer coefficient between the photovoltaic module cover plate and the outdoor environment. The radiative heat transfer coefficient between the photovoltaic module cover plate and the outdoor environment. The convective heat transfer coefficient between the inner surface of the self-insulating wall and the indoor environment. The radiative heat transfer coefficient between the inner surface of the self-insulating wall and the indoor environment. The convective heat transfer coefficient of the air gap. The radiative heat transfer coefficient between the backsheet of the photovoltaic module and the outer surface of the self-insulating wall; S 2. Collect environmental data and perform cubic spline interpolation on the acquired environmental data. The environmental data includes solar irradiance, ambient temperature, air temperature, and wind speed. The unknowns in the model include: photovoltaic module cover plate temperature, photovoltaic cell temperature, photovoltaic module backsheet temperature, air interlayer temperature, self-insulating wall outer surface temperature, self-insulating wall inner surface temperature, and photovoltaic module output power.

[0025] S 3. Substitute the fitting results into the steps. S In the unsteady-state heat transfer model established in section 1, the temperatures of the photovoltaic module cover plate / cell / backsheet, the air interlayer temperature, the output power of the photovoltaic module, and the internal / external surface temperatures of the self-insulating wall are solved.

[0026] Solar radiation energy absorbed by photovoltaic cells ,in, Let be the solar radiation absorption coefficient of the photovoltaic cell, and E be the solar radiation intensity projected onto the surface of the photovoltaic module. Transmittance of the cover plate for photovoltaic modules.

[0027] Convection heat transfer coefficient between photovoltaic module cover and outdoor environment The calculation formula is: (7) Under natural convection conditions , Nu The formula for calculating the number is: when hour, ,when , ; Under forced convection conditions , Nu The formula for calculating the number is: when hour, , when hour, ; Under mixed convection conditions , Nu The formula for calculating the number is:

[0028] In the formula, It is the acceleration due to gravity. The coefficient of volume expansion is 1. The temperature difference between the photovoltaic module cover and the outdoor air. Outdoor air thermal conductivity, The vertical height of the photovoltaic wall on the building facade. The viscosity of outdoor air at kinematic speed. a 1 represents the outdoor air thermal diffusivity. V This refers to the outdoor wind speed.

[0029] Radiative heat transfer coefficient between photovoltaic module cover plate and outdoor environment The calculation formula is: (8) In the formula, For the emissivity of the cover plate of the photovoltaic module, The viewing angle factor between the photovoltaic module cover plate and the sky. is the Stefan-Boltzmann constant.

[0030] Convection heat transfer coefficient of enclosed air jacket The calculation formula is: (9) in:

[0031] In the formula, This refers to the temperature difference between the backsheet of the photovoltaic module and the outer surface of the self-insulating wall. The thermal conductivity of the air in the air gap. The thickness of the air gap, The viscosity of air in the air gap is the kinematic viscosity. The thermal diffusivity of the air in the air gap.

[0032] Radiation heat transfer coefficient between the photovoltaic module backsheet and the outer surface of the self-insulating wall The calculation formula is: (10) In the formula, The emissivity of the photovoltaic module backsheet. The emissivity of the outer surface of the self-insulating wall.

[0033] The convective heat transfer coefficient between the inner surface of the self-insulating wall and the indoor environment The calculation formula is: (11) when hour, ,when hour, ;

[0034] In the formula, The temperature difference between the inner surface of the self-insulating wall and the indoor air. For indoor air thermal conductivity, The viscosity of indoor air movement. The indoor air thermal diffusivity.

[0035] The radiative heat transfer coefficient between the inner surface of the self-insulating wall and the indoor environment The calculation formula is: (12) In the formula, The emissivity of the inner surface of the self-insulating wall. The perspective factor between the inner surface of the self-insulating wall and the indoor air.

[0036] step S In section 3, the Runge-Kutta fourth-order model algorithm is used to solve the differential equations.

