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From: jfc@athena.mit.edu (John F Carr)
Newsgroups: talk.politics.misc,sci.misc
Subject: Re: efficiency / greenhouse effect / solar power satellites
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Date: 3 Apr 88 15:44:40 GMT
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In article <768@spdcc.COM> eli@spdcc.COM (Steve Elias) writes:
: sheesh.  you guys are missing my point regarding efficiency and solar
: power satellites.  pardon me for not being precise enough, and for 
: missing John's point regarding 'fixed power consumption.'  

: the point is that every joule sent down from the satellite will end
: up as waste heat on earth -- the efficiency of the ground based part
: of the system does not matter!  

But the more efficient the ground based part, the less power need be sent
down.

: this is true not for 'fixed power consumption', of course.
: it is true for 'fixed power transmission from the satellite'.

You are missing the point: SPS will not be put up just for fun; no one
will say, "I want to launch a 500MW SPS, whether or not anyone will buy
the power."   We will only use SPS if there is a demand for the power.
When demand is predicted to exceed supply, there are only two choices:
increase supply or reduce demand.  Decreasing demand is not practical,
and may not be possible.  So, we are left with the decision, "How do we
generate the extra power?"   The amount of heat which will be generated
to produce this power is P/eff.  The power consumption sets a lower bound
on heat, but efficiency is important.  (Assuming there is agreement that
demand for power will increase) we must assume fixed generating capacity,
and argue the relative merits of different systems.  How are earth-based
systems better?  I believe that, considering only thermal and poluution
problems, they are not.  Building a heat engine on the earth will also
add heat to the environment that would not otherwise be present.



   John Carr           "No one wants to make a terrible choice
   jfc@athena.mit.edu   On the price of being free"           -- Neil Peart