(1) The role and classification of bracket
The power generation efficiency of a solar cell module is directly related to the time, the intensity of sunlight, and the placement and tilt angle of the cell module. The design of its bracket system also plays an indispensable role in the construction and lighting power generation process. Low cost, easy maintenance and reliable installation, such as being able to withstand the impact of various loads such as rainwater corrosion, atmospheric corrosion, wind pressure load, snow load, etc., are the necessary conditions for solar photovoltaic power generation.
According to the requirements of different forms of solar photovoltaic power generation, the bracket system can be divided into tracking system series brackets, matrix solar brackets, single-column solar brackets, double-column solar brackets, wall solar brackets, roof solar brackets and other different specifications and models, or can be divided into roof installation system, ground installation system and building energy-saving integrated bracket installation system according to different installation methods.
At present, the commonly used solar photovoltaic support systems are divided into three types in terms of material: steel support, aluminum alloy support and concrete support. Aluminum alloy brackets are usually used in the roof solar energy of civil buildings. They are beautiful, durable, corrosion-resistant and light in weight. However, due to their low bearing capacity, they cannot be used in solar power plant projects. Concrete supports are mainly used in large-scale photovoltaic power stations. Because of their importance, they can only be placed in the wild and in areas with good foundations. Due to their strong stability, they can support large-sized panels. The performance of the steel bracket (Figure 1) is stable, the manufacturing process is mature, the bearing capacity is high, the anti-corrosion performance is excellent, and it has a beautiful and unique connection design, and the installation is simple and fast, and the steel and stainless steel parts made of structural anti-corrosion materials have a service life of more than 20 years.
(2) Design of bracket strength
In the design of the bracket, in order for the bracket to reach the load it bears, it is necessary to determine which material to use and how much to use, and then calculate the strength accordingly. The strength of the bracket is mainly determined by the fixed load, the component quality G, including the frame quality GM, the frame self-weight GK1+ and other masses GK2, that is, the fixed load G=GM+GK1+GK2.
①The analysis and parameter selection of the load and force of wind pressure.
Wind pressure load W refers to the sum of the wind pressure on the assembly and the wind pressure on the support. The wind pressure load formula acting on the array:
In the formula, W is the wind pressure load; Cw is the wind coefficient; . is the wind speed of air density, N·s2/m4; v is the reference of wind speed, m/s; S is the wind-receiving area, m2; a is the height compensation factor; I is the use factor; J is the environmental factor.
Among them, the altitude compensation factor varies with the altitude, and the speed pressure is also different, so the different wind pressure caused by the different altitude should be corrected. The height compensation factor is calculated by the formula a=(h/h0)1/n. In the formula, a is the height compensation factor; h is the height of the array to the ground; h0 is the reference height of 10m; n is the degree of change due to the increasing height, and the standard is 5. The usage factor generally takes a value of 1.0, and the environmental factor generally takes a value of 1.0.
In the case of different installation forms, corresponding factors shall be used.
②Snow load force analysis and parameter selection. Snow load calculation:
In the formula, S is the snow load; Cs is the slope factor; P is the average unit weight of the snow, which is equivalent to the weight of the snow at a thickness of 1 cm, N/m2. The general area is 19.6 N/m2 or more, and the snow is more The area is above 29.4N/m2; Zs is the vertical deepest depth of snow, cm; As is the total area of snow.
At present, there are two main ways to install the base of the photovoltaic support, one is the concrete foundation, and the other is the ground pile foundation. Considering the construction cost and the local geographical environment, most of the large-scale photovoltaic power stations in China currently use concrete foundations. Pile foundations are mostly used in foreign countries, such as Italy, Germany, Australia and other countries. For the consideration of land reuse, the economic costs are appropriately relaxed. For the ground matrix, two aspects should be paid attention to in terms of technology: one is the wind resistance requirements of the supports, and the other is the distance between the support matrices. Under the circumstance of ensuring wind resistance, the bracket adopts a mixture of steel structure and aluminum alloy, which can not only ensure the wind resistance of the bracket, but also ensure the overall appearance of the bracket.