空间薄膜抛物面聚光系统辐射能流密度的研究

结合薄膜聚光器的光学特性,同时考虑空间太阳形状模型、薄膜表面反射误差的概率模型,采用蒙特卡罗光线追迹法计算空间薄膜抛物面聚光系统接收面上辐射能流密度,分析薄膜聚光器的表面反射误差、焦径比、接收器的遮挡作用和接收器的位置对系统接收面上辐射能流密度分布的影响,为空间薄膜聚光系统的参数设计和性能分析提供参考。     

碟式抛物面太阳能聚能器焦面特性数值仿真

结合太阳能聚能器的光学特性,同时考虑了太阳不平行度、跟踪指向误差、镜面的反射误差以及焦面位置误差等误差因素,采用蒙特卡罗法对碟式抛物面太阳能聚能器的焦面特性进行了数值模拟分析,获得在等口径和等焦距条件下,边缘角对焦平面热流分布的影响,为碟式太阳能聚能器的设计和安装提供参考依据。     

新型太阳能聚焦器焦面能流分布仿真

考虑太阳光不平行度,应用蒙特卡洛光线跟踪法及光线的镜面反射定律,并采用数值模拟的方法分析了焦面位置误差、指向误差等对一种新型展开式太阳能聚焦器焦面光斑形状及能流分布的影响。结果表明:焦面位置误差绝对值越大,焦面光斑半径越大,焦面能流峰值越小;焦面误差绝对值相同时,焦面光斑形状及能流分布几乎一样;指向误差越大,光斑越偏离焦面中心,并且光斑由圆形逐渐演变成椭圆形,光斑长短径之比越大。结论可以为该新型空间太阳能聚焦吸热系统的设计提供参考依据。     

抛物面型聚光器聚焦光斑能流密度分布的计算

采用光线跟踪法对旋转抛物面型聚光器进行光路分析,应用蒙特-卡罗法计算焦平面上的能流密度分布,考虑了聚光器表面形状误差、跟踪误差、接收器位置误差、接收器遮挡作用、太阳形状、漫反射和不同半张角的影响,并通过实例计算证明了该方法的正确性。该方法为系统的优化设计和接收面处能流密度的测量提供理论依据。     

三维CPC太阳能聚集特性的数值模拟

根据几何光学原理,通过联合求解高次曲面方程,采用射线踪迹蒙特卡洛法(Monte-Carlo ray-tracing Method,MCRT)模拟了直射太阳光束在三维CPC内的传播过程.通过数值模拟,分析了三维CPC的太阳能聚集能流密度分布、方向分布和透过特性以及这些聚集特性参量随CPC高度截取比例、CPC最大接收角、跟踪误差等因素的变化.结果表明,三维CPC的出射面太阳能热流分布出现峰值;截顶后三维CPC的最大接收角不变,透过率性能有所改善.     

炉膛燃烧温度场三维可视化监测方法模拟研究

为了利用火焰图像监测装置检测到的炉膛燃烧辐射能分布图像信息重建三维燃烧温度场，作者提出了一种针孔成像条件下的快速方法计算CCD（Charge-Coupled Device，电荷耦合器件）靶面接收的辐射能。成像像素接收到的系统网格单元的辐射能的份额的计算结果和辐射能图像计算结果均体现了成像过程的方向选择性和辐射能传递规律的作用。针对炉膛燃烧三维温度场重建的严重病态问题建立了一种基于Tikhonov正则化的求解方法，对于单峰型三维温度分布重建模拟计算结果表明，即使辐射图像检测包含均方差达到0.11的误差，温度场重建误差仍能维持与测量误差基本相当的水平，温度分布可视化质量较高，各种图像检测组合方式的重建结果比较显示，炉膛四角沿高度方向每隔5m左右交叉对角布置两个辐射图像采集装置，能够获得较好的全炉膛温度场可视化结果。     

CPV系统中太阳能转换效率分析方法的探讨

太阳能转换效率是评价太阳能系统优劣的重要指标。在聚光光伏系统中,太阳能转换效率受太阳跟踪误差的影响较大。文章分析了太阳跟踪误差与太阳能转换效率之间的关系,提出了基于跟踪误差的太阳能转换效率误差分析法,填补了光伏产业中缺少太阳能转换效率评定标准的空白。文章以北京地区某日全天太阳光照辐射量数据为例,采用了两种经典的太阳位置算法,对文章所提出的误差分析法进行了验证说明。理论分析和验证表明,误差分析法可以作为评价太阳能系统能量转换效率的评定依据。     

