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1、Solar Tracking System: More Efficient Use ofSolar PanelsAbstract-This paper shows the potential system benefits of simple tracking solar system using a stepper motor and light sensor. This method is increasing power collection efficiency by developing a device that tracks the sun to keep the panel a
2、t a right angle to its rays. A solar tracking system is designed, implemented and experimentally tested. The design details and the experimental results are shown. Keywords-Renewable Energy, Power Optimization.IntroductionExtracting useable electricity from the sun was made possible by the discovery
3、 of the photoelectric mechanism and subsequent development of the solar cell a semi-conductive material that converts visible light into a direct current. By using solar arrays, a series of solar cells electrically connected, a DC voltage is generated which can be physically used on a load. Solar ar
4、rays or panels are being used increasingly as efficiencies reach higher levels, and are especially popular in remote areas where placement of electricity lines is not economically viable.This alternative power source is continuously achieving greater popularity especially since the realisation of fo
5、ssil fuels shortcomings. Renewable energy in the form of electricity has been in use to some degree as long as 75 or 100 years ago. Sources such as Solar, Wind, Hydro and Geo- thermal have all been utilised with varying levels of success. The most widely used are hydro and wind power, with solar pow
6、er being moderately used worldwide. This can be attributed to the relatively high cost of solar cells and their low conversion efficiency. Solar power is being heavily researched, and solar energy costs have now reached within a few cents per kW/h of other forms of electricity generation, and will d
7、rop further with new technologies such as titanium-oxide cells. With a peak laboratory efficiency of 32% and average efficiency of 15-20%, it is necessary to recover as much energy as possible from a solar power system.This includes reducing inverter losses, storage losses, and light gathering losse
8、s. Light gathering is dependent on the angle of incidence of the light source providing power (i.e. the sun) to the solar cells surface, and the closer to perpendicular, the greater the power. If a flat solar panel is mounted on level ground, it is obvious that over the course of the day the sunligh
9、t will have an angle of incidence close to in the morning and the evening. At such an angle, the light gathering ability of the cell is essentially zero, resulting in no output. As the day progresses to midday, the angle of incidence approaches 00, causing an steady increase in power until at the po
10、int where the light incident on the panel is completely perpendicular, and maximum power is achieved.As the day continues toward dusk, the reverse happens, and the increasing angle causes the power to decrease again toward minimum again.From this background, we see the need to maintain the maximum p
11、ower output from the panel by maintaining an angle of incidence as close to as possible. By tilting the solar panel to continuously face the sun, this can be achieved. This process of sensing and following the position of the sun is known as Solar Tracking. It was resolved that real-time tracking wo
12、uld be necessary to follow the sun effectively, so that no external data would be required in operation.2.The sensing element and signal processingMany different methods have been proposed and used to track the position of the sun. The simplest of all uses an LDR- a Light Dependent Resistor to detec
