Performance assessment of empirical models for prediction of daily and monthly average global solar radiation: the case study of Ibadan,Nigeria

In this study, the performance assessment of empirical models for modelling global solar radiation in Ibadan is presented. The empirical models are derived from the three basic models: Angstrom–Prescott model, Garcia model and Hargreaves–Sammani model. The data used in the analysis consist of daily average global solar radiation, daily average sunshine hours, daily average maximum temperature and daily average minimum temperature collected over a period of nine years (2000–2008). Regression constants are determined for each of the model for each months of the year. The study reveals that Garcia Quadratic model puts up the best overall performance. The model can predict the daily average global solar irradiation with Mean Absolute Error of 1.86?MJ?m^?2?day^?1, Root Mean Square Error of 2.7?MJ?m^?2?day^?1, Mean Absolute Percentage Error 9.34% and Coefficient of Determination (R²) of 0.68.     

Estimation of horizontal diffuse solar radiation from common meteorological parameters: a case study for Jeddah,Saudi Arabia

The measured data of global and diffuse solar radiation on a horizontal surface, number of sunshine hours, mean daily ambient temperature, maximum and minimum ambient temperatures, relative humidity and amount of cloud cover, for Jeddah (latitude 21° 42′ 37″ N, longitude 39° 11′ 12″ E), Saudi Arabia for the period (1996–2006) are analysed. The data are employed to develop empirical correlations between the monthly average daily diffuse fraction (H _d /H) or diffuse transmittance (H _d /H ₀) and various meteorological parameters such as relative number of sunshine hours (s/s ₀), ambient temperature T, relative humidity R _h and amount of cloud cover c _w. The derived correlations are evaluated by making comparisons between measured and calculated values of monthly average daily diffuse radiation H _d. All the proposed correlations are found to be able to predict the monthly and annual averages daily diffuse radiation with excellent accuracy. It is also inferred that, if the data of the monthly average daily global radiation H and number of bright sunshine hours s are not available, the values of H _d for the hot-humid zone of Saudi Arabia can be estimated with a reasonable accuracy from the correlations between H _d /H ₀ and the mean daily ambient temperature T.     

基于气象参数的混凝土结构日照温度作用分析

气象参数是分析日照环境下混凝土结构温度作用的关键参数之一。影响日照环境下混凝土结构温度场的气象参数主要有太阳辐射、气温和风速。本文分析了这些气象参数变化的一般规律,提出其时程分析模型,并从概率统计的角度分析了这些参数的分布规律,确定了具有一定重现期的气象参数代表值。最后以一个混凝土箱梁为例,利用这些气象参数代表值计算分析了其日照温度场,并根据计算温度场拟合得到竖向温差分布曲线。计算表明,分析日照环境下混凝土结构温度场时应考虑气象参数的随机分布。     

上海地区建筑能耗计算用典型年气象数据的研究

以同济大学某教学楼为研究对象,对比了用EnergyPlus模拟计算得到的全年耗电量和实测耗电量,研究了用于建筑能耗动态计算的5套典型年气象数据的可靠性,得出了CTYW气象数据最接近现实情况的结论。对其中影响较大的参数如室外气温、湿度和太阳辐射量进行分析和比较,指出所用5套典型年气象数据间的差异来自观测值的缺损和统计处理模型的不完善,特别是日射模型存在一定缺陷。     

Comparison of solar radiation data sources for design and performance appraisal of CSP systems in India

The choice of a solar radiation data source is expected to have a significant impact on the predicted performance of a concentrating solar power (CSP) system and consequently on its technical and financial feasibility. In the present study, an attempt has been made to analyse the effect of choice of various solar radiation data sources on the predicted performance of a CSP system at 13 different locations in 5 different climatic zones of India. It was observed that there is significant variation in the amount of annual electricity output obtained for various locations using different solar radiation data sources resulting in variations in levelised cost of electricity. For a 50-MW parabolic trough-based CSP plant located in Jaisalmer, the estimated value of annual electricity output varies from 63 to 124?GWh. For a CSP plant based on the central tower receiver technology, the corresponding range is from 106 to 145?GWh.     

