定日镜镜面弯曲机构设计及面形优化

Heliostat Surface Deformation Mechanism Design and Shape Optimization

塔式太阳能热电站存在着定日镜面形精度不足,反射光斑尺寸大的问题,限制着系统的转化效率和成本。针对该问题,通过光学分析建立理想定日镜面形模型,该面形为随时间与位置变化的抛物面的一部分;基于板壳力学提出一种平板弯曲机构,与传统镜面采取的一致刚度分布不同,对方形平板进行二维刚度分布设计,使简单、低成本的弯矩输入载荷可以实现定日镜所需面形;基于有限元分析、光线追迹、牛顿迭代优化等数值程序,计算机构对给定时刻太阳角的最优面形,以及在全年太阳角分布下静态最优化面形的平均光学效率;设计制造定日镜面形试验系统并进行了原理试验;仿真与试验结果表明,机构实现面形可有效减小反射光斑尺寸,效率高于普通平面镜,且结构简单成本低,易于制造与现场装调,为实际系统设计提供了参考思路。

Concentrating solar power tower has the problem that the heliostats have low precision shapes and large spot, which limits the system conversion efficiency and cost. Regarding this problem, firstly, the ideal heliostat shape model is built based on optical analysis. A compliant mechanism is proposed based on the plate bending theory. Different from the conventional mirror design with uniformly distributed stiffness profile, the proposed design tailored the two-dimensional stiffness of a square plate, which permitted to use couples of simple, low-cost bending moments to form the required heliostat shape. Numerical analysis is conducted including finite element analysis, optical ray-tracing, and Newton optimization. A heliostat prototype experimental system is designed and built. The simulation and experiment results show that the shape implemented by the proposed mechanism can reduce the spot size with a higher efficiency than the flat mirror. The proposed simple, low-cost mechanism provides a reference methodology for the practical system.