eli@spdcc.COM (Steve Elias) (04/02/88)
sheesh. you guys are missing my point regarding efficiency and solar power satellites. pardon me for not being precise enough, and for missing John's point regarding 'fixed power consumption.' the point is that 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! this is true not for 'fixed power consumption', of course. it is true for 'fixed power transmission from the satellite'. at least one reader would like to see Drake's notes on the subject; i'll be picking them up this weekend. if anyone wants to send him curses and slurs, i'll post his email address. (fat chance!).
jfc@athena.mit.edu (John F Carr) (04/03/88)
In article <768@spdcc.COM> eli@spdcc.COM (Steve Elias) writes:
: sheesh. you guys are missing my point regarding efficiency and solar
: power satellites. pardon me for not being precise enough, and for
: missing John's point regarding 'fixed power consumption.'
: the point is that 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!
But the more efficient the ground based part, the less power need be sent
down.
: this is true not for 'fixed power consumption', of course.
: it is true for 'fixed power transmission from the satellite'.
You are missing the point: SPS will not be put up just for fun; no one
will say, "I want to launch a 500MW SPS, whether or not anyone will buy
the power." We will only use SPS if there is a demand for the power.
When demand is predicted to exceed supply, there are only two choices:
increase supply or reduce demand. Decreasing demand is not practical,
and may not be possible. So, we are left with the decision, "How do we
generate the extra power?" The amount of heat which will be generated
to produce this power is P/eff. The power consumption sets a lower bound
on heat, but efficiency is important. (Assuming there is agreement that
demand for power will increase) we must assume fixed generating capacity,
and argue the relative merits of different systems. How are earth-based
systems better? I believe that, considering only thermal and poluution
problems, they are not. Building a heat engine on the earth will also
add heat to the environment that would not otherwise be present.
John Carr "No one wants to make a terrible choice
jfc@athena.mit.edu On the price of being free" -- Neil Peartpokey@well.UUCP (Jef Poskanzer) (04/04/88)
In the referenced message, eli@spdcc.COM (Steve Elias) wrote: }sheesh. you guys are missing my point regarding efficiency and solar }power satellites. Sheesh. Does this guy have a lot of nerve or what? He's just finished making a 99.9% fool of himself over the thermal balance issue, and now he wants us to believe: A) that eight intelligent people (John F Carr, G.Gleason, Jef Poskanzer, James W. Meritt, Karl Owen / Wayne Throop, Michael Friedman, T. Dave Hudson, and Ed Kaulakis) somehow don't understand something that one fool (Steve Elias) does understand; and B) that the efficiency issue matters at all, since the entire thermal balance issue has proven to be bullshit. Tell ya what, Stevie Baby. You go right on believing that ten one-gigawatt coal-fired power plants, with 30% thermal efficiency, heat up the Earth less than one ten-gigawatt rectenna with 90% efficiency. You'll be WRONG, but then Ronald Reagan is wrong a lot too, and he gets paid $200,000 / year. Meanwhile, the rest of us are going to IGNORE you. By the way Stevie, I think I've figured out why you get so pissed off whenever anyone displays intellect superior to yours. It's because it happens so often! It must get really tiresome, eh? Poor Baby. --- Jef Jef Poskanzer jef@lbl-rtsg.arpa ...well!pokey "Not only do I not suffer fools gladly, I don't suffer them AT ALL." -- Jerry Pournelle
eli@spdcc.COM (Steve Elias) (04/04/88)
John -- i'm not missing the points you make below. though maybe we should consult with Jef in order to see what my beliefs are. dealing with increased power demand is the crux of the issue... 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. i believe i am accurately stating this theory as i learned it from Frank Drake. if one accepts the premise that we do have the potential to need so much power such that many high capacity satellites would be necessary -- we do have to argue about the effects of this increase in solar flux. it may be a small percentage increase -- but it will occur continuously. this leads me to reiterate my question about the atmosphere's reaction to long term increases in solar flux... we've been told by an atmospheric scientist that the atmosphere reacts quickly to localized increases in thermal energy. i don't think there is one 'proven theory' as to how it would react to a long term global increase in solar flux. In article <4288@bloom-beacon.MIT.EDU> jfc@athena.mit.edu (John F Carr) writes: >You are missing the point: SPS will not be put up just for fun; no one >will say, "I want to launch a 500MW SPS, whether or not anyone will buy >the power." We will only use SPS if there is a demand for the power. >When demand is predicted to exceed supply, there are only two choices: >increase supply or reduce demand. Decreasing demand is not practical, >and may not be possible. So, we are left with the decision, "How do we >generate the extra power?" The amount of heat which will be generated >to produce this power is P/eff. The power consumption sets a lower bound >on heat, but efficiency is important. (Assuming there is agreement that >demand for power will increase) we must assume fixed generating capacity, >and argue the relative merits of different systems. How are earth-based >systems better? I believe that, considering only thermal and poluution >problems, they are not. Building a heat engine on the earth will also >add heat to the environment that would not otherwise be present. heat engines which use energy already present in the atmosphere or elsewhere on earth would not add net heat to the environment... agreed? i'm not saying these power sources are necessarily the 'best' -- just that they do exist...
