From: aldridge@netcom.com (Jacquelyn Aldridge)
Subject: Re: Solar Powered Roof
Keywords: solar power
Organization: Netcom - Online Communication Services  (408 241-9760 guest) 
Distribution: usa
Date: Mon, 12 Oct 1992 09:17:17 GMT

wolfone@ccwf.cc.utexas.edu (Patrick Chester) writes:

>In article <1992Sep30.170728.28862@csi.jpl.nasa.gov> mark@csi.jpl.nasa.gov (Mark Webster) writes:
>)
>)It seems as though eventually, solar power will become a more viable source
>)of energy.  Solar cells are becoming more efficient and cheaper, and hopefully,
>)the ecological impact of manufacturing them will be reduced or eliminated.  
>)Other forms of solar energy conversion are also making strides toward
>)viability.  One problem that I can see is lack of space.  I'm a desert lover and
>)I really don't want to see a lot of desert torn up to erect solar power plant
>)farms.  Floating them on the ocean makes them vulnerable to storms and may have
>)some sort of impact on ocean life.  And solar satellites are vulnerable to 
>)space debris, atomic oxygen, atmospheric and solar drag.  The method of transferring energy from orbit is also somewhat problematic.
>SPS stations were planned to be placed at geosynchronous orbit. How much atomic
>oxygen is up that high? As to space junk, a little armor can help against that.
>The problem w/the power transmission (main idea was w/microwaves) was the
>hysteria whipped up by some people. They were claiming you could cook a city
>with it if the beam were knocked off course or if terrorists got the controls
>to the aiming computers. I doubt the *focused* beam would boil water with the
>energy per square centimeter it transmits. 10 gigawatts is a lot of power, but
>if it's spread over a 10km diameter beam how much would that do? 
>Anybody w/calcuator and a physics textbook want to calculate that? I have a
>calculator but no equation.
>)
>)So, I have and idea.  How about we cover the roof of every building, commercial, public and hell, even residential with solar cells.  If you fly over LA, black roofs as far as the eye can see.  Even erect them over freeways on light weight frames that can't hurt anything if they fall during an earthquake (only a problem in California and the area around New Madrid Missouri).  
>)
>)Whattaya think? Flame away. Just post please.
>Too late. It's already been featured in a science fiction novel. A future 
>Pheonix Arizona had the entire city effectively covered by solar panel arrays.
>It was nicknamed "Frozen Shade" and left the entire city below it in permanent
>night. Author might have been trying to say something when it says that the 
>city was covered because some ecologists, none of which lived in the city, 
>forced that system on them because they wouldn't let nuclear power be used and
>wouldn't let the power company put it all in the desert. Oh well.
>)
>)Mark
>)
>)On an intimate quest for knowledge.
>Read some hard science fiction. Not a flame. A serious, hard felt recomendation.


>-- 
>--------------------------------------------------------------------------------
>Patrick Chester            |"The earth is too fragile a basket in which to keep
>wolfone@ccwf.cc.utexas.edu |  all your eggs." Robert A. Heinlein
>Politically Incorrect      |"The meek shall inherit the earth. The rest of us
>Future Lunar Colonist      |  are going to the stars." Anonymous

>--------------------------------------------------------------------------------

	Nothing difficult about that, it's grammer school geometry.
10 km diameter beam. Circumference = 2 pi r. So the area of the beam is 
approximately 30 square kilometers. And it takes 1000 times 1000 square 
meters to make a square kilometer. So you are going to have 30 million
square meters. I'm not going for centimeters. I'll discuss why later.
	Now we've got 30 times a million and in science math that's 3 times
10 to the 7th square meters. A gigabyte is 1 times 10 to the 9th.
	Now we drag out the calculator. We divide the power by the area to
get the power per area. The power is 10 times 10 to the ninth watts
			the area  is  3 times 10 to the seventh square
meters

So the power per area is 3.33 times 10 to the second watts. That's about
333 watts per square meter. 

	Another down and dirty approximation...a square meter is about the
area of 9 little microwave ovens. So you're power per microwave oven area
would be about 37 watts. That doesn't sound so bad does it? (sarcasm)

	It would add about 37 watts to an area about the size of your head
though. And we all know how fat and water absorbs microwaves. (Just joking)
{Or am I? :(   }
	
	I don't think anyone is seriously proposing using solar collectors
in space anymore. Maybe later, better technology. Right now, given the
radiation up there, the mechanical hazards, and the cost of putting them
panels up there and maintaining them...it isn't even sane let alone
feasible. 
	
Yours, Jackie                            Physicists are allowed to use
approximations, :)

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