Solar and Earth Radiation

2001 ◽  
Author(s):  
Fred V. Brock ◽  
Scott J. Richardson
Keyword(s):  
Solar Radiation ◽  
Physical Quantity ◽  
Unit Area ◽  
Solid Angle ◽  
Global Solar Radiation ◽  
Radiant Flux ◽  
Direct Solar Radiation ◽  
Radiant Intensity ◽  
The Earth ◽  
Earth Radiation

This chapter is concerned with the measurement of solar radiation that reaches the earth’s surface and with the measurement of earth radiation, the long wave band of radiation emitted by the earth. The unit of radiation used in this chapter is the Wm-2. Table 10-1 lists some conversion factors. Radiant flux is the amount of radiation coming from a source per unit time in W. Radiant intensity is the radiant flux leaving a point on the source, per unit solid angle of space surrounding the point, in W sr-1 (sr is a steradian, a solid angle unit). Radiance is the radiant flux emitted by a unit area of a source or scattered by a unit area of a surface in Wm-2 sr-1. Irradiance is the radiant flux incident on a receiving surface from all directions, per unit area of surface, in Wm-2. Absorptance, reflectance, and transmittance are the fractions of the incident flux that are absorbed, reflected, or transmitted by a medium. Global solar radiation is the solar irradiance received on a horizontal surface, Wm-2. This is the sum of the direct solar beam plus the diffuse component of skylight, and is the physical quantity measured by a pyranometer. Direct solar radiation is the radiation emitted from the solid angle of the sun’s disc, received on a surface perpendicular to the axis of this cone, comprising mainly unscattered and unreflected solar radiation in Wm-2. At the top of the atmosphere this is usually taken to be 1367 W m-2 ± 3% due to changes in the earth orbit and due to sunspots. The direct beam is attenuated by absorption and scattering in the atmosphere. The direct solar radiation at the earth’s surface is the physical quantity measured by a pyrheliometer. Diffuse solar radiation (sky radiation) is the downward scattered and reflected radiation coming from the whole hemisphere, with the exception of the solid angle subtended by the sun’s disc in Wm-2. Diffuse radiation can be measured by a pyranometer mounted in a shadow band, or it can be calculated using global solar radiation and direct solar radiation.

scholarly journals Direct Solar Radiation and Atmospheric Turbidity in Mikołajki in the Years 1971–1980 and 1991–2000

2009 ◽  
Vol 2 (1) ◽  
pp. 19-33
Author(s):  
Joanna Uscka-Kowalkowska
Keyword(s):  
Solar Radiation ◽  
Solar Irradiance ◽  
Direct Solar Radiation ◽  
Spectral Structure ◽  
Solar Constant ◽  
Air Masses ◽  
Atmospheric Turbidity ◽  
The Earth

Abstract The present study deals with the changing amount of incoming direct solar radiation and the optical state of the atmosphere in Mikołajki in the years 1971-1980 and 1991-2000. The highest level of solar irradiance in these two decades occurred on 23rd June 1977 and amounted to 1043.9 W·m-2. Compared to the first decade analysed, the percentage of the solar constant reaching the Earth in the second decade was higher. The spectral structure of the radiation also changed - the share of the shortest waves (λ<525 nm) increased, whereas the amount of waves with a wavelength of 710 nm or more decreased. In both study periods the annual course of solar extinction (expressed in terms of Linke’s turbidity factor) turned out to have been typical, with the highest values in summer and the lowest in winter. In the years 1991-2000, in all seasons, a lower atmospheric turbidity was observed in comparison with the years 1971-1980. The atmospheric turbidity was also analysed with relation to the air masses. In both decades in question the lowest turbidity occurred in arctic air masses and the highest in tropical air masses. An improved optical state of the atmosphere was observed in all considered air masses, though the biggest decrease in turbidity was found in polar air masses, particularly in the polar maritime old air (TLAM2 dropped by 0.75) and polar continental air (by 0.70).

scholarly journals Empirical Models for the Evaluation of Global Solar Radiation in the Different Sites of Nepal

2019 ◽  
Vol 5 (1) ◽  
pp. 67-73
Author(s):  
B. P. Pant ◽  
K. N. Poudyal ◽  
B. Acharya ◽  
B. Budha
Keyword(s):  
Solar Radiation ◽  
Alternative Energy ◽  
Meteorological Parameters ◽  
Global Solar Radiation ◽  
Vital Role ◽  
Empirical Models ◽  
Model Order ◽  
The Earth ◽  
Good Possibility ◽  
Better Than

To operate many phenomenon’s on the earth surface such as physical, chemical and biological process solar radiation plays vital role. A common practice is to estimate average daily global solar radiation (GSR) using appropriate empirical models for the areas lacking the actual measured values. In this context several single and multiple meteorological parameters were selected to estimate the GSR for Jumla, Nepalgunj and Kathmandu. In order to validate the selected models various statistical test were employed. The selected models were compared on the basis of statistical errors. In the statistical analysis the value of root mean square error (RMSE) and coefficient o determination R2 is found to 0.15.0.23, 0.26 and 0.98, 0.96, 0.96 respectively for Jumla, Nepalgunj and Kathmandu in Samuel model. These values were comparatively better than other models. It is concluded that Samuel model (order three) is the best among the used models. The established result uncover that there is a good possibility of solar energy as a alternative energy source in Nepal.

scholarly journals Estimating Angstrom-Prescott Coefficients for India and Developing a Correlation between Sunshine Hours and Global Solar Radiation for India

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
R. C. Srivastava ◽  
Harsha Pandey
Keyword(s):  
Solar Radiation ◽  
Mathematical Models ◽  
Global Solar Radiation ◽  
Model Parameters ◽  
The Earth ◽  
Energy Needs ◽  
Sunshine Hours ◽  
One Year ◽  
Huge Challenge ◽  
Sunshine Hour

The amount of solar energy that reaches the earth in one hour is sufficient to supply the world's energy needs for one year. Harvesting this energy efficiently is a huge challenge. In most countries including India, the number of observing stations is inadequate. Therefore, it is essential that some reliable mathematical models be developed to estimate the solar radiation for places where measurements are not carried out and for places where measurement records are not available. In this paper, Angstrom-Prescott model parameters are estimated for seven different sites in India, and a correlation is developed for India, which is found to be a good fit. Also a correlation is developed for predicting the solar radiation using only sunshine hour data.

scholarly journals Calculated the diffuse and direct parts of global solar radiation in Baghdad city for the period (1983-2005) depending on clearness index by applying the two world models of Liu -Jordan

2019 ◽  
Vol 12 (25) ◽  
pp. 94-104
Author(s):  
Gheidaa Sabeeh Al-Hassany
Keyword(s):  
Solar Radiation ◽  
Global Solar Radiation ◽  
Measured Data ◽  
Direct Solar Radiation ◽  
Clearness Index

In this paper solar radiation was studied over a region of Baghdad (Latitude 33.3o and longitude 44.4o). The two parts of global solar radiation: diffuse and direct solar radiation were estimated depending on the clearance index of measured data (Average Monthly mean global solar radiation). Metrological data of measured (average monthly mean diffuse and direct solar radiation) were used to comparison the results and show the agreement between them. Results are determined by applying Liu and Jordan two models (1960). Excel 2007program is used in calculation, graphics and comparison the results.

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