leonard@bucket.UUCP (Leonard Erickson) (04/05/88)
In article <768@spdcc.COM> eli@spdcc.COM (Steve Elias) writes:
<sheesh. you guys are missing my point regarding efficiency and solar
<power satellites. pardon me for not being precise enough, and for
<missing John's point regarding 'fixed power consumption.'
<
<the point is that 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!
<
<this is true not for 'fixed power consumption', of course.
<it is true for 'fixed power transmission from the satellite'.
The efficiency of the ground station matters because we'll be dealing with
the *useful* energy recieved. Thus a higher efficiency means a better
ratio of usable power to (initial) waste which means a smaller total
heat input.
Heres a list of power sources and whether or not they "add" heat that
would not otherwise be present.
coal adds
oiil adds
natural gas adds
wood does not add appreciably
nuclear fission adds
nuclear fusion adds
ground based solar adds
space based solar adds
hydroelectric does not add
wind does not add
tide does not add
We are near the limits for hydro power (unless you wish to totally mess up
river systems. Wind is far too undepenable. And tidal power on any large scale
will have massive ecological consquences.
Wood was singled out from the other fuels because the energy it releases
was accumulated *recently* and thus probably won't have *too* great an effect.
So the *sole* issue for all the practical power sources is how to get the
most useful power with the least (initial) waste heat. For all the sources
that are listed as adding, space-based solar would appear to add the least
"extra" heat. (to my knowlegde none of the others even come close to a
9 to 1 ratoi (ie 90% of the heat is useful))
--
Leonard Erickson ...!tektronix!reed!percival!bucket!leonard
CIS: [70465,203]
"I used to be a hacker. Now I'm a 'microcomputer specialist'.
You know... I'd rather be a hacker."sw@whuts.UUCP (WARMINK) (04/05/88)
Just a thought: how much energy does it take to put up one of these solar power satellites? - extracting raw materials (satellite + lauch vehicle) - manufacturing - transportation - fuel(s) for launch vehicle - heating / airconditioning of working enviroments How long wil it take to re-coup this initial energy use? This is only a half :-) thought... -- ------------------------------------------------------------------------------ "We demand rigidly defined areas of | Stuart Warmink, APT UK Ltd. doubt and uncertainty" (Vroomfondel) | <ihnp4>!whuts!sw -----------> My opinions are not necessarily those of APT UK Ltd. <-----------
throopw@xyzzy.UUCP (Wayne A. Throop) (04/06/88)
> 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
throopw@xyzzy.UUCP (Wayne A. Throop) (04/06/88)
> 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. 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. 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. 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. -- 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
throopw@xyzzy.UUCP (Wayne A. Throop) (04/06/88)
> eli@spdcc.COM (Steve Elias) > heat engines which use energy already present in the atmosphere > or elsewhere on earth would not add net heat to the environment... > agreed? Not agreed. Slightly modify it and I'll agree: Heat engines which use *heat* energy (or energy already destined to become heat) already present in the atmosphere or elsewhere on earth would not add net heat to the environment... but that would rule out petrochemical, nuclear, and essentially all ground-based solar power schemes (including biomass) as well as space-based solar power schemes. It would leave wind, tide, thermocline, perhaps some restricted forms of geothermal power and the like. But EVEN SO, the use of these forms of power to the point where thermal pollution is a significant worldwide threat would imply a vast, vast increase in industrial activity on earth, which would have deadly effects far before the thermal effects of the competition would be dangerous. Basically, thermal pollution is the wrong thing to worry about first. (Not that it shouldn't be worried about at all, mind you...) -- 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
leonard@bucket.UUCP (Leonard Erickson) (04/06/88)
In article <774@spdcc.COM> eli@spdcc.COM (Steve Elias) writes:
<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. i believe i am accurately
<stating this theory as i learned it from Frank Drake.
