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The Light is Green




Insolation, Albedo, Perihelion, and other cool stuff

From a solar orbit of 1 AU (astronomical unit) the average intensity of the solar flux is 1350 W/m2 (that's the available power that has run every living thing on Earth for the past 4.5 billion years.)

The actual flux varies throughout the year, both due to the earth's distance from the sun, and the thickness of the atmosphere as affected by the axial tilt if the planet.  That's to say the seasons.

For quick calculations 1kW·m2 makes for really easy math.  

The solar cell folks use a number of standard conditions, a common one is 900W/m2 which takes the average losses in the atmosphere, like dust, water vapor, scattering, etc. into consideration.

When precise calculations are required, we use tables that have been developed by decades of measurements.  The building industry uses these values and they are accepted as the standards by architects, engineers, inspectors, operators, and owners;  that's good enough for us.



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Updated: 09/11/10 19:31