1、外文文献跟踪器太阳能自动Solar TrackerDecember 15, 2005Duke University Smart House Pratt School of EngineeringThe Solar Tracker team was formed in the fall of 2005 from five students in an ME design team, and a Smart House liaison. We continued the work of a previous solar tracker group. The task was to design a
2、 prototype tracking device to align solar panels optimally to the sun as it moves over the course of the day. The implementation of such a system dramatically increases the efficiency of solar panels used to power the Smart House. This report examines the process of designing and constructing the pr
3、ototype, the experiences and problems encountered, and suggestions for continuing the project 1.IntroductionSolar tracking is the process of varying the angle of solar panels and collectors to take advantage of the full amount of the suns energy. This is done by rotating panels to be perpendicular t
4、o the suns angle of incidence. Initial tests in industry suggest that this process can increase the efficiency of a solar power system by up to 50%. Given those gains, it is an attractive way to enhance an existing solar power system. The goal is to build a rig that will accomplish the solar trackin
5、g and realize the maximum increase in efficiency. The ultimate goal is that the project will be cost effective that is, the gains received by increased efficiency will more than offset the one time cost of developing the rig over time. In addition to the functional goals, the Smart House set forth t
6、he other following goals for our project: it must not draw external power (self-sustaining), it must be aesthetically pleasing, and it must be weatherproof.The design of our solar tracker consists of three components: the frame, the sensor, and the drive system. Each was carefully reviewed and teste
7、d, instituting changes and improvements along the design process. The frame for the tracker is an aluminum prismatic frame supplied by the previous solar tracking group. It utilizes an A-frame design with the rotating axle in the middle. Attached to the bottom of this square channel axle is the plat
8、form which will house the main solar collecting panels. The frame itself is at an angle to direct the panels toward the sun (along with the inclination of the roof). Its rotation tracks the sun from east to west during the day. The sensor design for the system uses two small solar panels that lie on
9、 the same plane as the collecting panels. These sensor panels have mirrors vertically attached between them so that, unless the mirror faces do not receive any sun, they are shading one of the panels, while the other is receiving full sunlight. Our sensor relies on this difference in light, which re
10、sults in a large impedance difference across the panels, to drive the motor in the proper direction until again, the mirrors are not seeing any sunlight, at which point both solar panels on the sensor receive equal sunlight and no power difference is seen. After evaluation of the previous direct dri
11、ve system for the tracker, we designed a belt system that would be easier to maintain in the case of a failure. On one end of the frame is a motor that has the drive pulley attached to its output shaft. The motor rotates the drive belt which then rotates the pulley on the axle. This system is simple
12、 and easily disassembled. It is easy tointerchange motors as needed for further testing and also allows for optimization of the final gear ratio for response of the tracker.As with any design process there were several setbacks to our progress. The first and foremost was inclement weather which deni
13、ed us of valuable testing time. Despite the setbacks, we believe this design and prototype to be a very valuable proof-of-principle. During our testing we have eliminated many of the repetitive problems with the motor and wiring so that future work on the project will go more smoothly. We also have
14、achieved our goal of tracking the sun in a hands-off demo. We were able to have the tracker rotate under its own power to the angle of the sun and stop without any assistance. This was the main goal set forth to us by the Smart House so we believe our sensed motion prototype for solar tracking will
15、be the foundation as they move forward in the future development and implementation of this technology to the house. 2. Concepts and Research2.1 Tracking TypeOur group used a brainstorming approach to concept generation. We thought of ideas for different solar tracking devices, which proved difficul
16、t at times due to the existing frame and concept presented to us by Smart House. Other concepts were generated through research of pre-existing solar tracking devices. Originally our concept generation was geared towards creating a completely new solar tracker outside of the constraints of the previ
17、ous structure given to us by Smart House. This initial brainstorming generated many concepts. The first one was a uni-axial tracking system that would track the sun east to west across the sky during the course of a day and return at the end of the day. This concept presented the advantage of simpli
18、city and presented us with the option to use materials from the previous structure (which was also intended to be a uni-axial tracker) in construction. Another more complex concept was to track the sun bi-axially which would involve tracking the sun both east to west and throughout the seasons. The
19、advantage of this concept was a more efficient harvesting of solar energy. The third concept was to only track throughout the seasons. This would provide small efficiency gains but nowhere near the gain provided by tracking east to west. The different structures we came up with to accomplish trackin
20、g motion included a rotating center axle with attached panels, hydraulic or motorized lifts which would move the main panel in the direction of the sun, and a robotic arm which would turn to face the sun. The clear efficiency gains coupled with the simplicity of design of the uni-axial tracking syst
21、em and the existence of usable parts (i.e. motor and axle) for the rotating center axle structure, led us to the choice of the East to West tracking, rotating center axle concept. 2.2 StructureOnce the method of motion was chosen, it was necessary to generate concepts for the structural support of t
22、he axle. Support could be provided by the triangular prismatic structure which was attempted by the previous Smart House solar tracker group or through the use of columns which would support the axis on either side. While the prismatic structure presented the advantage of mobility and an existing fr
23、ame, the columns would have provided us with ease of construction, simple geometric considerations, and ease of prospective mounting on the roof. Due to the heightened intensity of time considerations, the previous financial commitment to the prismatic structure by Smart House, and our limited budge
24、t, the presence of the pre-existing frame proved to be the most important factor in deciding on a structure. Due to these factors we decided to work within the frame which was provided to us from the previous Solar Tracker group. 2.2 Tracking MotionOnce the structural support was finalized we needed
25、 to decide on a means to actualize this motion. We decided between sensed motion, which would sense the suns position and move to follow it, and continuous clock type motion, which would track the sun based on its pre-determined position in the sky. We chose the concept of continuous motion based on
26、 its perceived accuracy and the existence of known timing technology. During the evaluation stage, however, we realized that continuous motion would prove difficult. One reason was the inability to draw constant voltage and current from the solar panels necessary to sustain consistent motion, result
27、ing in the necessity for sensing the rotation position to compensate. Continuous motion also required nearly constant power throughout the day, which would require a mechanism to store power. Aside from these considerations, the implementation of a timing circuit and location sensing device seemed d
28、aunting. After consulting Dr. Rhett George, we decided on a device using two panels and shading for sensed motion.3. Detailed Design3.1 FrameThe frame was designed from one inch square aluminum tubing, and a five foot long, two inch square tube for the axle. It is constructed with a rigid base and t
29、riangular prismatic frame with side supporting bars that provide stability. The end of the axle is attached to a system of pulleys which are driven by the motor. It is easily transported by removing the sides of the base and folding the structure.3.2 SensorOur sensing panels are bolted to the bottom
30、 of the main solar panel frame and braced underneath with half inch L-brackets. The mirrors are attached to the inside of the sensing panels and braced by L-brackets as well. The whole structure attaches easily to the main panel frame which is attached to the main axle using four 2-inch U-bolts. A t
31、hird panel is bolted to the structure to return the main panels direction towards the horizon of sunrise. 3.3 How the Sensor WorksOur sensor creates movement of the motor by shading one of the panels and amplifying the other when the system is not directly facing the sun. The two sensing panels are
32、mounted parallel to the main panels symmetrically about the center axle with two mirrors in between them. The shading on one of the panels creates high impedance, while the amplified panel powers the motor. This happens until the panels receive the same amount of sunlight and balance each other out
33、(i.e. when the sensing panels and main panels are facing the sun.). We initially attempted using a series configuration to take advantage of the voltage difference when one of the panels was shaded (Appendix C). This difference, however, was not large enough to drive the motor. We subsequently attempted a parallel configuration which wou
