As a clean and pollution-free energy, solar energy has a very broad
development prospect. Solar power generation has become the fastest growing
technology in the world. However, the utilization of solar energy is greatly
affected by natural conditions such as topography, topography, location, clouds
and rain. There are problems of intermittency and the direction and intensity of
light changing with time. This puts forward higher requirements for the
collection and utilization of solar energy. . At present, many solar panel
arrays are basically fixed, do not fully utilize solar resources, and have low
power generation efficiency.
According to research, in solar photovoltaic power generation, under the
same conditions, the power generation capacity of automatic tracking power
generation equipment is 30% higher than that of fixed power generation
equipment. The author proposes a new type of automatic solar tracking system
that uses self-made sensors to monitor the sun's illumination angle and uses
silicon photovoltaic cells to be self-powered. This system not only has a simple
structure and low cost, but also does not require manual intervention in the
tracking process. In the case of complex weather changes, , the system can also
work normally and has broad application prospects. And based on the design idea
of the tracking system, application simulation tests were conducted.
1. System composition and working principle
The automatic tracking system is mainly used to drive 10~20kW solar panels.
The solar panel frame automatically follows the direction of the sun's relative
motion from the initial position to the west and rotates in an intermittent
manner, so that the solar panels of the photovoltaic power generation system
maintain in a larger power output state.
After sunset, the rotation reset circuit in the rotation control circuit
automatically starts, driving the solar panel frame of the photovoltaic power
generation system to rotate to the initial position and enter a dormant state.
In the morning, when the sun rises, the circuit starts and the control circuit
automatically searches for the sun. On the one hand, this device has low energy
consumption. On the other hand, it uses silicon photovoltaic cells to provide
self-power. Under the same power demand conditions, it can effectively reduce
energy consumption and reduce the installation cost of solar cell projects. The
basic composition of the tracking system is shown in Figure 1.
The solar cell automatic tracking system is mainly divided into the
mechanical part and the solar automatic tracking control circuit part. The
mechanical part is mainly composed of silicon photovoltaic sensor detection
circuit, dual-axis mechanical tracking and positioning system and battery; the
solar automatic tracking control circuit is mainly composed of sensing signal
processing circuit, microcontroller circuit, drive circuit and other parts. The
entire device achieves the following goals: ① Works safely and reliably,
ensuring that the panels can face the sun during the designed tracking time; ②
Automatically returns to the original working position at night to prepare for
the next day's work needs; ③ It has fault diagnosis function. When it fails, the
battery panel will stop working to prevent damage to the mechanism; ④ Use
silicon photovoltaic cells and batteries to work with self-sufficient power,
without the need for external power supplies; ⑤ Adopt intermittent working
methods to save energy consumption.
The tracking system uses four pieces of 1cm2 silicon photovoltaic cells to
form a sensor, 2 pieces in a group, with an included angle of 30° to 60°,
forming a wedge-shaped photoelectric sensor, which detects the horizontal and
vertical angles of the sun respectively, and controls the mechanical part
through the drive circuit.
The mechanical part adopts a two-axis mechanical tracking and positioning
system, which is mainly composed of a panel bracket, a base, two rotating shafts
and a DC horizontal drive motor. The entire solar panel and silicon photovoltaic
cell detection device are installed on the upper panel bracket in Figure 1. The
tracking device is designed as a dual-axis mechanical tracking and positioning
system, which can track in two directions: horizontal azimuth angle and vertical
altitude angle at the same time. Under the control of the drive circuit, the
battery panel can be freely rotated 270° in the horizontal direction and 0~90°
in the vertical direction. The horizontal and vertical control systems have
their own sensors, signal amplification circuits, and motor control systems
respectively, which drive the solar concentrator to always work at a maximum
direct angle of 90° to the sun's rays.
