Diffuse Radiation Data Research Articles

TRNSYS Modeling of flat plate and vacuum tube solar collector systems for residential use under equatorial middle altitude climate condition

In this work, residential solar systems were simulated to predict feeding domestic hot water, using TRNSYS (TraNsient SYstem Simulation software), under the operating conditions in Cuenca, Ecuador. The type of research is quantitative and with a correlational approach. Using data from an experimental test, a technical sheet was prepared that sought to identify the main variables to be applied in the model. The diffuse and direct radiation data were obtained by applying the isotropic diffuse model. When simulating in the software, the results show that the system presents an efficiency of 56.54% when heating water in a range of 30° to 45 °C. For the validation of the model, the chi-squared statistical test was applied, with which it was determined that the simulated data follow the same distribution as the real data.

Evaluation of models for prediction of diffuse solar radiation and comparison with satellite values

The diffuse radiation data are one of the important parameters required in solar energy projects. However, this parameter has not been measured in everywhere of Turkey. In the present study, models in the open literature for the determination of horizontal diffuse radiation with clearness index are investigated and, new models are developed for thirteen provinces over the Eastern Anatolia Region (EAR) of Turkey where the diffuse radiation values are not existing. In the monthly average, these models have a relation between the diffuse coefficient (Hd/Ho) and the diffuse fraction (Hd/H) with the daily clearness index. The most appropriate models based on NASA – Surface meteorology and Solar Energy (NASA-SSE) values are determined. For this, the diffuse radiation data taken from the NASA-SSE and calculated from the models are compared for the locations mentioned in the study. The validation of the correlations obtained to predict the diffuse radiation over the EAR for which experimental data are not available is firstly tested by using the NASA-SSE satellite data. The performances of the models are indicated with the statistical test methods as mean absolute bias error (MABE), root mean square error (RMSE), the mean bias error (MBE), and mean relative error (MRE). The results indicate that some models are reasonably well to forecast the diffuse radiation. In addition, the diffuse radiation predictions of the new correlations obtained in the study are compared with satellite data. When the diffuse radiation values taken from the NASA-SSE and calculated from the models are compared, it is seen that the Model 4 for Ağrı, Bingöl, Bitlis, Elazığ, Erzincan, Hakkari, Iğdır, Kars, and Muş, Model 14 for Erzurum, Model 20 for Malatya and Tunceli, and Model 11 for Van indicate the best performance. According to the RMSE values of twenty models in the literature and the NASA-SSE, the best result among all provinces is obtained from the Model 11 with 0.2385 MJ m−2 day−1 for Van.

Quality control of diffuse solar radiation component with satellite-based estimation methods

In order to analyze solar systems, it is very important to determine the accurate solar radiation components belonging to any region. These components are defined as the beam and diffuse. The diffuse radiation component may not always be determined accurately since it is mostly affected by many geographical factors and climatic features in addition to the location parameters. Therefore, this work aims to compare and evaluate the validity of global and diffuse estimation methods for nine locations in Turkey. The satellite-based estimation methods (HELIOSAT, Meteonom, and PVGIS) mentioned in the literature were used to estimate global and diffuse radiation. These selected methods were statistically tested with accurate ground measured data. For HELIOSAT, the global radiation is varying −0.02 and 0.03, and 0.010 and 0.035, respectively, Relative MBE and Relative RMSE. Similarly, the diffuse radiation values are −0.020 and 0.025 for Relative MBE, and 0.015 and 0.030 for Relative RMSE. The goodness of the fit values for the HELIOSAT method shows a very good agreement with at least 97% confidence level of global and 91% of diffuse radiation values. Thus, HELIOSAT method shows a trustworthy alternative to the ground measurement data when reliable global and diffuse radiation data are not available.

