平板太阳能集热器的热性能

平板太阳能集热器的主要部件是吸收板。吸收板由做成一体的金属板和管构成,板的表面涂黑,以增强对太阳能的吸收。吸收板的底部和边缘用隔热材料隔热,以减少吸热板对周围大气的热损失。吸热板的上面盖有透明盖板,太阳光透过盖板,被吸收板吸收,同时它还限制盖板和吸收板之间的空气流动,减少吸收板的散热。传热流体(一般用水),通过吸收板中的管道流动,把吸收板吸收的太阳热传送     

波纹板太阳能集热器吸热板表面太阳辐照度分布特性研究

采用蒙特卡洛射线追踪法,研究不同季节和安装角度等关键参数对波纹板太阳能集热器与平板太阳能集热器吸热板表面太阳辐照度的影响,并对得到的数据进行分析。模拟结果显示,在相同安装角度下,波纹板太阳能集热器吸热板表面太阳辐照度比平板太阳能集热器大。二者相差的百分比随光线对集热器的入射角而变化,入射角较小时,相差的百分比较大。90°安装时,冬季波纹板太阳能集热器累积辐照度比平板太阳能集热器提升6.2%,夏季二者接近。40°安装时,冬季和夏季波纹板太阳能集热器累积辐照度分别比平板太阳能集热器提升7.1%和6.9%。     

适用于农村的太阳能集热器

本文介绍一种成本低、效率高,适用于广大农村地区的新型太阳能集热器的研究成果。整个太阳能集热器是由贮热材料——砂块与埋在其表面下的塑料管路组成。将砂块上表面用通常的涂料涂黑,以提高太阳能辐射的吸收率,水在管内流过,热能是经砂块     

盘式聚光系统吸热器热性能实验研究

该文研究设计制作了平顶锥形吸热器,安装在一部盘式聚光系统上,利用水作工质,进行了热性能实验研究.按照定流量、变流量及当地天气情况,测试了一段时间内吸热器进出口的温度变化,分析了吸热功率和热效率.实验显示,当太阳直射辐射的辐照度升高,不论是定流量还是变流量状态,吸热功率变化趋势相同(均增加);热效率变化趋势则不同,定流量状态下降低,变流量状态下升高.研究表明,利用盘式聚光系统通过吸热器对水进行加热,所涉及的太阳直射辐射辐照度和工质状态是影响盘式聚光系统吸热器的吸热功率和热效率的重要因素.以上研究,对太阳能中高温利用及实际研发一套盘式太阳能热发电系统有一定参考作用.     

基于碟式聚光的太阳能盘管吸热试验与模拟

为开发适合太阳能布雷顿循环的压缩空气吸热器,利用碟式聚光系统,在实际太阳辐射下研究盘管式空气吸热器运行特性。试验表明,压缩空气出口温度可达800℃以上,最高热效率达到61.2%,最大吸热功率为30.6 kW。利用Fluent建立吸热器的三维稳态模型,获得吸热器内的温度分布,指出减小采光孔尺寸,可大幅降低吸热器的辐射和对流损失,将吸热效率从56.8%提高到75.8%。建立吸热器的一维瞬态模型,阐明实际太阳辐射波动条件下吸热器的瞬态运行特性,模拟结果与试验结果的最大平均相对误差为10.7%,结果可为太阳能布雷顿循环系统的高温气体吸热器的设计与运行提供重要参考。     

双玻光伏组件PV/T集热器特性及实验研究

利用双玻光伏组件设计了一种新的PV/T(photovoltaic/thermal)太阳能集热器,并对其热转换和传输特性进行研究.制备了透光率分别为50％和10％的2种双玻光伏组件PV/T空气集热系统样机,并对其特性进行实验研究.结果表明透光率50％的PV/T太阳能集热器,其吸热板温度高于双玻光伏组件温度,透光率10％P...     

