Values Of Global Solar Radiation Research Articles

Fourier transforms Investigation of Global Solar Radiation at True Noon: in the Desert climatology

The aim of this work has been to obtain a typical annual time a function by the application of a calculation procedure based on a Fourier analysis to global solar radiation data of nine years at Helwan Egypt from June 1991 to August 1999. This function allows us to estimate the most probable values of the horizontal daily global solar radiation for every day of the year at Helwan Egypt. It is confirmed that the harmonic model presents an important percentage with 98% confidence bounds. The applied method permits its application to the new measurements of solar radiation that are being carried out, This will be necessary because of the number of years used in this study.

Global and diffuse solar irradiances in urban and rural areas in southeast Brazil

The seasonal evolution of daily and hourly values of global and diffuse solar radiation at the surface are compared for the cities of Sao Paulo and Botucatu, both located in Southeast Brazil and representative of urban and rural areas, respectively. The comparisons are based on measurements of global and diffuse solar irradiance carried out at the surface during a six year simultaneous period in these two cities. Despite the similar latitude and altitude, the seasonal evolution of daily values indicate that Sao Paulo receives, during clear sky days, 7.8% less global irradiance in August and 5.1% less in June than Botucatu. On the other hand, Sao Paulo receives, during clear sky days, 3.6% more diffuse irradiance in August and 15.6% more in June than Botucatu. The seasonal variation of the diurnal cycle confirms these differences and indicates that they are more pronounced during the afternoon. The regional differences are related to the distance from the Atlantic Ocean, systematic penetration of the sea breeze and daytime evolution of the particulate matter in Sao Paulo. An important mechanism controlling the spatial distribution of solar radiation, on a regional scale, is the sea breeze penetration in Sao Paulo, bringing moisture and maritime aerosol that in turn further increases the solar radiation scattering due to pollution and further reduces the intensity of the direct component of solar radiation at the surface. Surprisingly, under clear sky conditions the atmospheric attenuation of solar radiation in Botucatu during winter – the biomass burning period due to the sugar cane harvest – is equivalent to that at Sao Paulo City, indicating that the contamination during sugar cane harvest in Southeast Brazil has a large impact in the solar radiation field at the surface.

Methods and strategy for modeling daily global solar radiation with measured meteorological data – A case study in Nanchang station, China

Abstract Solar radiation is a primary driver for many physical, chemical and biological processes on the earth’s surface, and complete and accurate solar radiation data at a specific region are quite indispensable to the solar energy related researches. This study, with Nanchang station, China, as a case study, aimed to calibrate existing models and develop new models for estimating missing global solar radiation data using commonly measured meteorological data and to propose a strategy for selecting the optimal models under different situations of available meteorological data. Using daily global radiation, sunshine hours, temperature, total precipitation and dew point data covering the years from 1994 to 2005, we calibrated or developed and evaluated seven existing models and two new models. Validation criteria included intercept, slope, coefficient of determination, mean bias error and root mean square error. The best result ( R 2 = 0.93) was derived from Chen model 2, which uses sunshine hours and temperature as predictors. The Bahel model, which only uses sunshine hours, was almost as good, explaining 92% of the solar radiation variance. Temperature based models (Bristow and Campbell, Allen, Hargreaves and Chen 1 models) provided less accurate results, of which the best one ( R 2 = 0.69) is the Bristow and Campbell model. The temperature based models were improved by adding other variables (daily mean total precipitation and mean dew point). Two such models could explain 77% (Wu model 1) and 80% (Wu model 2) of the solar radiation variance. We, thus, propose a strategy for selecting an optimal method for calculating missing daily values of global solar radiation: (1) when sunshine hour and temperature data are available, use Chen model 2; (2) when only sunshine hour data are available, use Bahel model; (3) when temperature, total precipitation and dew point data are available but not sunshine hours, use Wu model 2; (4) when only temperature and total precipitation are available, use Wu model 1; and (5) when only temperature data are available, use Bristow and Campbell model.