The analysis on applicability of hourly horizontal diffuse radiation estimation model of Shanghai Zone

For shading design and energy consumption simulation, hourly diffuse radiation data is necessary. In order to estimate the total solar radiation on surfaces with different spatial orientations, the knowledge of all components on the horizontal plane is required. Available measured data is, however, typically less. The 2004-2013 year’s measured data of Shanghai were localized revising of three categories models, comparing the measured data and estimation data by the correlation coefficient and error index. The results show that the three types of models have high accuracy at higher solar altitude and the accuracy of multi parameter logistic function is best. For stations with only daily solar radiation data, the third types of models can be used to calculate hourly diffuse solar radiation.

Impacts of diffuse radiation fraction on light use efficiency and gross primary production of winter wheat in the North China Plain

The increase of diffuse radiation fraction (kd) has been reported to significantly impact light use efficiency (LUE) and carbon uptake in terrestrial ecosystems. The impact of kd on LUE should be considered in crop models to accurately evaluate the effect of radiation changes on crop production. However, the magnitude of the kd effect is difficult to quantify because of the complicated interacting relationships among all of the meteorological parameters, as well as the changing effects for various ecosystem types and research sites. Eight site-years of flux data and two years of diffuse radiation data from two field ecosystems in the North China Plain were used to (1) compare the performance of five kd models, (2) explore the impacts of environmental factors on LUE and gross primary production (GPP) of winter wheat (Triticum aestivum L.), and (3) quantify the relationships between kd and both LUE and GPP of winter wheat. Comparison results showed that the kd model developed by Boland et al. performed the best of the five models evaluated. This model was chosen to calculate kd in this research. Path analysis show that kd was the main factor affecting LUE of winter wheat, explaining up to 55% of the variability in LUE. The relationship between kd and LUE was significantly linear (slope of about 0.326 g C mol−1). GPP initially increased and then decreased with increasing kd. A moderate radiation condition (kd = 0.53) was favorable for increasing GPP. The effect of kd on LUE should be added in the LUE module of APSIM-Nwheat to improve simulation accuracy. The results of this study highlight the importance of kd in correctly modeling LUE for winter wheat with a crop model and provide quantitative relationships between these two parameters. These relationships will be helpful in improving crop model simulation accuracy under changed climate conditions.

A Comprehensive Study of Ground Measurement and Satellite‐Derived Data of Global and Diffuse Radiation

The comparative study of measured and calculated data of India Meteorological Department (IMD) and National Aeronautics and Space Administration (NASA) for 23 locations of India for 15 years (1986–2000) is presented. Global and diffuse radiation data are used in the study and to make the study comprehensive, three statistical predictors, viz., mean percentage error (MPE), root mean square error (RMSE), and mean bias error (MBE) are used for the comparison. The results show that for global radiation, MPE is maximum of −36.65% for Shillong and minimum of 0.93% for New Delhi. MBE is found to be maximum of 1.63 kWh/m2 for Shillong while it is minimum (0.04 kWh/m2) for Nagpur. RMSE is maximum (2.14 kWh/m2) for Shillong and minimum for Ranchi (0.19 kWh/m2). For diffuse radiation, MPE is highest for Bhavnagar (100%) and lowest for Hyderabad (81.33%). MBE is maximum of −7.73 kWh/m2 and minimum of −4.62 kWh/m2 for Srinagar. RMSE is maximum for Bhavnagar (8.26 kWh/m2) and minimum for Srinagar (4.73 kWh/m2). © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13060, 2019

Study of monthly mean daily diffuse and direct beam radiation estimation with MODIS atmospheric product

Abstract Reliable diffuse and direct beam radiation data are critical for many scientific researches and engineering applications. While knowledge of radiation components is not sufficient due to the cost and maintenance and calibration of the measuring equipments. Exploring novel methods for estimating radiation components have therefore considerable significance. In this paper, twenty satellite-based models for estimating radiation components were developed using MOD08-M3 atmospheric product, and evaluated using measured radiation data at 15 sites across China. The best site-specific models for diffuse and direct beam radiation were proposed, with the average RMSE of 0.642 MJ m−2 (9.299%), and 0.736 MJ m−2(10.69%), respectively. General models for radiation components were also recommended for widespread applications. The study provides a simple but efficient alternative to obtaining solar radiation components data at regional scale using MODIS satellite data. For other places of interest, the coefficients of the proposed models can be calibrated following the guidelines provided in this study with relative ease, making our models appropriate for widespread applications.

