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。     

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。     

固定式光伏方阵最佳倾角的计算与分析

利用太阳辐射量和天空散射各向异性的模型,分析固定式光伏方阵最佳倾角,计算出7种不同倾角下的各月日总辐射量和平均日辐射量。在确定最佳倾角时,以夏半年和冬半年方阵面上接收到的平均日辐射量H_1和H_2为依据,呈现出H_1和H_2随倾角变化的曲线。结果表明,夏半年平均日辐射量H_1随倾角的增大逐渐减小,冬半年的平均日辐射量H_2随着倾角的增大呈现出先增后减的趋势,并在某个倾角处出现最大值。分别以张掖、拉萨、广州为例,计算上述地区不同倾斜面上的平均日辐射量,经过分析比较最终确定张掖、拉萨、广州地区的最佳倾角。     

高空飞艇薄膜太阳电池内辐射量计算研究

修正了任一方向的平面内太阳辐射计算模型,使之适用于编程计算各种倾角和方位角平面上的太阳辐射。在曲面上进行网格划分,生成若干个小平面,推导出平面法向量与倾角和方位角之间的关系式,逐个计算每个小平面上太阳辐射量,叠加后近似代替整个曲面上的太阳辐射量。运用此方法计算了高空飞艇的薄膜太阳电池上辐射量,并与此薄膜太阳电池在水平投影面内辐射量计算结果进行比较。结果表明,用水平投影面内辐射量代替薄膜太阳电池内辐射量有很大的偏差。因此,在高空飞艇能源系统性能详细分析阶段需要使用曲面内太阳辐射量计算模型,为随后的光电转换与能源系统计算提供准确的太阳辐射数据。     

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。     

中国南极中山站太阳能资源及光伏阵列最佳倾角研究北大核心CSCD

针对极区太阳能资源开发利用问题,文章研究了南极中山站地区太阳辐射的逐月、逐日分布情况,分析了太阳能资源状况;建立了适合极昼环境条件的斜面太阳辐射计算模型和中山站地区光伏阵列最佳倾角分析模型;确定了光伏阵列的最佳倾角。研究结果表明:夏季中山站地区太阳能资源较为丰富,在分析光伏阵列倾角时应重点考虑3月份和9月份的太阳辐射量;最佳倾角为64°,光伏阵列的前后距离应不低于8.7 m。     

多根并排时全玻璃真空管接收太阳辐射量计算模型与实验验证

为了估算太阳能集热装置在所使用地区接收的太阳辐射量和集热量,在综合已有的多根并排时单根全玻璃真空管接收太阳辐射量计算模型的基础上,选用一种计算模型,通过设计实验和实验实测,验证多根并排时全玻璃真空管接收太阳辐射量计算模型的正确性。实验结果表明:实验实测与通过真空管接收太阳辐射量模型计算数值结果吻合的很好,计算模型可以用来估算太阳能集热装置在所使用地区接收的太阳辐射量。     

双面光伏组件安装特点的模拟研究

针对影响双面光伏组件背面接收的太阳辐射量的因素进行了研究,应用PVsyst软件,以采用前后排光伏组件固定间距、固定式光伏支架安装的光伏发电系统为例,以草地作为代表地表特征,模拟分析了双面光伏组件在不同安装高度和不同安装倾角条件下其背面接收的太阳辐射量的变化情况。研究结果表明,当双面光伏组件的安装倾角一定时,其安装高度与其背面接收的有效太阳辐射量成正比;而当双面光伏组件的安装高度一定时,其安装倾角越小,双面光伏组件背面接收的有效太阳辐射量中地面反射辐射量的占比就越大。     

西部地区居住建筑太阳能采暖利用辐射分区

为区分西部地区居住建筑太阳能采暖的辐射资源差异,针对不同辐射资源强度的太阳能采暖设计开展太阳辐射分区研究。提出以光热采暖度日数辐射比、光电采暖度日数辐射比作为太阳辐射分区指标。为计算南向立面辐射量、光伏板在最佳倾角下接收到的辐射量,通过对比3种太阳辐射模型选择适宜西部地区使用的模型。选择西部地区12个省(自治区、直辖市)的46座城市作为分区数据源,采用聚类分析得到4个居住建筑太阳能采暖辐射区域,并对各区域的太阳能建筑采暖利用潜力进行分析。     

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。     

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.     

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.     

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.     

Optical and thermal properties of compound parabolic concentrators

Compound Parabolic Concentrators (CPC) are relevant for solar energy collection because they achieve the highest possible concentration for any acceptance angle (tracking requirement). The convective and radiative heat transfer through a CPC are calculated, and formulas for evaluating the performance of solar collectors based on the CPC principle are presented. A simple analytic technique for calculating the average number of reflections for radiation passing through a CPC is developed; this is useful for computing optical losses. In most practical applications, a CPC will be truncated because a large portion of the reflector area can be eliminated without seriously reducing the concentration. The effects of this truncation are described explicitly. The paper includes many numerical examples, displayed in tables and graphs, which should be helpful in designing CPC solar collectors.     

Solar photoreactors comparison based on oxalic acid photocatalytic degradation

Solar heterogeneous photocatalytic degradation of oxalic acid in water is carried out in four different solar photoreactors: a parabolic trough concentrator (PC), a tubular collector (TC), a compound parabolic collector (CPC), and a V-trough collector (VC). The reactors operate under equal conditions of solar irradiance, collection surface and fluid flow rate to ensure a better comparison between the systems. The effects of TiO₂ catalyst concentration and radiation incidence angle on the degradation are studied. Oxalic acid degrades without appreciable generation of intermediates, and a simple kinetic model is proposed to describe the process. There are differences in the degradation rates depending on the collector geometry. The CPC shows the best overall performance in terms of accumulated energy, followed closely by the VC. Incidence angle affects the total amount of energy collected but does not reduce very much the efficiency of the reactors to use this energy in the photocatalytic process.