反射式线性菲涅尔集热器性能的实验研究与模拟分析

采用热网络法建立菲涅尔集热系统CPC腔式接收器的数值传热模型,搭建集热器系统,实验研究集热器效率、CPC腔的集热性能。利用数值传热模型分析太阳辐照度、镜场宽度、工质入口温度和质量流量的变化对系统出口温度和效率的影响,以期为菲涅尔集热器出口参数的控制提供依据。实验数据验证了模型的有效性,模拟结果显示,质量流量对工质出口参数影响最大;镜场宽度和辐照度对集热效率的影响最为显著;菲涅尔集热器的热效率可达68%。     

线性菲涅尔集热器光学特性实例分析与模拟

对线性菲涅尔集热器的聚光性能和光学效率进行了模拟与计算.根据几何光学原理,对集热器镜场各项光学损失(如余弦损失、阴影与遮挡损失)建立数学模型,计算出每项光学损失对应的光学效率.再用TracePro光学软件建立集热器的几何模型,利用光线追踪的方法,模拟入射到镜场的光线在模型空间的传播.光线在模型表面发生吸收、反射和散射等过程,追踪每束光线的光通量,计算得到集热器的光学效率和聚光比等性能参数.结果表明:通过数学模型和光学软件模拟得出的集热器光学效率一致,2种方法分别从细节与整体上剖析了影响集热器光学性能的因素,在集热器设计中可以结合使用,互相补充.     

线性菲涅尔集热器镜场设计理论与光学分析

文章介绍了线性菲涅尔反射镜场的设计方法与数学模型,分析了镜场模型的光学特性和镜场的各项光学损失,并计算了集热器的光学效率。在镜场反射镜数目一定的情况下,研究了光学效率随吸收器高度、镜面间隔与镜面宽度变化的规律。研究结果表明:吸收器高度对镜场的余弦损失、阴影遮挡损失影响较大,吸收器高度增加,集热器光学效率随之增加;镜面间隔变化对镜场余弦损失影响很小,对阴影与遮挡损失的影响很大,镜面间隔增大,阴影与遮挡损失迅速减小;镜面宽度对镜场余弦损失影响很小,太阳入射倾角较小时,镜面宽度对阴影与遮挡损失影响较大,镜面宽度增大这种损失迅速增大。     

小型菲涅尔定焦线聚光系统关键参数影响特性研究

基于线性菲涅尔透镜聚光特性和极轴式跟踪原理,提出一种采用圆弧腔体吸收器的小型菲涅尔定焦线聚光系统。采用蒙特卡洛光线追迹方法与数理统计原理,详细研究太阳赤纬角、太阳时角和腔体内表面吸收率等关键参数对聚光系统光学性能的影响。结果表明,腔体内表面吸收率对光学效率因子的影响最显著,其次为太阳赤纬角、太阳时角。腔体内表面吸收率分别为1.00、0.85、0.75时,系统平均光学效率因子分别为0.950、0.865、0.799。太阳赤纬角对能流均匀性影响最显著,其次为太阳时角、腔体内表面吸收率。在太阳赤纬角分别为0°、8°、16°、23.45°时的平均均匀因子分别为0.507、0.519、0.561、0.612。该系统可减少余弦损失、降低焦线偏移对端部损失的影响。     

水冷型PV/T集热器的换热性能研究

光伏/光热(Photovoltaic/Thermal,PV/T)集热器集光伏发电与太阳能低温热利用于一体,可以同时输出电和热,是前景较好的新型太阳能利用技术。文章利用Fluent软件数值模拟了多进多出形式的水冷型PV/T集热器,分析了水的入口温度、流速及辐射强度对光伏电池温度及出口水温的影响。研究显示,在最佳匹配条件下,集热器的光电转化率和光热转化率能得到综合提高。     

基于三角形腔体的菲涅尔线聚焦集热系统研究

该文设计一种基于三角形腔体的菲涅尔线聚焦集热系统,通过搭建测试平台,在实际天气条件下测试腔体有无盖板、腔体内铜管表面有无覆盖黑漆和太阳直射辐照度等因素对腔体出口温度及系统集热效率的影响。研究结果表明：光洁铜管腔体增加盖板后,集热效率由22.10%增加至25.82%;而黑漆铜管腔体增加盖板后,系统集热效率由30.40%下降至29.50%。光洁铜管表面覆盖黑漆后,腔体无盖板情况下的系统集热效率由21.94%增加至34.57%;腔体有盖板情况下的系统集热效率由25.26%增加至29.91%。太阳直射辐照度对腔体出口温度波动影响显著,但对系统集热效率的影响不明显。     