A semi-empirical model for estimating diffuse solar near infrared radiation in Thailand using ground- and satellite-based data for mapping applications

This work has developed a semi-empirical model for estimating monthly average hourly diffuse solar near infrared (NIR) radiation in Thailand. Diffuse NIR radiation data were recorded at four stations in Thailand namely, Chiang Mai (18.78oN, 98.98oE), Ubon Ratchathani (15.25oN, 104.87oE), Nakhon Pathom (13.82oN, 100.04oE) and Songkhla (7.20oN, 100.60oE). Our analysis has shown that diffuse NIR radiation is related to cloud, precipitable water and cosine of solar zenith angle in terms of an exponential function. Therefore, the model was formulated with these parameters and validated with independent diffuse NIR measurements. The result showed that diffuse NIR radiation from the model and that from the measurements were in reasonable agreement with root mean square difference and mean bias difference of 16.7% and 1.5%, respectively. The semi-empirical model was used to generate diffuse maps of NIR for the country which displayed both diurnal and seasonal variations.

A simplified model exploration research of new anisotropic diffuse radiation model

More accurate new anisotropic diffuse radiation model (NADR model) has been proposed, but the parameters and calculation process of NADR model used in the process are complex. So it is difficult to widely used in the simulation software and engineering calculation. Based on analysis of the diffuse radiation model and measured diffuse radiation data, this paper put forward three hypotheses: (1) diffuse radiation from sky horizontal region is concentrated in a very thin layer which is close to the line source; (2) diffuse radiation from circumsolar region is concentrated in the point of the sun; (3) diffuse radiation from orthogonal region is concentrated in the point located at 90 degree angles with the Sun. Based on these hypotheses, NADR model is simplified to a new simplified anisotropic diffuse radiation model (NSADR model). Then the accuracy of NADR model and its simplified model (NSADR model) are compared with existing models based on the measured values, and the result shows that Perez model and its simplified model are relatively accurate among existing models. However, the accuracy of these two models is lower than the NADR model and NSADR model due to neglect the influence of the orthogonal diffuse radiation. The accuracy of the NSADR model is higher than that of the existing models, meanwhile, another advantage is that the NSADR model simplifies the process of solution parameters and calculation. Therefore it is more suitable for calculating the diffuse radiation of the inclined plane.

A new anisotropic diffuse radiation model

Through the analysis of distribution of diffuse radiation in the sky, the sky diffuse radiation is divided into four zones. Based on the concept of radiation intensity and solid angle, the corresponding integral equation is established in each zone to build a new theoretical model of anisotropic diffuse radiation. Radiation enhancement coefficients in the new theoretical model are solved from the instantaneous diffuse radiation data received by 30°, 45°, 60° inclined planes, then new model and existing models are compared with the diffuse radiation data received by 90° inclined planes. The results demonstrate that for existing models, Perez model is the most accurate, followed by Liu and Jordan model. Among the second generation models, Klucher model, Hay model, Skartveit and Olseth model are relatively accurate. While compared with existing models, NADR model is more consistent with the measured values. Further comparative analysis shows that for east and north orientations, Perez model and NADR model are more accurate; for south and west orientations, Liu and Jordan model and NADR model are more accurate. Klucher model is well agreed with the measured data in different inclinations. Hay model and Skartveit and Olseth model are relatively accurate on 30° tilt surface, and Temps and Coulson model is also relatively accurate on 45° tilt surface. NADR model is in good agreement with the measured data on 60° and 90° tilt surface. On the whole, NADR model is more accurate than the existing models.

