1-kW級聚光型太陽追蹤器結構變形與追日偏差分析; Analysis of Structural Deformation and Concentrator Misalignment in a 1-kW Solar Tracker

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Title:	1-kW級聚光型太陽追蹤器結構變形與追日偏差分析;Analysis of Structural Deformation and Concentrator Misalignment in a 1-kW Solar Tracker
Authors:	方君元;June-Yuan Fang
Contributors:	機械工程研究所
Keywords:	太陽追蹤器;有限元素分析;solar tracker;finite element analysis
Date:	2011-07-22
Issue Date:	2012-01-05 12:31:18 (UTC+8)
Abstract:	本研究主旨在利用有限元素分析法(FEA)，探討一個1-kW級聚光型太陽光電系統之太陽追蹤器在受到重力以及風力作用之影響下，其結構變形和聚光模組的追日偏差量。研究中使用之有限元素模型是依據國立中央大學開發的太陽追蹤器實際尺寸而建立。分析的條件分別為無風之自重狀態，以及在風速為7 m/s和12 m/s之情況，在每個風速作用下又各別分為風從太陽追蹤器的正面、側面以及背面吹來三種風向。此外，在不同季節之運轉條件下，聚光模組的傾斜角度又分為三種不同的設定參數。藉由量測此太陽追蹤器二個選定位置在實際操作情況下之應變變化，與模擬結果作比對，可驗證本研究所建立的有限元素分析模型之正確性。比對結果顯示，模擬結果之應變改變趨勢和實驗結果一致，此一致性證實本研究所建立之有限元素分析模型之正確性，確實可適用於分析聚光型太陽光電系統之結構變形。根據von Mises準則，模擬結果顯示此太陽追蹤器在受到重力加上風速為7 m/s或12 m/s的作用下，各個組件將不會有結構永久變形之情形發生。模擬結果亦顯示此追蹤器在不同追日角度下，聚光透鏡的追日偏差量的變化趨勢與其鏡面法向量方向位移大小的變化趨勢一致。因此，藉由找到擁有較大法向量方向位移的聚光透鏡，即可找到產生較大追日偏差量的聚光透鏡。所有分析情況中，在模組傾角設定為1o(夏至)時，以及風速為12 m/s從太陽追蹤器的側面吹來之情況下，聚光透鏡會有最大的追日偏差量，其值為0.142o。由於此數值小於此聚光模組的可接受角度的0.5o，所以預期此太陽追蹤器在風速為12 m/s的作用下仍可以正常運作，不會有明顯的發電效率下降，同時在正常的運作之下，不會有結構破損之情形發生。 The purpose of this study is to investigate the effects of gravity and wind loadings on structural deformation and concentrator misalignment in a 1-kW high concentrator photovoltaic (HCPV) system using finite element analysis (FEA) approach. A three-dimensional (3-D) FEA model was constructed for a roll-tilt form of solar tracker in an HCPV system developed at the National Central University. Several loading conditions, including gravity only and gravity plus wind speeds of 7 and 12 m/s blowing toward the front (wind direction of 0o), lateral (wind direction of 90o), and rear (wind direction of 180o) sides of the solar tracker, were applied to calculate the stress distribution and structural deformation. Three changeable tilt angles of 24.5o (the spring/autumn equinox), 1o (the summer solstice), and 48o (the winter solstice) for the concentrator modules were also taken into account. Meanwhile, the concentrator misalignment induced by the structural deformation was calculated. A comparison of the simulation and measurement results of strain change at two selected locations in the given solar tracker during field operation was made to validate the constructed FEA model. A reasonable agreement of the simulation and measurement results was found such that the constructed FEA model was validated to be effective in assessment of the structural integrity of an HCPV system. No structural failure was predicted for all components in the given solar tracker under all the given loading conditions according to von Mises failure criterion. An agreement in the trend of variation of concentrator misalignment and normal displacement of Fresnel lens in each concentrator module was found. Therefore, the concentrator with a greater misalignment could be readily identified from the corresponding normal displacement distribution. For all the cases investigated, the maximum concentrator misalignment was of 0.142o for a wind speed of 12 m/s with wind direction of 90o for the tilt angle of 1o (the summer solstice) and it was within the range of an acceptance angle of 0.5o for the given concentrator module. Consequently, the given HCPV system can operate safely under the effects of wind speeds of 7 and 12 m/s with a good efficiency in power generation.
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