Performance of compound parabolic concentrators with polygonal apertures
Performance of compound parabolic concentrators with polygonal apertures
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DOI：
10.1016/j.solener.2013.06.023
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发表时间：
2013-09
期刊：
影响因子：
6.7
通讯作者：
T. Cooper;Fabian Dähler;G. Ambrosetti;A. Pedretti;A. Steinfeld
中科院分区：
文献类型：
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作者：
T. Cooper;Fabian Dähler;G. Ambrosetti;A. Pedretti;A. Steinfeld
用蒙特卡罗光线追迹法研究了具有N边多边形进出光孔的CPCs的光学性能。多边形CPC是通过围绕下面旋转的CPC的圆孔外接规则多边形来形成的。得到的侧壁是挤压的具有一维曲率的2D CPC型材，因此与旋转CPC相比，可制造性得到了改进。此外，这些设计可以均匀地平铺在平面或曲面上，对于需要多个吸振器的应用来说，间隙损失最小。感兴趣的主要属性是光学效率，其定义为入射到入射光孔的辐射功率的分数，该入射功率到达出射光孔。给出了几何形状、反射率和表面误差对光学效率的影响。在分析这些影响时，导出并利用了一种计算平均反射次数的新方法。此外，还考察了浓缩器出口的流量分布。特别是对于较大的接受角，具有合理边数的多边形CPC的性能接近于旋转CPC的性能，这可以被认为是多边形CPC Forn→-∞的极限情况。结果表明，正方形CPC(n=4)具有良好的反常行为，在小接受角下的性能优于5边和6边设计。在固定式太阳能聚光器和碟形、塔式和槽式初级聚光器等应用中，多边形聚光器有望成为旋转聚光器的廉价替代品。
The optical performance of CPCs havingn-sided polygonal inlet and outlet apertures is investigated by Monte-Carlo ray-tracing. The polygonal CPCs are formed by circumscribing regular polygons about the circular apertures of an underlying revolved CPC. The resulting side walls are extruded 2D CPC profiles with 1-dimensional curvature thus profiting from improved manufacturability compared to the revolved CPC. Furthermore, these designs may be uniformly tiled on flat or curved planes with minimal gap loss for applications requiring multiple absorbers. The principal property of interest is the optical efficiency defined as the fraction of radiant power incident on the inlet aperture which reaches the outlet aperture. The effect of geometry, reflectivity, and surface errors on the optical efficiency is presented. In analyzing these effects, a new approach for calculating the average number of reflections is derived and utilized. Additionally, the flux distributions at the outlet of the concentrators are examined. Especially for large acceptance angles, the performance of polygonal CPCs with reasonable numbers of sides is found to approach that of the revolved CPC, which may be considered a limiting case of the polygonal CPC forn→ ∞. It is found that the square CPC (n= 4) has some favorable anomalous behavior, with performance surpassing that of designs with 5 and 6 sides for small acceptance angles. Polygonal CPCs show promise as less expensive alternatives to the revolved CPC for applications including stationary solar concentrators, and secondary concentrators for dish, tower, and trough primaries.