Modelling the effects of changes in solar radiation on gross primary production in subtropical evergreen needle-leaf plantations

Aims Solar radiation is the energy source of terrestrial ecosystem carbon and water cycles. Observation shows that solar radiation has experienced noticeable variations in recent decades and significantly impacted on plant photosynthesis. Our objective was to investigate the impacts of changes in solar radiation on gross primary production (GPP) at the Qianyanzhou eddy tower site in subtropical forest in China. Methods We first established the relationship between diffuse radiation fraction and clearness index based on the observed solar radiation and diffuse radiation data. Then, a two-leaf ecological process model, the Boreal Ecosystem Productivity Simulator (BEPS), was used to simulate the impacts of different changes in solar radiation on shaded GPP, sunlit GPP, and canopy GPP in the typical subtropical evergreen needle-leaf plantations. Important findings Results showed that the effects of changes in solar radiation on shaded leaves predominantly determined the changes in the canopy photosynthesis as the shaded leaves contributed 67% to the total GPP. The impacts of changes in solar radiation on GPP varied inter-annually due to variations in the intensity and distribution of solar radiation from year to year. The GPP during 2003–2005 reached maximum when the solar radiation changed by –5.44%, –1.83%, and 6.26% in each year, respectively. Increased solar radiation enhanced the GPP during May and June, but reduced the GPP from July through September. The shaded leaves responded to changes in radiation differently in different seasons, and the sunlit and shaded leaves had different responses in the same season. Consequently, there were patterns of apparent offset in the total GPP and reduced sensitivity to changes in solar radiation on an annual basis. The changes in solar radiation had the smallest impact on GPP when the clearness index was at 0.43.

Estimating Global, Diffuse Solar Radiation for Chhor and Validation with Satellite-Based Data

The study of solar irradiation has been carried out for the first time over Chhor (city of Sindh province in Pakistan). In the present work, measured data of bright sunshine hour of the regions have been used to estimate monthly average daily global and diffuse solar radiation. Regression coefficients a and b have been calculated from the first-order Angstrom type correlation for the city using relationship given by Tiware and Sangeeta. The results obtained through four empirical models i.e., Angstrom, Liu and Jordon, Page, Hawas and Muneer were compared with values obtained from NASA Satellite-based Global and Diffuse radiation data. A good agreement was found between satellite-based values with Muneer and Hawaas model. The global irradiation is found high from April to July for the period of study. The statistical error tests—mean bias error, root mean square errors are used to validate the estimates using satellite-based data. MBE has lowest values for diffuse solar radiation than global radiation and shows over estimation. The value of coefficient of determination implies that 98.7 % of NASA can be accounted by estimation of global solar radiation Chhor. Low values of variance suggest that the correlation is best fitted.

Intercomparability of isotropic and anisotropic solar radiation models for different climatic zones of India

In present communication, a methodology is described to compute total radiation falling on inclined plane by employing the measured global and diffuse radiation data on horizontal surface of India. Five stations Jodhpur, Kolkata, Bangalore, New Delhi, and Srinagar representative of five different climatic zones—hot and dry, hot and humid, temperate, composite and cold, respectively are chosen for the study.The measured data of 15 years (from 1986 to 2000) are exploited and statistical analysis is carried out for the monthly mean daily data. Isotropic model of Liu and Jordan and anisotropic model of Hay are applied in the estimation of total radiation on tilted plane facing south with various slopes and an inter‐comparison between these two models is made to ensure their adaptability in different climatic regions of India. Four tilt angles viz. latitude, latitude +15°N, latitude‐15°N and 22.5°N are considered and both the models are used for computation of total radiation to test whether variation in tilt angles affect the reliability of models for any particular climatic zone.Furthermore, for realistic predictions, accuracy of isotropic and anisotropic models is tested through three statistical parameters and isotropic model is found fit for first four climatic zones of India while for cold region, performance of anisotropic seems better. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 925–932, 2014