双面受热太阳能平板接收器热性能模拟研究

为提高太阳能光热转换效率,建立同轴非完整型平移抛物面聚光系统。分析双面受热平板接收器的能量传递及转换过程,采用热阻网络图的分析方法建立平板接收器的理论计算模型。利用MATLAB 7.0软件编制程序实现了平板接收器的热性能计算。在结构参数、环境参数和进口参数确定的情况下,当吸热板导热系数、厚度和吸热板表面发射率变化时,分析温度、能量及热性能的变化趋势。研究表明：导热系数和吸热板厚度达到一定数值,继续增加对于提高接收器的热性能基本没有太大意义;吸热板表面发射率对热性能影响显著,采用发射率为0.1的选择性涂层可实现能量最大转化;环境温度在0～30 ℃变化时,双面受热比单面受热的热效率提高了8.18%～37.01%。     

聚光太阳能吸热管的吸热传热特性

基于太阳能选择性吸收涂层的辐射性能,建立聚光太阳能吸热管光热耦合传输的数理模型,理论研究聚光太阳能吸热管的吸热传热特性。研究表明,吸热管壁温度随着聚光能流密度增加而线性升高,而吸热效率在中等聚光能流密度时达最大值。太阳能选择性吸收涂层性能对吸热传热有重要影响,具有低红外发射系数涂层的系统吸热效率明显较高,而红外辐射能量损失率则在中等聚光能流密度时最小。管内强迫对流可以显著提高吸热管效能,吸热效率随流速增加而提高,而管壁温度则显著下降。     

太阳能路面空心板块单元力学分析与模型制备

为了确定合理的太阳能路面模型,提出一种由表层透光保护板、中层太阳电池板和底座预制混凝土空心板3层组成的新型空心板块太阳能路面结构,通过建立合理的三维有限元模型进行受力数值模拟,确定空心板块结构尺寸,并制作太阳能路面空心板块单元模型,测试相应的力学性能和发电效能。结果表明,板长、板宽、侧壁厚与透光板厚对其应力和变形的影响显著,由此确定适宜的空心板块单元尺寸为:整体50 cm×50 cm×25 cm,透光板50 cm×50 cm×2 cm,底座板50 cm×50 cm×23 cm,其中底板厚和侧壁厚均为10 cm。同时,在标准轴载作用下,最不利荷位处透光板的表面弯沉为3.743 mm,透光板对电池板吸收太阳能有一定的阻碍作用,阻碍系数为1.53。所制备的太阳能路面空心板块单元模型能满足行车和发电要求,可为进一步研究太阳能路面提供借鉴。     

基于黑体模型对碟式斯特林发电装置集热腔的优化设计

通过对吸热器所处的集热腔建立辐射换热模型,经计算有40%进入集热腔的太阳能未被吸收,导致吸热器的光热转化效率较低。基于对集热腔的黑体模型假设,分析产生上述现象的原因,在此基础上提出对吸热器表面进行人工处理镀黑镍的方法以提高吸热器对太阳能的吸收效率,并对结构进行优化设计,可进一步使吸热器对太阳能的吸收效率提高到90%以上,有利于提高碟式斯特林发电装置的发电功率及效率。     

Effective absorbability of “translucent cover—radiation absorbing heat-exchange panel” system of flat solar collectors

An analytic expression making it possible to calculate the effective absorbability of the “translucent cover-radiation absorbing heat-exchange panel” system of flat solar collectors considering the absorbability of the translucent cover is presented. A practical example of the calculation of the effective absorbability of the examined system with single-layer translucent cover as a function of the integral coefficient of total solar radiation reflection of the radiation absorbing surface of the heat-exchange panel is given.     

Periodic heat flux through a three layered slab

This communication presents a derivation of an explicit expression for the periodic variation of thermal flux through a composite slab (insulation-concrete-insulation or concrete-insulation-concrete), with one face exposed to solar radiation and atmospheric air and the other face in contact with room air at constant temperature. It is seen that for maximum or minimum load levelling of the periodic heat flux the thicknesses of the outer layers of the composite slab are equal.     

