Optical collection efficiency and orientation of a solar trough medium-power plant installed in Italy

Parabolic trough collectors were investigated, applying the study results to a plant prototype installed in Florence (Italy) for residential supply. Ray tracing simulations examined optical characteristics and collection performance on the base of prototype geometry and functionality. The purpose was to control the realisation errors and overcome the difficulties arising in the development of the solar trough plant. The paper summarises the results of several studies analysing the interactions between collection efficiency, angular misalignments, mirror deformations, sun tracking and trough placement. The mirror deformations are reproduced introducing an original procedure. The unusual subject of imprecision in trough axis placement is discussed.     

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.     

立体探测技术在探测陷落柱中的应用

从地震槽波勘探和瞬变电磁法两方面对立体探测技术在探测陷落柱中的应用进行了探讨。利用地震槽波勘探对陷落柱的基本形态进行了探测,使用瞬变电磁法对槽波异常区进行了富水性探测。最后针对物探异常区利用最少的钻孔进行了验证,更好地确定了陷落柱的边界及富水性,为巷道掘进提供有力的地质保障。     

Infrared temperature measurements on solar trough absorber tubes

The temperature distribution on solar trough absorber tubes determines thermal losses and hotspots can lead to material stress and limit absorber tube lifetime. The concentrated solar radiation, however, makes it difficult to determine the temperature on solar absorbers. Temperature sensors that require contact to the measurement object are not appropriate and even pyrometry fails, when external light sources interfere. Only solar-blind pyrometry offers reliable temperature readings without perturbation through reflected solar radiation. This paper presents two concepts for a pyrometric solar-blind measurement on solar trough absorber tubes. One solar-blind approach is a spectral measurement range in regions, where the solar spectrum shows gaps due to the discrete absorption of the atmosphere. Another possibility for a solar-blind pyrometric temperature measurement results from the optical behavior, i.e. the distinct angle dependence of the directional reflectance and emittance of a typical selective trough absorber coating. First experimental results are shown and the accuracy and performance advantages and disadvantages of the setups are reported and discussed.     

Experimental Study on Performance Enhancement of Evacuated Tube by Constant Heat Flux Mode

The evacuated tube collector with U shape copper absorber tube is considered for the analysis. The experimental investigation is conducted on parabolic trough collector with U shape tube as absorber tube. The effect of the sudden fluctuations in the solar radiation on the performance of the collector is reduced by means of evacuated tube collector filled with thermic fluids. The analysis is performed with different thermic fluids such as dowtherm, therminol66, glycol water and ethylene glycol, are filled in the annular space between inner glass tube and U shape copper absorber tube. The experimentation is carried out at various mass flow rates from 20 to 100 LPH with the step-up flow rate of 20 LPH. A comparative study is carried out on various parameters such as effect of mass flow rate over instantaneous efficiency, useful heat gain and work input, etc. The characteristic curve of cylindrical parabolic trough collector (PTC) is also discussed. Experimental results show that, ethylene glycol gives better efficiency over mass flow rate and therminol66 gives best power heat ratio. Heat transfer mediums and its properties [specific heat capacity, thermal conductivity and dynamic viscosity] for all specified heat transfer fluids are also discussed. The results obtained with various specified heat transfer fluids filled in the annulus space of evacuated tube are compared with plain evacuated tube. It is observed that there is significant enhancement of overall instantaneous collection efficiency of the parabolic trough collector.     

Performance of an intermittently tracked cylindrical parabolic trough

The distribution of local concentration ratios over a flat plate absorber used with an intermittently tracked cylindrical parabolic trough is studied for two values of the rim angle. The amount of energy collected by an intermittently tracked solar concentrator, oriented in various tracking modes, at different times of the year, for two typical latitudes, is also calculated. The results are presented graphically and discussed.     

槽式聚光集热系统加热真空管的特性及应用研究

建立了槽式聚光集热真空管装置的数学模型,并与实验结果进行了对比。理论计算结果与实验结果吻合较好,误差在5.2％以内,表明可用所建立的模型对聚光式真空管加热流体的性能进行分析。在太阳辐射强度及聚光面积变化的情况下,分析了通过聚光真空管内流体的性能特性。还给出了利用槽式聚光装置驱动太阳能吸附制冷的应用实例。     

Solar-electric water purification using photocatalytic oxidation with TiO2 as a stationary phase

Devices for the photocatalytic oxidation of organic impurities in water are described. The aqueous stream passes over illuminated titanium dioxide attached to glass mesh, or coated as a thin film on the inside of a glass coil. Illumination may be internal using a 20 W blacklight fluorescent lamp, or external with a parabolic trough solar reflector. Decomposition rates were determined for salicylic acid, phenol, and 2- and 4-chlorophenol in single-pass and continuous recirculation modes. Up to 50% decomposition, the destruction versus illumination curves obey first-order kinetics to a good approximation over a wide range of concentrations. The positive deviation from the apparent rate constant, noticeable when the destruction is more extensive, systematically increases with reaction time. In the single-pass mode, and using solar illumination reflected by the parabolic trough, a one thousandfold decrease in a salicylic acid concentration of 1380 μg dm⁻³ was achieved. Some aspects of using these devices as domestic water purifiers are discussed.     

柴油机喷油系统中的空泡及其对发动机性能的影响

本文论述了柴油机喷油系统中出油阀紧帽腔、高压油管、油嘴盛油槽处空泡的测试及其产生与溃灭过程.供油系统中是否存在空泡,可从压力波尾部的振荡情况来判断.文中还阐明了空泡对发动机燃油消耗与不规则喷射影响的机理.     

