基于PLC的槽式聚光集热器跟踪系统的设计

采用PLC对槽式太阳能聚光集热器跟踪系统电气控制系统进行设计,达到槽式聚光集热器跟踪系统自动控制的目的,并实现了远程监控。采用PLC进行数据采集和过程控制,利用计算机实现远程实时监控,提高了槽式太阳能聚光集热器跟踪系统的精度及稳定性。该槽式太阳能热利用跟踪系统达到了国内先进水平,提高了其市场竞争力。     

槽式太阳能集热器运行特性分析

分析与研究了槽式太阳能聚光集热器运行特性,建立了槽式太阳能聚光集热器运行特性参数的数学模型,应用该模型以我国西部太阳能热发电的典型地区为计算地点,对槽式太阳能聚光集热器的太阳入射角余弦、入射角修正系数、遮挡系数、端部损失及镜场运行效率等运行特性参数进行了计算。结果表明：槽式太阳能集热器正午时刻入射角余弦达到最小值,余弦效应最为明显;遮挡损失和端部损失对槽式集热器的运行影响总体不大,在日出、日落时刻会发生遮挡效应,最大端部损失发生在正午时刻;槽式太阳能聚光集热器镜场效率正午时刻之前单调下降,正午时刻后,随高度角的下降而单调增加,在正午时刻达到最小值,夏至日镜场效率峰值约为0.74,冬至日的峰值约为0.47,差值约为0.27。     

槽式太阳能聚光集热技术

详细讨论了槽式太阳能聚光集热技术的最新进展,对不同聚光集热器支撑机构进行了对比分析.结果表明,EUROTROUGH聚光器的支撑机构性能最优.此外,还对抛物面聚光镜和主要的槽式太阳能集热管技术进行了讨论分析.     

新型槽式太阳能聚光集热器的研究与试验

设计了一种新型槽式太阳能聚光集热器,分析了工作原理和设计参数,建立了由该集热器组成的太阳能集热系统,并进行了试验测试。文章给出了采用不同接收器的升温曲线和效率计算值,对不同布置方式的集热性能进行了比较。试验结果表明,该装置具有较高的集热效率,运行温度在80℃时,效率达到35%以上。     

槽式太阳能集热管热性能评估方法

真空集热管是槽式太阳能聚光集热系统的核心部件之一.集热管工作过程中通过辐射换热、对流换热和热传导的方式将热量传递给环境,这部分传递到环境中的热量称为集热管的热损失.真空集热管的热损失是聚光集热系统热损失或总能量损失的主要组成,在很大程度上决定着聚光集热器的光-热转换效率,因此对集热管热性能的正确评估对聚光集热系统的研究至关重要.本文对槽式太阳能集热管热性能的计算、评估分析方法等进行了分析.     

DSG太阳能槽式集热器聚光特性模拟

在槽式集热器光学理论的基础上,以DSG太阳能槽式真空集热器为研究对象,建立DSG集热器模型,并运用蒙特卡罗光线追踪法进行辐射计算及分析.通过研究集热器几何聚光比和边界角对集热器吸热管表面圆周方向热流密度分布的影响,获取了集热器的聚光特性.结果表明：计算结果与文献数据吻合良好;随着几何聚光比的增大,吸热管表面圆周方向的热流密度分布趋势不变,数值相应增大;随着集热器边界角的减小,热流密度的最大值增大,热流密度的分布曲线向圆周角-90°方向偏移相应的角度.     

槽式太阳能聚光集热器传热性能研究

建立了槽式太阳能聚光集热器单侧吸收高热流密度的传热数学模型.该传热数学模型将金属吸热管壁面所能接受到的非均匀热流简化为矩形分布,考虑了金属吸热管管壁的周向导热,选取Dudley的试验数据验证了传热数学模型的可靠性并分析了影响集热器传热特性的主要因素.通过Fluent软件研究了槽式太阳能聚光集热器金属吸热管的周向温度分布规律.结果表明:该传热数学模型具有一定可靠性;流体温度、太阳辐射强度和流体体积流量是影响集热器管内换热特性和管壁周向温度分布的主要因素.     

一种复合抛物面槽式太阳能聚光集热器的性能研究

对一种新型复合抛物面槽式太阳能集热器进行了光学仿真和热性能研究。介绍了聚光器的设计与工作原理,在计算机上对其进行了三维建模,利用蒙特卡洛光线追迹模拟不同入射角、不同安装误差偏角的情况下,圆柱形聚光接收体表面上能流分布特征及光学效率的变化规律。光学仿真结果表明,当镜面反射率为0.92,在太阳光线入射角为0~7.5°时,光线接收率为99.36%~51.51%,聚光效率为92.14%~48.1%。室外测试结果显示,装置热效率为43.2%。     

槽式太阳能热发电站的设计

针对槽式热发电系统的集热器进行分析,讨论了集热器的光学效率和集热管热损失模型,在此基础上利用Solar Advisor model 2010软件并结合经验数据,模拟和计算了槽式太阳能热发电系统的集热器面积,为槽式太阳能热发电站设计提供理论依据。     

槽式太阳能集热器热性能实验测试

针对天津市槽式太阳能集热系统性能测试平台,对不同太阳辐射强度、入口流体温度以及不同工质流量状况下集热效率和集热管压降变化规律进行实验测试,通过测试数据对槽式太阳能集热器热性能进行分析.试验结果表明:在天津地区槽式太阳能集热器集热效率可以达到66.1％;太阳辐射强度的增强,会提高集热效率,并且集热器进出口的压降会随之降低...     