The control circuit part is mainly composed of a single-chip microcomputer
system, which has the advantages of low cost, low power consumption, high degree
of intelligence, and few instructions. With the 8-bit microprocessor AT89C2051
as the core, combined with the internal logic chip and peripheral circuit
components, the device intermittently controls the biaxial mechanical mechanism
to track the movement of the sun through signal detection and processing. The
power of the mechanical mechanism is provided by a DC motor, and can be
controlled according to the The mechanical shape and size of the solar cell
power adjustment device enable control of solar panels of different areas.
The design principle of the control circuit part is shown in Figure 2. In
the circuit of Figure 2, silicon photovoltaic cells are used as the orientation
detection element. When the sunlight is not direct, the silicon photovoltaic
cells in the same group receive different intensity of light. This difference
will lead to different voltages of the silicon photovoltaic cells. The voltage
generated in the group can be used to judge the intensity of light in different
directions through the voltage comparator. The comparison result of the signal
comparator (1 high level, 0 low level) is sent to the single-chip microcomputer
89C2051. The single-chip microcomputer control circuit is based on the input
signal. The running program controls the steering of two DC motors: one controls
the left and right rotation in the horizontal plane; the other controls the up
and down rotation in the vertical plane, so that the solar panel can always be
perpendicular to the sun.
In order to reduce power consumption, intermittent control mode is adopted,
and the intermittent time can be adjusted arbitrarily according to requirements.
This design adopts an intermittent time of 0.5h and uses timing detection sensor
signals to control the rotation of the dual-axis mechanical tracking and
positioning system. When not rotating, most of the microcontroller is in a sleep
state, and the power consumption at this time is 15% of normal operation.
2. Software design
The software design of the automatic tracking system adopts a modular
structure, and the judgment process of the tracking mode is completely
implemented by the software. After the system starts working, the system program
starts timing and calls the signal acquisition program regularly. The circuit
begins to detect the external interrupt signals P1.0 and P1.7. The external
interrupt signal is the level signal of the silicon photovoltaic cell sensor and
its variation. If there is an external interrupt When the signal meets the
adjustment conditions, the adjustment subroutine is entered to adjust the angle
of the battery panel. In order to meet the needs of full automation, the system
also determines whether it is daytime by detecting external interrupt signals
and automatically turns on or off the tracking mode. This can prevent
meaningless tracking at night and reduce battery consumption. If the battery
voltage is lower than a certain value, the system will sound an alarm and cut
off the power supply circuit to meet its own needs.
Once the interrupt condition is established, the system begins to enter the
adjustment subroutine. The adjustment subroutine will first detect the last
recorded horizontal azimuth angle α and vertical azimuth angle β, and then
perform horizontal summing based on the detected signals of P1.0 and P1.7.
Vertical azimuth adjustment. The adjustment process is mainly completed by
controlling the A and B motors of the dual-axis mechanical tracking and
positioning system. After the adjustment is completed, it returns to the main
program of the system.
The solar automatic tracking system does not require additional energy
input and can automatically detect day and night. It has the characteristics of
low cost, high accuracy, and flexible use. Even in the case of complex weather
changes, the system can work normally and improve the utilization efficiency of
solar energy.
3. Application of solar power generation system in urban gardens
The device has practical value and is especially suitable for urban garden
facilities and traffic lighting. Urban gardens, especially public green spaces,
are the main places for urban residents' activities. They are equipped with a
large number of public service facilities, so they have become a large energy
consumer. The garden green space occupies a wide area. If wires are laid to
supply power to the facilities in the garden, the cables will hinder the view
and increase the burden of daily maintenance. Using solar power generation
systems to supply power to public facilities in gardens and green spaces not
only eliminates many troubles and disadvantages caused by laying wires and
cables everywhere, but also facilitates daily maintenance and reduces
maintenance costs.
Solar power generation facilities in gardens and green spaces are generally
used for night lighting and greenhouse power supply. Inverters can be used for
power supply in greenhouses and greenhouses. The system structure is shown in
Figure 3.
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