In reply to Jed Rothwell's message of Mon, 14 Nov 2011 22:32:11 -0500: Hi, [snip] ><mix...@bigpond.com> wrote: > >> >> This figure is too high. The amount intercepted by the Earth is 5 million >> quads >> per annum above the atmosphere, and then some of this is directly >> reflected back >> into space by cloud cover. >> > >Where did you get that info?
The intensity of Solar radiation above the atmosphere is about 1300 W / m^2. Multiply by the cross sectional area of the planet (not the surface area as is incorrectly done on the web page below) and you get the total power, which may be expressed as quads / annum. > >I looked all around for that. I found that one site that expresses the >number in quads, and it seemed to compare to the others that show the value >in different units. > >http://www.ecoworld.com/energy-fuels/how-much-solar-energy-hits-earth.html > >Is there a more authoritative and detailed site than this? > >Most of them discuss solar insolation in units such as square meters for >various locations. That is needed for solar energy planning. They do not >include a planet-wide analysis. You cannot extrapolate from local >insolation given the extremes at the poles. That's why you use the maximum figure & the area of a cross section (i.e. Pi * r^2), which BTW is the area of the shadow that the planet would cast on a flat surface. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