13、t light intensity changes on the surface of the resistor. Other methods, such as that published by Jeff Damm in Home Power, use two phototransistors covered with a small plate to act as a shield to sunlight, as shown in Fig. 1. Fig.1 Alternative solar tracking methodWhen morning arrives, the tracker
14、 is in state A from the previous day. The left phototransistor is turned on, causing a signal to turn the motor continuously until the shadow from the plate returns the tracker to state B. As the day slowly progresses, state C is reached shortly, turning on the right phototransistor. The motor turns
15、 until state B is reached again, and the cycle continues until the end of the day, or until the minimum detectable light level is reached. The problem with a design like have a narrow range of sensitivity, this is that phototransistors once in a circuit under set bias conditions. they have been set
16、up It was because of this fact that solar cells themselves were chosen to be the sensing devices. They provide an excellent mechanism in light intensity detection- because they are sensitive to varying light and provide a near-linear voltage range that can be used to an advantage in determining the
17、present declination or angle to the sun. As a result, A simple triangular set-up was proposed, with the two solar cells facing opposite directions, as shown in Fig. 2.Fig.2 Set-up of solar reference cellsIn its rest position, the solar cells both receive an equal amount of sunlight, as the angle of
18、incidence, although not 900, is equal in both cases as seen in Fig. 3.Fig.3Solar reference cells at rest position It can be seen in Fig. 4 that as the sun moves in the sky, assuming that the solar tracker has not yet moved, the angle of incidence of light to the reference panels will cause more ligh
19、t to fall on one cell than the other. Fig.4 Solar reference cells at a significant angle to the sunThis will obviously cause a voltage difference, where the cell that is facing the sun will have higher potential than the other. This phenomenon will result in a detectable signal at each cell, which c
20、an be processed by a suitable circuit. 3.A prototype solar trackerThe final stage involved coupling the circuitry to the motor and mounting it onto the bracket. The final product is seen complete in Fig. 5.Fig.5 A prototype solar trackerIt has a Solarex 9W solar array made of polycrystalline silicon
21、 mounted on the flanges, which was borrowed from the tech officers.Quite simply having two test subjects carried out testing. The first scenario involved removing the panel from the tracker and laying it in a flat orientation. The output was connected to a load that would dissipate 9W that would mat
22、ch the panels rating 9W at 12V corresponds to a current of 0.75A, so by Ohms law; a load resistance was calculated as being . A 50W resistor was the closest value found and was connected to the panel. The tracking device still requires power, but a 12V battery that is connected in a charging arrange
23、ment with the solar panel supplies it. The voltage across and current through the load was monitored using two separate multimeters, and was recorded every half- hour on a clear day into an Excel spreadsheet. The readings were taken on a span of days that possessed similar conditions including no cl
24、oud cover. The readings are shown below in a graph generated by Excel in Fig. 6. Fig.6 Experimental resulte of power increase for tracked panelIt is possible to calculate a percentage increase and an average increase by writing the appropriate calculations in excel. It was found that in this case, t
