On Mon, Nov 14, 2011 at 9:32 PM, Jed Rothwell <jedrothw...@gmail.com> wrote:
> <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 first sentence in the 2nd section in the wikipedia article on solar energy: "The Earth receives 174 petawatts (PW) of incoming solar radiation (insolation) at the upper atmosphere. Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans and land masses." 174 PW for one year is close to 5 million quads. > You cannot extrapolate from local insolation given the extremes at the > poles. > It's simpler than that. Multiply the solar insolation at one astronomical unit (1366 W/m^2) (i.e. above the atmosphere), and multiply by the *cross-sectional area* of the earth (pi*r^2), to give the total incident power (174 PW).
