Re: Understanding nanotech

ronkean@juno.com
Tue, 31 Aug 1999 03:01:36 -0400

On Mon, 30 Aug 1999 23:15:56 -0500 "Billy Brown" <ewbrownv@mindspring.com> writes:
> 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.

A technicality: Houses in the US are normally fed with 240 volts single phase center-tapped, on three wires. One wire is the neutral or ground, and the other two wires each carry 120 volts relative to ground, with 240 volts between the two live wires. The 240 is used for running heat pumps, air conditioners, and some clothes dryers and water heaters. The 120 is used for most everything else. So when the two live wires are each carrying 200 amps, which is what the 200 amp rating means, the total power is 240 volts x 200 amps, or nominally 48 KW, assuming unity power factor.

>
> 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
>

Those numbers work out to 5.7x10^4 KW per person, modeling the earth as a disk of the given radius, facing the sun. But the earth's population is now reported to be 6 billion rather than 3 billion.

Ron Kean

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