采用真空柱状接收器的碟式集热器光热特性研究

提出利用柱状真空管作为碟式太阳能聚光系统的接收器,强化碟式抛物面太阳能聚光器的接收效率、降低系统对跟踪精度的要求,进而降低整个系统的工程造价,实现系统低成本运行。对系统结构进行光学和传热性能分析,给出几何聚光比随接收器几何参数的变化规律。结果表明,接收器在跟踪误差为0.5°时,几何聚光比仍可达到理想情况时的80%。结合传热学计算和Tracepro光学仿真,得到接收器热损失系数随接收表面温度,以及局部能量聚光随跟踪误差的变化规律,为此类碟式太阳能聚光集热器的优化设计提供依据。     

普通平板玻璃的太阳透过率

平板玻璃具有良好的透光性,它在太阳能装置中应用十分广泛。通常,人们用太阳透过率这个物理量来描述玻璃的透光性能。其大小等于透过玻璃的太阳辐射能沉密度与投射在玻璃上的太阳辐射能流密度的比值。测定玻璃太阳透过率的方法很多。简单的可借助一块直射辐射表,在阳光下分别读出透过玻璃和不透过玻璃两种条件下的测量值,即可算得该玻璃的太阳透过率。但是,由于到达地面的太阳辐射能流密度受     

热水器最佳倾角的计算方法

为了使太阳能热水器,尽可能地接受太阳辐射能,必须使热水器的采光面法线始终对准太阳,这样在一年中无论什么季节,一天中无论什么时刻,热水器所收集到的辐射能都是最多的。要使热水器跟踪太阳,就必须设置较为复杂的跟踪系统,势必大大增加其成本和造价。所以,常用的热水器为固定式采光面,不     

碟式聚光器的月光聚光比分布计算模型

碟式聚光器和塔式聚光器均是点聚光系统,为了用月光法间接测量塔式聚光系统的聚光比分布,适宜用聚光稳定的碟式聚光器研究不同月相的光源亮度分布对聚光比分布的影响。主要建立月光下碟式聚光器的聚光比分布计算模型,首先依据拍摄的月相灰度图像建立分块均匀的光源亮度分布模型,再基于三维激光扫描点云数据生成准确的反射镜面形;在光线追迹过程中均匀采样镜面上的反射点,且考虑聚光器的跟踪误差;镜面的光学误差与光源的亮度分布合并为等效的光源亮度分布。模拟聚光比分布与实验聚光比分布的余弦相似度α>95%,光学模型准确性高。     

基于三角腔体吸收器的透射式菲涅尔定焦线系统聚光特性分析

为解决线性菲涅尔太阳能集热系统单轴跟踪过程中出现的聚光焦线偏移以及降低系统跟踪能耗等问题,提出一种透射式菲涅尔定焦线太阳能聚光器.该聚光器采用极轴跟踪方式与线性菲涅尔透镜定期滑移调节方式相结合,可实现固定焦线聚光.将该聚光器与三角腔体吸收器所组成的太阳能集热系统,利用基于蒙特卡罗光线追迹法的TracePro光学软件分析...     

Numerical simulation and experiment research of radiation performance in a dish solar collector system

The Monte Carlo ray-tracing method is applied and coupled with optical properties to predict the radiation performance of solar concentrator/cavity receiver systems. Several different cavity geometries are compared on the radiation performance. A flux density distribution measurement system for dish parabolic concentrators is developed. The contours of the flux distribution for target placements at different distances from the dish vertex of a solar concentrator are taken by using an indirect method with a Lambert and a charge coupled device (CCD) camera. Further, the measured flux distributions are compared with a Monte Carlo-predicted distribution. The results can be a valuable reference for the design and assemblage of the solar collector system.     

Radiation performance of dish solar concentrator/cavity receiver systems

The Monte-Carlo ray-tracing method is applied and coupled with optical properties to predict radiation performance of dish solar concentrator/cavity receiver systems. The effects of sunshape and surface slope error have been studied and the corresponding probability models are introduced in this paper. Taking into account the above-mentioned factors, we show that the directional features of the focal flux affect the radiation flux distribution of cavity receiver, present criteria for the characterization of directional attributes, and describe a method for their calculation. Based on the concept of equivalent radiation flux, an upside-down pear cavity receiver is proposed in view of directional attributes of focal flux. Receiver design and modelling guidelines are presented. The uniformity performance of the wall flux is compared with five traditional geometries.     

