Jul 12, 2021 Solar panels

Solar panel design method and structure design

Solar panel design methods and examples
First of all, the production process of solar panels includes customers placing orders. The company designs drawings according to the technical requirements of the customers for solar panels, and the production department manufactures them according to the drawings. What is generally included in the drawing? Let’s look at a few examples below.
①The size of the glass, the size of the aluminum alloy frame, the size of the cell (full and after dicing), the technical requirements of the open circuit voltage, the layout of the solar panel (including the row spacing and column spacing of the cell, the cell and the aluminum alloy The distance of the border, etc.).
②In addition to ①, the dimensions of EVA film, bus bars, tinned solder tape, and backplane are increased, and detailed technical requirements and laser scribing requirements are given.
③In addition to the layout of the solar panel, technical requirements for the installation of the junction box have also been added.

Next, design a 10W solar panel (power deviation requirement: +0.5W; open circuit voltage requirement: (9V). Assuming that you have a 125mm x 125mm monocrystalline silicon cell with two main grids on hand (Pmax measured under standard test conditions: ~2. 4W; Uoc: ~0.5V), give the design ideas, and determine the solar panel shape and module size according to the design (the distance between the cell and the cell is required to be greater than 1mm; the spacing between the cell string and the cell string is greater than 5mm; The distance between the edge of the glass is greater than 30mm; the distance between the bus bar leads is 50mm and the distance from the edge of the glass is 50mm).
The design process is as follows:

  1. Determine the number of solar cells
    Because the power of the solar panel is directly proportional to the area of ​​the solar cell, the number of cells required for a 10W solar panel is
    N=Pset/P max=10W/2.4W~10.5W/2.4W =4.2 ~4.4
    Taking into account the power loss during the solar panel packaging process, N=4.5 here.
  2. Determine the number of dicing solar cells
    The open circuit voltage of the solar panel is proportional to the number of solar cells connected in series, so to meet the 9V open circuit voltage requirement, the number of cells in series is
    M=Uoc.set/Uoc =9V/0.5V=18
    Because M=4N, it is necessary to divide a single 125mmx125mm single-crystal silicon cell with two main grids into four equal divisions, and then weld 18 cells in series.
  3. Board type design
    M=18=6×3=9 x2
    Considering the beauty of the solar panel, here is M=6×3, and the panel diagram is shown in Figure 1.
Figure 1 Solar panel design panel type diagram

Structural design of solar panels
The solar panel is only a component that provides electrical energy in the photovoltaic power generation system. Therefore, the structural design only considers the mechanical strength of the panel glass and aluminum alloy frame, that is, its own structural strength. For the combination of solar panels and buildings, in terms of structural design, in addition to the structure of the solar panel itself, it should also include the structure between the solar panel and the building.

According to the different combination of solar panels and buildings, photovoltaic buildings can be divided into two categories: One is BAPV (Building Attached Photovoltaic), that is, the photovoltaic array is attached to the building, and the building acts as a support for the photovoltaic array. The other is BIPV (Building Integrated Photovoltaic), that is, solar panels appear as a building material, and solar panels become an integral part of the building, such as photovoltaic roofs, photovoltaic curtain walls, and photovoltaic lighting roofs. The combination of photovoltaic arrays and buildings is a commonly used form of BIPV, especially when combined with building roofs. The integration of photovoltaic arrays and buildings is an advanced form of BIPV, which has higher requirements for solar panels. Solar panels must not only meet the functional requirements of photovoltaic power generation, but also take into account the basic functional requirements of the building. Common installation methods combined with buildings are shown in Table 1.

Serial numberBuilding partsInstallation method
1roofRoof tile type
1roofRoof tilt angle setting type
1roofRoof building type
2wallWall installation type
2wallWall building material type
3windowWindow building material type
3windowDaylighting window type
4otherSunshade type
4otherShutter type
Table 1 Common installation methods combined with buildings

Compared with BAPV, BIPV has higher requirements on the structure of solar panels. In addition to the structural safety of solar panels, the structural safety of solar panels involves the structural safety of solar panels. For example, the wind load on the roof of high-rise buildings is much larger than that on the ground, whether the strength of ordinary solar panels can withstand, whether it will affect the normal operation of the solar panels when deformed by the wind, etc. , It also involves the safety of the connection mode of the fixed components. The installation and fixation of the components is not a simple fixation of the installation of air-conditioning, but the corresponding structural calculations for the fixing points of the connecting parts, and full consideration of various unfavorable conditions during the use period. The service life of buildings is generally more than 50 years, and the service life of solar panels is also more than 20 years. The structural safety of BIPV cannot be underestimated. Structural design is a factor related to the working condition and service life of solar panels. The frame structure and fixing method of common modules are relatively simple. When combined with the building, its working environment and conditions have changed, and its structure also needs to be combined with the building. For example, the frame of ordinary components such as the frameless curtain wall of the hidden frame and the drainage of the lighting roof is no longer applicable. For BIPV, solar panel is a kind of building material, used as a building curtain wall or lighting roof, so it needs to meet the safety and reliability requirements of the building. The glass of the solar panel needs to be thickened and has a certain resistance to wind pressure. At the same time, the solar panel also needs to have a certain degree of toughness, and it can be deformed to a certain extent under the action of wind load, and this deformation will not affect the normal operation of the solar panel.

When a photovoltaic cell is used as a building maintenance material, its strength and stiffness must first be analyzed in detail. The structural safety check of the entire system should include but not limited to the following aspects:
① Check the strength and rigidity of battery components (panel materials).
② Check the strength and rigidity of the supporting member (keel).
③ Calculation of the connection between the battery assembly and the supporting member.
④ Calculation of the connection between the supporting member and the main structure.

Solar panel design method and structure design