具有二次聚光器的新型大开口槽式太阳集热器设计与光学性能分析

针对大开口和更高运行温度的槽式太阳能热发电系统,提出一种可实现高聚光比、低辐射热损及能流密度均匀的新型槽式太阳集热器,即在集热管内放置外壁具有太阳选择吸收膜层和内壁具有反射膜层二次聚光器的大开口槽式太阳集热器。建立圆弧为微元段的自适应设计新方法,提出3种典型的二次聚光器面型,利用蒙特卡洛光线追迹方法仿真新型集热器的能流密度分布特性,验证该光学仿真方法,分析影响集热器光学性能的各种因素。结果表明,该集热器可显著提升集热效率。     

A new trough solar concentrator and its performance analysis

The operation principle and design method of a new trough solar concentrator is presented in this paper. Some important design parameters about the concentrator are analyzed and optimized. Their magnitude ranges are given. Some characteristic parameters about the concentrator are compared with that of the conventional parabolic trough solar concentrator. The factors having influence on the performance of the unit are discussed. It is indicated through the analysis that the new trough solar concentrator can actualize reflection focusing for the sun light using multiple curved surface compound method. It also has the advantages of improving the work performance and environment of high-temperature solar absorber and enhancing the configuration intensity of the reflection surface.     

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.     

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。     

Numerical Investigation of Energy-Efficient Receiver for Solar Parabolic Trough Concentrator

In this paper, a thermal analysis of an energy-efficient receiver for solar parabolic trough concentrator is presented. Various porous receiver geometries are considered for the performance evaluation of a solar parabolic trough concentrator. Numerical models are proposed for a porous energy-efficient receiver for internal heat gain characteristics and heat loss due to natural convection. The internal flow and heat transfer analysis is carried out based on a RNG k-? turbulent model, whereas external heat losses are treated as a laminar natural convection model. The numerical models have been solved using the commercial engineering package, FLUENT. The thermal analysis of the receiver is carried out for various geometrical parameters, such as fin aspect ratio, thickness, and porosity, for different heat flux conditions. The inclusion of porous inserts in tubular receiver of solar trough concentrator enhanced the heat transfer about 17.5% with a pressure penalty of 2 kPa. The Nusselt number correlation is proposed based on the extensive numerical data for internal heat transfer inside the receiver. The proposed model is compared with more well-known natural convection models. A comparative study is carried out with different porous geometries to evolve an optimum configuration of energy-efficient receivers.     

Static solar concentrator with vertical flat plate photovoltaic cells and switchable white/transparent bottom plate

A new type of static solar concentrator is proposed to match the aesthetic features of towns. The concentrator consists of vertical plate solar cells and white/transparent switchable bottom plate, which is operated with external power. The bottom is switched to be a diffuse reflection white surface when the cell generates electric power, and switched to be a light transmissible transparent surface when the cell does not deliver power. The light collection of this concentrator was analyzed by using multiple total internal reflection model and ray tracing simulation. For the same ratio of the area of the solar cells to that of the collector surface, the collection efficiency for the proposed concentrator is about half of that of the conventional concentrator for flat plate cell, and nearly equal to that of the concentrator for the embedded spherical silicon solar cells.     

Performance evaluation of v-trough solar concentrator for water desalination applications

The working principle and thermal performance of a new v-trough solar concentrator are presented in this paper. Compared with the common parabolic trough solar concentrators, the new concentrator has two parabolic troughs which form a V-shape with the focal line at the bottom of the troughs. This is beneficial for the installation and insulation of the receiver, and the shadow on the reflective surface is avoided. The new v-trough collector does not require high precision tracking devices and reflective material. And therefore the cost of the system could be significantly reduced. Various experimental tests were carried out both outdoor and indoor using different types of receiver tubes. The results show that the collector system can have thermal efficiency up to 38% at 100 °C operating temperature. System modelling was used to predict the rate of fresh water produced by four different solar collector systems which include both static and one-axis solar tracking technologies. Comparison of the solar collectors at different temperature ranges for humidification/dehumidification desalination process using specific air flow rate were considered. At each temperature range, suitable solar collectors were compared in the aspect of fresh water production and area of solar collector required. Results showed that the new v-trough solar collector is the most promising technology for small to medium scale solar powered water desalination.     

抛物面槽式聚光器的风致响应分析与优化

该文首先通过在湖南大学HD-3大气边界层风洞中对聚光器模型进行测压试验,获得聚光器各测点在不同工况下的风压时程;然后通过有限元软件对聚光器的风致响应进行分析,获得反射镜的峰值位移响应和风振系数,并给出最不利工况下的位移响应分布云图;最后对聚光器构件截面尺寸进行优化。分析结果表明:在各工况下峰值位移响应最大值均出现在反射镜长边中点附近的边缘部位;优化后的单个聚光器的总体重量比原结构降低约6%。     

Development and experimental investigation of a compound parabolic concentrator

The numerical simulation and experimental validation of a compound parabolic concentrator (CPC) are presented. The solar device had an aperture area of 1.33 m², a real concentration ratio of 3.5, an acceptance half angle of 15°, and a carbon steel (or aluminum) tubular receiver with an outer diameter of 0.0603 m and coated with a commercial selective surface. Experimental tests were performed using water as working fluid at solar noon; the inlet temperatures used varied from 30 °C to 70 °C and the mass flow rates from 0.05 kg/s to 0.25 kg/s. A comparison of the experimental results with the numerical model developed was carried out. The results of the thermal efficiency, outlet temperature, and pressure drop were compared and found to be in close agreement with the experimental data. Therefore, the model is a reliable tool for the design and optimization of compound parabolic concentrators. Because the numerical model is based on the application of physical laws, it is possible to extrapolate its use with confidence to other fluids, mixtures, and operating conditions. Copyright © 2011 John Wiley & Sons, Ltd.