25、he fixed panel provided an average of 39% of its 9W, or 3.51W, calculated over a 12- hour period. By contrast, the tracked solar panel achieved an overall 71 % output, or 6.3W over the same time frame. At the earlier and later hours, the power increase over the fixed panel reached up to 400%.This am
26、ounts to an average 30% increase in power simply by maintaining the solar panel as perpendicular as possible to the sun. To ensure that power was not being wasted, the device itself was also monitored for current drawn to power itself. When the device was at rest, an ammeter was placed in series wit
27、h the battery. The total current at 12V was measured as only 4mA, which corresponded to a power dissipation of 48mW under no load. 4. Discussion A solar tracker was proposed, designed and constructed. The final design was successful, in that it achieved an overall power collection efficiency increas
28、e from only 39% for a fixed panel to over 70% for the same panel on the tracking device. In terms of real value, this means that the overall cost of a system can be reduced significantly, considering that much more power can be supplied by the solar array coupled to a solar tracking device. By extra
29、cting more power from the same solar panel, the cost per watt is decreased, thereby rendering solar power much more cost-effective than previously achieved using fixed solar panels.The high outlay in a solar tracking system has been a factor that discouraged tracking as a means of increasing overall
30、 solar efficiency. Many commercial units cost in excess of US $2000 for a unit that can track the sun while bearing a panel of considerable weight. The device presented in this thesis is capable of supporting a load of at least 8 kg, the average weight of a 75 W solar panel, owing to its simple cons
31、truction and the high torque capabilities of the motor. The parts used for this device were also extremely low-cost, with the total value using parts found from scrap sources being a total of about A $ 30, including all electronic components and solar reference cells. The geared support was removed
32、from an old security camera, the stepping motor from an old printer, and all other parts, excluding the 9W solar panel, were sourced from various scrap items. However, if all these parts would have to be purchased, the cost would be projected at no more than A$ 100.A single axis tracker such as the
33、one made offers a great power increase over a fixed solar panel, but a two-axis tracker would provide more power still. This could be a subject for further development.Solar tracking is by far the easiest method to increase overall efficiency of a solar power system for use by domestic or commercial
34、 users. By utilising this simple design, it is possible for an individual to construct the device themselves. 5. ConclusionA solar tracker is designed employing the new principle of using small solar cells to function as self-adjusting light sensors, providing a variable indication of their relative
35、 angle to the sun by detecting their voltage output. By using this method, the solar tracker was successful in maintaining a solar array at a sufficiently perpendicular angle to the sun. The power increase gained over a fixed horizontal array was in excess of 30%.6.References Fahrenburch, A and Bube
36、, R. 1983, Fundamentals of solar cells, AcademicPress, New York. Partain, L.D.1995,Sollar Cells and their applications, John Wiley& ,Sons. New York. E Weise, R Klockner, R Kniel, Ma Sheng Hong, Qin Jian Ping, Remote Power Supply Using Wind and Solar energy-a Sino-German Technical Cooperation Project
37、, Beijing International Conference on Wind Energy, Beijing, 1995. Wichert B, Lawrance W, Friese T, First Experiences with a Novel Predictive Control Strategy for PV-Diesel Hybrid Energy Systems, 1999. Duryea S, Syed I, Lawrence W, An Automated Battery Management System for Photovoltaic Systems, Inte
