1、大學畢業設計外文翻譯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 t

2、he panel at 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

3、 discovery 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

4、. solar arrays 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 realisa

5、tion of fossil fuel's 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,

6、 with solar power 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 generat

7、ion, and will drop 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

8、gathering losses. light gathering is dependent on the angle of incidence of the light source providing power (i.e. the sun) to the solar cell's 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

9、 the day the sunlight 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 p

10、ower until at the point 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 ma

11、intain the maximum power 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 r

12、eal-time tracking would 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 depende

13、nt resistor to detect 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

14、arrives, the tracker 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 phototransis

15、tor. the motor turns 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.

16、 they have been set 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

17、 in determining the 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 sunlig

18、ht, as the angle of 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

19、will cause more light 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 a

20、t each cell, which can 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 pol

21、ycrystalline silicon 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 dissipa

22、te 9w that would match the panel's rating 9w at 12v corresponds to a current of 0.75a, so by ohm's 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 c

23、onnected in a charging arrangement 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 simi

24、lar conditions including no cloud 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

25、was found that in this case, the 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 pa

26、nel reached up to 400%.this amounts 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 am

27、meter was placed in series with 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

28、 collection efficiency increase 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 s

29、olar tracking device. by extracting 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

30、 a means of increasing overall 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 p

31、anel, owing to its simple construction 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. t

32、he geared support was removed 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 si

33、ngle axis tracker such as the 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

34、 use by domestic or commercial 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 variabl

35、e indication of their relative 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.refe

36、rences fahrenburch, a and bube, 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 s

37、ino-german technical cooperation project", 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 ma

38、nagement system for photovoltaic systems, international 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 re

39、forms, cambridge university press, 1994. damm, j. issue #17, june/july 1990. an active solar tracking system, homebrew magazine.太陽能跟蹤系統：太陽能電池有效利用摘要-文章介紹了使用步進電機和光傳感器跟蹤太陽的簡單方法潛在的好處，用此方法可以提高功率、效率，高級裝置可以跟蹤太陽以保持部分光線垂直照射，并有太陽能跟蹤系統的設計，實施和實驗測試、細節的設計和實驗結果。關鍵詞-可再生能源，優化功率1.前言近幾年來，太陽能電池板的半導體光電材料能轉換成直接使用的直流電壓，使太

40、陽能通過光電原理發電成為現實。使用太陽能電池板陣列，就是將一系列的太陽能電池板連接，直流電壓產生可實際使用的負荷。越來越多的太陽能電池板或面板正在使用，且效率達到很高的水平，而在偏遠地區經常使用的供電線路是不經濟的。這種取之不盡，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。其實早在75或100年前可再生能源用于發電的形式，已經在一定程度上被使用，如太陽能，風能，水能和地熱不同程度上都被成功地得到充分利用，使用最廣泛的是水力和風力發電。太陽能發電在全世界使用不太普及，這主要因為太陽能電池板成本較高和轉換效率低。太陽能發電正在大力研究，太陽能發電成本現在已經能達到幾美分內以每千瓦/小

41、時的發電量。由于新技術的使用，太陽能發電成本會進一步下降，如鈦氧化物電池，實驗室發電效率為32 ，平均效率的15-20 ，太陽能發電系統已經能代替可再生能源。能量損失包括減少逆變損失，儲存損失，光聚集的損失。聚光依賴于光源的入射角，入射角在太陽能電池板表面接近垂直，其功率最大。如果一個單位的太陽能電池板將被安裝在水平地面，很顯然，在這一天，所有的太陽光入射角接近早上和晚上。在這樣一個角度來看，聚集太陽光能基本上是零，因此沒有產生電能。隨著時間的流逝，以中午太陽光的入射角為零度 ，穩步增加，直到太陽光入射角垂直于太陽能電池板，其功率達到最大。相反，當到黃昏時，越來越多因角度引起的功率，其功率再次

42、降到最低。在這種情況下，我們認為有必要保持輸出功率最大，保持入射角接近垂直最好。由太陽能電池板傾斜，不斷面對太陽，這是可以實現的。這一過程的遙感控制和以下的敘述，被稱為太陽能跟蹤。為了解決對太陽的現實時跟蹤，有必要采取有效的太陽光照，這樣任何數據（太陽光照）都能運行。2 .敏感元件和信號處理最簡單的方法就是使用一個ldr燈，通過察覺燈表面發亮強度來改變跟蹤器的位置。另外一種方法，如杰夫達姆發明主頁電源，就是利用太陽光照射在兩個光電晶體管上，并提出了許多跟蹤太陽方法。如圖1所示：a狀態 b狀態 c狀態圖.1供選擇的太陽跟蹤的方法當清晨來臨，跟蹤器便圖a所示：左邊的光電晶體管被啟動，發出信號使得電

43、動機持續轉動直到金屬板形成陰暗面，使得跟蹤器返回并且呈現圖b所示；而隨著時間慢慢過去，不一會便轉到c圖，繼而啟動右邊的光電晶體管。電動機又會轉動直到再次出現圖b所顯示的狀態，周而復始直至夜幕降臨，或是直到達到最小探測光的程度。設計好像有一個狹窄的感光度范圍，感光度是在光電晶體管電路偏置條件下成立的。正是由于這個原因成立，太陽能電池板本身被選為是遙感裝置，提供一個很好的光照強度檢測機制。因為遙感裝置很敏感，不同的光線提供一個近似線性電壓范圍，在傾斜或歪曲的陽光，由這個范圍來確定有用的光線。因此，這是一個兩個太陽能電池板相反方向而立簡單的三角形裝置。如圖2所示：圖.2太陽參比室設定在其他位置太陽能

44、電池板能接收同等數量的陽光，雖然入射角不是90度 ，相當于一下這兩種情況，如圖3所示：圖.3太陽參比室休息位置隨著太陽的移動，如圖4所示，假設太陽能跟蹤器尚未改變入射角，即將造成很多的太陽光不能利用。圖.4太陽參比室相對太陽的有效角度這將明顯地導致電壓區別，太陽電池板對比其他將有更高發展潛力。 在太陽板面上這種現象產生一個可發現的信號，可以由一條適當的電路處理。3.a原型太陽跟蹤儀最后階段參與耦合電路，把電機安裝在支架上。最終完整的產品如圖5 所示：圖.5原型太陽跟蹤儀它有一個由安裝在輪緣上的多晶硅組成的solarex 9w太陽能電池板列陣，該裝置的制作靈感來自于那些技術人員。簡單地說有兩個測試對象進行測試。第一種情況是消除跟蹤器和平面安裝位置的誤差，輸出連接到負載，將消除9瓦，符合控制板的功率規定為9瓦，而在12伏的對應電流0.75安 ，因此由歐姆定律來計算負載的電阻為16歐。50瓦的負載是最接近控制板的測試值，跟蹤器設備仍然需要電力，太陽能電池板連接在一個充電的12v電池上給跟蹤器設備供電，負載電壓和電流通過兩個單獨的