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太阳光谱分布曲线,太阳辐射光谱分布曲线,Solar Radiation Spectrum
Air Mass是形容光在大气中传播的距离。1 Air Mass,或者AM1,是指地球大气层的厚度。AM0是指外太空的太阳辐射,不受大气层的影响。AM1.5的功率密度大约是1000W/m2,AM0的功率密度大约是1360W/m2,这些被定义为太阳常数。
对于光伏测试(地面应用),标准测试条件被定义为25℃下,强度为一个太阳常数1000W/m2(1 SUN),并且一个太阳光谱分布等效于AM1.5G。对于太阳能模拟系统的分类,一个光谱辐射分布的标准已经被确立。
太阳光谱
日射量,在一个给定的面积和给定的时间下,地球表面太阳辐射总能量比外太空减少高达45%,主要是由于反射和吸收造成的。在到达地球表面的太阳辐射中,约有一半位于电磁波的可见光部分。即便如此,全球太阳能潜力也是巨大的。每年到达地球表面的太阳能总量超过能源消耗总量大约10000倍。
光伏太阳能电池的大部分损失(50%以上)与光谱匹配有关(半导体材料吸收能量的带隙不可能跨越整个太阳能光谱)。太阳模拟系统辐射的关键在于匹配,尽可能的与地球表面太阳辐射光谱分布相匹配。
The Sun emits radiation from X-rays to radio waves, but the irradiance of solar radiation peaks in the visible wavelengths (see figure below). Common units of irradiance are Joules per second per m2 of surface that is illuminated per nm of wavelength (e.g., between 300 nm and 301 nm), or W m–2 nm–1 for the plot below. These units are the units of spectral irradiance, which is also simply called irradiance, but as a function of wavelength. To get the total irradiance in units of W m–2, the spectral irradiance should be integrated over all the wavelengths.
Note the following for the solar spectrum:
About half of the energy is in the visible wavelengths below 0.7 μm. We can tell this by doing a quick integration.
O3 and O2 absorb much of the UV irradiance below 300 nm high in the atmosphere.
About 70% of the visible irradiance makes it all the way to sea level.
O3 absorbs a little of the visible irradiance.
A significant fraction of the visible irradiance is scattered by clouds and aerosol. Some is reflected back out into space so that this portion never deposits energy in the Earth system.
There are large wavelength bands in which water vapor, CO2, and O3 absorb infrared irradiance.
For solar wavelengths at which the absorptivity is high, the solar irradiance at sea level is small. Note that the big absorbers of infrared irradiance are water vapor, carbon dioxide, and ozone.
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