Screening of high melting point phase change materials (PCM) in solar thermal concentrating technology based on CLFR

We have investigated the suitability of high melting point phase change materials for use in new, large scale solar thermal electricity plants. Candidate materials for latent heat thermal energy storage are identified and their operating parameters modeled and analysed. The mathematical characteristics of charging and discharging these storage materials are discussed. Several high melting point, high conductivity materials are shown to be suitable and advantageous for use with solar thermal electricity plants, such as Sydney University’s novel, low cost CLFR and MTSA collector systems, as well as existing parabolic trough and tower technologies.     

Solar electricity prospects in Oman using GIS-based solar radiation maps

This paper discusses solar power prospects in Oman. First, the geographic and topographic information about Oman are presented. The methodology of producing solar radiation maps using GIS tools is then discussed. The results obtained show very high potential of solar radiation over all the lands of Oman during the whole year. A slope analysis has allowed calculating the yearly electricity generation potential for different Concentrated Solar Power (CSP) technologies such as the parabolic trough, parabolic dish, tower, and concentrated PV. For instance if only 10% of the land of Oman with a slope less than 1% is considered an exploitable land for the parabolic trough CSP technology, then the total calculated potential of yearly electricity generation would be about 7.6 million GWh, which is many multiples of (680 times) the current generation supply in Oman which was about 11,189 GWh in 2007.     

多排槽式反射镜风压分布及干扰研究

为研究多排槽式反射镜不同位置处的风荷载特性及其互相干扰,对单个反射镜及多排反射镜进行缩尺为1/40的刚性模型测压试验,试验变量为测压模型的风攻角、风向角以及其在群镜中的位置。首先测得各工况下镜面的风压分布数据,绘制镜面风压系数等值线图和反射镜力系数变化曲线,然后分析了反射镜互相干扰对镜面风荷载的影响。研究表明：中间列首排反射镜所受风荷载最大,其阻力系数是单镜的2倍,中间列其余排反射镜阻力系数为单镜的30%~70%;边缘列首排反射镜阻力系数为单镜的1.88倍,其余各排在单镜的1.20倍以上;建议将镜场分为4类区域分别进行结构设计。     

太阳能电池聚光器的模拟优化

设计了三种槽式太阳能电池聚光反射器模型：梯形、圆弧形和抛物线形,在光学软件Fred中建立模型,利用软件提供的光线跟踪方法,针对其有、无跟踪太阳两种情况进行优化,得出了在这两种情况下,不同几何聚集比（C=1．5,2,2．5,3,3．5）时的最佳形状参数（倾角θ或高底比Hd）,为实际生产加工过程提供了指导,最后对比了三种聚光反射结构的优缺点。     

Optimization of parabolic trough solar collectors

The results of a detailed optical analysis of parabolic trough solar collectors are summarized by a few universal graphs and curve fits. These graphs enable the designer of parabolic trough collectors to calculate the performance and optimize the design with a simple hand calculator. The method is illustrated by specific examples that are typical of practical applications. The sensitivity of the optimization to changes in collector parameters and operating conditions is evaluated.     

Economic analysis of power generation from parabolic trough solar thermal plants for the Mediterranean region—A case study for the island of Cyprus

In this work a feasibility study is carried out in order to investigate whether the installation of a parabolic trough solar thermal technology for power generation in the Mediterranean region is economically feasible. The case study takes into account the available solar potential for Cyprus, as well as all available data concerning current renewable energy sources policy of the Cyprus Government, including the relevant feed-in tariff. In order to identify the least cost feasible option for the installation of the parabolic trough solar thermal plant a parametric cost–benefit analysis is carried out by varying parameters, such as, parabolic trough solar thermal plant capacity, parabolic trough solar thermal capital investment, operating hours, carbon dioxide emission trading system price, etc. For all above cases the electricity unit cost or benefit before tax, as well as after tax cash flow, net present value, internal rate of return and payback period are calculated. The results indicate that under certain conditions such projects can be profitable.     

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%。     

用于槽式太阳能光热发电过热一体式蒸汽发生器的概念设计

文章提出了一种兼具过热段可用于槽式太阳能光热发电系统蒸汽发生器的概念机型．介绍了它的功能及运行原理。针对光热发电系统的特点对其主体结构进行了设计,使之能够适应大温差、变负荷的运行工况。从经济性和安全性的角度出发,对其运行方案及控制方案进行了分析。     

Influence of errors of trough pointing and fin alignement on the geometrical concentration ratio of focusing parabolic concentratiors

The geometrical behaviour of a focusing parabolic trough with a fin receiver has been studied in detail keeping in view the interesting application of this system for photovoltaic conversion of solar energy through double-sided and multiple-junction edge illuminated solar cells. Results regarding the influence of the pointing errors of the trough and alignment errors of the fin on the geometrical concentration rato of the system are presented.     

Ray trace evaluation of solar concentrators including limb darkening effects

The different correlations used to calculate intensity distribution over the sun's disc are compared. A new correlation is suggested which predicts the values to within ± 1.5 per cent of the experimental values. The distribution of local concentration ratio over a flat absorber placed in the focal plane of a cylindrical parabolic trough and that of a polygonal trough is determined using a ray-tracing technique.     

Analysis of internal helically finned tubes for parabolic trough design by CFD tools

This paper has analysed the effect of the utilization of internal finned tubes for the design of parabolic trough collectors with computational fluid dynamics tools. Our numerical approach has been qualified with the computational estimation of reported experimental data regarding phenomena involved in finned tube applications and solar irradiation of parabolic trough collector. The application of finned tubes to the design of parabolic trough collectors must take into account features as the pressure losses, thermal losses and thermo-mechanical stress and thermal fatigue. Our analysis shows an improvement potential in parabolic trough solar plants efficiency by the application of internal finned tubes.