Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site utastro.UUCP
Path: utzoo!watmath!clyde!burl!mgnetp!ihnp4!zehntel!hplabs!hao!seismo!ut-sally!utastro!nather
From: nather@utastro.UUCP (Ed Nather)
Newsgroups: net.followup
Subject: Re: Alternate Energy & Microwaves
Message-ID: <369@utastro.UUCP>
Date: Sun, 12-Aug-84 16:09:31 EDT
Article-I.D.: utastro.369
Posted: Sun Aug 12 16:09:31 1984
Date-Received: Tue, 14-Aug-84 05:02:59 EDT
References: <4196@utzoo.UUCP>
Organization: UTexas Astronomy Dept., Austin, Texas
Lines: 38

[]
   >They have another big advantage:  microwave-to-electricity conversion can
   >be quite efficient (70-80%), whereas converting sunlight to electricity is
   >dismally inefficient (15% is good for solar cells).  Of course, the power
   >satellite itself probably uses solar cells, but it is out in space,
   >where (a) the sun shines 24 hours/day, and (b) the waste heat does not
   >go into Earth's biosphere.
   >-- 
   >				Henry Spencer @ U of Toronto Zoology

a) The sun shines 24 hours/day everywhere, not just out in space, but it may
be difficult to get a satellite far enough away from the earth so it never
passes through its shadow, particularly if it is in synchronous orbit, which
means it goes around once in 24 hours, and must therefore be at 25,000 miles
altitute.

b) If the solar cells aren't there to convert the heat into electricity (i.e.
make some use of 15% of it) then it will *all* go into the earth's bioshphere
if it isn't reflected back into space.  The "saved" 15% will presumably get
converted into work somewhere, which degrades into heat, which enters the
earth's biosphere.  So where is the "waste?"

c) If the Sunsat is put up it will be bright enough to rival the full moon,
just from reflected light alone (the moon reflects ~8%, is bigger but is
*much* farther away, and the inverse-square law does a bit of good) ...
which means ground-based astronomy goes out of business, since most of the
interesting observations of quasars, distant galaxies, black hole candidates
and vibrating stellar corpses are confined to "dark time," when the moon is
nearly aligned with the sun and the night sky is dark.

d) If all astronomers become shoe salesmen or zoologists then who will be
watching when the Klingons come?

-- 

                                 Ed Nather
                                 {allegra,ihnp4}!{ut-sally,noao}!utastro!nather
                                 Astronomy Dept., U. of Texas, Austin