复合抛物面聚光器在线性菲涅尔聚光上的应用

简述了线性菲涅尔的聚光原理及国外研发机构的相关应用现状,针对聚光器面临的技术难题,研制出一种复合抛物面聚光器,简要介绍其组成结构及反光板曲面形状.结合该技术在世界首座屋顶式太阳能菲涅尔热发电站上的应用并经过相关测试.论证了此聚光器技术具有明显的优势和广阔的应用前景,提高了线性菲涅尔聚光集热器在太阳能热发电、中温工业应用等领域的市场竞争力.     

一种圆柱面线聚焦菲涅尔式太阳能中温集热系统的研究

介绍了一种利用圆柱面线聚焦菲涅尔镜组成的太阳能集热系统,该系统主要由圆柱面线聚焦菲涅尔镜、二次聚光器、太阳跟踪器、加热油箱和负载等部件组成;给出了圆柱面线聚焦菲涅尔镜的设计思路,利用注塑成型方法生产出圆柱面线聚焦菲涅尔镜,然后利用该镜搭建线聚光太阳能中温集热系统,并在实际天气下对系统性能进行测试。结果表明,在日照充分的天气下,本系统的平均集热效率约为40%,集热效果良好。     

基于DSP的线性菲涅尔太阳能集热系统设计与实现

针对线性菲涅尔太阳能集热系统普遍存在遮挡和阴影等特点,提出了一种设计方法,并设计了一套线性菲涅尔太阳能集热系统。在该系统中,镜场微弧面反射镜按照一定初始角度安装,并通过设计的DSP单轴跟踪控制器,控制反射镜跟踪太阳,将太阳光线反射到镜场上方固定安装的三角形腔体吸收器上,实现太阳能集热。通过精度检测实验和光学镜场模型仿真,验证了该系统应用于线性菲涅尔太阳能的正确性和可行性。     

线性菲涅尔反射式太阳能集热系统的设计与试验研究

本文研究了线性菲涅尔反射式太阳能集热系统,基于几何光学原理计算模拟了线性菲涅尔反射镜镜场和复合抛物面的接收系统,在减少末端损失的基础上设计了系统的机械结构,制作了线性菲涅尔反射式太阳能集热系统的装置,并进行了集热性能的实验测试。测试结果表明,该系统在9倍聚焦倍率下,导热油的最高温度可达176.2℃,系统的平均瞬时热效率约为53%,很好地实现了其集热性能。     

电磁联动追日跟踪技术在线性菲涅尔聚光上的应用

通过对电磁联动追日跟踪装置的结构和优点的阐述,结合该技术在世界首座屋顶式2.5MW太阳能菲涅尔热发电站上应用,论证了电磁联动追日跟踪技术具有明显的优势和广阔的应用前景,提高了线性菲涅尔聚光集热器在太阳能热发电、中温工业应用等领域的市场竞争力.     

跟踪及安装精度对菲涅尔定向光输运装置的影响

该文基于对菲涅尔定向装置的研究，搭建其集热性能测试实验平台，并采用TracePro光学模拟软件，建立菲涅尔定向光输运装置的光学模型。在进行模型验证后，模拟分析跟踪误差和安装误差对光学效率的影响。研究结果表明：俯仰角、旋转角的跟踪误差会导致菲涅尔定向光输运装置光学效率的降低，并且俯仰电机误差范围应控制在±0.1°，方位电机误差范围应控制在±0.5°；当菲涅尔定向光输运装置中定向光输运器抛物反射面的焦点与菲涅尔透镜的聚光焦点存在安装误差时，菲涅尔定向光输运装置光学效率普遍下降，最大偏移量不宜超过0.1。但当偏移量不超过0.5时，将定向光输运器向下侧偏移或将菲涅尔透镜向上偏移，有利于提高菲涅尔定向光输运装置（LTF-SC）光学效率。该研究结果为菲涅尔定向光输运装置和菲涅尔中央接收式太阳能高温集热系统领域的研究和应用提供参考。     

