From: Robert J. Bradbury (bradbury@www.aeiveos.com)
Date: Tue Aug 31 1999 - 22:09:59 MDT
On Tue, 31 Aug 1999, dan wrote:
> ... a typical household really will be able to use solar and geothermal
> energy, contributing zero net heat to the environment to achieve a
> lifestyle that is wildly luxurious by today's standards.
True. Energy resources of the future that we can use will exceed
by many orders of magnitude (> 10^5) what we actually require.
>
> If the energy budget is computed to be constrained by global
> warming, then there is no true constraint: we can use lazers
> to beam energy into space to dump the heat. This is a violation
> of the second law of thermodynamics: The earth is not a closed system.
>
Yes, I understand the thermodynamics part, but I've never seen
anyone propose a real "physical system" that would allow the
efficient removal of the waste heat/entropy. There are some
interesting suggestions regarding slow ballistic transport
and fast ballistic transport in Frank & Knight (1997)
[http://www.ai.mit.edu/~mpf/Nano97/paper.html {esp. Sect 7.1}],
but I've never seen anyone discuss the nuts and bolts of such an
approach.
While I agree that beaming the entropy into space is a great
idea, I'm under the impression that there are significant
losses when you attempt to drive energy "uphill" (say
from waste heat generated by nano-assembly, into light
light as laser emissions). The best energy efficiency
that I know of for lasers is ~60%, and that is in diodes
lasers converting from electricity into light. Unless you
can propose a system that is >90% efficient at converting heat
into laser energy, I don't think your argument buys us much.
It is certainly true that we could circulate the heat in a
cooling fluid into the upper atmosphere, but one faces losses
here due to gravity and friction.
I really do think we are limited as far as planetary heat
production.
Robert
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