CMIP5气候模式对未来30年太阳辐射变化的预估研究

使用CMIP5中33个全球气候模式的模拟数据,选择中位数集合方案,分别在RCP4.5和RCP8.5情景下对2006~2050年全球所有天气条件下地表接收到的太阳辐射、无云条件下地表接收到的太阳辐射、相对湿度、近地层风速、近地层气温和云量的变化进行预估研究。结果表明:1)在RCP8.5情景下,气温的增温率在50°N以北地区最大,达0.12 K/a。同时北半球增温率大于南半球,陆表气温的增温率大于海表气温;2)在RCP4.5和RCP8.5情景下,中国东南部和欧洲中东部地区的地表太阳直接辐射呈现较大正趋势;3)在所选3个区域中,不同RCP情景下地表太阳辐射均呈现正趋势,其中在RCP8.5情景下法国波尔多地表太阳辐射呈现最大正趋势。     

Practical procedure for predicting non-uniform temperature on the exposed face of arch dams

Temperature distribution on the exposed face (especially the downstream face) of arch dams is non-uniform, to a certain extent, due to the variation in solar radiation striking the surface. However, the temperature at the same elevation across the dam axis is generally assumed to be uniform in the design specifications for arch dams because there is no accepted procedure for defining the non-uniform temperature field. In this paper, a practical model for predicting the non-uniform temperature of the exposed face is presented by considering both solar radiation and shading effects. The ASHRAE clear sky model was adopted to calculate the solar radiation, and a ray-tracing algorithm was used to analyze the shade of surrounding terrain and the structure per se. The real-life case study presented in this study shows that the proposed model was effective in simulating and accessing reasonable thermal distribution. Subsequently, the case study also reveals that the non-uniform temperature had a significant effect on surface thermal stress and crack propagation.     

Solar heating of a fluid through a semi-transparent plate: Theory and experiment

A theoretical and experimental study of solar radiation passing through a thin semi-transparent slab to heat a fluid is presented. The system of differential equations describing the temperature of the slab and the fluid as a function of time is derived and solved; the theoretical curves generated by the solution for the fluid temperature are compared with experimental readings obtained using water as the fluid and acrylic plastic (methyl---methacrylate) as the semi-transparent material. The theoretical solution assumes that the solid absorbs radiation according to Beer's law and that the fluid completely absorbs the transmitted radiation. The transient theoretical fluid temperature curves for heating oil through plastic and through an opaque (copper) plate are compared; a general criterion for steady-state has been derived, showing that, for the same parameters of solar intensity, convection coefficients, ambient temperature and container dimensions, the fluid temperatures attained by using semi-transparent materials are considerably higher than those obtained with opaque plates.     

Transmission and storage characteristics of sinusoidally excited walls—A review

This paper summarises developments in the theory of the behaviour of the walls of a room when subjected to diurnal variations of ambient temperature and solar radiation, and the implications it has for the temperature within the room. It summarises successively analytical work on the transmission characteristics of a slab, and a slab with inside and outside films describing radiation and convective processes on each side of a simple wall. It continues with a discussion of these characteristics for multilayer walls as found directly and through matrix methods and provides a similar discussion of wall heat storage characteristics, as determined analytically. Electrical analogue and numerical methods are discussed. These characteristics form an essential part of procedures for estimating variation of temperatures within a room and the work in this connection of Shklover,²⁵ Muncey⁴⁷ and Danter and Loudon¹ is outlined.     