菲涅尔反射聚光灶面设计

依据菲涅尔反射聚光原理,在挠性平板上压制出象唱片一样的同心圆沟槽,通过表面处理,做成反射式聚光器,可以得到结构简单、体质轻便、价格较低、功能多样的太阳能聚光灶。     

基于透射式菲涅尔聚光器的PV/T 系统性能研究

采用光线追踪的方法对外表面为圆形截面、椭圆形截面和抛物线形截面的3种类型的菲涅尔透射聚光器进行分析。利用光学仿真对比分析3种不同聚光器的聚光性能,分析其在聚光效率、跟踪误差敏感性以及入射光轴向倾斜对接收效率影响等方面的优劣。加工直径为1 m的圆形聚光器样件,基于该聚光器构建太阳能光伏光热一体化系统(photovoltaic/thermal system,后文简称PV/T系统),以砷化镓高聚光电池作为接收器,在实际的典型天气下对透射式菲涅尔聚光PV/T系统进行试验研究,测试接收装置的温度分布、系统电能和热能的输出特性以及热电综合利用率。结果表明:晴朗天气下透射式菲涅尔聚光PV/T系统中午时段的发电效率最大可达18%,冷却水得热效率最大值约为45%,在中午时段(11:00~13:00)辐照大于900 W/m2时,热/电总利用效率可保持在55%以上。     

线性菲涅尔反射式太阳能热发电系统研究进展及应用

介绍了线性菲涅尔反射式太阳能热发电系统的特点及及其优点,论述了现阶段对线性菲涅尔反射式太阳能热发电系统最新的理论及实验研究进展,最后介绍了线性菲涅尔反射式太阳能热发电站的应用情况。     

线性菲涅耳太阳能聚光系统

线性菲涅耳聚光反射装置是对连续抛物面聚光镜的一种离散化近似,因由法国工程师Fresnel发明而得名。线性菲涅耳太阳能热发电技术在太阳能热发电系统中非常有用,尤其是在需要安装大面积的镜场时,对成熟的槽式太阳能聚光热发电系统形成强有力的竞争。简要介绍了线性菲涅耳聚光反射装置的技术特点及发展现状。     

Thermal performance of linear Fresnel reflecting solar concentrator with trapezoidal cavity absorbers

Thermal performance of the four identical trapezoidal cavity absorbers for linear Fresnel reflecting solar device were studied and compared. The absorbers were designed for operating in conjunction with a prototype Fresnel solar reflector. Rectangular and round pipe sections were used as absorber by placing in the trapezoidal cavity. The absorber pipes were coated with ordinary dull black board paint and black nickel selective surface. The bottom of the cavity was provided with plane glass to allow the solar radiation to be reflected from the Fresnel reflector. The other three sides of the cavity absorber were insulated to reduce heat loss. Thermal performance of the Fresnel reflecting concentrator with each trapezoidal cavity absorber was studied experimentally at different concentration ratio of the reflector. The study revealed that the thermal efficiency was influenced by the concentration ratio and selective surface coating on the absorber. The thermal efficiency decreased with the increase in the concentration ratio of the Fresnel reflecting collector. The selective surface coated absorber had a significant advantage in terms of superior thermal performance as compared to ordinary black painted absorber. The round pipe (multi-tube) receiver had higher surface area to absorb solar energy as compared to rectangular pipe receiver. Thermal efficiency of the solar device with round pipe absorber was found higher (up to 8%) as compared to rectangular pipe absorber.     