[0037] Example See Figure 1 , Figure 2Building-integrated photovoltaic (BIPV) walls refer to a new type of eco-friendly building that integrates photovoltaic modules into a self-insulating wall, safely converting solar energy into electricity. It combines architectural decoration, photovoltaic power generation, and insulation, fully showcasing the building's multifunctionality and ecological advantages. The photovoltaic module consists of eight layers: a sub-frame, cover glass, EVA film, photovoltaic cells, POE film, PET film, EVA film, and back glass, similar to laminated glass commonly used in construction. The BIPV wall is constructed with horizontal and vertical lightweight steel keel frames. The vertical keels are connected to the wall using steel plates and L-shaped angle steel, while the horizontal keels are fixed using aluminum alloy extrusions and screws. The photovoltaic modules are fixed to the keel frame via aluminum alloy sub-frames, with structural sealant filling the gaps between the sub-frames to secure the modules and achieve edge sealing. When the photovoltaic modules are integrated with the self-insulating wall at a certain distance, a sealed air gap of a certain thickness is formed between the glass back panel and the outer surface of the self-insulating wall, allowing internal airflow.

[0038] See Figure 3 The heat transfer network diagram of the building photovoltaic wall system in this invention is shown below. The nodes in the diagram are numbered from top to bottom as follows: Node 1, Node 2, Node 3, Node 4, Node 5, and Node 6. Node 1 is the photovoltaic module cover plate surface, which exchanges heat with the outdoor environment via convection / radiation and with the photovoltaic cells via heat conduction. Node 2 is the photovoltaic cell, which conducts heat with the photovoltaic module cover plate / backsheet surface. Node 3 is the photovoltaic module backsheet surface, which exchanges heat with the air gap via convection, with the outer surface of the self-insulating wall via radiation, and with the photovoltaic cells via heat conduction. Node 4 is the air gap, which exchanges heat with both the photovoltaic module backsheet surface and the outer surface of the self-insulating wall. Node 5 is the outer surface of the self-insulating wall, which exchanges heat with the air gap via convection, with the photovoltaic module backsheet surface via radiation, and with the inner surface of the self-insulating wall via heat conduction. The sixth node, 6, is the inner surface of the self-insulating wall, which exchanges heat with the indoor environment through convection / radiation and conducts heat with the outer surface of the self-insulating wall.

[0039] See Figure 3 The unsteady-state energy equation for the photovoltaic module cover plate (first node 1) in the building photovoltaic system is the same as that in equation (1).

[0040] The unsteady-state energy equation for the photovoltaic cell (second node 2) is the same as equation (2).

[0041] The unsteady-state energy equation for the backsheet of the photovoltaic module (third node 3) is the same as that in equation (3).

[0042] The unsteady-state energy equation for the air interlayer (fourth node 4) is the same as that for equation (4).

[0043] The unsteady energy balance equation for the outer surface of the self-insulating wall (node ​​5) is the same as that for equation (5).

[0044] The unsteady energy balance equation for the inner surface of the self-insulating wall (node ​​6) is the same as that for equation (6).

[0045] In the unsteady-state energy balance equation of the photovoltaic module cover plate, the left side of the equation is the increment of the internal energy of the photovoltaic module cover plate, the first term on the right side of the equation is the convective heat transfer between the photovoltaic module cover plate and the outdoor environment, the second term is the radiative heat transfer between the photovoltaic module cover plate and the sky, and the third term is the conductive heat transfer between the photovoltaic module cover plate and the photovoltaic cells.

[0046] In the unsteady-state energy balance equation of a photovoltaic cell, the left side of the equation represents the increase in the internal energy of the photovoltaic cell, the first term on the right side represents the heat transfer between the photovoltaic module cover plate and the photovoltaic cell, the second term represents the heat transfer between the photovoltaic module backsheet and the photovoltaic cell, the third term represents the solar radiation energy absorbed by the photovoltaic module, and the fourth term represents the electrical energy output by the photovoltaic module.

[0047] In the unsteady-state energy balance equation of the photovoltaic module backsheet, the left side of the equation is the increase in the internal energy of the photovoltaic module backsheet, the first term on the right side of the equation is the convective heat transfer between the photovoltaic module backsheet and the air gap, the second term is the radiative heat transfer between the photovoltaic module backsheet and the outer surface of the self-insulating wall, and the third term is the conductive heat transfer between the photovoltaic module backsheet and the photovoltaic cells.

