CPC式集热器放置倾斜角的选择方法

借鉴太阳能热水器放置的最佳倾角计算方法,研究复合抛物面聚光器(CPC)式集热器的辐射量计算模型,并给出南北轴放置时的最佳倾角计算思路。还结合南京、敦煌地区探索CPC式集热器的最大辐射量I_(max)与其最大接收角θ_(max)和放置倾角β之间的关系,最佳倾角的确定可使接收的辐射能至少提高5%。     

倾斜面上太阳辐射计算与最佳位置确定

在对常用典型气象年的构成以及上海地区太阳辐射资源的分析基础上,利用Ecotect软件模拟了不同方位角和倾角下斜面接收太阳辐射的变化,并对太阳能集热装置安装方位角和倾角进行了最优化研究。研究表明：以最大年辐射总量为指标,上海地区太阳能集热装置最佳位置为方位角30°,倾角26°。计算结果与两组实验值对比表明,最大相对误差为3．8％。本文计算结果可为实际工程中太阳能集热装置的安装布置提供参考。     

深圳不同气象条件下各朝向太阳辐射分布特征

利用深圳地区搭建的多朝向太阳辐照与光伏发电效率测量系统2013—2017年120个朝向光伏组件实测数据,分析入射太阳辐射最佳朝向及其时间变化规律,不同气象条件下各朝向辐射的表现特征,以及方位角和倾角的差异对辐射影响的程度,得出:1)年均太阳辐射最大值的倾斜面为-15°/10°,即光伏发电最佳方位角南偏东15°,最佳倾角10°;3—10月份最佳倾角较低,在0°～20°之间,11月份—次年2月份最佳倾角在30°～50°之间,最佳朝向的月平均辐射量比水平面上要高出6.6%;对于可调倾角的光伏电站,每年可进行4次调节(4月份0°、7月份10°、9月份20°、11月份40°),就可达到较高的发电效率。2)深圳的多云天气最多,累计辐射值超过了1/3,因此多云天气时的太阳能利用也极具价值;3)深圳地区太阳辐射与气象条件关系密切,且东侧辐射值往往大于西侧。     

大型平板型/真空管太阳集热器阵列排布问题研究

研究了安装在水平地面上的平板型,真空管太阳集热器的排布问题,建立了大型平板型/真空管太阳集热器阵列排布的几何模型,针对给定的集热器阵列,计算了在不同集热器倾角、间距、方位角下整个阵列所接收到的全年太阳辐照度及接收效率,分析了集热器倾角、间距、方位角对集热器阵列性能的影响.同时计算了集热器阵列在不同纬度和倾角情况下的最佳间距,在计算结果的基础上给出了集热器最佳间距和当地纬度及集热器倾角的函数关系式.     

基于实测数据的可调式太阳能光伏板倾角计算分析

基于BSRN3000太阳辐射观测系统近3年的全年度太阳能气象实测数据,利用C#编程语言计算分析了呼和浩特地区倾角可调式太阳能光伏板表面接收的太阳辐射,推导出该地区光伏板的全年、半年、季节和每月的最佳倾角,并得出了半年调整是该地区的光伏板倾角调整的最适合方案。与全年最佳倾角相比,半年调整倾角方案的年辐射总量提高了5%左右。在呼和浩特当地进行了各种倾角的试验测定,所测得的数值与计算值吻合较好,验证了计算的准确性。     

光伏方阵最佳倾角的计算

确定独立光伏方阵的最佳倾角时，不应以太阳辐射强度最弱月份为依据，而应综合考虑方阵面上太阳辐射强度的均衡性和极大性，根据夏半年和冬半年倾斜面上所接收到的太阳辐射量进行判断。本文给出了我国６３个地区光伏方阵最佳倾角的计算结果。     

屋顶光伏系统阵列布局研究

采用PVsyst 6.06提供的Preze数学模型分析光伏阵列接收太阳辐射的特点,模拟计算长沙地区倾斜面上的太阳辐射量,利用逐步寻优法确定特定时期内该地区屋顶光伏阵列接收最大太阳辐射量的最佳倾角和朝向;利用阴影原理,简便推导屋顶南北坡面光伏阵列间距的计算方法,并分析阵列间距随屋顶坡度和倾角的变化规律。     