太阳光不平行度对太阳能聚集性能影响的数值研究

对大型对日定向的碟式太阳能反射聚集器,通过数值模拟研究了太阳光不平行度与定向跟踪精度对聚光性能的影响。通过建立锥形光束的概率模型,采用蒙特卡洛法直接模拟了太阳光经碟式反射聚集器后在焦平面上产生的能流分布。比较了不同定向跟踪精度下,不同口径比的反射聚集器对太阳光与平行光的聚集性能差别。     

Development and performance analysis of a two‐axis solar tracker for concentrated photovoltaics

This study presents a two‐axis solar tracking system equipped with a small concentrator module for electricity generation through a multijunction solar cell. The system can accurately track the sun without the need of calibration for an extended period and operate as a stand‐alone system. High‐precision solar tracking was achieved by a combination of open‐loop and closed‐loop controls. A camera tracking sensor was introduced as a feedback device in closed‐loop control. Two different types of solar concentrator modules were designed and fabricated. Their concentration ratios were analyzed against solar tracking errors by means of ray tracing software. One is made up of a paraboloidal primary concentrator and a paraboloidal secondary reflector, whereas the other has a paraboloidal primary concentrator and a hyperboloidal secondary reflector. Both modules showed an almost identical concentration ratio of 610 provided that the solar tracker is pointing perfectly at the sun. However, their performance differs considerably when tracking error is present. The maximum power output was obtained near solar noon with multijunction cells, whose average solar conversion efficiency was 21%, much higher than that of conventional photovoltaic systems. Copyright © 2015 John Wiley & Sons, Ltd.     

Computation of the solar irradiance incident on concentrating collectors based in Turkey

This study aims to provide thorough information on the solar radiation received by the five main design types of concentrating collectors for the conditions of Turkey. These are namely, compound parabolic concentrator with north-south axis and east-west axis alignment, parabolic trough with north-south axis and east-west axis tracking, and concentrator with two-axis tracking. Either daily or hourly means of solar radiation are calculated for different slope, orientation and area concentration ratio (or half-acceptance angle). In this study, a computer program, based on previously developed correlations, is used. Through the graphical display, the results are presented for the six climatologically different stations which are representative of the country's conditions. With some modifications, the results will be valid for almost all known designs of concentrating collectors.     

Concentration distributions in cylindrical receiver/paraboloidal dish concentrator systems

Concentration distributions on a cylindrical receiver in a paraboloidal dish concentrator are computed for space applications (no atmosphere). A geometric optics method is applied which integrates over the solar disk and the concentrator projected surface, and maps analytically, in implicit closed form, through the concentrator and onto the receiver. Finite sunshape, concentrator surface errors, and pointing system zero-mean and constant offset errors are considered. Results define the section of the receiver surface which receives the majority of the concentrated flux, where the receiver's aperture might be located. Results are given in terms of concentrator geometry, concentrator total system error tolerance, receiver geometry, and pointing offset error. In cases with pointing offset error (nonzero mean pointing error), circumferentially varying concentration distributions are shown.     

Efficiency assessment for a small heliostat solar concentration plant

In this paper, a small non‐imaging focusing heliostat is presented, and an analytical model for assessing its performance is described. The main novelty of the system lies in the tracking mechanism and the mirror mount, which are based on off‐the‐shelf components and allow a good trade‐off between accuracy and costs. The concentrator mirrors are moved by this two‐axis tracking machinery to reflect the sun's rays onto a fixed target, the dimensions of which can be varied to suit the user's needs. A prototype plant to be located in central Italy was designed and simulated with a ray‐tracing algorithm, and it comprises 90 heliostats for a total reflective area of 7.5 m². The reflected solar rays are tracked taking the mechanical positioning errors of the tracking system into account. The total flux of radiation energy hitting the target was determined, and intensity distribution maps were drawn. Simulations showed that the system's optical efficiency can exceed 90% in summer, despite the tracking errors, mainly because of the smaller distance between the heliostats and the receiver. The solar concentration ratio over a receiver of 250 mm in diameter reached 80 suns with a very good uniformity. Over a 400‐mm receiver, the concentrated radiation was less uniform, and the solar concentration ratio reached 50 suns, with a higher optical efficiency and collected solar radiation. The present concentration ratio is still suitable for many applications ranging from the electric power production, industrial process heat, and solar cooling. Copyright © 2014 John Wiley & Sons, Ltd.