太阳能技术在哈密石油基地的应用研究（上）

一太阳能技术在哈密石油基地应用的优势 哈密市地处东经93°31′,北纬42°49′,拥有丰富的光热资源。全年日照时间3309．6～3360．3h,年平均日照时间3358h,日照百分率76％,太阳辐射年总量近6400MJ／（m^2·年）,是全疆年总辐射值最多的地区。哈密市春分日、秋分日和冬至日正午太阳高度角分别为47°05′、47°05′和23°47′。太阳能技术在哈密石油基地应用的地理优势明显。     

CPC不同方位辐射量及最佳倾角计算

针对复合抛物面集热器(CPC)接收辐射量和集热性能受方位角和倾角影响的关系.分别分析了CPC不同放置方式下接收到的太阳辐射及对应最佳倾角,得到方位角与最佳倾角的关系,结合不同地区研究CPC最大太阳辐射量与倾角、方位角之间的关系.结果发现,大多数地区全年最佳倾角位于当地纬度附近,相差5°以内,侧重冬半年使用应采用较大的倾...     

太阳能资源分布

中国地处北半球欧亚大陆的东部,主要处于温带和亚热带,具有比较丰富的太阳能资源。根据全国700多个气象台站长期观测积累的资料表明,中国各地的太阳辐射年总量大致在3．35×10^3MJ／m^2～8．40×10^3MJ／m^2之间,其平均值约为5．86×10^3MJ／m^2。     

基于集热影响系数d的太阳能烟囱集热效率分析

针对呼和浩特地区太阳辐照资源,以太阳能烟囱为研究对象,在呼和浩特地区应用太阳能烟囱进行可行性分析。太阳能烟囱在定集热棚半径定壁温条件下,对不同集热棚倾角进行数值模拟计算,引入集热影响系数d,对集热棚内流场努赛尔数(Nu)进行分析,比较不同倾角下温度场、压力场、速度场、集热效率。研究表明,集热棚集热影响系数d存在最大值,在不同集热棚倾角下,集热棚内温度场、压力场、速度场变化较大,集热效率存在最大值。认为在定集热棚半径条件下,集热棚倾角选取10°作为呼和浩特地区太阳能烟囱集热棚倾角更经济适合。修正了以往国内外太阳能烟囱集热棚倾角的选取方法。     

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。     

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。     

低温多效太阳能海水淡化装置最优集热系统的匹配研究

利用实际天气的太阳辐射值,根据一套低温四效太阳能海水淡化系统稳态实验数据,通过模拟计算,研究分析与该海水淡化系统匹配的太阳能集热系统参数,给出太阳能集热系统集热器面积和储热水箱容量、海水淡化系统启动和暂停温度等参数的最佳取值范围,计算了该装置的年淡水产量,为太阳能海水淡化装置的设计提供一种有效地方法.     

加速开拓国内光伏市场的可行性分析

一中国太阳能资源分布和应用潜力 我国太阳能资源分布的主要特点有：太阳能的高值中心和低值中心都处在北纬22°～35°这一带,青藏高原是高值中心,四川盆地是低值中心;太阳年辐射总量,西部地区高于东部地区,而且除西藏和新疆两个自治区外,基本上是南部低于北部;由于南方多数地区云雾雨多,     

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。     

多曲面聚光免跟踪式太阳能空气取水器的实验研究

设计了一个由多曲面聚光器聚光集热的太阳能空气取水器,介绍了系统的工作原理。对聚光器的特点及固定倾角安装时的全年工作时数进行预测。结果表明,对北纬40°地区,全年只需调整一次安装倾角,当聚光器以30°和60°固定倾角安装时,聚光效率大于80%的月平均日工作时数全年都能大于6 h,可满足系统的聚光要求。采用硅胶颗粒作为吸附材料,对装置在实际天气下的产水性能进行测试,给出吸附和脱附过程的温度随时间的变化曲线。结果表明,装置的产水量明显与最大脱附温度有关,当最大脱附温度为125℃时,总产水量为460 g。脱附过程最大的太阳能利用效率为20.3%。     

