zben@umcp-cs.UUCP (10/28/83)
[From the virtual flamethrower of ZBEN] The most cogent argument I have heard against the satellite solar power idea is the resultant increase in heat pollution. Thats right. Those big solar panels out there are tantamount to increasing the absorption of solar power by the earth. The fact that it is organized as electricity and will be used to do useful work is only a local eddy; eventually every watt we pull down from space will (by the 2nd law of thermo) be released as heat upon the earth. In the Larry Niven "Known Space" series the Pierson's Puppeteers solved the problem in a unique way: they moved their planet to another orbit farther from its sun. I think the solar satellites are yet another government give-away to the high-tech aerospace industries. We have plenty of desert right here on earth, with the advantage of breathable air for the repairmen. Even if we set up the collectors in the desert, it will have a second-order effect on local heat flows. It would be equivalent to transporting some amount of death valley's heat right into downtown L.A.... zben ...seismo!umcp-cs!zben zben@umd2.ARPA
henry@utzoo.UUCP (Henry Spencer) (11/01/83)
Setting up solar panels in the desert is *much worse* than solar power
satellites as far as heat pollution goes. Why? Because solar cells
are quite inefficient (15% is very good performance!) and the solar
radiation they absorb would otherwise be reflected and re-radiated right
back out into space! Solar power satellites put the inefficient part
of the process out in space, where it doesn't contribute to Earth's
heat input. The net result is that power-satellite power adds rather
less heat to Earth than ground-based solar power. In fact, power
satellites add less heat to Earth per kilowatt of useful power than
almost any other power-generation system. Strange but true.
--
Henry Spencer @ U of Toronto Zoology
{allegra,ihnp4,linus,decvax}!utzoo!henryeder@ssc-vax.UUCP (Dani Eder) (11/01/83)
1 November 1983
I'd like to make two comments about the 'heat problem'. First, it is true
that the energy finally produced by an SPS is eventually converted to waste
heat, ALL useful work produces heat as the final byproduct. The advanteges
of SPS are that there is less waste heat initially, and it can be compensated
for.
In a conventional power plant, only about 33% of the prime mover power
is converted into electricity. Thus three times as much heat is produced as
useful energy. With an SPS, the added flux in microwaves can be compensated
for because the recieving antenna or 'rectenna' on the ground is made of
metal, rather than ordinary earth. The net result is .4 units of heat for
each unit of useful energy with an SPS, versus 3 units of heat / unit useful
energy with conventional sources.
Second, with ground based solar, either thermal or photovoltaic, you are
covering the ground with a very dark surface, thus increasing the absorbtion
of solar energy and causing the very problem you speak of.
Dani Eder
ssc-vax!eder
Boeing Aerospace
a
of er,dietz%usc-cse%USC-ECL%SRI-NIC@sri-unix.UUCP (11/03/83)
In reply to ZBEN's "cogent" argument against SPS: [ZBEN] The most cogent argument I have heard against the satellite solar power idea is the resultant increase in heat pollution. Thats right. Those big solar panels out there are tantamount to increasing the absorption of solar power by the earth. I thought I addressed this issue in one of my messages. Space solar power actually has comparatively low thermal pollution, compared to other energy sources. The reason is quite simple: the thermodynamically limited part of the light-to-electricity conversion process is done in orbit. The SPS radiates its waste heat INTO SPACE, not into a cooling tower (or whatever) on earth. The power transmission process (microwaves & power lines) dissipates into the biosphere as heat maybe 10-15% of the energy delivered to the user. In contrast, ground based thermal electrical generators (fossil fuel, fission, fusion, thermal solar, geothermal) waste at least three fifths of the produced energy as heat (150% of the delivered electrical power). Ground based solar is also a thermal polluter. Deserts are fairly reflective (~35% of the energy is reflected), so much of the sunlight hitting them goes right back into space. A power plant, be it a power-tower or a solar cell array, will decrease this figure to about 5%. The result is that ground based solar puts about 110% of the delivered power into useless waste heat (over and above what the desert would have absorbed). Hardly a "second order" effect! The only electricity sources I can think of that produce less thermal pollution than SPS are wind and hydroelectric -- but I wouldn't be suprised to find that if you extracted enough energy from the wind temperature differences between locations on the Earth's surface would increase. In