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From: throopw@xyzzy.UUCP (Wayne A. Throop)
Newsgroups: talk.politics.misc,sci.misc
Subject: efficiency / greenhouse effect / solar power satellites
Message-ID: <745@xyzzy.UUCP>
Date: 5 Apr 88 18:31:44 GMT
References: <22678@bbn.COM> <5564@well.UUCP> <761@spdcc.COM> <4195@bloom-beacon.MIT.EDU> <763@spdcc.COM> <2997@sfsup.UUCP> <768@spdcc.COM>
Organization: Data General, RTP NC.
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> eli@spdcc.COM (Steve Elias)
> 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!  

It is true that every joule sent down ends up as waste heat.  However,
the efficency of the ground based part of the system dictates how many
joules per second are sent to serve a fixed load.

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

Again correct.  But that isn't a kosher way of comparing various power
generation/distribution schemes.  The only fair way to compare (as far
as I can see) is to compare net thermal load added per useful unit power
delivered.  In doing this calculation, many forms of earth-based solar
power lose out to SPS, as do all forms of petrochemical power and
nuclear power.  The only forms of power production that have a prayer of
being better off thermally are wind, water, "thermocline" or biomass
powered.  And these are likely to have large environmental impact as the
alteration of winds, watersheds, ocean thermoclines, or large-scale
harvesting impacts the local biota.

--
You can lead a yak to water but you can't teach an old dog to make a
silk purse out of a pig in a poke.
                                                --- Opus
-- 
Wayne Throop      <the-known-world>!mcnc!rti!xyzzy!throopw