利用繞射光柵設計可透光的分光式平面太陽能集光器
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2022
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本論文提出一種可透光的分光式太陽能集光器，設計不同周期的傾斜梯型光柵和分層光柵分別做為第一段和第二段偏折光結構。第一段偏折光結構利用光柵與全內反射將入射波長為 400~600nm 的太陽光偏折並耦合到下方的楔型導光板(Tapered Light Guide Plate, TLGP)中，再經由內部全反射將該光線收集到 TLGP 端面。第二段偏折光結構利用光柵與全內反射將穿透第一段偏折光結構的太陽光中入射波長為 600~900nm 的太陽光耦合並偏折到下方的楔型導光板中，再經由內部全反射將該光線收集到 TLGP 端面。並利用嚴格耦合波分析(Rigorous Cupled-Wave-Analysis, RCWA)對不同類型的光柵結構進行優化，使得一階繞射效率最大化。經過模擬最佳化後，最佳模型的第一、第二段光柵繞射效率分別達 83%和 88%。最後在導光板尾端附加一個額外的複合拋物面聚光器（Compound Parabolic Concentrator, CPC）以進一步提高輸出光線的光線幾何集中倍率達 7.6。在假設模型位處北緯 25.05 度的台北、朝南安置的情況下，以單軸轉動追跡太陽每日 8:00 到 16:00 東昇西落，針對 400~900 nm 的太陽光譜，整體系統的全年平均效率為 70%。對於漫射可見光的整體透光率約 27%。
In this study, a light-transmissible spectroscopic solar concentrator is proposed. Using slanted trapezoidal grating and layered grating with different periods are designed as the first and second transmissive-deflection components respectively. The first component deflects the incident sunlight with wavelengths of 400-600 nm at a large angle into the Tapered Light Guide Plate (TLGP) below, and then the light propagates to the TLGP end face through internal total reflection. The second component deflects the incident sunlight with wavelength of 600-900 nm that passes the first component at a large angle into the TLGP below, and then the light propagates to the TLGP end face through internal total reflection. Different types of grating structures are optimized by Rigorous Coupled-WaveAnalysis (RCWA) to maximize the first-order diffraction efficiency. After optimization, the diffraction efficiencies of the first and second gratings of the best model are 83% and 88%, respectively. Finally, an additional optical element such as a compound parabolic concentrator (CPC) is attached to the end of the light guide plate to further increase the geometric concentration ratio of the output light up to 7.6. Assuming that the model is located in Taipei at 25.05 degrees north latitude and is placed tilting to the south for tracing the sun from 8:00 to 16:00 every day by uniaxial rotation, for the solar spectrum of 400~900 nm, the average annual efficiency is 70%, and the overall transmittance for ambient diffuse light is about 27%.
In this study, a light-transmissible spectroscopic solar concentrator is proposed. Using slanted trapezoidal grating and layered grating with different periods are designed as the first and second transmissive-deflection components respectively. The first component deflects the incident sunlight with wavelengths of 400-600 nm at a large angle into the Tapered Light Guide Plate (TLGP) below, and then the light propagates to the TLGP end face through internal total reflection. The second component deflects the incident sunlight with wavelength of 600-900 nm that passes the first component at a large angle into the TLGP below, and then the light propagates to the TLGP end face through internal total reflection. Different types of grating structures are optimized by Rigorous Coupled-WaveAnalysis (RCWA) to maximize the first-order diffraction efficiency. After optimization, the diffraction efficiencies of the first and second gratings of the best model are 83% and 88%, respectively. Finally, an additional optical element such as a compound parabolic concentrator (CPC) is attached to the end of the light guide plate to further increase the geometric concentration ratio of the output light up to 7.6. Assuming that the model is located in Taipei at 25.05 degrees north latitude and is placed tilting to the south for tracing the sun from 8:00 to 16:00 every day by uniaxial rotation, for the solar spectrum of 400~900 nm, the average annual efficiency is 70%, and the overall transmittance for ambient diffuse light is about 27%.
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太陽能集光器, 繞射光柵, Solar concentrator, Diffraction grating