Spatiotemporal variability analysis of diffuse radiation in China during 1981–2010

Abstract. Solar radiation is the primary driver of terrestrial plant photosynthesis and the diffuse component can enhance canopy light use efficiency (LUE), which in turn influences the carbon balance of terrestrial ecosystems. In this study we calculated the spatial data of diffuse radiation in China from 1981 to 2010, using a radiation decomposition model and spatial interpolation method based on observational data. Furthermore, we explored the spatiotemporal characteristics of diffuse radiation using GIS and trend analysis techniques. The results show the following: (1) The spatial patterns of perennial average of annual diffuse radiation during 1981–2010 are complex and inhomogeneous in China, generally lower in the north and higher in the south and west. The perennial average ranges from 1730.20 to 3064.41 MJ m−2 yr−1 across the whole country. (2) There is an increasing trend of annual diffuse radiation in China from 1981 to 2010 on the whole, with mean increasing amplitude of 7.03 MJ m−2 yr−1 per decade. Whereas a significant downtrend was observed in the first 10 years, distinct anomalies in 1982, 1983, 1991 and 1992 occurred due to the eruptions of El Chinchon and Pinatubo. (3) The spatial distribution of the temporal variability of diffuse radiation showed significant regional heterogeneity in addition to the seasonal differences. Northwestern China has the most evident downtrend, with highest decreasing rate of 6% per decade, while the Tibetan Plateau has the most evident uptrend, with highest increasing rate of up to 9% per decade. Such quantitative spatiotemporal characteristics of diffuse radiation are essential in regional scale modeling of terrestrial carbon dynamics.

A framework and methodology for reporting geographically and temporally resolved solar data: A case study of Texas

This paper presents a framework and methodology for reporting measured solar radiation data. Geographically and temporally resolved solar data have been calculated for all 254 counties in Texas using geospatial interpolation of data from 24 existing terrestrial measurement locations. Hourly global, direct, and diffuse horizontal radiation data have been obtained from 15 measurement sites at the Texas Solar Radiation Database, a project at The University of Texas at Austin, and from 9 sites at the National Solar Radiation Database. Average radiation fluxes and peak insolation have been calculated using daylight hours in addition to the total energy in kWh∕m2day. The methodology presented in this paper provides solar insolation data in a convenient format for engineers, scientists, policy-makers, homeowners, and consumers to assess the potential of solar energy at the county resolution. This methodology enables informed decisions about the economic viability of solar installations at particular locations and with useful diurnal and seasonal fidelity. These results are presented in a series of maps, figures, and tables included in this paper.

Correlation for Diffuse Radiation from Global Solar Radiation and Sunshine Data at Beijing, China

Solar radiation data are essential for the work of energy planners, engineers, and agricultural scientists. However, most solar radiation recording stations measure only global radiation in China. It is, therefore, necessary to elaborate correlations between the rarely available diffuse radiation and other climatic data. In the present study, 10-year data (1995–2004) of daily global diffuse solar radiation and sunshine duration obtained at Beijing meteorological station of China was analyzed to guide future projects. Nine models correlating the diffuse fraction (Kd) with both the clearness index (Kt) and percentage possible sunshine (S/S0) and each variable separately were tested. The accuracy of the correlations is performed in terms of the two widely used statistical indicators, mean bias error, and root mean square error. The results indicate that the correlations relating Kd with both Kt and S/S0 are more reliable than using each variable separately and Model 9 is preferred for its accuracy. The recorded data of Zhengzhou meteorological station are compared with the corresponding values predicted by Model 9 of Beijing. Model 9 provides predictions very close to the measured values of Zhengzhou. Therefore, it may be concluded that Model 9 can be used for estimating diffuse solar radiation for locations of semiwet region of the north of China where only global solar radiation and sunshine duration are available.

Modeling Spatio-Temporal Dynamics of Optimum Tilt Angles for Solar Collectors in Turkey.