38、rnational Journal of Renewable Energy Engineering, Vol I, No 2, Aug 1999. Twidell J, Weir J, Renewable Energy Systems, Chapmanand Hall, 1994 Centre for Resources and Environmental Studies,ANU, Sustainable, Energy Systems Pathways for Australian Energy Reforms, Cambridge University Press, 1994. Damm,
39、 J. Issue #17, June/July 1990. An active solar tracking system, HomeBrew Magazine.太阳能跟踪系统：太阳能电池有效利用摘要-文章介绍了使用步进电机和光传感器跟踪太阳的简单方法潜在的好处，用此方法可以提高功率、效率，高级装置可以跟踪太阳以保持部分光线垂直照射，并有太阳能跟踪系统的设计，实施和实验测试、细节的设计和实验结果。关键词-可再生能源，优化功率1.前言近几年来，太阳能电池板的半导体光电材料能转换成直接使用的直流电压，使太阳能通过光电原理发电成为现实。使用太阳能电池板阵列，就是将一系列的太阳能电池板连接，直流电压
40、产生可实际使用的负荷。越来越多的太阳能电池板或面板正在使用，且效率达到很高的水平，而在偏远地区经常使用的供电线路是不经济的。这种取之不尽，用之不完可代替的新能源得到普及，主要原因是化石燃料的不足。其实早在75或100年前可再生能源用于发电的形式，已经在一定程度上被使用，如太阳能，风能，水能和地热不同程度上都被成功地得到充分利用，使用最广泛的是水力和风力发电。太阳能发电在全世界使用不太普及，这主要因为太阳能电池板成本较高和转换效率低。太阳能发电正在大力研究，太阳能发电成本现在已经能达到几美分内以每千瓦/小时的发电量。由于新技术的使用，太阳能发电成本会进一步下降，如钛氧化物电池，实验室发电效率为3
41、2 ，平均效率的15-20 ，太阳能发电系统已经能代替可再生能源。能量损失包括减少逆变损失，储存损失，光聚集的损失。聚光依赖于光源的入射角，入射角在太阳能电池板表面接近垂直，其功率最大。如果一个单位的太阳能电池板将被安装在水平地面，很显然，在这一天，所有的太阳光入射角接近早上和晚上。在这样一个角度来看，聚集太阳光能基本上是零，因此没有产生电能。随着时间的流逝，以中午太阳光的入射角为零度 ，稳步增加，直到太阳光入射角垂直于太阳能电池板，其功率达到最大。相反，当到黄昏时，越来越多因角度引起的功率，其功率再次降到最低。在这种情况下，我们认为有必要保持输出功率最大，保持入射角接近垂直最好。由太阳能电池
42、板倾斜，不断面对太阳，这是可以实现的。这一过程的遥感控制和以下的叙述，被称为太阳能跟踪。为了解决对太阳的现实时跟踪，有必要采取有效的太阳光照，这样任何数据（太阳光照）都能运行。2 .敏感元件和信号处理最简单的方法就是使用一个LDR灯，通过察觉灯表面发亮强度来改变跟踪器的位置。另外一种方法，如杰夫达姆发明主页电源，就是利用太阳光照射在两个光电晶体管上，并提出了许多跟踪太阳方法。如图1所示：A状态 B状态 C状态图.1供选择的太阳跟踪的方法当清晨来临，跟踪器便图A所示：左边的光电晶体管被启动，发出信号使得电动机持续转动直到金属板形成阴暗面，使得跟踪器返回并且呈现图B所示；而随着时间慢慢过去，不一会
43、便转到C图，继而启动右边的光电晶体管。电动机又会转动直到再次出现图B所显示的状态，周而复始直至夜幕降临，或是直到达到最小探测光的程度。设计好像有一个狭窄的感光度范围，感光度是在光电晶体管电路偏置条件下成立的。正是由于这个原因成立，太阳能电池板本身被选为是遥感装置，提供一个很好的光照强度检测机制。因为遥感装置很敏感，不同的光线提供一个近似线性电压范围，在倾斜或歪曲的阳光，由这个范围来确定有用的光线。因此，这是一个两个太阳能电池板相反方向而立简单的三角形装置。如图2所示：图.2太阳参比室设定在其他位置太阳能电池板能接收同等数量的阳光，虽然入射角不是90度 ，相当于一下这两种情况，如图3所示：图.3
44、太阳参比室休息位置随着太阳的移动，如图4所示，假设太阳能跟踪器尚未改变入射角，即将造成很多的太阳光不能利用。图.4太阳参比室相对太阳的有效角度这将明显地导致电压区别，太阳电池板对比其他将有更高发展潜力。 在太阳板面上这种现象产生一个可发现的信号，可以由一条适当的电路处理。3.A原型太阳跟踪仪最后阶段参与耦合电路，把电机安装在支架上。最终完整的产品如图5 所示：图.5原型太阳跟踪仪它有一个由安装在轮缘上的多晶硅组成的Solarex9W太阳能电池板列阵，该装置的制作灵感来自于那些技术人员。简单地说有两个测试对象进行测试。第一种情况是消除跟踪器和平面安装位置的误差，输出连接到负载，将消除9瓦，符合控
45、制板的功率规定为9瓦，而在12伏的对应电流0.75安 ，因此由欧姆定律来计算负载的电阻为16欧。50瓦的负载是最接近控制板的测试值，跟踪器设备仍然需要电力，太阳能电池板连接在一个充电的12V电池上给跟踪器设备供电，负载电压和电流通过两个单独的万用表监测，并每隔一个半小时记录一次，其记录储存到Excel电子表格。每天都是数据输送到下一个天，包括那天是阴天。数据显示图如Excel所在图6：图.6实验结果功率增加追踪小组百分比增加是可以计算的。在Excel中表写出相应的平均增加量，发现在这种情况下，在12小时内平均每个控制板增加39%，计算得到的功率是9瓦或是3.51瓦。相比之下，太阳能电池板跟踪实
46、现整体的输出增加71%，或在同一时间内增加6.3瓦，在早晨以后的时候，在控制版面上功率增加能达到400%。只要保持太阳对太阳能电池板的垂直照射，就相当于功率平均提高30%。为了确保功率提高，设备本身也安装一套提高功率的测试装置。当该装置不工作时，一个电表被安装在电池上，电压一直保持在12伏，因为只有四毫安，这就相当于一个在没负载时功率为48毫瓦。4.讨论太阳能跟踪器从方案提出到最后的修改，最终的方案终于设计成功，因为设计方案整体功率聚集率比原方案增加39%，跟踪器装置对太阳利用率均超过70%。按实际的价值来算，这就意味着设计方案的总体成本明显的降低很多，考虑到太阳能电池板陈列的耦合跟踪器更有利
47、于提供电力，因此提高太阳能电池板的功率能降低发电成本，从而太阳能跟踪器式发电比以前固定式太阳能电池板发电提高了效益。但是太阳能跟踪器费用高昂，成为太阳能电池板提高效率的一个阻碍因素。太阳能跟踪器在许多商业单位以2000美元为一单位，且单位数量很少。在本论文谈到跟踪器装置至少能承受8公斤，平均每公斤太阳能电池板能发电75瓦。由于该装置结构简单和使用高转矩电动机，因此该设备的成本极低，甚至有的部分元件可以使用废弃原料来代替，包括所有的电子元件和太阳参比室，所以估计总体价值是30美元。齿轮传动支架可以从监控器上拆，步进电机可以从旧打印机上拆，以及其他的零件都可以从其他的地方上拆下来用，但是不包括9瓦
48、太阳能电池板，因此所有的零件都来自各种废品，但是如果所有的零件都必须购买的话，费用估计也超不过100美元。一轴太阳能跟踪器比固定太阳能电池板发电功率高，而两轴跟踪器的发电功率更高。这也是对太阳能利用的进一步的发展。这个太阳能跟踪器是迄今为止最简单的设计方案，如果太阳能发电效率进一步的被提高的话，能在家庭用户或个体商业使用。这个简单的设计方案有可能被未来建筑师采用。5.总结太阳能跟踪器的的设计依据创新原则，采用小型太阳能电池板并能通过光传感器自我调节， 太阳相对角度通过传感器探测能得到一个电压输出读数。使用这个方法，太阳能跟踪器系统能成功地保持太阳能电池板列阵与太阳光线垂直，比太阳能电池板固定在
49、水平面上功率增加30%。6.参考文献 Fahrenburch 和Bube ，太阳能电池根本性，纽约：学术出版社，1983年。 Partain ，LD约翰威利之子，Sollar细胞及其应用，纽约，1995。 魏泽，马胜红，秦其黯平，研究克洛克纳和Kniel，远程电源使用风能和太阳能，中德技术合作项目，北京国际会议上风能，北京，1995。 Wichert，劳伦斯钨赖斯吨，第一次经验，新型预测和控制光伏柴油混合能源系统， 1999。 杜里埃硫，赛我，劳伦斯钨自动电池管理系统的光伏系统，国际期刊可再生能源工程， 1999-8-2。 Twidell J ，Weir J，可再生能源系统。 Chapmana
