There are three commonly used control methods of slewing drive for solar tracking system: uniform speed control method, light intensity control method and space-time control method.
1. Uniform speed control method
Since the earth's rotation speed is fixed, it can be assumed that in the morning the sun rises in the east and moves westward due south and sets. The sun moves at a constant speed of 15°/ h at azimuth, moving once in 24 hours. The altitude Angle is equal to the local latitude as a polar axis. The tracking process is to rotate the solar panel fixed on the polar axis at the speed of 15°/ h of earth rotation, so as to track the sun and keep the solar panel plane perpendicular to the solar rays.
This method is simple to control, but difficult to install and adjust, and difficult to determine and adjust the initial Angle.
2. Light intensity control method
In altitude Angle and azimuth Angle tracking, two photosensitive cells are respectively used as the sun position sensors. Four photosensitive cells are mounted in a transparent glass tube. Each pair of photosensitive cells is separated by an intermediate separator and placed symmetrically on both sides of the separator.
When the panel is aimed at the sun, the sunlight is parallel to the diaphragm, and the two photosensitive cells have the same amount of light sensitivity and the same output voltage. When the sunlight is slightly deviated, the shadow of the baffle falls on one of the photosensitive cells, making the two photosensitive cells have different photosensitive capacity and output voltage. According to the change of output voltage, bearing slew drive
for solar energy tracking control is carried out.
This method is characterized by high measurement accuracy, simple circuit and easy implementation, but it can not be tracked in cloudy and overcast environment.
3. Space-time control method
The orbit of the sun is related to many complicated factors such as time, season, local longitude and latitude. Therefore, the above related data can be pre-entered into the microprocessor. By looking up the table and calculating the sun azimuth Angle and altitude Angle through the program, the synchronization of time and space is realized, and the actual Angle is finally obtained to realize accurate control. The method has high precision and good adaptability, but the program is complex and difficult to implement.