Standards solar radiation

Moon, P., Proposed standard solar-radiation curves for engineering use. J. Franklin Inst. 230, 583-617 (1940). 

Specific solar radiation conditions are defined by the air mass (AM) value. The spectral distribution and total flux of radiation outside the Earth s atmosphere, similar to the radiation of a black body of 5,900 K, has been defined as AM-0. The AM-1 and AM-1.5 are defined as the path length of the solar light relative to a vertical position of the Sun above the terrestrial absorber, which is at the equator when the incidence of sunlight is vertical (90°) and 41.8°, respectively. The AM-1.5 conditions are achieved when the solar flux is 982 Wm2. However, for convenience purpose the flux of the standardized AM-1.5 spectrum has been corrected to 1,000 Wm2. 

In principle, there are two ways to achieve the radiometric calibration of an instrument measuring solar radiation. The first is by comparison to a standard radiation source of known output and the second by comparison to a prototype standard instrument that is capable in measuring the same radiometric quantity. The fist can be applied to broadband detectors only if their spectral response over the whole range of the radiation source is known with sufficient accuracy. The second method requires that the standard instrument has exactly the same spectral response, which is rather unlikely to occur. 

In the PV cells, germanium or gallium compounds provide electricity when exposed to solar radiation. The absorbance spectrum of the PV cell material can go from UV wavelength ( 250 nm) to IR radiation ( 1,500 nm). The conversion efficiency of standard PV cells is between 10 and 15%. 

From Equation (5), it is clear that the basic parameter that decides the light harvesting ability of the photocatalyst is its band gap. The ideal limiting efficiencies for conversion of solar radiation calculated by Equation (5) as a function of the band-gap wavelength for standard AM 1.5 solar irradiation in a single band-gap device are represented in Figure 9. 

D65, daylight, with a CCT of 6500K is defined by the CIE. The International Standards Organization Standard ISO 10977 (1993) refers to this fact. D65 is also known as D6500 or Standard Illuminant D by the CIE, represents daylight over the spectral range 300 to 830 nm was first adopted in 1966. This standard is not a particular lamp but an internationally agreed to spectral power distribution for solar radiation, issued by the CIE as "Technical Report, Solar Irradiance," first edition... 

Xenon lamps are the basis of many international standards for replicating 1D 5 and ID testing conditions. They are valued not only for their high correlation with actual solar radiation but also for their high intensity which translates into reduced testing times and more efficient use of both human, equipment and physical resources. 

Figure 8 is displayed the SPD of solar radiation in Miami both and filtered through an Atlas window-glass filter. It is evident that because one represents (Normal Solar Radiation) and the other the standard, there is no equivalence between the two. The Expert Working Group for ICH QIB erred in specifying the "D /ID emission standard." No such emission standard exists. 

GU/p) represents the extinction over ail wavelengths between A. and per unit volume of aerosol in the size range between and dp + d(dp). It is independent of the particle size distribution function. For a refractive index, m = 1.5, G(dp) has been evaluated for the standard distribution of solar radiation at sea level, using Mie scattering functions. The result is shown in Fig. 5.8 as a function of particle size. 

Figure 11. Ratio of global radiation fluxes (normalized to cloudless conditions) for erythemal radiation, UV-A radiation and total solar radiation in dependence on cloudiness, separated for cases when the sun is free or when the sun is totally covered by clouds. Bars indicate -t- 3 standard deviation of the mean.

It is well known that the spectral distribution and irradiance of the solar radiation at the Earth s surface depend on the location and is subjected to seasonal and diurnal variations. Therefore, a reference spectrum is needed as a basis for comparison with the spectral energy distribution of artificial light sources. Data from CIE No. 15 1971 (colorimetry official recommendations of the International Commission on Illumination) that recommend a standard illuminant D65 with a scheduled color temperature of approximately 6500 K have been used as a basis over the years. 

According to the standard, unless otherwise specified, exposure racks should face the equator. The standard considers rack position at different latitudes, and the respective rack adjustments at certain periods of the year, and indicates that in most nondesert areas maximum annual UV exposure is provided by exposure at an angle of the latitude angle minus 10°. Besides, the standard considers at-latitude racks, 45° racks, 90° racks, horizontal racks (instead, 5° south exposure is recommended, to provide moisture runoff), and other angle racks. Materials and types of construction of test racks are also considered, as well as instruments for measuring solar radiation, ambient temperature and relative humidity, and their calibration procedures. 

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