平板光伏阵列间隔处的太阳能利用及评估

分析光伏阵列阴影随时间的变化关系以及相邻光伏阵列间隔距离的确定方法。在光伏平板以最佳倾角安装并设定相邻光伏阵列间隔距离的前提下,以合肥地区为例,分析阵列间隔处光照随时间的分布规律以及可回收的能量。提出光伏阵列间隔处太阳能的复合抛物槽(CPC)光热利用方法,并分析CPC有效接收面积与能量收集效率的关系。     

辽河入海口地区倾斜面太阳辐射研究

文章利用在辽河入海口地区测得的太阳辐射数据,比较了现有的17个倾斜面太阳辐射计算模型在不同天气工况下的准确性。分析结果表明：阴天工况下Gueymard模型精度最高,其次是各向同性模型;多云工况下,Willmott模型与实测值较为吻合;晴天工况下,Reindl模型的综合表现状况最好;在不区分天气工况下,Willmott模型和Reindl模型的精度较高。同时,通过改写Reindl模型的各向同性组分建立新的计算模型,用实测数据分析在不区分天气条件下新模型的精度,结果显示新模型的计算精度明显提高。利用logistic函数建立小时散射辐射分数与小时晴空指数的关系,并采用新模型计算辽河入海口地区冬季不同倾斜面单位面积所接收的太阳辐照量,结果表明,对于冬季的辽河入海口地区,太阳能采集装置布置的最佳方位角为-20～30°、倾角为50～70°,总太阳辐射量最高可达1 200 MJ/m²。     

非正南方向太阳集热器面积补偿的理论研究

该文以昆明和北京为例,对我国南北地区分别选用平板型管翼式集热器和圆柱吸热体真空管集热器进行了模拟计算。结果显示,水平面上日均太阳辐射、环境温度、屋顶方位及倾角对集热面积补偿有不同程度的影响;其中,屋顶方位角和倾角是影响集热器处于非正南和正南方向且最佳倾角时采光面积之比A/A0的主要因素。本文的研究成果可为太阳能建筑一体化设计提供部分有价值的参考数据。     

倾角与方位角对张北地区光伏发电特性的影响

为使光伏组件获取更多的太阳辐照,需设置合适的倾角和方位角。通过2018年8月份在张北地区记录的辐照数据,计算得到张北地区光伏组件的最佳倾角。设置倾角为0°、30°、60°、90°、120°和150°的光伏组件,记录光伏组件的电压电流数据,分析不同天气下倾角和方位角对发电特性的影响。研究发现,光伏组件在该月的月最佳倾角为18.5°,晴天的日最佳倾角为27.1°,多云、阴天、雨天分别为18.0°、3.7°、0.2°。倾角对于发电特性的影响主要在于光伏组件接收的直射辐照大小,晴天和多云时30°倾角光伏组件的发电量最高,雨天和阴天水平光伏组件的发电量则最高。方位角对于发电特性的影响来源于直射辐照在一天中照射方向的变化,晴天和多云时方位角影响较大,阴天和雨天时影响很小。     

独立风光互补供电系统能量配比性能分析

对全年不同方位角和倾角的太阳能辐射量进行数值模拟,得知方位角南偏西30°倾角35°的倾斜面接收的太阳能辐射量最大。对光伏组件和风力发电机的功率输出影响因素进行了仿真,利用仿真结果计算全年的风光出力,由计算最佳倾斜面的太阳能辐射量和当地实际气象参数数据对风光互补匹配特性进行统计分析,得知风能与太阳能最佳配比为1:0.85,为以后风光互补供电系统的设计提供参考依据。     

