# Re: Understanding nanotech

Michael S. Lorrey (retroman@turbont.net)
Wed, 01 Sep 1999 00:22:53 -0400

Billy Brown wrote:
>
> Robert J. Bradbury wrote:
> > However, the calculation assumes that every person on the planet can
> > find *some* use for his 10 kg allocation of robots consuming ~100KW
> > of power. Right now most of the people on the planet don't come
> > close to consuming 100KW. A standard house (with 200 Amp service,
> > probably above average), only pulls 20KW when it is maxed out.
>
> Something is seriously wrong with these numbers. My handy reference lists
> the solar constant at 1340 W/m^2, and the mean radius of the Earth is
> 6.37x10^6 m. Multiply that out, divide by 3 billion people, and you get an
> approximate natural energy budget of 5.6x10^4 KW per person. We should be
> able to use whatever fraction of that we care to actually harvest without
> fear of creating a global heat problem.
>
> Billy Brown, MCSE+I
> ewbrownv@mindspring.com

Problem is:
a) the solar constant is measured from space. At the ground its about 1 kw/sq meter. Then subtract the 2/3 of the earth's surface that is ocean, then subtract the percentage of the rest of the surface we choose to use for other purposes, then count the fact that your solar constant (after adjusted for the attentuation of the atmosphere, and for the percent of cloud cover reflecting a chunk back into space) is only at the equator, and the further you get from the equator the more it deteriorates (a sine function), because of the declination of the sun toward the horizon (not straight up), plus the fact that only half of the earth is exposed to sunlight at any given time.... do the math.

Mike Lorrey