Correlation of global solar radiation values estimated and measured on an inclined surface for clear days in Bogotá

An empirical expression developed to estimate global solar radiation in clear days, on inclined surfaces located at any geographical position, is presented. This expression allows determining the global solar radiation in a specific day of the year, considering the attenuation of radiation in the atmosphere, the air mass factor, astronomic geometric and geographic parameters, and in particular, the altitude. Data calculated with this expression were correlated with those obtained experimentally in Bogotá, Colombia (74°4′W, 4°35′N and 2580 m altitude). The correlation of the calculated with the experimental data yielded a coefficient of 0.9980, which indicates the reliability of the former and that the developed expression facilitates the construction of data bases with information on solar radiation potential in ample regions characterized by their locations at different altitudes above sea level. These data bases will supply preliminary information on sites adequate for the installation of photovoltaic systems.

Simulação estocástica de atributos do clima e da produtividade potencial de milho utilizando-se distribuição triangular

O objetivo deste trabalho foi simular a produtividade potencial da cultura de milho, pelo método de Monte Carlo, utilizando um modelo agrometeorológico estocástico. O experimento foi conduzido em Piracicaba, SP, a 22º42'30''S, 47º38'30''W, e altitude de 546 m, o clima da região é do tipo Cwa (tropical úmido). Foram utilizados os valores médios diários de temperatura (de 1917 a 2002) e radiação solar global (de 1978 a 2002). Para comparar os dados reais com os simulados, foram utilizados índices de desempenho estatístico. Observou-se que os modelos probabilísticos, desenvolvidos para a simulação de dados médios diários de temperatura e de radiação solar global, geraram valores semelhantes aos observados por meio da distribuição triangular, a qual pode ser utilizada em modelo estocástico, para previsão da produtividade potencial de milho, nas diferentes épocas de semeadura.

Radiação solar em ambiente protegido cultivado com tomateiro nas estações verão-outono do Rio Grande do Sul

O crescimento e desenvolvimento de uma planta dependem da intensidade, qualidade e duração da radiação solar. Por esse fator ser de importância vital às plantas, o presente trabalho objetivou fazer uma avaliação sobre sua variação, bem como sobre a sua disponibilidade no interior do ambiente protegido durante o ciclo do tomateiro nas estações verão-outono em Pelotas, Rio Grande do Sul. O experimento foi conduzido de janeiro a junho de 2003 no Campus da Universidade Federal de Pelotas (latitude 31°52'S; longitude 52°21'W e altitude de 13m), em estufa plástica disposta no sentido Leste-Oeste, com área de 180m². A cultivar utilizada foi "Flora-dade", semeada em 24/01/03, transplantada no dia 28/02/03, sendo a última colheita em 12/06/03. Avaliou-se a radiação solar global externa (Rgext) e interna (Rgint), transmitância, radiação fotossinteticamente ativa (RFA) e o albedo da cultura a partir de sensores eletrônicos conectados a um "datalloger". Durante o ciclo da cultura, o total de Rgext foi 1161,21MJ m-2, enquanto a Rgint foi 881,85MJ m-2. A Rgint e a RFA apresentaram valores médios diários de 8,5MJ m-2 dia-1 e 3,4MJ m-2 dia-1, respectivamente. A transmitância média da cobertura plástica à radiação solar global foi de 76%. O albedo médio diário da cultura foi 0,23, com albedo de 0,17 nos estádios iniciais, 0,26 no período de máximo crescimento e 0,23 no final do ciclo.