any case wind and hydro can't supply more than a small fraction of the energy we'll need. If you're still worried about thermal effects of SPS, you can make the rectenna reflective (polished sheet aluminum, say). The intensity of the microwave beam is only 1/2 that of sunlight (at the center; at the edges it's much less), so this looks feasible. Beyond that, you can move manufacturing into orbit (assuming delivering the goods to earth doesn't dissipate too much energy in the atmosphere). After that, you can move consumption into orbit -- space colonies! [ZBEN] I think the solar satellites are yet another government give-away to the high-tech aerospace industries. We have plenty of desert right here on earth, with the advantage of breathable air for the repairmen. But ground based solar can't supply more than about 5% of the nation's electricity needs. Beyond that, you need to solve the problem of large scale electrical energy storage -- a very hard problem. And it isn't completely obvious that ground based solar is cheaper than space based. A large concentrator mirror could conceivably be easier to build, aim and maintain in orbit. It could certainly be far less massive than ground based heliostat arrays. Paul Dietz (dietz@usc-ecla)
zben@umcp-cs.UUCP (11/04/83)
[..] Most of the refutations of my argument have been of the form: "the Earth is sooooo big (usually followed by some numbers in exponential notation) that it couldn't possibly be a significant effect". Some of the others are worth more thought. What makes you think that, given a few sites that seem to be feasable, every podunk community and every third world nation won't want to install their own version? We seem to be very good as a species at scaling things up to the point the original assumptions become meaningless. There was a general feeling just a few years ago that the Earth was "soooo big" that burning fossil fuel could not possibly shift things. Now the newspapers are full of stories that the greenhouse effect is on the way and that there is nothing that we can do to stop it. I don't want to see that happening anew... How many aerosol spray cans does it take to bring burning vengance from ultraviolet radiation? D*mmit, there *are* no "quick fixes". Just fools searching for them. That includes fusion, satellite solar, oil-from-coal, and just about anything but conservation and appropriate technology. Unfortunately these aren't sexy enough to motivate spoiled techno whiz-kids... Santoyana said that those who didn't understand the mistakes of the past were doomed to repeat them. Don't y'all wish I wuz around when fission power was the latest greatest "quick fix"? (A friend of the Devil is a friend of mine...) Ben Cranston ...seismo!umcp-cs!zben zben@umd2.ARPA
betsy@dartvax.UUCP (11/07/83)
I quite agree: there ARE no quick fixes. Furthermore, there are no permanent fixes, even including conservation and 'appropriate technology'. (I suspect my definition of 'appropriate' may be broader than yours, but let that pass.) The best we can hope for from any technology is to move the 'threshold of catastrophe' farther away. Coal mines and woodstoves are having visible,tangible effects on our environment right now, while satellite power may pose threats a hundred years away. Personally, I'll take the hundred-year threat over the this-week threat any day. You may call this 'mortgaging our posterity's futures'; I call it 'trusting to our posterity's intelligence'. Betsy Perry decvax!dartvax!betsy
mcewan@uiucdcs.UUCP (mcewan ) (11/08/83)
#R:umcp-cs:-340800:uiucdcs:12700044:000:628
uiucdcs!mcewan Nov 6 17:33:00 1983
D*mmit, there *are* no "quick fixes". Just fools searching for them.
That includes fusion, satellite solar, oil-from-coal, and just about
anything but conservation and appropriate technology.
English translation: *MY* solution is the only solution, and anyone who
disagrees is just not as {intelligent,enlightened,omniscient} as I, so
don't waste your time trying to think of alternatives, and don't listen
to those fools who think there may be another alternative.
Considering your grasp of the effects of SPS as demonstrated by your earlier
article, I think I'll hear out the fools.
Scott McEwan
uiucdcs!mcewandswankii@uok.UUCP (11/14/83)
#R:umcp-cs:-340800:uok:7900001:000:550 uok!dswankii Nov 10 14:52:00 1983 Do areas like, say, Death Valley reflect energy (heat) in such a way that it can escape into space? Obviously light can get out else you couldn't see the land masses from space but heat is a much longer wave than visible light. My reason for asking is: if sunlight comes in a window, more energy comes in than escapes by reflection. If this is true in the case of Death Valley then you wouldn't increase the heat load of the planet. Please; no flames. If I'm wrong send me a letter telling me why. David Swank II ctvax!uokvax!uok!dswankii