菲涅尔太阳能集热器驱动的冷热电联供系统热力性能分析

为了提高冷热电联供系统的灵活性和热力学性能,将线性菲涅尔集热器、吸收式热泵、有机朗肯循环、地源热泵相结合,提出了一种基于线性菲涅尔太阳能集热器的新型冷热电联供系统。在EES软件中建立了提议系统和参考系统的热力学模型,将提议冷热电联供系统和参考系统的性能进行比较,并分析了一些关键参数对系统性能的影响。结果表明：该系统在设计工况下,一次能源利用率可达到78.04%,太阳能发电效率为8.2%,热电比为10.13;与参考系统相比,节约了一次能源11.8%,提高了系统满足用户负荷的灵活性;夏季辐照强度每增加100 W/m²,一次能源利用率约增加0.95%,太阳能发电效率增加2.73%;在热分配比为0.2时,系统一次能源利用率最大为80.5%;热电比随着辐照强度和热分配比的增大而减小,当热分配比增大0.4时,夏季系统热电比下降了86.2%,冬季热电比下降了84.9%。     

线性菲涅尔式太阳能热发电技术发展概况

针对该技术的原理及特点、发展历程、应用现状、未来的发展趋势以及应用前景作了相关介绍。     

线性菲涅耳集热器接收器对镜场的遮挡研究

带有二次反射器的线性菲涅耳聚光集热器,虽然其接收器表面的能量分布更均匀,但也增加了接收器对反射镜场的遮挡。本文采用理论计算和模拟两种方式对已设计的线性菲涅耳集热器二次反射器对镜场的遮挡情况进行分析,先通过理论计算得出二次反射器对西边三块初级反射镜遮挡角θni的范围,然后利用光线追踪软件模拟出安装和不安装二次反射器两种情况下到达初级反射镜的光线数目,根据光线数目变化情况得出西边三块反射镜的遮挡角变化范围分别为70º ~ 90º、54º ~ 72º和42º ~ 58º,同时引入光线损失率来衡量二次反射镜对镜元遮挡的影响,结果得出安装二次反射器后镜元光线损失率最大值达到23.53%。     

基于菲涅尔聚光的太阳能砷化镓电池热特性分析

以菲涅尔三级聚光器和三结砷化镓太阳电池芯片为研究对象,利用Trace Pro模拟菲涅尔高倍聚光条件下电池芯片表面的能流密度分布,并将结果导入ANSYS中作为三结砷化镓太阳电池芯片的边界条件。通过有限元模拟了电池芯片的温度和热流分布,并利用热-结构耦合分析法,得到了电池芯片的热应力分布。结果表明:三级聚光器能有效提高聚焦光斑能量均匀性、增大系统接收角,从而降低热应力,提高光伏系统的整体性能。     

An improved thermal and electrical model for a solar photovoltaic thermal (PV/T) air collector

In this paper, an attempt is made to investigate the thermal and electrical performance of a solar photovoltaic thermal (PV/T) air collector. A detailed thermal and electrical model is developed to calculate the thermal and electrical parameters of a typical PV/T air collector. The thermal and electrical parameters of a PV/T air collector include solar cell temperature, back surface temperature, outlet air temperature, open-circuit voltage, short-circuit current, maximum power point voltage, maximum power point current, etc. Some corrections are done on heat loss coefficients in order to improve the thermal model of a PV/T air collector. A better electrical model is used to increase the calculations precision of PV/T air collector electrical parameters. Unlike the conventional electrical models used in the previous literature, the electrical model presented in this paper can estimate the electrical parameters of a PV/T air collector such as open-circuit voltage, short-circuit current, maximum power point voltage, and maximum power point current. Further, an analytical expression for the overall energy efficiency of a PV/T air collector is derived in terms of thermal, electrical, design and climatic parameters. A computer simulation program is developed in order to calculate the thermal and electrical parameters of a PV/T air collector. The results of numerical simulation are in good agreement with the experimental measurements noted in the previous literature. Finally, parametric studies have been carried out. Since some corrections have been down on thermal and electrical models, it is observed that the thermal and electrical simulation results obtained in this paper is more precise than the one given by the previous literature. It is also found that the thermal efficiency, electrical efficiency and overall energy efficiency of PV/T air collector is about 17.18%, 10.01% and 45%, respectively, for a sample climatic, operating and design parameters.     