Performance analysis of Azimuth Tracking Fixed Mirror Solar Concentrator

The fixed mirror solar collector (FMSC) fixes reflector and mobiles receiver to collect solar energy. However, this type of concentrator has a low efficiency and short operating duration in practical applications. In this paper, we propose to install the FMSC on an azimuth tracking device (ATFMSC) and the reflectors are arranged by intermission to avoid the shading of neighbor reflector for incidence angle of less than 10° to improve its optical performance. Through the integration of the reflected solar radiation distribution function over any reflection point, and then the whole collector aperture, we develop the analytical expressions of various system efficiencies to numerically simulate the performance of ATFMSC with evacuated tube receiver in different design parameters. It is validated by the ray tracing results. The result shows that the mean annual net heat efficiency of the whole system would be up to 61% with the operating temperature of 400 °C, which is higher than parabolic trough collector and traditional FMSC. This is because the longitudinal incidence angle of ATFMSC always remains zero by tracking the sun azimuth, so the end loss of the concentrator can be avoided and enables it to operate with high efficiency continually.     

Review on Development of Small Point-Focusing Solar Concentrators

The technology of small point-focusing concentrator of solar energy has been developing rapidly in recent years owing to its compact structure and high collecting efficiency. This report presents important developments of small point-focusing concentrator in the past decade. This kind of solar concentrator refers to the parabolic dish concentrator, the point-focusing Fresnel lens, and the Scheffler reflector. Technological advances of these concentrators and the related performances have been presented. There are three main mirror fabrication technologies for dish concentrator, which are high polishing metal, silver-glass mirror and vacuum-membrane. Polymethyl methacrylate is widely used as material in Fresnel lens. Many scholars have proposed new lens shape to improve the uniformity of focusing. The Scheffler reflector has a characteristic of fixed focus, but its design parameters are not perfect so current research focuses on the theoretical calculation of the mirror. In addition, typical applications of the small point-focusing concentrator in photovoltaic system, solar thermal system, solar chemical system, and day-lighting system are summarized. Upon listing the important publications in open literature, a category of main applications of such kind of solar collector is provided based on the working characteristics of the system.     

Linear Fresnel lenses, their design and use

A linear Fresnel lens (LFL) designed according to Fermat's principle is slightly modified with respect to used technology for mass production from glass. Manufactured Fresnel lenses are used in a fully tracking concentrating collector with aperture about 36 m² and in a collector with stationary concentrator and movable absorber, which may serve as solar collector with temperature and illumination control. A combination of linear Fresnel lenses with PV cells may reduce cost of autonomous solar installations.     

Optical performance analysis of an innovative linear focus secondary trough solar concentrating system

The parabolic trough solar concentrating system has been well developed and widely used in commercial solar thermal power plants. However, the conventional system has its drawbacks when connecting receiver tube parts and enhancing the concentration ratio. To overcome those inherent disadvantages, in this paper, an innovative concept of linear focus secondary trough concentrating system was proposed, which consists of a fixed parabolic trough concentrator, one or more heliostats, and a fixed tube receiver. The proposed system not only avoids the end loss and connection problem on the receiver during the tracking process but also opens up the possibility to increase the concentration ratio by enlarging aperture. The design scheme of the proposed system was elaborated in detail in this paper. Besides, the optical performance of the semi and the whole secondary solar trough concentrator was evaluated by using the ray tracing method. This innovative solar concentrating system shows a high application value as a solar energy experimental device.     

Theoretical and experimental analysis on efficiency factors and heat removal factors of Fresnel lens solar collector using different cavity receivers

The efficiency and heat removal factors are useful parameters for evaluating the thermal performance of concentrating solar collectors. In this work, the efficiency factors and heat removal factors of Fresnel lens solar collectors using different kinds of point-focus cavity receivers were obtained both theoretically and experimentally. An experimental unit was built, whereby eight kinds of cavity receivers, namely: conical, spherical, cylindrical, hemispherical, positive cone frustum, reverse cone frustum, heteroconical and domical, were tested and analyzed. It is found that the theoretical results agree well with the test results. For the point-focus Fresnel lens solar collector, the conical cavity receiver showed the best thermal performance, with a highest theoretical heat removal factor of 0.868. Effect of conical cavity parameters on the efficiency and heat removal factors were studied. Results showed that under given operation conditions, the optimum aperture diameter of the cavity, the optimum inside diameter of the receiver tube and the optimum vertex angle of the cross section through the symmetric axis of the receiver are 80 mm, 15 mm and 60°, respectively. For better thermal performance, the geometrical concentration ratio of the studied Fresnel lens solar collector should be more than 500.     