建筑节能分析太阳总辐射模型研究综述

太阳辐射是建筑节能分析的重要基础气象参数,实测数据远远不能满足需求,理论计算是目前获取辐射数据的主要途径。将常用水平面太阳总辐射模型归纳为气象参数、空间插值和基于DEM三类,详述了各自的原理和计算方法。对三类模型在建筑节能分析中的适用性进行了分析,展望了建筑节能分析用太阳辐射模型的发展趋势:气象参数模型与DEM模型的融合。     

An Analytical Study on global radiation and meteorological parameters for India

ABSTRACT

A study is carried out for global radiation (global horizontal and global tilted radiation) and meteorological parameters (humidity and temperature) recorded for a period of one year (2011) at the National Institute of Solar Energy (NISE), Gwal Pahri (28.42°N, 77.15°E), India. Maximum global horizontal radiation of 7.22?kWh/m² is recorded in the month of June while minimum of 0.91?kWh/m² is observed in February. The highest value of the tilted radiation 7.27?kWh/m² is recorded in March and the lowest value 0.90?kWh/m² is noticed in February. The maximum temperature of 36.5°C and humidity of 87.6% are observed in the months of June and July, respectively. Conversely, minimum temperature of 6.1°C and humidity 21.7% are noticed in the months of January and April, respectively. Furthermore, meteorological parameters have been correlated with global radiation on horizontal and tilted surface. The study is vital for the performance analysis of different solar energy applications.     

Mathematical modelling of solar radiation incident on tilted surface for photovoltaic application at Bhopal,M.P., India

In general, solar radiations are the combination of beam plus diffuse and ground-reflected radiation. The availability of recorded data on a tilted surface is very rare due to lack of measuring equipment and techniques involved. In this study, a standard procedure is adopted for estimation of solar radiation on a tilted surface for a location in Central region of India. Solar radiation is estimated for three tilted positions: First, solar collector tilt equal to latitude angle, second, solar collector tilt equal to latitude angle +15° and third, solar collector tilt at latitude ?15°. Total global solar radiation estimated on the inclined surface for various photovoltaic (PV) modules was used to obtain the annual energy yield based on the estimated value. It was found that on an average, 14?kWh/m² of annual energy output can be obtained for monocrystalline solar PV module corresponding to the inclination of 23.26° latitude at Bhopal.     

RTK-GPS在广州新电视塔变形监测中的应用研究

高耸结构在强风、地震和温度变化作用下,容易产生过大的变形,从而危及结构安全。日照变形是超高层结构常见的变形形式之一,是评价结构健康状况的重要参数,在施工和运营阶段均需进行变形监测。本文以在建的广州新电视塔(塔高610m)为研究背景,利用RTK-GPS测量技术和高精度全站仪对其施工进行了全程日照变形监测。分析表明,当一天内的环境温度变化较大时,塔体的水平位移明显增大;随着电视塔高度的增加,塔体变形也相应增大;核心筒和钢结构的位移变形趋势基本一致等。观测结果验证了监测方案的合理性,对超高层建筑施工安全、施工验收和相应规范的改进具有重要的参考指导作用。     

桥梁结构日照温度作用研究综述

为深化对桥梁结构日照温度问题的认识,从桥梁结构日照温度场分布特性、研究方法、温度作用模式与取值方式等方面,综述桥梁结构日照温度作用国内外研究现状,探讨后续的研究重点和发展方向。研究结果表明：桥梁温度场有着典型的周期性时程特征和不均匀空间特征,主要受结构形式、气候和地理环境3类因素的影响,存在明显的桥型间和地域性差异;桥梁日照温度场以数值模拟与实桥测试为主要研究方法,数值模拟中太阳辐射和对流换热的选取尚不统一,基于气象数据开展长期实桥测试十分必要,且应重视测点布置以充分反应桥梁温度非线性分布规律;现有研究多采用多次抛物线、指数曲线和多折线来描述桥梁的温度梯度形式,普遍基于气象参数相关性和统计分析来获得温度作用取值;桥梁日照温度作用的主要发展方向应关注于组合构桥梁温度场的实桥测试与温度作用模式的研究、不同地域和复杂地形条件下桥梁温度作用实测分析,以及大跨复杂结构桥梁日照温度场精细化模拟。     

Accounting for the uncertainties in the estimation of average shear wave velocity using V S– N correlations

Site-specific seismic hazard analysis is crucial for designing earthquake resistance structures, particularly in seismically active regions. Shear wave velocity ( V _S) is a key parameter in such analysis, although the economy and other factors restrict its direct field measurement in many cases. Various V _S–SPT– N correlations are routinely incorporated in seismic hazard analysis to estimate the value of V _S. However, many uncertainties question the reliability of these estimated V _S values. This paper comes up with a statistical approach to take care of such uncertainties involved in V _S calculations. The measured SPT– N values from all the critical boreholes were converted into statistical parameters and passed through various correlations to estimate V _S at different depths. The effect of different soil layers in the boreholes on the Vs estimation was also taken into account. Further, the average shear wave velocity of the top 30 m soil cover ( V _S30) is estimated after accounting for various epistemic and aleatoric uncertainties. The scattering nature of the V _S values estimated using different V _S– N correlations was reduced significantly with the application of the methodology. Study results further clearly demonstrated the potential of the approach to eliminate various uncertainties involved in the estimation of V _S30 using general and soil-specific correlations.