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The latter standard represents the spectral distribution of global irradiance incident on a 37° tilted surface facing the sun at an air mass of 1.5. The integrated irradiance amounts to 1000 W/m 2 . This standard spectrum is mandated by IEC to evaluate the rating of photovoltaic (PV) solar cells in the absence of optical concentration.
The specific value of 1.5 has been selected in the 1970s for standardization purposes, based on an analysis of solar irradiance data in the conterminous United States. [9] Since then, the solar industry has been using AM1.5 for all standardized testing or rating of terrestrial solar cells or modules, including those used in concentrating systems.
I (x, t ; r 1, ν) is defined to be such that a virtual source area, dA 1, containing the point P 1, is an apparent emitter of a small but finite amount of energy dE transported by radiation of frequencies (ν, ν + dν) in a small time duration dt, where = (,;,) (), and where θ 1 is the angle between the line of propagation r and the normal P 1 N 1 to dA 1; the effective destination of ...
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The two forms have different dimensions and units: spectral irradiance of a frequency spectrum is measured in watts per square metre per hertz (W⋅m −2 ⋅Hz −1), while spectral irradiance of a wavelength spectrum is measured in watts per square metre per metre (W⋅m −3), or more commonly watts per square metre per nanometre (W⋅m −2 ...
Mathematically, for the spectral power distribution of a radiant exitance or irradiance one may write: =where M(λ) is the spectral irradiance (or exitance) of the light (SI units: W/m 2 = kg·m −1 ·s −3); Φ is the radiant flux of the source (SI unit: watt, W); A is the area over which the radiant flux is integrated (SI unit: square meter, m 2); and λ is the wavelength (SI unit: meter, m).
The field of spectroradiometry concerns itself with the measurement of absolute radiometric quantities in narrow wavelength intervals. [1] It is useful to sample the spectrum with narrow bandwidth and wavelength increments because many sources have line structures [2] Most often in spectroradiometry, spectral irradiance is the desired measurement.
In radiometry, radiant exposure or fluence is the radiant energy received by a surface per unit area, or equivalently the irradiance of a surface, integrated over time of irradiation, and spectral exposure is the radiant exposure per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength.