Talk about how to install & design solar mounting system with reliability and cost-effectiveness? ?

2020-04-08 10:02
The importance of the solar mounting system is self-evident. The important guarantee for the long-term, stable and safe operation of photovoltaic power plants depends on it. This article focuses on a variety of typical brackets in photovoltaic systems, analyzes from the aspects of ensuring system power generation, safety, structural stability and reliability, and puts forward the issues that should be focused on in the design or selection of solar system mounting brackets, and puts forward Theoretical mechanics analysis, finite element analysis and experimental test analysis
Reliability and cost-effectiveness are needed. How to install and design solar mounting structure?

2. Introduction of typical stent applications
This article mainly categorizes the installation occasions. According to the actual situation of photovoltaic power station construction over the years, photovoltaic systems are mostly installed in the following occasions:
2.1 Tile roof installation system (including ceramic tiles, slate tiles, asphalt tiles, etc.)
The tile roof installation system is generally a residential household system, especially the villa residences in developed countries such as Europe, America, the United Kingdom, and Australia, as well as domestic high-end villas and rural residences. The unit quantity of this type of installation system is generally small, mostly small systems of 2KW ~ 10KW. The installation of the tile roof needs to be designed according to the structure of the house (tile shape, material and span of the supporting beam, slope, etc.), weather, wind pressure, snow pressure and other information. The bracket and hook fittings shown in Figure 1 can be applied to most tile roof installations at home and abroad.
2.2 Color steel tile roof installation system (including trapezoidal tile, angle chi type, upright lock type)
Color steel tile roof installation systems are mostly industrial plants, which are more common in industrial parks. The structure of this installation is shown in Figure 2. Different color steel tile types can use different installation supports or fixtures. The bracket type clamped by the fixture should be preferred. The structure is easy to install, does not damage the roof, and has no water leakage problems.