As others have pointed out, this level of power demand is *totally*
unreasonable for a *long* time to come. And I rather expect that most
of the industry that would demand such levels of power would have moved
into space by then anyway...
<>You are missing the point: SPS will not be put up just for fun; no one
<>will say, "I want to launch a 500MW SPS, whether or not anyone will buy
<>the power." We will only use SPS if there is a demand for the power.
<>When demand is predicted to exceed supply, there are only two choices:
<>increase supply or reduce demand. Decreasing demand is not practical,
<>and may not be possible. So, we are left with the decision, "How do we
<>generate the extra power?" The amount of heat which will be generated
<>to produce this power is P/eff. The power consumption sets a lower bound
<>on heat, but efficiency is important. (Assuming there is agreement that
<>demand for power will increase) we must assume fixed generating capacity,
<>and argue the relative merits of different systems. How are earth-based
<>systems better? I believe that, considering only thermal and poluution
<>problems, they are not. Building a heat engine on the earth will also
<>add heat to the environment that would not otherwise be present.
<
< heat engines which use energy already present in the atmosphere
< or elsewhere on earth would not add net heat to the environment...
<
< agreed? i'm not saying these power sources are necessarily the
< 'best' -- just that they do exist...
ANY heat engine has to work on a temperature *difference* at there are
rather strict limits on how much of that difference can be converted
to power. And if we need power at the levels you are worried about (1% of
the solar flux!!!), I fail to see where you will find the temperature
differences with out causing a *major* ecological disaster!
If you are talking geothermal, you *will* be adding heat not otherwise
present ON THE SURFACE OF THE EARTH (you'd be cooling down the lower
layers of the crust, but *that* won't affect climate, a 50 to 100 degree
Celsius rise in surface temperature of an area will!)
If you are thinking of the systems to use the temperature difference
between the surface of the ocean and the depths, at the power levels
you are thinking of you will quite likely cause a change in ocean
current patterns that will make El Nino look trivial.
--
Leonard Erickson ...!tektronix!reed!percival!bucket!leonard
CIS: [70465,203]
"I used to be a hacker. Now I'm a 'microcomputer specialist'.
You know... I'd rather be a hacker."eli@spdcc.COM (Steve Elias) (04/06/88)
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...
jfc@athena.mit.edu (John F Carr) (04/07/88)
In article <789@spdcc.COM> eli@spdcc.COM (Steve Elias) writes: >>> eli@spdcc.COM (Steve Elias) ::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. The energy from the sun was less in the past. More on this below. : 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... The Sun's luminosity has been increasing for the last 4 billion years. It has increased about 30% in this time. In addition to the slow increase, there are other, shorter period variations. There is a small variation associated with sunspots and random variation on a short timescale. Changes in the solar constant over longer periods, hundreds or thousands of years, are suspected but not confirmed (I am uncertain on the exact state of these theories; records of solar flux gdo not go back as far as temperature records; if the "little ice age" was a decrease in solar luminosity then there are changes of a few percent over a few hundred years). More important are the long period changes in the earth's orbit (periods of 10,000-30,000 years), one effect of which is the ice ages. The fact that the sun was much less luminous in the past has led to a theory (see Feb 88 Scientific American) that planets have a negative feedback controlling carbon dioxide level which tends to stabilize temperature where water is liquid. The time scale of the feedback mechanism is millions of years. Forests control CO2 on a shorter timescale, but are not sufficient to control even the present human output. For a temperature change to cause a runaway greenhouse effect would require a very long time; long enough to boil the oceans and release CO2 trapped in rock. No such delay is needed for CO2, which has already raised the temperature of the earth by 1-2 degrees (see Tuesday, Mar 29 (?) New York TImes). The issue is not whether SPS will be a problem. If we consume 1% of the solar flux worth of power on earth we will generate at least that much heat by any method (since the thermally harmless methods can not provide that much). The decisions which will eventually have to be made, if we continue our expansion, are: do we want heavy industries on Earth? if so, can we live with a few degrees increase in temperature? if we can't, how do we cool the earth? (a society which consumes so much energy should not have too much trouble building machines large enough to cool the earth) John Carr "No one wants to make a terrible choice jfc@athena.mit.edu On the price of being free" -- Neil Peart
eder@ssc-vax.UUCP (Dani Eder) (04/07/88)
