基于月光聚光先验信息和实测边界能流信息的太阳能塔式电站聚光能流密度成像方法

When a solar tower power plant is in the normal working state, the concentrated solar flux density over the receiver aperture by the heliostat field is high, non-uniform and changing with time. Thus, the project applicant has proposed a general dynamic imaging method of concentrated solar flux density over the large-are receiver aperture from the measured flux density values from the sensors on the aperture boundaries by the boundary interpolation reconstruction technique. As experiments show, when the heliostat field concentrates the sun lights onto the receiver aperture with one aiming point only, the concentrated solar flux density distribution is always close to an elliptical-Gaussian distribution. In this case, the concentrated solar flux density on the receiver aperture of a rectangular area can be fully mapped from the measured solar flux density values on the region border by the boundary interpolation reconstruction technique. When the heliostats in the field track the sun with multiple aim points on the receiver aperture, or the concentrated solar flux density distribution much a bit deviates from an elliptical-Gaussian distribution, the flux density distribution can be best fitted with a mixture of several bivariate functions which are suitable for interpolation reconstruction. Thus, the flux density distribution for each component function can be reconstructed separately, and then the sum of the reconstructed flux density distributions gives the total flux density distribution on the receiver aperture. This project will use the test plant of Badaling solar thermal tower. The moonlight concentrating tests of the heliostat field will be carried out in some clear nights, following the working modes of the solar tower in daytime. Then some typical concentrated solar flux density distributions are indirectly measured (or estimated). Based on the fitting expressions and knowledge of the typical solar flux density distribution of the receiver aperture on the tower, the dynamic solar flux density distribution on the receiver aperture can be mapped from the real-time flux density readings on the rectangular region borders using the boundary interpolation reconstruction technique.

塔式太阳能热发电站的定日镜场向塔顶吸热器聚光，在吸热器采光面形成高强度非均匀能流密度，且能流密度分布随时间不断变化。针对大面积吸热器采光面聚光能流密度分布的动态测量问题，本项目提出基于实时边界能流信息的通用边界插值重建成像方法。大量实验证明，当定日镜场单目标点跟踪聚光时，聚光能流密度分布总接近某个椭圆形高斯分布；吸热器采光面上的能流密度分布，可由矩形区域边界上实测的能流密度值直接边界插值重建。若定日镜场多目标点跟踪聚光，或聚光能流密度分布与椭圆形高斯分布偏差较大时，可用多个适合边界插值重建的二元函数的混合形式最佳拟合，再间接地边界插值重建聚光能流密度分布，即分别直接插值重建，再叠加合成。本项目依托八达岭塔式太阳能热发电站，通过多工况的先验月光聚光实验，间接获得一些典型的定日镜场聚光能流密度分布；在对典型聚光能流密度分布分工况拟合的基础上，实现基于实时边界能流信息的边界插值重建成像方法。

本项目有5个关键的阶段性研究内容和成果：①月光测光站的研制，②线聚光定日镜的搭建和实验研究，③定日镜场中秋圆月夜的聚光实验，④碟式聚光器的研制、光学计算模型以及聚光实验研究，⑤提出新的定日镜场聚光能流密度分布间接测量法。.月光测光站的跟踪器能准确跟踪太阳或月亮，弱光照度计连续测量月光法向直射照度值，是计算月光聚光比的参考照度值；长焦CCD相机，连续采集月月亮图像，监测和分析跟踪器的跟踪误差。.模拟和实验研究表明，线聚光定日镜的聚光光斑变化快，聚光比低，聚光比分布测量误差大，宜用聚光更稳定的碟式聚光器代替，研究不同光源对聚光比分布的影响。.2018年中秋夜，延庆塔式电站定日镜场聚月光实验，CCD相机系统和照度传感器阵列测得了实验值，国内第一次用月光法得到塔式电站聚光比分布的初步结果，打通了技术路线，是一项重要的研究进展。.建立了两种不同的碟式聚光器聚光比分布计算模型，都包含基于月亮图像生成归一化光源亮度分布模型。模拟和实验结果显示，对日光和不同月相的月光，碟式聚光器的聚光比分布的相似度高，月光聚光比分布与日光聚光比分布之间的差异，可通过重复平滑滤波补偿。.多月相的月光聚光比分布平滑滤波到日光聚光比分布的方法，有望应用于定日镜场聚光比分布的间接测量。晴朗月夜测量时，碟式聚光器和定日镜场同时运行，共享平滑滤波次数；碟式聚光器作为参考设备，包含着月光测光站的功能，也用于确定当前月相和工况下重复平滑滤波的次数。.总之，以聚光稳定的碟式聚光器分别对太阳和月亮聚光，通过光学计算和实验对比，研究光源的差异；取一些典型工况，定日镜场夜间对月聚光，获得在吸热面上的聚光比分布，借助简单的平滑滤波，转化成日光聚光比分布，再与对应时刻的太阳法向直射辐射相乘，便得聚光能流密度分布。.本项目探索性强，难度大，室外的测试研究，受天气影响，不确定因素多，但本项目还是取得了一些重要的研究进展，能看到成功的希望的光。