[0048] In the unsteady-state energy balance equation of the air gap, the left side of the equation is the increase in the internal energy of the air gap, the first term on the right side of the equation is the convective heat transfer between the back sheet of the photovoltaic module and the air gap, and the second term is the convective heat transfer between the air gap and the outer surface of the self-insulating wall.

[0049] In the unsteady-state energy balance equation of the outer surface of the self-insulating wall, the left side of the equation is the increment of the internal energy of the outer surface of the self-insulating wall, the first term on the right side is the convective heat transfer between the outer surface of the self-insulating wall and the air gap, the second term is the radiative heat transfer between the photovoltaic module backsheet and the outer surface of the self-insulating wall, and the third term is the conductive heat transfer between the outer surface of the self-insulating wall and the inner surface of the self-insulating wall.

[0050] In the unsteady-state energy balance equation of the inner surface of the self-insulating wall, the left side of the equation is the increase in the internal energy of the inner surface of the self-insulating wall, the first term on the right side of the equation is the convective heat transfer between the inner surface of the self-insulating wall and the indoor environment, the second term is the radiative heat transfer between the inner surface of the self-insulating wall and the indoor environment, and the third term is the conductive heat transfer between the inner surface of the self-insulating wall and the outer surface of the self-insulating wall.

[0051] In this embodiment, the Stefan-Boltzmann constant The value takes .

[0052] The basic solution process in this embodiment is as follows: a fourth-order Runge-Kutta program is used to solve the problem. Before calculating the differential equation, cubic spline interpolation is performed on the solar irradiance, ambient temperature, sky temperature, and outdoor wind speed.

[0053] In practice, the collected environmental data is arranged according to a time series. A smooth cubic polynomial curve is constructed between adjacent data points using cubic spline interpolation, resulting in a continuous and smooth environmental data change curve, thus enabling the acquisition of accurate environmental data values ​​at any given time. This processed data is then substituted into the previously established unsteady-state heat transfer model, and the calculation is progressively advanced using a fourth-order Runge-Kutta algorithm. In each step, based on the current physical quantity values ​​and their derivatives, approximate values ​​for the next physical quantity are calculated according to the specific formulas of the fourth-order Runge-Kutta algorithm. Through continuous iteration, the temperatures of the photovoltaic module cover plate, cells, and backsheet, the air gap temperature, the photovoltaic module output power, and the internal and external surface temperatures of the self-insulating wall are ultimately determined, providing a complete dynamic temperature distribution of the building's photovoltaic wall.

[0054] In summary, this invention provides a method for calculating the dynamic temperature distribution of building-integrated photovoltaic (BIPV) walls. By establishing an unsteady-state heat transfer model and combining it with the acquisition and processing of environmental data, this method can accurately simulate the dynamic temperature distribution of BIPV walls under different environmental conditions. This method not only considers the heat conduction, convection, and radiation heat transfer between different layers of the photovoltaic modules, but also fully considers the complex heat transfer process between the self-insulating wall and the indoor and outdoor environments, thus ensuring the accuracy and reliability of the calculation results. Furthermore, the use of the Runge-Kutta fourth-order model algorithm to solve the differential equations further improves the accuracy and stability of the calculation. This method is of great significance for guiding the design, optimization, and operation management of BIPV walls, and helps promote the widespread application and development of building-integrated photovoltaic technology.

[0055] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for calculating the dynamic temperature distribution of building-integrated photovoltaic (BIPV) walls, characterized in that, Includes the following steps: step S 1. Establish an unsteady-state heat transfer model for building photovoltaic walls; step S 2. Collect environmental data and perform cubic spline interpolation on the collected environmental data; step S 3. Substitute the fitting results into the steps. S In the unsteady-state heat transfer model established in section 1, the temperatures of the photovoltaic module cover plate / cell / backsheet, the air interlayer temperature, the output power of the photovoltaic module, and the internal / external surface temperatures of the self-insulating wall are solved.