A study of solar radiation climate at Cairo urban area, Egypt and its environs

The measured values of the hourly global solar radiation, G, and its diffuse component, D, on a horizontal surface for a 12-year period (1992–2003) have been collected and used to examine the solar radiation characteristics in the urban area of Cairo, Egypt. The corresponding values of the diffuse fraction of global radiation, K, have been calculated. Diurnal variations of the results have been investigated. Also, the daily total values and their monthly and seasonal means, as well as their frequency distributions, have been calculated and investigated. The results reveal that Cairo has annual mean values of G, D, and K equal to 18.57, 6.10 MJ m−2 and 0.35, respectively. The seasonal and climatic effects on the fluctuation of the results are discussed. These effects were particularly large during the winter and spring months owing to the high fluctuation of the atmospheric conditions with respect to the amount of water content, clouds, and concentration of aerosol and dust particles. It was found that the reduction of G due to the effect of clouds is small (2.8%), which in turn reflects the low degree of cloudiness over Cairo due to the impacts of urbanization. A comparative study has also been done to investigate the effect of urbanization processes on the global radiation values received at urban Cairo. It was found that G values received during the non-urbanized period (1969–1973) highly exceeded the radiation values received during the recent urbanized period (1999–2003) for all months of the year, and the annual mean of the relative reduction was found to be 17.63%. Copyright © 2006 Royal Meteorological Society

New methodologies to estimate the hourly global solar radiation; Comparisons with existing models

This paper describes two new friendly and reliable approaches to estimate hourly global solar radiation on a horizontal surface even with a pocket calculator. Such fast and reliable predictions for the hourly solar radiation are necessary for the real-time management of both the solar energy sources, like a PV generator output in the one hand and the power loads, on the other. The predicted global solar hourly radiation values are compared with estimates from two existing packages and the recorded solar radiation for the two biggest cities of Greece. The two methodologies presented in this paper can be applied to any other site.

Determinação dos coeficientes da equação de Angstron para a região de Palotina, Estado do Paraná

This work aimed at adjusting the Angstron’s equation coefficients, on monthly and annual basis, to the region of Palotina (24º17'S, 53º50'30'' W and 333m of altitude), Paraná, Brazil. The purpose was to determine the global solar radiation on a daily basis. Climatic data of global solar radiation and total daily sunshine, from 1982 to 2002 were used to fit the equation. Lower values (7,82MJ m-2) of global solar radiation were verified at months with north solar declination and higher values (22,07MJ m-2) at months with south solar declination, with annual mean value of 14,27MJ m-2. The radiation that reached the atmosphere top presented similar annual trend, with a lowest value of 21,58MJ m-2 on June 24th and highest value of 44,51MJ m-2 on January 1st. Annual mean value was of 33,45MJ m-2. Higher value of insolation ratio were obtained in the winter and lower values occurred in the summer, ranging from 0,13 to 0,97, with 0,58 as a mean value. The brightness index ranged from 0,32 to 0,55, and 0,55 constitute the maximum brightness index for the region of Palotina, Paraná

Estimation of global illuminance on inclined surfaces for clear skies

In the present work, we have studied the luminous efficacy of global solar radiation incident on vertical surfaces for clear skies (cloudless and rather clean skies) and mean hourly values of global solar radiation (i.e. averaged over each hour). Luminous efficacy models similar to those previously obtained for a horizontal surface have been developed using solar elevation as the independent variable. Thus, the hypothesis that the slope of the surface does not influence the general formulation of the model has been assumed. However, the final formulation of the models clearly depends on the insolation conditions of the inclined surface and, more specifically, on whether direct radiation is or is not incident on it. As a consequence, two different types of models have been proposed to take both insolation conditions into account. On the other hand, global luminous efficacy models have also been obtained as the best fits of the experimental data. Global illuminance has been estimated for the vertical surfaces considered, facing north, east, south and west, with the models obtained as the best fits of the experimental data and the other two types of models mentioned in the preceding paragraph. Comparison of the performance of models for global illuminance estimation has validated the initial hypothesis that the slope of the surface does not influence the general formulation of the model. The performances of the known Perez model and the proposed models are also compared.

RadEst3.00: software to estimate daily radiation data from commonly available meteorological variables

RadEst3.00 estimates and evaluates daily global solar radiation values at given latitudes. Radiation is calculated as the product of the atmospheric transmissivity of radiation times the radiation outside the earth atmosphere. Four models estimate the atmospheric transmissivity, based on the daily temperature range. Model parameters can be fitted over one or more years of data by iterative procedures. Graphical and statistical evaluations of the estimates are presented. Reports of the analysis can be exported in a variety of formats. Penman–Monteith or Priestley–Taylor reference evapotranspiration is estimated, using both measured and estimated radiation. Utilities are provided to process numerous files, or correct possible constant biases in the data. Samples of data for tropical and temperate sites are supplied with the software.