Effects of geometrical parameters of a dish concentrator on the optical performance of a cavity receiver in a solar dish‐Stirling system

Dish‐Stirling concentrated solar power (DS‐CSP) system is a complex system for solar energy‐thermal‐electric conversion. The dish concentrator and cavity receiver are optical devices for collecting the solar energy in DS‐CSP system; to determine the geometric parameters of dish concentrator is one of the important steps for design and development of DS‐CSP system, because it directly affects the optical performance of the cavity receiver. In this paper, the effects of the geometric parameters of a dish concentrator including aperture radius, focal length, unfilled radius, and fan‐shaped unfilled angle on optical performance (ie, optical efficiency and flux distribution) of a cavity receiver were studied. Furthermore, the influence of the receiver‐window radius of the cavity receiver and solar direct normal irradiance is also investigated. The cavity receiver is a novel structure that is equipped with a reflecting cone at bottom of the cavity to increases the optical efficiency of the cavity receiver. Moreover, a 2‐dimensional ray‐tracking program is developed to simulate the sunlight transmission path in DS‐CSP system, for helping understanding the effects mechanism of above parameters on optical performance of the cavity receiver. The analysis indicates that the optical efficiency of the cavity receiver with and without the reflecting cone is 89.88% and 85.70%, respectively, and former significantly increased 4.18% for 38 kW XEM‐Dish system. The uniformity factor of the flux distribution on the absorber surface decreases with the decreases of the rim angle of the dish concentrator, but the optical efficiency of the cavity receiver increases with the decreases of the rim angle and the increase amplitude becomes smaller and smaller when the rim angle range from 30° to 75°, So the optical efficiency and uniformity factor are conflicting performance index. Moreover, the unfilled radius has small effect on the optical efficiency, while the fan‐shaped unfilled angle and direct normal irradiance both not affect the optical efficiency. In addition, reducing the receiver‐window radius can improve the optical efficiency, but the effect is limited. This work could provide reference for design and optimization of the dish concentrator and establishing the foundation for further research on optical‐to‐thermal energy conversion.     

内聚光型太阳能光电-光热复合管的光学设计

根据非跟踪内聚光型太阳能光电-光热复合管的结构形式及其受光体的特殊需求,采用Winston的CPC设计原理,对圆管内具有特殊形状的半圆柱接收器的复合抛物面聚光器进行光学设计,得到了较为理想的聚光器设计曲线,并对结果进行数值仿真,给出各入射角的光线分布图和光强分布图。     

Optical performance and instantaneous efficiency calculation of linear Fresnel solar collectors

The main objective of this study is the investigation of the effect of the optical path of incident beam solar radiation on the performance of a linear Fresnel concentrating solar collector. The requirements regarding the kinematics of the reflectors are examined, allowing the effective focus of the reflected radiation on the receiver cover. A methodology for the calculation of the reflection angles of the sun rays incident on the mirrors, as well as of the incidence angles of the reflected rays on the cover, as a function of the sun position and the geometry of the collector is proposed. Specific scenarios, describing the effect of the solar radiation optical path on the collected heat, are formulated, each of them leading to a different form for the instantaneous efficiency equation. The evaluation and analysis of these scenarios, on the basis of actual operation conditions, has shown that the effect of the reflection and incidence angles throughout the modeling of the collector and the calculation of the useful thermal power cannot be neglected.     

二次反射多碟太阳能聚光器设计与性能分析

设计一种小规模的光线向下式焦点固定的多碟聚光集热系统,其特点是焦点固定,光线向下汇聚,吸热器开口向上,并提出该系统的追踪方式。通过对一次镜场和二次反射镜的分析和优化设计,使设计工况下吸热器入口的平均能流密度达到420 kW/m²,光学效率为87.4%,可为实现光线向下式焦点固定聚光系统的发展和优化提供技术方案。