追日偏差量測技術比較與聚光太陽光電系統之實測; Comparison of Techniques of Tracking Offset Angle and Field Tests of CPV System

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Title:	追日偏差量測技術比較與聚光太陽光電系統之實測;Comparison of Techniques of Tracking Offset Angle and Field Tests of CPV System
Authors:	林伯峻;Lin,po-chun
Contributors:	能源工程研究所
Keywords:	PSD;CCD;Webcam;追日偏差角量測技術;影像分離法;閉迴路追日控制系統;PSD;CCD;Webcam;Measurement technique of offset for sun-tracking;Image separation method;Closed-loop sun-tracking system
Date:	2013-07-25
Issue Date:	2013-08-22 12:03:12 (UTC+8)
Publisher:	國立中央大學
Abstract:	本文開發Webcam追日偏差角度量測技術，並針對中壢地區的聚光型太陽光電(CPV)系統進行實地測試。此外亦比較兩種機械視覺技術（CCD與Webcam）於不同日照條件下的不同演算法（三種影像分離法再計算太陽影像質心），結果顯示CCD與Webcam相機拍攝的太陽影像利用影像處理的Canny法能於不同日照條件有效計算太陽影像質心位置，即可定義追日偏差角。文中使用PSD (position sensitive device)和CCD二種追日偏差角量測技術來驗證Webcam方法的可行性，並實地測試中壢地區的兩個不同發電容量的CPV系統（閉迴路追日控制系統）。結果顯示這三種方法量測的偏差角度分布具相同趨勢， 12天量測顯示兩系統平均追日系統偏差角度約0.2o，多雲條件下平均偏差角度會比晴天下高出0.055o。1.5 kW CPV系統的最終發電量(Yf)為3.38 kWh/kW、性能比(PR)為52.3%。至於222 W CPV系統的Yf為2.66 kWh/kW、PR為43%，，造成此差異可能是受聚光元件老化影響與模組散熱不良影響。綜合這三種追日量測方法的優缺點如下：PSD儀器雖具高採樣頻率(5 ms)，但易低日照影響判別太陽位置；CCD和Webcam儀器可改善雲遮條件下拍攝的太陽影像，但需配合合適影像處理演算法；使用 Webcam相機比PSD和CCD儀器的成本低，但在低日照條件拍攝的太陽影像品質略低CCD相機，但考量其成本低廉，對追日量測應用具有相當實用價值。 This thesis developed a technique for measuring the offset of sun-tracking based on Webcam and tested the performance of concentrating photovoltaic system (CPV) in Jhongli area. For comparison, two devices (CCD and Webcam) with three image-separation methods (Canny, Sobel and clustering thresholding) were analyzed to find the centroid of the sun image. The results showed that using the Canny method can effectively identify the image centroid of sun image in wide range of insolation levels, thus the offset of sun-tracking can be obtained. Both measurement techniques of sun-tracking offset based on PSD (position sensitive device) and CCD were adopted to validate the accuracy of Webcam’s approach. In addition, two different CPV systems (222 W and 1.5 kW) were tested in Jhongli area. The results showed that measurements of offset using Webcam, CCD and PSD have the similar probability distributions. During accumulated period of 12 days, the results showed that average offset-angle of the two CPV systems were about 0.2o, and in cloudy conditions the average offset-angle was 0.055o higher than that of the sunny conditions. The larger CPV system (1.5 kW) generated a final electricity production (Yf) of 3.38 kWh/kW and performance ratio (PR) of 52.3%. Meanwhile, Yf was 2.66 kWh/kW and PR was 43% for another smaller CPV system (222 W). The main reason of such large difference may due to aging of concentrating optical lens and ineffective heat dissipation of module. Summary of the pro and con of these three measurement techniques of sun-tracking are as follows. Although the PSD apparatus has very high sampling rate (5 ms), it is easy affected by low irradiation condition, which cannot effectively identify the sun position. CCD and Webcam devices can improve images quality in low irradiation, yet they require proper algorithms of image-processing. Webcam is much cheaper than PSD or CCD, yet its images captured in low irradiations are slightly lower than that of CCD. Considering it low-cost advantage, it is a very practical technique in sun-tracking application.
Appears in Collections:	[Energy of Mechatronics] Electronic Thesis & Dissertation

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