Quantifying spatial and temporal variations in optimal tilt angle of a solar collector relative to a horizontal position assists in maximizing its performance for energy collection depending on changes in time and space. In this study, optimal tilt angles were quantified for solar collectors based on the monthly global and diffuse solar radiation on a horizontal surface across Turkey. The dataset of monthly average daily global solar radiation was obtained from 158 places, and monthly diffuse radiation data were estimated using an empirical model in the related literature. Our results showed that high tilt angles during the autumn (September to November) and winter (December to February) and low tilt angles during the summer (March to August) enabled the solar collector surface to absorb the maximum amount of solar radiation. Monthly optimum tilt angles were estimated devising a sinusoidal function of latitude and day of the year, and their validation resulted in a high R2 value of 98.8%, with root mean square error (RMSE) of 2.06°.

Estimation of monthly averaged direct normal solar radiation using elevation angle for any location

Light concentrators used in solar photovoltaic and solar thermal applications, and concentrates light by a factor of 10 or more, use only direct normal solar radiation, I N. A new method, called elevation angle constant (EAC) method, is developed to determine the resource potential of I N for different locations. This method is applicable to estimate the I N at any location in the world. The EAC method is based on empirical relations. The method calculates the elevation angle constant ( ε) for a given location and time. It uses readily available daily global and diffuse global radiation data to estimate the I N. This is different from existing methods which invariably uses hourly global and diffuse radiation. The values of I N are estimated for 12 locations across the world. The values of I N obtained using the EAC method have been compared with values obtained using the model-based approach (Appendix-1). The comparison is also done with the measured values for some stations. Ninety percent of the estimated values of I N using the EAC method for the stations like Angola, Egypt, Kuala Lumpur, Singapore, Brussels, Stuttgart, Ottawa, Birmingham, Los Angeles, Wellington, Perth and New Delhi are within ±5% of the values estimated by the model-based approach (Appendix-1).

Evaluation of solar radiation and its application for photovoltaic/thermal air collector for Indian composite climate

In this paper, an attempt has been made to evaluate cloudiness/haziness and atmospheric transmittance factors for the composite climate of New Delhi, India by considering the hourly data of global and diffuse radiation obtained for (i) the city region, experimentally observed and (ii) the flat land region obtained from the Department of Indian Meteorology, Pune. Cloudiness/haziness factor for the two models have been determined using simple regression analysis for clear sky condition for New Delhi. The comparison between the cloudiness/haziness and atmospheric transmittance factors for the composite climate of New Delhi for both the models and regions have been made. It has been observed that the cloudiness/haziness and atmospheric transmittance factors obtained by both models gave fair agreement within an accuracy of 0.57%. It has also been observed that there is a significant effect of region on beam and diffuse radiation due to cloudiness/haziness factors as expected. Further the data of solar radiation obtained from the Department of Indian Meteorology, Pune, have been used to evaluate the monthly performance of photovoltaic thermal (PV/T) air collector. It has been found that an overall thermal efficiency and exergy efficiency of PV/T air collector were about 50 and 14%, respectively. Copyright © 2006 John Wiley & Sons, Ltd.

Analysis of sky conditions using 40 year records of solar radiation data in China

Forty years of daily global and diffuse radiation data have been used to characterize the atmospheric optical conditions at 14 premium radiation stations in China. The clearness index (K T ), diffuse ratio (K D ), and diffuse coefficient (K C ) have been analyzed for long-term and seasonal variations, correlations of relative sunshine (R S ) versus clearness index and diffuse coefficient, respectively. Two polynomial models have been developed to simulate clearness index and diffuse ratio by using relative sunshine data and have been shown to be reasonable at most of the 14 stations. The results show that there are significant declining trends in clearness index and increasing trends in diffuse ratio at most of the 14 premium radiation stations, but there are no significant trends for diffuse coefficient. The seasonal variations of clearness index are determined by the regional climate and changes with relative sunshine.