In article <4086@whuts.UUCP>, sw@whuts.UUCP (WARMINK) writes: > Just a thought: how much energy does it take to put up one of these > solar power satellites? > - extracting raw materials (satellite + lauch vehicle) > - manufacturing > - transportation > - fuel(s) for launch vehicle > - heating / airconditioning of working enviroments > > How long wil it take to re-coup this initial energy use? > This is only a half :-) thought... > In the study of SPS made from Lunar Materials that I worked on, we found that 99% of the mass of an SPS could be made from lunar materials, and the other 1% was complex enough or had such rare-on-the-Moon materils that it was better to bring it from the Earth. You also have to launch 2% of the SPS mass in mining equipment and space factories to manufacture the other 99%. The net result is that 3% of the SPS mass must be launched from the Earth. The extraction cost of the parts launched from Earth I cannot give you a number for. A lot of that is complex equipment, like computers. The launch cost (in energy) is about 100 MegaJoules/kg for propellant. This exceeds the energy used in making metals by one to two orders of magnitude (kind of fuzzy number there). Let us assume that it takes 200 MJ per kilogram of payload to do everything on the ground we have to do. An SPS (large economy size - 5,000 MW) masses 100,000 metric tons Therefore 3000 tons (3,000,000 kg) must be launched. If we assume that 200 MJ are required for each kg, then 600 terajoules are required on Earth to launch the SPS. At a power output of 5 gigawatts, the energy payback takes 120,000 seconds, or 1.5 days. This neglects the considerable energy cost of building the receiving antenna on the ground, but memory fails at this point as to the mass of the antenna. Dani Eder/Boeing/Space Station Program ssc-vax!eder
throopw@xyzzy.UUCP (Wayne A. Throop) (04/08/88)
>, >>> eli@spdcc.COM (Steve Elias) >! throopw@xyzzy.UUCP (Wayne A. Throop) >!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%. But the fact that SPS is more efficent thermally puts the figure back up quite a lot. But I'm sure we can agree that we are talking at least a thousand times, and probably closer to ten thousand times, the current industrial activity. And again, this much industrial activity will totally destroy the biosphere long before thermal effects become important. > so 150 years is a bit of an overstatement, even with a ten year > doubling time for power needs. It very likely isn't much less than a century. (Also note that power needs are currently not doubling anywhere near as rapidly as 10 years, near as I can tell from the tables I've consulted.) > !And in thinking about this, it is well to remember that the sun is, > !itself, about 3% variable > 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? I beleive that good old Sol can vary by 3 or so percent its power output over very long periods of time, and has done so in the past. There is some evidence that there is a feedback loop that keeps temperature (relatively) stable over the long term in spite of at least this much, and maybe more, solar variation, but there is some evidence that we are near the limit of breaking the loop if the sun heats up much more (or anything heats up an equivalent amount, for that matter). The feedback loop is: when things get too cold, the biosphere dies back, carbon dioxide accumulates, greenhouse effect, earth heats back up. When earth gets "too" hot, tropical and aquatic bioshpere expands, plankton & rain forrests convert excess carbon dioxide to oxygen, opens the shutters on the greenhouse, earth cools back off. Unfortunately, we are in a warming trend, plants have pumped about as much CO2 out as they can, and we are tending to add more despite what the biosphere can do. Potential bad news. (Above hypothesis from memory and severely condensed, from a NOVA episode entitled "The Gaia Effect", if memory serves.) But again, thermal pollution is a very small factor in this, not particulary significant in the face of the other effects, and further, SPS would be a smaller thermal polluter than almost any alternative. > 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... True for albedo, but the CO2 effect is on the rate at which waste heat escapes to space by radiation. This would get rid of excess heat whatever the source. (If it works at all.) > i still hope to locate Frank Drake's notes on this subject. I would be very, very interested. I still don't beleive that thermal pollution is the most troublesome effect, and even if I did, I don't beleive that SPS is worse than, for example, ground-based solar power. So why Drake might single out SPS as environmentally dangerous is a mystery to me, one I'm currious to see a little more about. -- You know, when it's hot like this -- you know what I do? I keep my undies in the icebox. --- Marilyn Monroe in "The Seven Year Itch" -- Wayne Throop <the-known-world>!mcnc!rti!xyzzy!throopw
jwm@stdc.jhuapl.edu (James W. Meritt) (04/08/88)
As long as we are dreaming some incredible power requirements, any
comments on what the heck we will use so much FOR? It seems we are
worrying about the waste heat from enough raw power to lift almost
everything off the planet! (True, leaving something like venus.....