用实时监测法优化LED太阳能路灯

利用基于LabVIEW开发的虚拟仪器对蓄电池的充放电数据全天实时监测。旨在实现LED光源、蓄电池容量和太阳电池功率三者的最佳匹配。用同样的监测办法确定太阳电池板的最佳倾角和方位角及反光镜的有效利用。对两盏LED路灯的实测结果表明,在保证照度要求的前提下,太阳能路灯系统的成本大大降低,系统运行稳定可靠。     

获得最大日照度的协调控制方法的研究——多镜面聚光型太阳能光伏系统

针对目前太阳能聚光方式,提出了采用平面镜反射聚光的多镜面阵全跟踪聚光方案.首先描述了多镜面聚光型太阳能光伏系统的基本结构及其跟踪控制原理和方法.通过对多镜面阵聚光系统对太阳全方位跟踪控制分析,推出了太阳电池组件和平面镜阵在跟踪过程中方位角、倾角及空间位置变化的运动方程.通过建立了平面镜阵与太阳电池组件之间的运动关系,实现太阳电池组件跟踪控制以及平面镜阵之间的跟踪协调控制,并对此系统进行了定量分析和数值计算.     

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。     

Optimum tilt angle and orientation for solar collector in Brunei Darussalam

One of the important parameters that affects the performance of a solar collector is its tilt angle with the horizontal. This is due to the fact that the variation of tilt angle changes the amount of solar radiation reaching the collector surface. A mathematical model was used for estimating the total (global) solar radiation on a tilted surface, and to determine the optimum tilt angle and orientation (surface azimuth angle) for the solar collector in Brunei Darussalam on a daily basis, as well as for a specific period. The optimum angle was computed by searching for the values for which the total radiation on the collector surface is a maximum for a particular day or a specific period. The results reveal that changing the tilt angle 12 times in a year (i.e. using the monthly-averaged optimum tilt angle) maintains approximately the total amount of solar radiation near the maximum value that is found by changing the tilt angle daily to its optimum value. This achieves a yearly gain in solar radiation of 5% more than the case of a solar collector fixed on a horizontal surface.     

Effect of manual tilt adjustments on incident irradiance on fixed and tracking solar panels

Hourly typical meteorological year (TMY3) data was utilized with the Perez radiation model to simulate solar radiation on fixed, azimuth tracking and two axis tracking surfaces at 217 geographically diverse temperate latitude sites across the contiguous United States of America. The optimum tilt angle for maximizing annual irradiation on a fixed south-facing panel varied from being equal to the latitude at low-latitude, high clearness sites, to up to 14° less than the latitude at a north-western coastal site with very low clearness index. Across the United States, the optimum tilt angle for an azimuth tracking panel was found to be on average 19° closer to vertical than the optimum tilt angle for a fixed, south-facing panel at the same site. Azimuth tracking increased annual solar irradiation incident on a surface by an average of 29% relative to a fixed south-facing surface at optimum tilt angle. Two axis tracking resulted in an average irradiation increase of 34% relative to the fixed surface. Introduction of manual surface tilt changes during the year produced a greater impact for non-tracking surfaces than it did for azimuth tracking surfaces. Even monthly tilt changes only resulted in an average annual irradiation increase of 5% for fixed panels and 1% for azimuth tracked surfaces, relative to using a single optimized tilt angle in each case. In practice, the decision whether to manually tilt panels requires balancing the added cost in labor and the panel support versus the extra energy generation and the cost value of that energy. A Supplementary spreadsheet file is available that gives individual results for each of the 217 simulated sites.     