Exergetic optimization of a solar photovoltaic thermal (PV/T) air collector

In this paper, an exergetic optimization has been developed to determine the optimal performance and design parameters of a solar photovoltaic thermal (PV/T) air collector. A detailed energy and exergy analysis has been carried out to calculate the thermal and electrical parameters, exergy components, and exergy efficiency of a typical PV/T air collector. The thermal and electrical parameters of a PV/T air collector include solar cell temperature, back surface temperature, outlet air temperature, open‐circuit voltage, short‐circuit current, maximum power point voltage, maximum power point current, etc. An improved electrical model has been used to estimate the electrical parameters of a PV/T air collector. Furthermore, a new equation for the exergy efficiency of a PV/T air collector has been derived in terms of design and climatic parameters. A computer simulation program has been also developed to calculate the thermal and electrical parameters of a PV/T air collector. The results of numerical simulation are in good agreement with the experimental measurements noted in the previous literature. Moreover, the simulation results obtained in this paper are more precise than the one given by the previous literature, and the new exergy efficiency obtained in this paper is in good agreement with the one given by the previous literature. Finally, exergetic optimization has been carried out under given climatic, operating, and design parameters. The optimized values of inlet air velocity, duct length, and the maximum exergy efficiency have been found. Parametric studies have been also carried out. Copyright © 2010 John Wiley & Sons, Ltd.     

U型管式全玻璃真空管集热器热效率及性能研究

在能量平衡分析的基础上，建立了U型管式全玻璃真空管太阳能集热器热效率方程，推导了集热器热损系数、效率因子等性能参数的计算公式，理论计算热效率与实验数据吻合良好。计算分析表明，真空管热损系数与吸热管和环境温差并非线性关系，将其关联式按环境温度分段整理将使计算结果更接近实际；涂层发射比对集热器的热效率影响较大，降低涂层发射比是提高集热器效率的有效途径；采取适当的措施降低吸热管与肋片间的接触热阻后，采用U型管连接方式不会时热利用系统集热器效率造成太大影响。     

Performance analysis of a hybrid photovoltaic/thermal (PV/T) collector with integrated CPC troughs

In the present investigation a theoretical analysis has been presented for the modelling of thermal and electrical processes of a hybrid PV/T air heating collector coupled with a compound parabolic concentrator (CPC). In this design, several CPC troughs are combined in a single PV/T collector panel. The absorber of the hybrid PV/T collector under investigation consists of an array of solar cells for generation of electricity, while collector fluid circulating past the absorber provides useful thermal energy as in a conventional flat plate collector. In the analysis, it is assumed that solar cell efficiency can be represented by a linear decreasing function of its temperature. Energy balance equations have been developed for the various components of the system. Based on the developed analysis, both thermal and electrical performance of the system as a function of system design parameters are presented and discussed. Results have been presented to compare the performance of hybrid PV/T collector coupled with and without CPC. Copyright © 1999 John Wiley & Sons, Ltd.     

配合集热器的盐梯度太阳池热性能实验与分析

构建表面积为1.50 m×1.50 m的小型实验用盐梯度太阳池,并与平板太阳能集热器配合使用,分别对普通太阳池和集热增强型太阳池进行了储热、放热实验。实验研究与理论分析表明:单独盐梯度太阳池的放热量为3.5×103k J,热效率为13.6%;集热增强型太阳池放热量可以达到4.8×103k J,且热效率增至28.1%。另外后者下对流层温度最高可提升10℃以上,从而证明太阳能集热器可以有效提高太阳池热效率,增加下对流层储热量。此外,考虑了放热过程换热器对太阳池下对流层的扰动,对比实验前后的溶液浓度,可以看出实验后太阳池盐度曲线合理,非对流层呈良好梯度分布,太阳池稳定性并未遭到破坏。     

System performance studies on a photovoltaic/thermal (PV/T) air heating collector