May be the reason for leaving?)
How much power would be required to keep us cool? For instance, heat
pump it to gamma-hot radiators? Move a few cubit miles of dust to a
stable orbit between us & sol? Move the earth out to a cooler location?
As long as we are dreaming, dream BIG!!!!
Disclaimer: Individuals have opinions, organizations have policy.
Therefore, these opinions are mine and not any organizations!
Q.E.D.
jwm@aplvax.jhuapl.edu 128.244.65.5eli@spdcc.COM (Steve Elias) (04/08/88)
In article <758@xyzzy.UUCP> throopw@xyzzy.UUCP (Wayne A. Throop) writes: >>, >>> eli@spdcc.COM (Steve Elias) >But the fact that SPS is more efficent thermally puts the figure back up >quite a lot. But I'm sure we can agree that we are talking at least a >thousand times, and probably closer to ten thousand times, the current >industrial activity. And again, this much industrial activity will >totally destroy the biosphere long before thermal effects become >important. although it has been demonstrated that it would take thousands of times our present industrial activity to create power needs that equal the solar flux -- i believe that thermal considerations will become important long before that point; at a level !only! hundreds of times where we are now... clearly, needs equal to the solar flux would be disastrous. i suspect we would see some major negative environmental effects before then. >But again, thermal pollution is a very small factor in this, not >particulary significant in the face of the other effects, and further, >SPS would be a smaller thermal polluter than almost any alternative. thanks for all that info on biosphere feedback effects ! perhaps SPS is less of a thermal polluter than some of the more 'conventional' power generation schemes. there seem to be a couple of arguments against my points about thermal pollution, especially with regards to SPS. 1 -- thermal pollution is not important since power needs will never approach levels of hundreds or of times present needs. i understand that even hundreds of times present needs would not be more than a few percent of solar flux. i claim that such power needs are forseeable, if we manage to stick around. (perhaps folks here would like to see me take a one way trip to rec.arts.sf-lovers...) 2 -- SPS is not as much of a thermal offender as some other power sources. perhaps i am being unfairly harsh on SPS -- most current power sources could put us in a rather toasty boat if we expanded them to hundreds of times their present capacity, even those which don't produce CO2. i think that SPS would be a poor way to spend R&D $$. lots should go towards generation schemes which produce no CO2 and no thermal imbalance. humankind has got to learn to leave less of a footprint on the planet, as we continue to grow -- or we'll squish the earth one way or another. >> i still hope to locate Frank Drake's notes on this subject. > >I would be very, very interested. I still don't beleive that thermal >pollution is the most troublesome effect, and even if I did, I don't >beleive that SPS is worse than, for example, ground-based solar power. >So why Drake might single out SPS as environmentally dangerous is a >mystery to me, one I'm currious to see a little more about. a friend has located the notes... apparently there aren't any handy factors of ten to bolster my prejudice against SPS. i'll see the notes myself this weekend, and will summarize interesting sections. the notes are from a class i took in 1983... i don't think that Drake or myself would contend that SPS is thermally worse than ground based solar power... bye!
throopw@xyzzy.UUCP (Wayne A. Throop) (04/14/88)
> eli@spdcc.COM (Steve Elias) > i understand that even hundreds of times present needs would not > be more than a few percent of solar flux. Not quite. Even from 1 to 10 thousand (not hundred) times our present needs is only one percent of the solar flux. > humankind has got to learn to leave less of a footprint on the > planet, SPS seems a delightful way to do this, since the investment in them need not be wasted as industrial capacity is moved towards space. That is, if thermal effects dictate moving some of our industrial capacity, simply point the SPS at the new location, or move the industry onto the satellite. Any capacity built on the ground would be much harder to retarget. -- A is for Atom. They are all so small, That we have not really seen any at all. B is for Bomb. They are much bigger. So, mister, you better keep off of the trigger. --- Edward Teller -- Wayne Throop <the-known-world>!mcnc!rti!xyzzy!throopw