CPC设计原理

本文介绍一种复合抛物面聚光器(Comound Parabolic Coilector简称CPC)的设计方法。通过建立聚光器模型，引入边缘光线原理，并结合设计实例，导入曲线参数方程，对CPC的设计原理做一下简单描述。     

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。     

复合弹性太阳能聚光器的光学特性

近年来,由于非成象聚光器具有接受在入射角范围内辐射的能力,因此聚光器已被人们所注意。理想的柱面集中器,例如复合抛物面太阳能聚光器(CPC),对于一个给定的接受角θ_m,也就是C=1/sinθ,显示出了最高聚光比的可能性。近似CPC的聚光器已经提出,虽然这种聚光器与CPC比较起来光学性能有所减弱,但它可以容易地制造。     

漏斗式二级复合抛物面太阳能聚光器的优化设计

构造了一种由二级复合抛物面(CPC)叠置组成的漏斗式太阳能聚光器,对其性能进行了讨论.为改善第二级CPC的最大聚光角,重点对其进行了变尺寸设计,理论导出了各参数间的关系,给出了最优参数范围.指出,在合理配置第二级CPC各设计参数的条件下,其最大聚光角可达30°～35°,有效地增加了整体光漏斗的导光率和最大聚光角.在实际天气条件下,对一个实际二级复合抛物面太阳能聚光器进行了实验测试,给出了不同入射角条件下系统的导光性能曲线,对实验结果进行了讨论,指出了改进方向.     

常规单晶硅太阳电池在低倍聚光条件下应用研究

利用常规单晶硅光伏电池，在进行输出特性研究的基础上，设计研制出带有非对称复合抛物面聚光器的光伏发电系统。该系统利用聚光器的有效聚光比随季节的变化，使光电池上接收到的太阳辐射量全年相对均衡，结果不仅降低了发电成本而且可改善系统的可靠性。     

可用于建筑采暖的槽式复合抛物面聚光器光热特性研究

文章针对太阳能建筑采暖系统集热面积大、换热介质抗冻能力差的问题,设计了一种新型的槽式复合抛物面聚光建筑采暖系统,并分析了该系统中槽式复合抛物面聚光器的聚光原理。文章还建立了槽式复合抛物面聚光器的三维模型,而后利用光学仿真软件分析该聚光器的聚光性能,并搭建试验台研究空气流速对该聚光器光热转化效率的影响。分析结果表明:在光线入射偏角为10°的条件下,当接收体中心与聚光器底部的间距为90 mm时,槽式复合抛物面聚光器的光线接收率和聚光效率最优,分别为65.54%和60.25%;在实际天气条件下,槽式复合抛物面聚光器光热转化效率随空气流速增加而升高,当空气流速为4 m/s时,该聚光器的光热转化效率达到最大值,为76.73%。     

西班牙太阳能高温热利用的研究与思考

２００２年４月，我们中国可再生能源代表团一行在考察了希腊太阳能热利用后，又访问了西班牙。在西班牙我们主要考察了太阳能高温热利用西班牙高温热利用研究起步于２０世纪８０年代初。由于欧盟和本国政府的支持，目前已经形成了较大的研究规模。其研究中心基地设在西班牙南部Almelia地区。从事高温热利用研究的人员有近百人，欧洲各国在中心工作的留学生约有８０人。该研究中心的高温热利用研究的对象主要有槽式太阳能聚光器（PTC）、太阳能碟式高温聚光器、太阳能塔式聚光器和复合抛物面式（CPC）聚光器４种。前３种主要用于直接产生…     

消除复合抛物面聚光器二次反射的设计研究

建立未截短的原复合抛物面聚光器(CPC)、1/2截短CPC以及消除二次反射设计CPC的数学模型,根据光线追踪法和蒙特卡罗法,在几何聚光比为2~10内,计算CPC高度与出射光孔宽度的比值,并依据该比值分析CPC的经济性,计算CPC最佳均匀面上的非均匀度和最大辐照度,进而分析CPC聚光均匀性.结果表明:在相同几何聚光比下,消除二次反射设计CPC的经济性和聚光均匀性最好.     

具有折射棱镜盖的圆桶式CPC聚光器研制与性能测试

在圆桶式复合抛物面聚光器(CPC)聚光器研究的基础上,增加一个透明的折射棱镜上盖,并进行一系列的整体优化设计,研制出一种新的非跟踪CPC聚光器,并通过对焦点温度和砷化镓电池光伏转换电流值的实际测试方式,测其水平放置并在超出最大入射半角后的聚光度分别达到3.0和5.3倍,可实现较好的非跟踪聚光效果。但该聚光器材料选型或加工工艺会限制其聚光性能。若这些问题得以解决,具有较高聚光度的非跟踪复合抛物面聚光器将会得到开发应用。     

