外文文献--跟踪器太阳能自动.doc

精品文档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 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 prototype, 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 to 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 tracking 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 the 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 tested, 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 platform 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 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 results 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 drive 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 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 denied 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 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 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 difficult 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 previous 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 simplicity 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 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 tracking 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 system 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 the 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 frame, 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 budget, 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 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 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, resulting 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 daunting. 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 triangular 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 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 third 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 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 (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 would take advantage of the impedance of the shaded panel (Appendix C) and provide the current needed to drive the motor. Once the sensing mechanism has rotated from sunrise to sunset, the third panel, which is usually shaded, uses sunlight from the sunrise of the next day to power the motor to return the panels towards the direction of the sun. 4. ConclusionThroughout this project we enlisted the support of multiple resources (i.e. ME and EE professors, previous Smart House teams). We learned early on that a clear problem definition was essential to efficient design and progress. We struggled initially as we tried to design a tracking device that was different from the previous solar tracker groups attempt, without fully weighing the size of their investment and the advantages of using the existing frame for our purposes. As we worked with the fixed frame construction from the previous group we learned that variability of design is key, especially when in the initial phases of prototyping. After many setbacks in testing of the solar panels, we learned that when working with solar panels, much time needs to be set aside for testing due to the unpredictability of the weather.The actual implementation of using the prototype in its intended location on the Smart House roof requires weather-proofing to protect the wiring and electrical connections from the elements, housing for the motor, a bracing system to attach the structure to the roof, and possible redesign to eliminate excess height and simplify overall geometry. The efficiency of the sensor system could be improved by widening the mirrors or by placing blinders along the sides of the panels to decrease the effects of reflected and refracted light incident on the shaded sensing panel. 外文文献翻译太阳能跟踪器2005年12月15日杜克大学智能家居普拉特工程学院太阳能跟踪队成立于2005年秋季，由五名设计团队的队员组成，我们还与智能家居有联络工作。我们小组继续以前太阳能跟踪的工作，现在的任务是设计一个模拟跟踪装置，由于太阳光的方向在一天中是变化的，所以要最大限度地使太阳能电池板与太阳光线垂直。这种跟踪方式，可以很大地提高太阳能电池板的工作效率，并且可使太阳能电池板用来提供智能家居。这个报告审查过程中设计和构建的原型以及所得到经验和遇到的问题激励我们继续这一工程。一、导言太阳跟踪的过程是通过改变太阳能电池板的角度，这样的优势是能使太阳能电池板充分利用太阳能。这是通过旋转板子使其始终垂直于太阳的入射角实现的。工业上的初步测试表明，这个过程可以增加太阳能发电系统效率高达50。这同时也说明这是一个加强现有的太阳能发电系统特别有吸引力的研究。其目标是建立一个能完成太阳能跟踪，并实现最高的效率的跟踪机。其终极目标是本工程要符合成本效益，也就是说随着时间的推移将降低发展跟踪机的花费。另外，智能家居还为我们的工程提出了以下的4个目标：必须不吸取外部能源（自我维持），必须外观美丽，而且还要能防水。我们设计的太阳能跟踪器包括三大部分：结构，传感器和驱动系统。每个都在设计过程中被仔细审核和检测，实行跟踪。先前的太阳能跟踪团队设计的结构是一个铝棱柱形框架。它采用了一种“A-结构”设计并且旋转轴在中间，与方形电池板底部相连的是一个用来支撑集热板的平台。该框架本身有一个角度，此角度的度数由小组对当地实际情况调查而定，其旋转的轨道是系统随太阳从东到西转动，这一过程在白天进行。该系统所设计的传感器采用了两个小型太阳能板作为采集板。这些传感器面板用垂直的反光镜相连，除非反光镜镜面接收不到任何太阳光，不然它会把其中一个面板遮挡住，而使另外一个能够充分的接收到太阳光。我们的传感器依赖于这种差异，结果是两种差异很大的面板都可以驱动电机跟踪的方向，直到反光镜得不到任何太阳光，而此时双方的太阳能板上的传感器可以得到相同的太阳光，没有能量上的差别。在我们往用于跟踪直接驱动系统之后，我们设计了一个带系统以防系统在跟踪时失败，系统的一端是一个电机，能够传动皮带轮和输出。电机旋转传动皮带，再旋转滑轮上的轮轴。这个系统简单，且易于拆解，所以很容易根据需要将跟踪传动系统做进一步的改进和优化。正如任何设计过程中都会遇到很多问题，我们遇到的首要的问题是天气恶劣而否认我们珍贵的测试时间。尽管遇到挫折，我们依然相信，这样的设计与原型是非常有价值的。在我们的测试中，我们已经消除了许多重复的有关电机和绕线的问题，使得以后在这个项目上的研究更为顺利。我们用我们的模型完成跟踪太阳光线的演示，在没有任何外部辅助下，我们能让跟踪器依靠自己的能量旋转和停止，演示过程中没有任何援助。在今后的发展中将这项技术推广到普通家庭是联合国向我们提出智能家居的主要目标，我们也相信我们的研究一定能使太阳能跟踪向前迈出一步。二、观念和研究2.1跟踪模式我们小组用了一个集思广益的方法来界定概念。我们的思想理念是为了设计不同条件下使用的太阳能跟踪装置，因为它们克服了不同条件下的困难，再把可行的框架和概念介绍给我们的智能家居。其他的概念产生是通过研究事先存在的太阳能跟踪装置得到的。原来我们的概念是面向创造一个完全新的太阳能跟踪装置，以前的设计结构方法已经给我们的智能家居提供了思路。这一初步献策产生了许多观点：第一个观点是一个单向轴跟踪系统，该系统将追踪太阳从东到西横跨天空的全过程，检测每一段时间， 直到第二天结束。这一概念的提出很简单，我们选择使用的结构材料正在制作中；另一种更复杂的概念是双向轴跟踪系统，并在整个季节都能从东到西跟踪太阳。这种概念是较为高效率的利用太阳能；第三个概念是只随季节跟踪。这将提供小型效率收益，但远不及第二个概念提供的从东到西的跟踪装置。我们设计的跟踪装置结构包括一个旋转中心轴和附加板以及液压机或电动升降机，将提供主要方向的跟踪，还有一个机械臂将使它转到面对着太阳。清晰的效率收益，再加上设计简单的单向轴跟踪系统，以及以电机