Correlation between global ultraviolet (290–385nm) and global irradiation in Valencia and Cordoba (Spain)

This paper analyses hourly data of global ultraviolet (290–385nm) and global irradiation over a horizontal surface. The data was taken in Valencia (39.5°N, 0.341W) and Córdoba (37.51°N, 4°48W), (Spain) during the years 1996–1999. In order to estimate the ultraviolet solar radiation using global solar radiation values over a horizontal surface, the method of Foyo-Moreno et al. (Foyo-Moreno, I., J. Vida and L. Alados-Arboleda. J. Appl. Meteor. 1998, 38, 1020–1026) has been used. The results obtained with this method are satisfactory with a determination ratio r 2=0.98, RMSE=9.3%, MBE=0.5% for Valencia and r 2=0.99, RMSE=6.2%, MBE=0.3% for Córdoba.

Diurnal evolution of solar radiation at the surface in the city of São Paulo: seasonal variation and modeling

Seasonal variations in the diurnal evolution of the global, diffuse and direct solar radiation at the surface, the clearness index, diffuse fraction and direct fraction are described in detail for the City of Sao Paulo, Brazil. The description is based on measurements of global and diffuse solar radiation carried out over 5.25 years. The diffuse component was measured with a shadow-band device. The annual evolution of the amplitude of the diurnal cycle of all radiometric parameters indicates a seasonal pattern with two distinct periods: autumn-winter and spring-summer. About 10% of the observed period was characterized by clear sky days. This seasonal variation is determined by a larger incidence of clear sky days in the autumn-winter period. Reductions of up to 10% in hourly and daily values of global radiation were observed in conjunction with an increase in particulate matter concentration on clear sky days. The pollution effect may be responsible for the discrepancy, of 16%, found between local and more regional estimates of global solar radiation in Sao Paulo. The diurnal evolution of hourly values of monthly-averaged global and diffuse solar radiation were successfully estimated by the empirical expressions derived here. Daily values of monthly-averaged global solar radiation were satisfactorily estimated using the Angstrom expression.

Global solar radiation distribution and available solar energy potential in Tanzania

Solar energy is found to be the best source of energy for the rural poor. It is cheap and environmentally friendly. However its potential application in Tanzania is not well researched and documented. This paper describes a prospect on solar radiation distribution and available solar energy potential. Modelling of solar energy systems requires knowledge of incoming solar radiation. An empirical model based on meteorological data collected between 1965 and 1990 in Tanzania has been developed to estimate global solar radiation on horizontal surfaces. Meteorological parameters such as sunshine hours, relative humidity, air temperature and atmospheric conditions were used in the model. The values of global solar radiation predicted by the model are in close agreement with those measured for all locations and zones where the model has been tested. The deviation was found to lie between -5% and 5%. Measured and predicted mean monthly and mean annual global solar radiation values as observed from the developed radiation maps and graphs indicate that Tanzania has high solar power potential. The lowest annual average radiation value in the country is found to be 15 MJ m-2 day-1, while the maximum value is 24 MJ m-2 day-1. The lowest radiation value in the country is obtained in July (winter), which should be sufficient to satisfy the needs of rural family demands.

EVALUATION OF SYMMETRIC AND ASYMMETRIC CORRELATIONS TO PREDICT MONTHLY AVERAGE HOURLY GLOBAL SOLAR RADIATION

The present article deals with evaluating the relative performance of the correlations to predict symmetric and asymmetric monthly average hourly values of global solar radiation from corresponding daily values. It has been found that the symmetric correlation due to CoUares-Pereira and Rabl [7] and asymmetric form due to Satyamurty and Lahiri [9] perform satisfactorily over a wide range of locations tested.