Periodic thermal analysis and simple economics of collector and collector-reflector systems

This paper presents a simple transient thermal model for predicting the water temperature at any time during sunshine as well as off-sunshine hours using collector and collector-reflector systems. The transmittance-absorptance product used in theoretical calculation of the water temperature is taken as a function of solar altitude, solar azimuth angle, hour angle and tilt angle of collector and reflector. Fourier coefficients of the recorded data of solar intensity and ambient air temperature have been determined. Water temperature for the systems was determined at different water flow rates. The theoretical analysis is found to be in close agreement with experimental observations. From the theoretical and experimental recordings, it was found that water temperature in the range of 50–56.5°C can be had during sunshine hours using plane reflectors to collectors in a typical winter month. A simple economic analysis of the solar water heating systems has also been discussed. This can be used to calculate an optimum collector area.     

Improvement in artificial neural network-based estimation of grid connected photovoltaic power output

This paper presents a method to improve the accuracy of artificial neural network (ANN)–based estimation of photovoltaic (PV) power output by introducing two more inputs, solar zenith angle and solar azimuth angle, in addition to the most widely used environmental information, plane-of-array irradiance and module temperature. Solar zenith angle and solar azimuth angle define the solar position in the sky; hence, the loss of modeling accuracy due to impacts of solar angle-of-incidence and solar spectrum is reduced or eliminated. The observed data from two sites where local climates are significantly different is used to train and test the proposed network. The good performance of the proposed network is verified by comparing with existing ANN model, algebraic model, and polynomial regression model which use environmental information only of plane-of-array irradiance and module temperature. Our results show that the proposed ANN model greatly improves the accuracy of estimation in the long term under various weather conditions. It is also demonstrated that the improvement in estimating outdoor PV power output by adding solar zenith angle and azimuth angle as inputs is useful for other data-driven methods like support vector machine regression and Gaussian process regression.     

Efficient orientation impacts of box-type solar cooker on the cooker performance

The addition of a plane reflector to a box-type solar cooker increases the obtained cooker temperature and this depends upon the efficient orientation of the cooker. In order to find out the effect of the cooker orientation on its performance, the present analysis is carried out. A method is outlined to find out a reflector performance factor and an orientation factor that depend upon the elevation angle of the sun, the solar surface azimuth angle and the reflector tilt angle. The analysis is applied to a cooker placed at Aden (Yemen). The results indicate that with proper cooker orientation the improvement in the performance of the cooker due to the reflector reached during winter is more than 100% at lower elevation angles and is more than 60% at higher elevation angles. It is concluded that with the help of the analysis the optimum position for any place, for any day of the year and for any specific time of the day can be found.     

Properties of a general azimuth–elevation tracking angle formula for a heliostat with a mirror-pivot offset and other angular errors

The solar field of a central receiver system (CRS) is an array of dual-axis tracking heliostats on the ground beside or around a central tower, with each heliostat tracking the sun to continuously reflect the solar beam onto the fixed tower-top receiver. Azimuth–elevation tracking (also called altitude–azimuth tracking) is the most common and popular tracking methods used for heliostats. A general azimuth–elevation tracking angle formula was developed previously for a heliostat with a mirror-pivot offset and other typical geometric errors. The angular error parameters in this tracking angle formula are the tilt angle, ψ_t, and the tilt azimuth angle, ψ_a, for the azimuth axis from the vertical direction, the dual-axis non-orthogonal angle, τ₁ (bias angle of the elevation axis from the orthogonal to the azimuth axis), and the non-parallel degree, μ, between the mirror surface plane and the elevation axis (canting angle of the mirror surface plane relative to the elevation axis). This tracking angle formula is re-rewritten here as a series of easily solved expressions. A more numerically stable expression for the mirror-center normal is then presented that is more useful than the original mirror–normal expression in the tracking angle formula. This paper discusses some important angular parametric properties of this tracking angle formula. This paper also gives an approach to evaluate the tracking accuracy around each helistat rotational axis from experimental tracking data using this general tracking angle formula. This approach can also be used to determine the heliostat zero angle positioning errors of the two rotational axes. These supplementary notes make the general azimuth–elevation tracking angle formula more useful and effective in solar field tracking designs.