具有镜面反射和漫反射的CPC光学分析

对由镜面反射为主但是存在一定漫反射的复合抛物面聚光器(CPC)反射面构成的集热器，在存在太阳散射情况下进行了光吸收性能的分析，比前人只考虑集热器镜面反射和太阳光直射更加接近实际情况。方法是在利用光线追踪法对CPC反射面的镜面反射进行分析的基础上，结合辐射度算法定量计算了CPC反射面的漫反射和太阳光的散射分量对集热器的光学性能的直接影响。并通过CPC集热器瞬时效率测试验证了理论的正确性。通过该理论，可以在更接近实际的情况下对CPC集热器进行光学设计和计算，具有实际的应用价值。     

Optical and thermal properties of compound parabolic concentrators

Compound Parabolic Concentrators (CPC) are relevant for solar energy collection because they achieve the highest possible concentration for any acceptance angle (tracking requirement). The convective and radiative heat transfer through a CPC are calculated, and formulas for evaluating the performance of solar collectors based on the CPC principle are presented. A simple analytic technique for calculating the average number of reflections for radiation passing through a CPC is developed; this is useful for computing optical losses. In most practical applications, a CPC will be truncated because a large portion of the reflector area can be eliminated without seriously reducing the concentration. The effects of this truncation are described explicitly. The paper includes many numerical examples, displayed in tables and graphs, which should be helpful in designing CPC solar collectors.     

A thermal comparison performance of CPC with modified (duel-cavity) and non-modified absorber

The main objective of this work is the design and development of non-imaging solar collector systems for heating purposes. The aim is to increase the efficiency of the Compound Parabolic Concentrator CPC, by proposing a novel modification to the absorber. A modifications have been undertaken in the absorber design by introducing two cavities in the most appropriate location. The new design has been tested and compared with conventional designs to prove that the novel design of CPC with a dual cavities is ameliorate, as it was able to increase the efficiency considerably and at the same time reduces the heat losses. In this paper a comparative experimental results for CPC with two different absorber. The experiment was done under a real condition of sun. The comparative results was for the efficiency of each collector.     

Optical and thermal testing of a new 1.12X CPC solar collector

A new CPC collector is described and tested, both optically and thermally, in different configurations. This CPC has a receiver shaped as an inverted “V”, which was conceived to accommodate a large gap between itself and the reflector, without optical losses, a novelty which distinguishes this device from others previously proposed. Its acceptance angle was chosen to be large (56.4°, before truncation, and 76° after truncation) in order to allow for both fully stationary E.W. and N.S. possible orientations for the collector to be used. Collector height was chosen to allow for the inclusion of convection suppression mechanisms, to enhance the thermal performance of the collector at high temperature. Measurements of instantaneous efficiency are presented, for the collector in E.W. and N.S. orientation. Measurements are also presented for the instantaneous efficiency when a double cover configuration achieved with a Teflon film and a transparent insulation material of the honeycomb type are included. It is shown that the collector's low heat losses are reduced by roughly 30% trough the addition of such convection suppression devices.Based on these results, the average yearly performance is calculated and compared with the energy delivered by other collector types (flat pates, evacuated tubular collectors). It is shown that, up to 100°C, the present collector outperforms the others, and has a cost which is comparable, if not potentially lower than conventional flat plates.     

CONVECTIVE HEAT TRANSFER CORRELATIONS FOR AN ENCLOSED HORIZONTAL COMPOUND PARABOLIC CAVITY SOLAR THERMAL COLLECTOR

Correlations between Nusselt and Grashof numbers have been proposed for convective heat transfer in compound parabolic concentrating solar energy collectors (CPCs). The discrepancies between these correlations are discussed. CPC designs considered range from a tubular absorber with or without an envelope; with one or two concentric envelopes; with eccentric envelopes; with various levels of reflector truncation and for a range of system inclination angles.     

Optical performance analysis and design optimisation of multisectioned compound parabolic concentrators for photovoltaics application

Currently, all compound parabolic concentrators (CPCs) for photovoltaic (PV) application consist of reflecting surfaces in the form of a parabolic shape. However, parabolic shapes create non‐uniform illumination on the PV module, which significantly reduces the power output. To achieve high‐concentration ratio and uniform illumination on the PV module, this study proposes the use of flat reflector sections in a symmetric two‐dimentional CPC instead of the parabolic shape. This collector is called multisectioned compound parabolic concentrator (M‐CPC). However, the main challenge in designing such a concentrating system lies in the determination of the optimal number of flat sections and the width of each section so that the optical properties of the M‐CPC approaches that of the standard CPC. In this work, seven M‐CPCs having the same designing parameters but with different total number of flat reflector sections were designed. A detailed analysis of the optical performance was undertaken to optimase the M‐CPCs. The optimal design was based on‐high angular acceptance, low‐optical losses, high‐optical efficiency in a wide‐interval incidence angles, and uniform energy flux distribution on the PV module. Results from the ray trace simulation analysis show that the optimal M‐CPC is the design with a total number of seven flat reflector sections (ie, M‐CPC7). This design has high‐angular acceptance (100%) in a wide‐interval incidence angles, low‐optical losses (7%), and high‐optical efficiency of about 95% in a wide‐interval incidence angles. In addition, M‐CPC7 illuminates the PV module more uniformly than the standard CPC.     