Modelling the diffuse fraction of global solar radiation on a horizontal surface

For various applications it is necessary to know not only global solar radiation values, but also the diffuse and beam components. Because often only global values are available, there have been several models developed to establish correlations between the diffuse fraction and various predictors. These typically include the clearness index, but also may include the solar angle, temperature and humidity. The clearness index is the proportion of extraterrestrial radiation reaching a location, where the extraterrestrial value used in the calculation varies with latitude and time of year. These correlations have been developed using data principally from latitudes greater than 40°, often using only data from a few locations and with few exceptions have not used solar altitude as a predictor. Generally the data consist of hourly integrated values. A model has been developed using hourly data from a weather station set up at Deakin University, Geelong. Another model has also been developed for 15 minute data values in order to ascertain if the smoothing generated by using hourly data makes a significant difference to overall results. The construction of such models has been investigated, enabling an extension to the research, inclusive of other stations, to be performed systematically. A final investigation was carried out, using data from other Australian locations, to explain some of the considerable scatter by adding apparent solar time as a predictor, which proved to be significantly better than solar altitude. Copyright © 2001 John Wiley & Sons, Ltd.

Calculation of solar radiation using a methodology with worldwide potential

Surface meteorological observations from the DATSAV2 database provide the capability to use the METSTAT (meteorological/statistical) model to calculate hourly values of direct normal, diffuse horizontal, and global horizontal solar radiation for locations throughout the world. Opaque cloud cover, a key input parameter to the METSTAT model, is derived from the DATSAV2 layered cloud cover information. Resulting multiyear data sets include solar radiation and other meteorological data such as dry bulb temperature, dew point temperature, wind speed, and atmospheric pressure. Data filling procedures ensure that the multiyear data sets are serially complete. A minor revision to METSTAT improved solar radiation estimates for conditions of high cloud amounts and low ceiling heights. The methodology was applied to regions of Southern Africa and Saudi Arabia.

Empirical model development and comparison with existing correlations

This study utilized monthly mean daily values of global solar-radiation and sunshine duration at 41 locations in Saudi Arabia and developed an empirical correlation for the estimation of global solar radiation at locations where it is not measured. The paper also presents the comparison between the present correlation and other models developed under different geographical and varied meteorological conditions. The comparisons are made using standard statistical tests, namely mean bias error (MBE), root mean square error (RMSE), mean percentage error (MPE), and mean absolute bias error (MABE) tests. The errors are calculated using monthly mean daily measured and estimated values of global solar radiation at all 41 locations. The study found that the present correlation produced the best estimates of global solar radiation.

Modeling clear weather day solar irradiance in Baghdad, Iraq

A clear day model for the beam transmittance of the atmosphere is presented. The clear sky is modeled because this condition generally produces the maximum energy available. This maximum established the criteria from which engineers can design solar cells, space and process water heating equipment and estimate the thermal loading on buildings, etc. The model is based on five-years of daily global radiation data assembled from measurements at the Solar Energy Research Center at Baghdad, Iraq. The model offers the prediction of clear day hourly values of direct normal and global solar radiation for any day of the year at a given location with no required meteorological inputs. Modeled data are compared with observations, demonstrating good agreement for several days from different seasons. This model provides a baseline for solar energy researchers and is utilized for quality control of solar radiation parameters.

Global, direct and diffuse solar irradiance in Riyadh, Saudi Arabia

The regression coefficient of the well-known Angstrom correlation are determined for Riyadh city (the capital of Saudi Arabia) longitude 46° 14′E 24°55′N The relationship of the daily and monthly variation of the fraction of the diffuse solar irradiation to extrateresstrial H d H o = K d and the clearness index H H o = K T are obtained. The variation of the values of the average daily global solar radiation against the month of the year is reported. The value of K n defined as the ratio of direct normal Insolation, H bn measured in Riyadh to direct normal solar extraterrestrial radiation with the K T and K d were obtained. The daily diffused ratio H d H and the daily clearness index are shown as a function of the month of the year.