Xref: utzoo talk.politics.misc:8791 sci.misc:1271
Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!bloom-beacon!spdcc!eli
From: eli@spdcc.COM (Steve Elias)
Newsgroups: talk.politics.misc,sci.misc
Subject: Re: efficiency / greenhouse effect / solar power satellites
Message-ID: <789@spdcc.COM>
Date: 6 Apr 88 12:21:03 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>
Reply-To: eli@spdcc.COM (Steve Elias)
Followup-To: sci.misc
Organization: S.P. Dyer Computer Consulting, Cambridge MA
Lines: 73

In article <747@xyzzy.UUCP> throopw@xyzzy.UUCP (Wayne A. Throop) writes:
>> eli@spdcc.COM (Steve Elias)
>> my contention is that to meet a large increase in power demands with solar
>> power satellites will add something on the order of one percent or so to 
>> the total energy flux that the earth receives.

!This is true iff the "increase in power demands" itself is about a
!percent of the total solar flux reaching earth.  My personal feeling is
!that by the time people demand that much power to maintain their
!lifestyles, they had better be using that power primarily in space, and
!not on the earth.  If not, I'd guess that earth would soon become an
!untenable place to live for anything much more complicated than lichen,
!whether or not thermal effects of that much power use are considered.

	awfully good points.  i hope we make it into space, too.
	lichen don't make very good co-workers and friends...

!Looking in tables and such I think that the current energy use by humans
!on earth is something like 6x10^18 cal/yr.  The current solar flux
!reaching earth is something like 1x10^24 cal/yr.  That is, if human
!energy consumption was totally supported by SPS, and doubles every 10
!years, and none of this consumption moves to space, we would see 1
!percent of solar flux delivered to earth from our SPS system in about
!150 years.

	as i mentioned in a previous article, the earth's albedo multiplies
	down the incident solar flux by nearly 70%.
	so 150 years is a bit of an overstatement, even with a ten year
	doubling time for power needs.

!And in thinking about this, it is well to remember that the sun is,
!itself, about 3% variable, so that a small hicup in solar activity could
!swamp this effect for another 300 years at least.

	could Wayne or anyone elaborate on this??  i'm under the impression
	that the hiccups he refers to are sun-spots.  they affect the solar
	wind, but not the radiated EM energy from the sun, as far as i know.
	does anyone have more information on this?  

	what is the predicted effect if the radiated energy from the sun
	did rise by 3% for a few hundred or thousand years??  

	Dani Eder mentioned that the incident energy from the sun in the
	far past might have been far greater than it is now -- and we didn't
	slide into thermal runaway back then...  perhaps cloud cover changes
	and resulting albedo changes did provide negative feedback and stem
	any possible thermal runaway.

	in the case of solar power satellites -- such negative feedback
	might indeed occur, and reduce the 'naturally' received solar flux.
	but any negative feedback due to albedo changes would
	not affect the solar power receiver stations themselves...  they
	would continue to soak up the same energy and release it as heat...

!And, as I said to start out, we would have far, far more serious
!problems than thermal pollution if we had 100,000 times our current
!industrial activity, and if it (and we) were still confined to the earth.

	this much industrial activity would indeed equal incident solar
	flux.  here's more of the same 'back of the envelope' stuff:

	reduce the 100,000 by .7 to indicate albedo effects...
	surmise that a power use of 10% of incident solar flux would put 
	us at a a possibly dangerous point...  and...

	7,000 times out present industrial activity would
	put us at a possibly dangerous point...  (using the methods 
	described so far in this group).  

	i still hope to locate Frank Drake's notes on this subject.
	as any SETI fans out there know, he is awfully good with factors
	and powers of ten -- i suspect that his notes will throw a few
	such factors in favor of his 'thermal paranoia' argument, so 
	the '7000' number can be reduced further...