Figure 1 The main bracket form of tile roof and commonly used hook accessories Figure 2 The main bracket form of color steel tile roof and commonly used support accessories
2.3 Reinforced concrete flat roof installation system
Concrete flat roof installation systems are also mostly industrial plants. This kind of roof mostly adopts a loading type installation form that does not damage the roof. The load calculation determines the weight to be loaded, and a slotted cement block or loading tray is used for ballasting. This structure is shown in Figure 3. Figures 4 and 5 show the integrated components and bidirectional bracket products independently developed by Trina Solar with independent intellectual property rights. The integrated component products have the following significant features: (1) innovative ideas, pre-installed brackets ; (2) Fewer accessories and simpler logistics; (3) Quick installation and easy operation; (4) Comes with ground connection.
Figure 3 Common brackets for flat roofs 4 Integrated components for Trina Solar integrated installation 5 Bidirectional mounting bracket system
2.4 Ground installation system
The ground installation system is dominated by large-scale photovoltaic power stations, and is planned to be built on non-cultivated land such as deserts, Gobi, and wasteland in areas rich in solar energy. The large-scale ground photovoltaic power station supports are fixed, single-axis tracking, and dual-axis tracking. The tracking type has a significant gain in system power generation, but it has a large footprint, high cost, and high operation and maintenance costs. Considering the economy, it is still mainly based on fixed installation. Figure 6 shows the commonly used ground installation. Due to space limitations, we will not start a follow-up discussion here.
(A) Spiral pile type (b) Cement foundation type (c) Plug-in type
Figure 6 Common ground solar mounting structure forms
3. Structural design and key technologies of system installation support
The photovoltaic installation bracket must first be suitable for the installation occasion, as far as possible to be organically integrated with the installation environment, and ensure that the installation is firm, reliable and stable, and as beautiful as possible.
3.1 Applicability requirements
As mentioned above, the photovoltaic system can be installed on many occasions, different occasions and environments, and even the same type of installation system, depending on the roof structure, surrounding environment, weather information, etc., different 
solar mounting structures will be required. Therefore, the installation site Conduct a detailed site survey to design and adopt the structural form that best matches the photovoltaic system.
3.2 Strength, stiffness, stability and reliability requirements
The structural design should meet the requirements of strength, rigidity and stability, and the design service life should not be less than 25 years. Reliability directly affects the power generation of the system and thus affects the return on investment. The 25-year service life puts higher requirements on the reliability of the system. This requires the system to occur in natural disasters such as storms, snowstorms, earthquakes, and floods in harsh climates. It can still operate stably and reliably. At the same time, problems such as premature aging of materials and severe corrosion should be avoided. The design of the strength, stiffness and stability of the solar mounting structures needs to be designed according to the most unfavorable conditions of the load effect combination (self weight, wind load, snow load, maintenance load, etc.).
3.3 Power generation guarantee and economic requirements
In the design of photovoltaic systems, the installation angle and spacing of components are two very important parameters that directly affect the power generation of the system. The installation inclination and azimuth are generally determined by the latitude of the location and the characteristics of the installation occasion. The installation inclination and spacing are generally designed in accordance with the principle that the components are not blocked from 9:00 to 15:00 on the winter solstice. In the actual engineering design, Trina Solar Small System Technology Department uses RETScreen, PVSYST and other professional software to conduct a comprehensive economic evaluation of system power generation, system costs, and floor space (occupation cost) at different inclination angles to obtain The best yield thus determines the best installation inclination. ☞☞ China's provinces and cities photovoltaic power plant optimal installation inclination and speed check table
3.4 Building safety requirements
During the design and construction of the photovoltaic system installed on the roof of the building, the following issues should be noted: (1) The bearing capacity of the building needs to be calculated to confirm whether it can be installed or it needs to be reinforced before installation; (2) Avoid damage to the roof The original waterproof layer, if damaged, needs to be re-waterproofed to ensure that there is no water leakage problem. The form that does not damage the roof should be preferred in the design; (3) The photovoltaic array should avoid installation across the expansion joints, settlement joints, and deformation joints of the building In order to prevent the components from leaking and falling off due to deformation and displacement of the building; (4) When the photovoltaic module is installed as a balcony enclosure, it must meet the relevant building code requirements, such as the balcony fence of the middle-rise and high-rise residences should not be less than 1.1 m; (5) When installing parallel to the roof, sufficient ventilation and heat dissipation gaps should be left. Poor ventilation and heat dissipation will affect the power generation of the system; (6) The design and selection of photovoltaic brackets should take into account the safety and safety of construction Convenience, especially high-altitude and complex roof installation systems require special consideration.
4. Structural performance analysis
No matter where the photovoltaic system is installed, it is necessary to ensure the wind resistance and snow performance of the bracket itself. In order to ensure the safe and reliable operation of the photovoltaic system during the 25-year service life, to avoid problems such as array collapse and being overturned , It is necessary to check and check the bearing capacity, stiffness and stability of the bracket.
4.1 Theoretical mechanical analysis
At present, the specification for the calculation of the load of the
 solar mounting system has not yet been formed. Generally, the calculation can be carried out according to the requirements in the “Code for Loads of Building Structures”. The calculation formulas of wind load and snow load in this code are: wk = βz * μs * μz * wo and sk = μr * so. In the specific analysis and calculation, the accurate selection of coefficients and the effective combination of different loads must also be considered to determine The most unfavorable stress situation.
Where: wk is the wind load standard value (kN / m2); βz is the wind vibration coefficient at height z; μs is the wind load carrier type coefficient; μz is the wind pressure height change coefficient; wo is the basic wind pressure (kN / m2) ; Sk is the standard value of snow load (kN / m2); μr is the snow distribution coefficient of the roof area; so is the basic snow pressure (kN / m2).
4.2 Finite element software analysis
The structural analysis of the scaffold can be optimized with structural analysis software PKPM or SAP2000, or with FEA analysis software such as ANSYS and ABQUS. Figure 7 shows the SAP2000 analysis model and result diagram of the mounting bracket structure of a project. Figure 8 shows an example diagram of parts check using ANSYS.
4.3 Test and analysis
Generally, the following experiments can be carried out to test the performance of the scaffold: (1) to ensure the quality of the materials used by chemical composition testing; (2) to use a film thickness meter to test the thickness of the hot-dip zinc steel and aluminum alloy anodized film to ensure that The product has sufficient corrosion resistance; (3) further test the corrosion resistance of the material through the salt spray test to ensure a 25-year service life; (4) pass the pull-out resistance test to test the installation accessories against positive wind pressure The pull-out force of the system ensures the reliability of the installation system; (5) The wind load carrier coefficient of the bracket can be accurately obtained through the wind tunnel test, and the bearing capacity of the bracket can be accurately calculated, but the cost of the wind tunnel test is relatively high, so the actual There are few applications in the design of 
 solar mounting system, which may be used in the development of some new products.

V. Conclusion
In the early stage of the construction of photovoltaic power plants, solar mounting system products did not receive the attention they deserved. With the increase in installations, the problems gradually leaked out, causing huge losses to the project. In the long run, improving the performance and quality of the mounting brackets will allow the system to operate safely and reliably for 25 years. I believe this is necessary and correct to ensure maximum investment efficiency. The issues that should be paid attention to in the stent design proposed in this paper and the structural optimization accounting method can effectively make the photovoltaic system stent achieve the perfect unification of reliability and economy.

Various efficient and flexible solar mounting structure solutions waiting for you here! Welcome to consult !
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