A computer simulation model is presented for the analysis of a solar photovoltaic/thermal (PV/T) hybrid collector with air as heat transfer fluid and algorithm for making quantitative prediction regarding the performance of the system is described. Thermal efficiency curves for the solar PV/T hybrid collectors corresponding to various type of absorbers have been derived. In order to appreciate the model, numerical calculations have been made for evaluating the system performance corresponding to typical climate of Delhi, India     

Optimization of a solar photovoltaic thermal (PV/T) water collector based on exergy concept

In this paper, the optimization of a solar photovoltaic thermal (PV/T) water collector which is based on exergy concept is carried out. Considering energy balance for different components of PV/T collector, we can obtain analytical expressions for thermal parameters (i.e. solar cells temperature, outlet water temperature, useful absorbed heat rate, average water temperature, thermal efficiency, etc.). Thermal analysis of PV/T collector depends on electrical analysis of it; therefore, five-parameter current–voltage (I–V) model is used to obtain electrical parameters (i.e. open-circuit voltage, short-circuit current, voltage and current at the point which has maximum electrical power, electrical efficiency, etc.). In order to obtain exergy efficiency of PV/T collector we need exergy analysis as well as energy analysis. Considering exergy balance for different components of PV/T collector, we obtain the expressions which show the exergy of the different parts of PV/T collector. Some corrections have been done on the above expressions in order to obtain a modified equation for the exergy efficiency of PV/T water collector. A computer simulation program has been developed in order to obtain the amount of thermal and electrical parameters. The simulation results are in good agreement with the experimental data of previous literature. Genetic algorithm (GA) has been used to optimize the exergy efficiency of PV/T water collector. Optimum inlet water velocity and pipe diameter are 0.09 m s⁻¹, 4.8 mm, respectively. Maximum exergy efficiency is 11.36%. Finally, some parametric studies have been done in order to find the effect of climatic parameters on exergy efficiency.     

The study of the performance and efficiency of flat linear Fresnel lens collector with sun tracking system in Iraq

Two flat linear Fresnel lenses and two absorbers connected in series. Tracking system is constructed so that it tracks the sun in two directions. Thermal and optical losses are introduced. The thermal efficiency of the first lens is higher than the second lens and reaches 0.65. The FLFL all-day collector efficiency reaches 0.58 and it varies depending on weather condition.     

相变蓄热式PV/T集热器的试验研究

为冷却光伏组件,用定型相变材料填充管板式PV/T集热器,并以无集热器组件和保温材料填充的集热器为参照组,进行了工质(水)温升及对组件冷却效果的试验。试验结果表明:采用相变材料填充的相变蓄热式集热器能明显降低组件温度,并提高了热能利用率,其冷却效果和工质温升均优于保温材料填充式集热器;在流量为30 L/h的开式水冷条件下,相变材料填充式集热器工质(水)的平均温升为5.6℃,平均获得热能702k J/h,组件温度平均降低了6.8℃,理论光电转换效率提高了3.4%;使用相变蓄热式集热器的组件温度变化约滞后于太阳辐射变化2 h,最低效率时刻避开了辐射值最大时刻,全天效率得到提高。     

Performance optimization of a photovoltaic/thermal collector using microencapsulated phase change slurry

In a photovoltaic/thermal (PV/T) collector, a portion of absorbed solar energy is transformed into electrical energy, and the remaining part is transformed into thermal energy. Increasing waste heat collection and energy conversion rates are important to improve the performance of the PV/T collector. The utilization of microencapsulated phase change slurry (MPCS) in a PV/T collector to cool photovoltaic modules is an effective way, and electrical and thermal performances of the collector are improved. To investigate influences of operating parameters on performances of PV/T collector, numerical simulation is put into effect to analyze influences of the mass fraction of MPCS on the collector performance. The influences of MPCS mass flow rate and collector channel height on collector performances are also studied. When the flow rate is 0.005 kg/s and the channel height is 0.010 m, the PV/T collector obtains the best net efficiency with a MPCS mass concentration of 20 wt%. But electrical efficiency difference between 15 and 20 wt% is not obvious. With the growth in mass fraction, PV temperature drops more and more slowly because outlet fluid has not fully melt. Take PV/T collector performances into consideration, 15 wt% MPCS is a better choice to cool photovoltaic modules.