Output variation of photovoltaic modules with environmental factors — II: seasonal variation

This study investigated how seasonal changes in cell temperature and spectral solar radiation effect the seasonal variation in photovoltaic (PV) module conversion efficieny for CdS–CdTe and two-layer tandem-amorphous silicon (for simplicity referred to as CdS and 2L A Si, respectively). First, using the measured data, the ratio of the spectral solar radiation available for solar cell utilization to the global solar radiation (denoted hereafter as “available spectral ratio”), the mean cell temperature, and the conversion efficiency for each month were obtained, and seasonal variations were analyzed. Mean cell temperature and available spectral ratio seasonal changes were found to be 9% for CdS and 16% for 2L A Si.The CdS conversion efficiency increased during summer by 7%, whereas 2L A Si exhibited a more substantial 14% variation. During summer, although the spectral ratio available to CdS increases, the conversion efficiency does not increase by the same amount, because of an increase in cell temperature. Similarly, although 2L A Si, experienced a much greater increase in available spectral ratio and had a better overall performance, there was still only a 2% variation, because of the cell temperature increases.If the basic characteristics of solar cell output for various types are compared with the variation in environmental factors, such as irradiance, cell temperature and spectral solar radiation, it is possible to calculate the precise output of a solar cell. Accordingly, it is possible to evaluate the seasonal variation in conversion efficiency for each solar cell type and utilize this information to optimize the PV power system.     

Study of the distribution of the absorbed solar radiation on the performance of a CPC-type ICS water heater

An Integrated Collector Storage (ICS) solar water heater was designed, constructed and studied with an emphasis on its optical and thermal performance. The ICS system consists of one cylindrical horizontal tank properly mounted in a stationary symmetrical Compound Parabolic Concentrating (CPC) reflector trough. The main objective was the design and the construction of a low cost solar system with improved thermal performance based on the exploitation of the non-uniform distribution of the absorbed solar radiation on the cylindrical storage tank surface. A ray-tracing model was developed to gauge the distribution of the incoming solar radiation on the absorber surface and the results were compared with those from a theoretical optical model based on the average number of reflections. The variation of the optical efficiency as function of the incident angle of the incoming solar radiation along with its dependence on the month during annual operation of ICS system is presented. The ICS device was experimentally tested outdoors during a whole year in order to correlate the observed temperature rise and stratification of the stored water with the non-uniform distribution of the absorbed solar radiation. The results show that the upper part of the tank surface collects the larger fraction of the total absorbed solar radiation for all incident angles throughout the year. This is found to have a significant effect on the overall thermal performance of the ICS unit. In addition, the presented results can be considered important for the design and the operation of ICS systems consisting of cylindrical tank and CPC reflectors.     

DSG太阳能槽式集热器动态特性

采用数值模拟方法,分析了以水,水蒸气为工质的DSG槽式集热器的动态流动与传热特性.首先建立了管内流体的一维多相流动与传热模型,并利用差分法对该模型进行求解,计算结果与现有文献数据吻合较好.分析了稳态条件下,集热器出口流体工质参数受太阳辐射强度、流体质量流量、人口温度和入口压力的影响规律.在动态分析中,研究了辐射强度变化所导致的出口参数变化特性.从阶跃响应和脉冲响应的分析中得出,虽然热惯性存在,但短期的辐射强度波动对出口温度仍有较大影响,但对出口压力的影响较小.辐射波动将对一次直通DSG系统出口温度产生很大波动.     

利用我国气象卫星遥感资料估算黄河源区净辐射辐照度的研究

以黄河源区为研究区域,利用我国静止气象卫星(FY-2D)及极轨气象卫星(FY-3A)资料,估算黄河源区一天中不同时刻的净辐射辐照度的空间分布。在晴天条件下,利用计算的向下太阳辐射照度,结合卫星遥感资料估算的地表反照率,得出地表太阳辐射收支。利用卫星遥感估算地表发射率和地表温度资料,结合地面观测站的气象观测资料,得到大气向下的长波辐射和地面向上的长波辐射值。在阴天条件下,借助FY-2D云顶的反照率资料,根据太阳辐射在大气中的衰减过程,推求透射比系数,进而得出阴天条件下地表净短波辐射照度。