拉萨太阳能集热器竖排安装最佳倾角分析

太阳能集热器的集热量与集热器的安装倾角有关。在竖排集热器朝正南向放置时,其集热量与集热器安装倾角之间存在一定的函数关系。结合拉萨地区典型年气象资料,通过对不同安装倾角真空管太阳能集热器在整个采暖季的集热量动态计算分析和寻优,结果表明：真空管型太阳能集热器在该地区的最佳倾角为46°,考虑到拉萨整个地区的纬度和气象条件不同,建议最佳安装倾角范围为40°～50°。     

Solar position algorithm for solar radiation applications

There have been many published articles describing solar position algorithms for solar radiation applications. The best uncertainty achieved in most of these articles is greater than ±0.01° in calculating the solar zenith and azimuth angles. For some, the algorithm is valid for a limited number of years varying from 15 years to a hundred years. This report is a step by step procedure for implementing an algorithm to calculate the solar zenith and azimuth angles in the period from the year −2000 to 6000, with uncertainties of ±0.0003°. The algorithm is described in a book written by Jean Meeus in 1998. This report is written in a step by step format to simplify the complicated steps described in the book, with a focus on the sun instead of the planets and stars in general. It also introduces some changes to accommodate for solar radiation applications. The changes include changing the direction of measuring azimuth angles to be measured from north and eastward instead of being measured from south and eastward, and the direction of measuring the observer’s geographical longitude to be measured as positive eastward from Greenwich meridian instead of negative. This report also includes the calculation of incidence angle for a surface that is tilted to any horizontal and vertical angle, as described by Iqbals in 1983.     

风光互补电动汽车储能电站系统优化设计

通过对唐山市区太阳能和风能资源状况调查分析,对全年不同方位角和倾角上的太阳能辐射量进行模拟计算,得出南偏东9.8°方向、倾角为39.7°的倾斜面上接收的太阳能辐射量最大,其值为1.62×106Wh/m2。研究中对3kW风力发电机和1kW光伏发电系统的发电量进行了计算,并以1辆纯电动轿车为负载进行了容量配比优化,设计了风力发电系统、风光互补系统及光伏系统三种不同的方案,经过对各方案的经济性、可靠性及稳定性分析,得出最佳的设计方案为风光互补发电系统,该系统风力发电装机容量为3kW,光伏发电装机容量为8.96kW。     

Effect of inclination on the performance of CPC solar energy collectors

A theoretical numerical model of thermal transfer in a line-axis, symmetric, compound parabolic concentrating solar energy collector (CPC) is presented. The effect of the angle of axial inclination of an east-west aligned CPC and hence the effect of the latitudinal and tracking configuration of the CPC system on performance is investigated. The angle of inclination is taken into consideration in the determination of both internal and external convective heat transfer. The convective, radiative, conductive and overall heat transfer coefficients and system efficiency for various angles of inclination, concentration ratios and insolations was determined, and are presented as graphs of heat transfer variation and Hottel-Whillier-Bliss characteristic curves respectively.     

Performance modeling and investigation of fixed, single and dual-axis tracking photovoltaic panel in Monastir city, Tunisia

Presented in this paper was an overview on research works on solar radiation basics and photovoltaic generation. Also, a complete PV modeling and investigation on the effect of using multi-axes sun-tracking systems on the electrical generation was carried out to evaluate its performance using the case study of the Monastir city, Tunisia. The effects of azimuth and tilt angles on the output power of a photovoltaic module were investigated. The instantaneous increments of the output power generated by a photovoltaic module mounted on a single and dual-axis tracking system relative to a traditional fixed panel were estimated. The results show that the yearly optimal tilt angle of a fixed panel faced due to the south is close to 0.9 times Monastir latitude. The gain made by the module mounted on a single-axis tracking panel relative to a traditional fixed panel was analyzed. The monthly increments of the gain are more noticeable for two critical periods which correspond to those surrounding the summer and the winter solstice dates. It reaches the value of 10.34% and 15% in the summer and winter solstice periods, respectively. However, the yearly gain relative to a fixed panel installed with the yearly optimal tilt angle is 5.76%. In some applications, covering loads at early morning or late afternoon hours and in order to more optimize the solar systems exploitation suggest the adjustment of the PV panel orientation to azimuth angles different from the south direction by using a dual-axis tracking installation. The gain made by this recommendation relative to a traditional fixed panel is evaluated. This gain reaches 30% and 44% respectively in the winter and summer solstice days.     

