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Direct normal irradiance (DNI), or beam radiation, is measured at the surface of the Earth at a given location with a surface element perpendicular to the Sun direction. [ 6 ] [ failed verification ] It excludes diffuse solar radiation (radiation that is scattered or reflected by atmospheric components).
This is typically specified as average DNI (Direct Normal Irradiance) greater than 5.5-6m kWh/m 2 /day or 2000 kWh/m 2 /yr. Otherwise, evaluations of annualized DNI vs. GNI/GHI (Global Normal Irradiance and Global Horizontal Irradiance) irradiance data have concluded that conventional PV should still perform better over time than presently ...
Direct normal irradiance spectra calculated with SMARTS 2.9.5 for increasing air mass (0 to 10), using the same atmospheric conditions as the ASTM G173 standard. Air mass 0 corresponds to the extraterrestrial spectrum, [1] marked as Top of Atmosphere (TOA).
The actual direct solar irradiance at the top of the atmosphere fluctuates by about 6.9% during a year (from 1.412 kW/m 2 in early January to 1.321 kW/m 2 in early July) due to the Earth's varying distance from the Sun, and typically by much less than 0.1% from day to day.
Direct insolation is equal to the solar irradiance above the atmosphere minus the atmospheric losses due to absorption and scattering. While the solar irradiance above the atmosphere varies with the Earth–Sun distance and solar cycles , the losses depend on the time of day (length of light's path through the atmosphere depending on the solar ...
A wide range of concentrating technologies exists: ... (direct normal irradiance, global horizontal irradiance) are mapped below: North America. South America.
DNI Meaning. These days, we have plenty of forms of communication—from phones, computers, social media and more. This has led to plenty of ways to communicate as well, like using shorthand and ...
The global irradiance on a horizontal surface on Earth consists of the direct irradiance E e,dir and diffuse irradiance E e,diff. On a tilted plane, there is another irradiance component, E e,refl, which is the component that is reflected from the ground. The average ground reflection is about 20% of the global irradiance.