Wentworth Institute of Technology Solar Tracker Technical Description Andrew Demedeiros, Ryan Ferguson, Bradford Powers 10/5/2009
Contents Introduction... 3 The Solar Tracker... 3 Operating Principles... 3 Technical Specifications... 4 Images and Illustrations... 5 2
Introduction The demand for alternative energy technologies is the greatest it has ever been. Solar energy represents one of the best clean power options currently available. Unfortunately solar panels generate only a very small percentage of the power required by the average household. Therefore, it is of great importance to optimize the power collected by each individual cell. The Solar Tracker A solar tracker is a device which allows the solar cell freedom of motion to follow the sun throughout the course of the day, focusing the highest possible amount of light energy directly onto the panel surface. By doing this, the efficiency of the cell can be increased by as much as 30-40%. For optimal sun tracking, the system has two axis of freedom. The system is also be weather proof since the unit will need to be mounted outside. For this purpose all electrical devices must be enclosed in a water-tight container. The base of the unit is versatile to be able to mount anywhere and on any surface. A specifically designed light-sensing unit communicates with two high-torque direct current motors to aim the solar panel towards the brightest part of the sky. The entire system is controlled by a low-power microcontroller system. All of the electronic systems are powered directly from the power collected by the panels and stored in a battery. The ultimate priority of the electric system will be minimal power consumption. Operating Principles This design has freedom of movement around two axes and can therefore lock-on to the sun at any location in the sky. For example, in the morning the panel will rotate in the direction of the rising 3
sun and tilt at the most extreme angle such that the panel is offered the best exposure. At noon when the sun is directly over head the panel will tilt back down to rest. Finally as the sun begins to set the panel will rotate to the new westward direction. Since the panel can only tilt through 90, the base must rotate 180 from morning to evening. The systems sensor unit consists of four light-to-frequency converters which feed their output signal directly into the microcontroller for processing. This sensor data is then fed into the software control loop which makes the decision of where the sun is relative to the four light sensors. Based on the sensor information, the control program commands the motor to adjust the solar panel s heading and tilt angle. This done through two motor controllers which translate the digital control signal from the microcontroller into high power signal which drives the motors. Each DC motor has its own dedicated motor controller. Technical Specifications The following table outlines the technical specifications of the solar tracking system. Materials Frame Base 1020 Steel Polyvinyl Chloride Dimensions Length 433 mm Width 324 mm Height (0 ) 100 mm Height (90 ) 376 mm Panel Mount Length 423 mm Width 276 mm 4
Electrical Voltage 12 V Current 2 A Motors (2x) Voltage 12 V RPM 6 RPM Torque 7.3 N-m The entire unit price is estimated to be approximately $200 for the model shown here. This price does not include the solar panel. Images and Illustrations Figure 1 shows a computer model of the base frame and rotating base. Not shown is the solar panel which would be mounted on the tilting part of the frame. Figure 1 - Tracker frame (no solar panel shown) Figure 2 shows a photograph of the actual tracker prototype. In this image the solar panel and light sensors are visible. 5
Figure 2 Photograph of the prototype 6