Correlations for natural convective heat exchange in CPC solar collector cavities determined from experimental measurements

A detailed experimental study was undertaken to analyse the natural convective heat transfer in CPC cavities, a complex function of collector orientation, geometrical aspect ratios and thermal boundary conditions at the enclosure walls. Results are reported for CPC solar collectors with full-, three quarter- and half-height reflectors, C_R = 2 and a 100 mm wide flat plate absorber. Experiments were conducted using a purpose built solar simulator under controlled lab environment employing realistic boundary and thermal conditions. The effects of simultaneous tilting of the solar collectors about both transverse and longitudinal axes, truncation of the reflector walls and inlet water (collector heat removal fluid) temperature on the natural convective heat flow characteristics inside the CPC cavity have been determined. It is concluded that the correlations developed for prediction of natural convection characteristics in rectangular, annuli and V-trough enclosures are not appropriate for application to CPC solar collectors with divergence ranging from 150% to 300%. Based on the experimental data a correlation is presented to predict the natural convection heat loss from the absorber plate of solar collectors for a range of water inlet temperatures.     

Design and Development of a Lens-walled Compound Parabolic Concentrator-A Review

Compound parabolic concentrator(CPC) is a representative among solar concentrators, one of whose disadvantage is that the concentration ratio limits the half acceptance angle. Based on this, researchers put forward a novel structure, named the lens-walled CPC. This paper reviews the design and development of lens-walled CPC. The structure of the symmetric and asymmetric lens-walled CPC and the improved ones are presented, and their indoor and outdoor performances are also illustrated. The lens-walled CPC has a larger half acceptance angle and a more uniform flux distribution that is suitable for PV application. Furthermore, the life-cycle assessment for building integrated with PV is performed and it shows that the energy payback time of such integrated system has a significant advantage. In addition, future research areas are also indicated that may provide more functions and more stable performance. The design methods and developmental directions given in this study would provide many references in solar optical research and solar concentrator optimization.     

Integrated collector storage solar systems with asymmetric CPC reflectors

New types of ICS solar systems were designed and outdoor tests of experimental models were performed. The systems consist of single cylindrical horizontal water storage tanks placed inside stationary truncated asymmetric CPC reflector troughs of different design. We used high emittance absorber surface, low cost curved reflectors, iron oxide glazing and thermal insulation at the non illuminated tank surfaces, aiming towards cost effective ICS systems with satisfactory heat preservation during the night. Four experimental models of different designs were constructed and tested to determine their performance regarding their mean daily efficiency and thermal losses during the night. The new ICS systems were compared to an ICS system with symmetric CPC reflectors of similar construction and dimensions and also to a typical Flat Plate Thermosiphonic Unit (FPTU). Test results showed that the ICS systems with asymmetric CPC reflectors present almost the same mean daily efficiency and better preservation of hot water temperature during the night, compared to the ICS system with the symmetric CPC reflectors. The comparison with the FPTU system confirmed the satisfied daily operation of all ICS systems and their moderate storage heat preservation during the night. Theoretical results showed acceptable thermal performance of all ICS systems regarding annual operation.     

Design and Investigation of Heat Transfer in a New Adsorbent Bed With CPC for Solar Adsorption Refrigeration Systems

This article presents the design and the heat transfer study in a novel adsorbent bed with compound parabolic concentrator (CPC) for solar adsorption chillers. The objectives of the study were to investigate the heat transfer in the adsorbent bed experimentally, and to verify the fins layout through finite-element analysis (FEA) simulation. CPCs with different concentration ratios were experimentally tested and an appropriate design of CPC was selected for a prototype. The prototype was designed with the objective of improving the heat and mass transfer ability of the adsorbent bed. Fins were placed in the transverse direction under the receiver area of each CPC. Spaces were provided from three sides of the adsorbent for easy movement of the refrigerant. FEA software was used to study the effect of the fins layout and fins pitch. The experimental results showed that the heat was efficiently transferring up to the end and extended parts of the bed. Simulation results indicated that the present strategy of placing the fins in a transverse direction gives uniform heat distribution compared to a fins layout with fins placed in a longitudinal direction. The proposed design scheme will be helpful to improve the system performance by increasing the heat and mass transfer ability of an adsorbent bed.     

CPC不同方位辐射量及最佳倾角计算

针对复合抛物面集热器(CPC)接收辐射量和集热性能受方位角和倾角影响的关系.分别分析了CPC不同放置方式下接收到的太阳辐射及对应最佳倾角,得到方位角与最佳倾角的关系,结合不同地区研究CPC最大太阳辐射量与倾角、方位角之间的关系.结果发现,大多数地区全年最佳倾角位于当地纬度附近,相差5°以内,侧重冬半年使用应采用较大的倾...