Photovoltaic module bracket refers to a metal or non-metal supporting structure that fixes photovoltaic modules in a certain orientation (inclination), arrangement and spacing according to the geography, climate and solar resource conditions of the power station construction site. The main function of the photovoltaic module bracket is to support the module panel while striving to obtain the maximum power output of the entire photovoltaic power generation system. Choosing the right photovoltaic support can not only reduce the project cost, but also reduce the maintenance cost in the later stage. If the life cycle of solar photovoltaic panels is 30 years or even longer, then the photovoltaic bracket can be regarded as the backbone of photovoltaic power plants in a certain sense, which can provide reliable support for photovoltaic panels.
In order to make full use of solar radiation resources, the application of tracking brackets in current centralized photovoltaic power plants is becoming more and more common. Compared with the traditional fixed bracket, the tracking bracket has an automatic controller and rocker switch, switching power supply, DC motor and other driving equipment added to the structure, so it is usually called a photovoltaic module bracket tracking system.
1. Classification of photovoltaic module brackets
Photovoltaic module supports are divided into three types: concrete supports, steel supports and aluminum alloy supports. Steel supports can be divided into carbon steel and stainless steel. The steel bracket has stable performance, mature manufacturing technology, high bearing capacity and easy installation. It is the most commonly used bracket material category for large-scale photovoltaic power plants in China. The concrete support is used as the foundation support part of the steel support in part of the power station design. Aluminum alloy is more suitable for building roof photovoltaic power generation projects because of its light weight, beautiful and durable characteristics.
Photovoltaic module brackets are divided into installation methods and functional characteristics, and can be divided into two categories: fixed photovoltaic brackets and tracking photovoltaic brackets (see Table 1)
|Big category||Secondary classification||Features|
|Fixed bracket||Best inclination fixed||Install with the maximum inclination of the local average radiation at a fixed angle to obtain the maximum cumulative radiation at a fixed angle|
|Fixed bracket||Fixed angle adjustable||At the turning point of the change of the sun’s incident angle, adjust the inclination angle of the bracket regularly to increase the absorption of direct sunlight and increase the radiation amount in each season|
|Fixed bracket||Inclined roof fixed||Fixed installation with inclined roof inclination to seek a balance between roof bearing capacity adaptability and radiation loss|
|Tracking bracket||Flat single axis tracking bracket system||The component square array can track the sun along a horizontal axis in the east-west direction to obtain a large amount of radiation, which is widely used in low-latitude areas|
|Tracking bracket||Oblique single axis tracking bracket system||The component square array rotates with a tracking axis in the east-west direction while setting a certain inclination to the south, and rotates around the tilt axis to track the azimuth of the sun to obtain greater radiation, which is suitable for applications in high-concentration areas|
|Tracking bracket||Dual-axis tracking bracket system||The component square array uses two axis rotation (vertical axis, horizontal axis) to track the sun’s rays in real time to ensure that the sun’s rays are perpendicular to the panel surface at every moment, so as to obtain the maximum amount of radiation, suitable for use in various latitudes.|
2.The structural characteristics of the tracking bracket
The automatic tracker system of the tracking bracket mainly includes three parts: the tracking bracket, the driving device and the controller (see Figure 1)
The driving device mainly consists of a driving motor, a rotary reducer and an anchor arm, which is used to drive the beam to drive the solar panel to follow the operation.
Controllers and sensors are the “brains” of the tracking system, which are used to control the movement of the driving device and to ensure proper rotation of the tracking bracket to ensure that the photovoltaic modules track the sun.
1). The working principle of the controller
The controller automatically controls the action of the driving device according to the program, and the driving device pushes the rotating beam to rotate to ensure that the photovoltaic module tracks the movement of the sun. The controller adopts time control algorithm, even if it is rainy weather, it will automatically track reverse movement. Every morning, the driving device will slowly rotate the components from the horizontal position to the east and point to the sunrise, while avoiding obstruction between the components; then, gradually follow the sun’s movement from east to west, and return to the horizontal position at noon. In the afternoon, it turns to face west; in the evening, it returns to the horizontal position.
2). The functional characteristics of the tracking system
Mainstream tracking systems should generally have the following features:
(1) Callback. The tracking algorithm adopts automatic callback (anti-shadow algorithm) technology to avoid the occlusion between tracking in the east-west direction in the morning and evening, and improve the system’s power generation.
(2) Gale protection. During strong winds, the tracker provides automatic protection. When the wind speed is greater than a certain threshold, the tracker will activate the automatic protection function to automatically adjust the current position of the tracking bracket to a preset safe position to protect the field equipment.
(3) Consistency. The tracker uses time control technology to calculate the exact position of the sun every hour of the day, and is not affected by the external environment such as clouds and photosensitive components, and has good consistency.