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Solar energy is becoming increasingly attractive as we grapple with global climate changes. However, while solar energy is free, non-polluting, and inexhaustible, solar panels are traditionally fixed. As such, they cannot take advantage of maximum sunlight as weather conditions and seasons change. This article describes an FPGA- and embedded processor-based system-on-a-chip (SOC) implementation of a prototypical solar-tracking electricity generation system that improves the efficiency of solar panels by allowing them to align with the sun's movements.
Integrated design for faster development, greater flexibility
For optimal efficiency, solar panels should be perpendicular to sunlight, when the illumination is strongest. But since the direction of sunlight changes during the course of a day and from season to season, a high-performance solar tracking system can maximize usage of the panels.
A team of students from Yuan Ze University in Taiwan applied embedded design techniques and a SOC architecture to create an FPGA-based solar tracking system. This system uses two motors as the drive source, conducting an approximate hemispheroidal 3-D rotation on the solar array within a certain amount of space. This rotation allows the system to track the sun in real time to efficiently perform photoelectric conversion and production. To reduce control problems, the two drive motors are decoupled, i.e., the rotation angle of one motor does not influence that of the other motor. Similarly, one motor does not bear the weight of the other. This implementation minimizes the system's power consumption during operation and increases efficiency and the total amount of electricity generated.
This application uses an Altera Nios II configurable embedded processor to perform solar tracking. The design combines the processor with the two-axis motor tracking controller, memory, and I/O interfaces into one Cyclone II FPGA. This integration accelerates development while maintaining design flexibility, reduces the circuit board costs with a single-chip solution, and simplifies product testing. The design includes three modes:
Balance positioning - a tilt switch prevents the solar panels from hitting the mechanism platform and damaging it or the motor.
Automatic mode - the system receives sunlight onto the cadmium sulphide (CdS) photovoltaic cells where the CdS acts as the main solar tracking sensor. The sensor feeds back to the FPGA controller through an analog-to-digital (A/D) converter. The processor is the main control core and adjusts the two-axis motor so that the platform is optimally located for efficient electricity generation.
Manual mode - this mode is available if the system requires maintenance or repair.
Solar Tracking Control Architecture -- Click on image to enlarge. |
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