Determining optimum tilt angles and orientations of photovoltaic panels in Sanliurfa, Turkey

The performance of a photovoltaic (PV) panel is affected by its orientation and its tilt angle with the horizontal plane. This is because both of these parameters change the amount of solar energy received by the surface of the PV panel. A mathematical model was used to estimate the total solar radiation on the tilted PV surface, and to determine optimum tilt angles for a PV panel installed in Sanliurfa, Turkey. The optimum tilt angles were determined by searching for the values of angles for which the total radiation on the PV surface was maximum for the period studied. The study also investigated the effect of two-axis solar tracking on energy gain compared to a fixed PV panel. This study determined that the monthly optimum tilt angle for a PV panel changes throughout the year with its minimum value as 13° in June and maximum value as 61° in December. The results showed that the gains in the amount of solar radiation throughout the year received by the PV panel mounted at monthly optimum tilt angles with respect to seasonal optimum angles and tilt angel equal to latitude were 1.1% and 3.9%, respectively. Furthermore, daily average of 29.3% gain in total solar radiation results in an daily average of 34.6% gain in generated power with two-axis solar tracking compared to a south facing PV panel fixed at 14° tilt angle on a particular day in July in Sanliurfa, Turkey.     

The Sun’s apparent position and the optimal tilt angle of a solar collector in the northern hemisphere

In this paper, the Julian dating system is adopted to calculate the Sun’s apparent position. Both the sunshine duration and the optimal installation angle of a fixed solar collector are obtained for different time periods and latitudes in the northern hemisphere. To simulate different operating environments, both kinds of radiation flux are considered, i.e. extraterrestrial radiation and the global radiation calculated using an empirical model. The results show that Julian dating system is precise enough to predict the Sun’s locus according to analyses of the solar declination and the azimuth and elevation angles. The orientation that a solar collector must be installed at can be roughly estimated by determining the sunshine duration. The majority of the Sun’s path lies in the southern sky over a year, and hence the sunshine duration in the southern sky is longer, except for locations with latitudes below 1.5°. The yearly optimal angles are positive (approximately 0.91 and 0.76 multiplied by the latitude for extraterrestrial and global radiation, respectively), for latitudes below 65^o. Above this, the curves are flatter, and the differences between the two types of radiation flux become greater. The ratio of the yearly irradiation captured by a collector installed at its yearly optimal angle to that captured by the ground surface increases with latitude, and reaches a maximum of 1.71 and 1.35 near latitudes of 65° for extraterrestrial and global radiation, respectively. The efficiency of a solar collector decreases when operating in a cloudy environment. The amount of global radiation incident on the ground surface is about 0.51-0.66 times that of extraterrestrial radiation throughout the hemisphere.     

Upper bounds for the yearly energy delivery of stationary solar concentrators and the implications for concentrator optical design

Compound parabolic concentrator (CPC) type collectors have been viewed as the optimal design for totally stationary concentrators. However the CPC is ideal only for uniform incident solar flux averaged over the energy collection period. The actual yearly-averaged incident flux map turns out to be highly non-uniform, as a function of projected incidence angle, which implies that concentration can be increased markedly if optical collection efficiency is compromised. The question then becomes: what concentrator angular acceptance function is best matched to nature's radiation flux input, and how much energy can such a concentrator deliver? The recently-invented tailored edge-ray concentrator (TERC) approach could be used to determine optimal reflector contours, given the optimal acceptance angle function. We demonstrate that totally stationary TERCs can have around three times the geometric concentration of corresponding optimized stationary CPCs, with greater energy delivery per absorber area, in particular for applications that are currently being considered for stationary evacuated concentrators with the latest low-emissivity selective coatings, e.g. solar-driven double-stage absorption chillers (at around 170°C) and solar thermal power generation (at around 250°C).