2. The method for calculating dynamic temperature distribution in a building-integrated photovoltaic (BIPV) wall as described in claim 1, characterized in that, The steps S In section 1, the unsteady heat transfer model includes: Unsteady-state energy balance equation for photovoltaic module cover plate: （1） Unsteady-state energy balance equation of photovoltaic cells: （2） Unsteady-state energy balance equation for photovoltaic module backsheet: （3） Unsteady energy balance equation of air gap: （4） Unsteady energy balance equation for the outer surface of a self-insulating wall: （5） Unsteady energy balance equation for the inner surface of a self-insulating wall: （6） In equations (1) to (6), d For thickness, For density, c For specific heat capacity, T For temperature, R For thermal resistance, Solar radiation energy absorbed by photovoltaic modules The output power of the photovoltaic module; where, d、 c, T, R The subscripts are as follows: cover Represents the cover plate for photovoltaic modules, subscript pv Represents photovoltaic cells, subscript backer Represents the backsheet of a photovoltaic module, subscript fluid Represents a closed air gap, subscript wall,out Represents the outer surface of a self-insulating wall, subscript wall,in Represents the inner surface of a self-insulating wall, subscript amb Represents outdoor air temperature, subscript sky Represents sky temperature, subscript in Represents indoor temperature, subscript cover- pv Represents the thermal resistance from the photovoltaic module cover plate to the photovoltaic cell, subscript pv-backer Represents the thermal resistance from the photovoltaic cell to the backsheet of the photovoltaic module, subscript wall This represents the thermal resistance of a self-insulating wall. The convective heat transfer coefficient between the photovoltaic module cover plate and the outdoor environment. The radiative heat transfer coefficient between the photovoltaic module cover plate and the outdoor environment. The convective heat transfer coefficient between the inner surface of the self-insulating wall and the indoor environment. The radiative heat transfer coefficient between the inner surface of the self-insulating wall and the indoor environment. The convective heat transfer coefficient of the air gap. The radiative heat transfer coefficient is the coefficient between the backsheet of the photovoltaic module and the outer surface of the self-insulating wall.

3. The method for calculating dynamic temperature distribution in a building-integrated photovoltaic (BIPV) wall as described in claim 2, characterized in that, The steps S In 2, the aforementioned The formula for calculation is: in, Let be the solar radiation absorption coefficient of the photovoltaic cell, and E be the solar radiation intensity projected onto the surface of the photovoltaic module. Transmittance of the cover plate for photovoltaic modules.

4. The method for calculating dynamic temperature distribution in a building-integrated photovoltaic (BIPV) wall as described in claim 2, characterized in that, The steps S In 2, the aforementioned The formula for calculation is: （7） In equation (7), Outdoor air thermal conductivity, The vertical height of the photovoltaic wall on the building facade. Nu for Nu number.

5. The method for calculating dynamic temperature distribution in a building-integrated photovoltaic (BIPV) wall as described in claim 4, characterized in that, The The formula for calculation is: （8） In equation (8), For the emissivity of the cover plate of the photovoltaic module, The viewing angle factor between the photovoltaic module cover plate and the sky. is the Stefan-Boltzmann constant.

6. The method for calculating dynamic temperature distribution in a building-integrated photovoltaic (BIPV) wall as described in claim 4, characterized in that, The The formula for calculation is: （9） In equation (9), The thermal conductivity of the air in the air gap. The thickness of the air gap.

7. The method for calculating dynamic temperature distribution in a building-integrated photovoltaic (BIPV) wall as described in claim 4, characterized in that, The The formula for calculation is: （10） In equation (10), The emissivity of the photovoltaic module backsheet. The emissivity of the outer surface of the self-insulating wall.

8. The method for calculating dynamic temperature distribution in a building-integrated photovoltaic (BIPV) wall as described in claim 4, characterized in that, The The formula for calculation is: （11） In equation (11), The thermal conductivity of indoor air.

9. The method for calculating dynamic temperature distribution in a building-integrated photovoltaic (BIPV) wall as described in claim 4, characterized in that, The The formula for calculation is: （12） In equation (12), The emissivity of the inner surface of the self-insulating wall. The perspective factor between the inner surface of the self-insulating wall and the indoor air. is the Stefan-Boltzmann constant.

10. The method for calculating dynamic temperature distribution in a building-integrated photovoltaic (BIPV) wall as described in claim 1, characterized in that, The steps S In section 3, the Runge-Kutta fourth-order model algorithm is used to solve the differential equations.

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