Orbiting solar panels' day may be near

[Lionel Mandrake]

Source: Los Angeles Times

A new federal study released Wednesday concluded that continued increases in oil prices may finally make the generation of solar power in orbit economically competitive. The orbiting power plants would reduce the nation's dependence on imported oil and help reduce the production of carbon dioxide that is contributing to global warming, according to the report led by the National Security Space Office, part of the Department of Defense.

"This is a solution for all mankind," said former astronaut Buzz Aldrin, chairman of the spaceflight advocacy group, ShareSpace Foundation. Aldrin joined a group of other space advocacy organizations to unveil the report in Washington.

Since the Space Age began 50 years ago, scientists have dreamed of launching acres of photovoltaic cells into orbit and beaming the electricity electromagnetically to Earth's surface but have stumbled over the project's high cost and the technical difficulties.

The report estimated that in a single year, satellites in a continuously sunlit orbit could generate an amount of energy nearly equivalent to all of the energy available in the world's oil reserves.

Read more: http://www.latimes.com/news/printedition/asection/la-sci-spacesolar11oct11,1,336119.story?coll=la-news-a_section

---

Buzz Aldrin et al. have the wrong stuff this time. They are ignoring a few inconvenient truths:

1. There is no such thing as a continuously sunlit orbit.

2. Even if there were, it wouldn't help.

3. The least impractical orbit for this hair-brained scheme (see comment #5) would be sunlit about half the time.

4. The power would have to be be sent to the earth as microwaves, which would spread out to cover a large area of the earth's surface. That entire area could only be used as a receiving antenna. Anyone entering the area would be cooked.

5. To minimize the area of the receiving antenna, the satellites would have to be in low earth orbit, where they orbit the earth in about 90 minutes. Each power generating satellite could transmit power to a particular antenna for only a few minutes during each 90 minute orbit.

6. To ensure that the satellite would pass over the receiving station during every orbit, the station would have to be either on the equator or at one of the poles.

7. Most of the demand for electricity is at mid-latitudes.

8. Therefore, the electricity would have to be transported over long distances in locations where construction and maintenance would be difficult, expensive, and not under any one nation's control.

[jpak]

1. Plus, another excuse to militarize space and justify their existence

"We have to protect our vital space energy assets..."

[Crayson]

62. A microwave ray gun in space...

NO THANKS!
And that's nothing else what was described.

[glowing]

2. Doesn't this tie into the HAARP program that they are messing with..

[Lionel Mandrake]

15. I don't see the connection.

For info on HAARP, see: http://en.wikipedia.org/wiki/High_Frequency_Active_Auroral_Research_Program

[glowing]

17. Transmitting technology....

[midnight armadillo]

41. No, not in the slightest

HAARP is a high altitude heater. Why it has this bizarre pseudoscience reputation is beyond me.

[Orsino]

3. LEO would also get around the inverse-square loss...

...that would greatly reduce the efficiency of placing them in an otherwise-convenient geosynchronous orbit twenty-two thousand miles higher.

[ewagner]

8. Yep...

Inverse square law is a stumbling block... :hi:

[Orsino]

16. I gotta wonder...

...what's so great about Earth orbit? Wouldn't it be a hell of a lot cheaper to build your solar farm on the frickin' ground? Aren't they a bit easier to maintain there?

[ewagner]

23. I'd say so...

plus there are added benefits...

a) sunlight converted directly to usable electricity w/o an interim step
b) easier to feed directly into a grid.

and what else?

what else?

Oh yeah....launching satellites is FRIGGIN EXPENSIVE!

[Mika]

82. Ya think the Chinese would give a discount on launching satellites?

Maybe Bongwater could get the contract.

[pitohui]

39. solar panels on the ground destroy habitat

since the oceans are all but dead, maybe if there was a way to float them on the oceans i'd be for it

and i'm certainly for solar panels on every rooftop since that's dead habitat anyway

solar panels on the ground are just as destructive or more destructive than landfills or mines or anything else that pretty much completely destroys the habitat for wild plants and animals -- believe you me, we humans won't give up a scrap of acreage of farmland or office space in manhattan for a solar farm, it will be our wilderness that is sacrificed -- i have personally only seen large solar panels on the ground in nevada/arizona

[TheWraith]

77. That too. People underestimate the amount of area solar cells would require.

To supply the entire United States' energy, you'd need over 70,000 square miles of solar cells and associated support facilities, which is about two thirds the size of Nevada.

I will just say, the oceans are anything but dead--we may be fishing them out, but there are a lot of other things out there that we don't eat.

[LongTomH]

65. Terrestrial Solar Power has its limitations.

Orsino asks:

...what's so great about Earth orbit? Wouldn't it be a hell of a lot cheaper to build your solar farm on the frickin' ground? Aren't they a bit easier to maintain there?

Solar power on earth is limited in several ways:

1. The day-night cycle. This gets to be more of a problem during long winter nights.
   
2. Cloud cover. Solar photovoltaic cells can use even diffuse light coming through clouds; but, the clouds do attenuate the amount of energy available.
   
3. Solar angle: This is rarely mentioned; but, it's more of a problem than you'd think. A solar panel puts out it's greatest electrical output when the sun is shining directly into it; the output is greatly reduced when the sunlight comes in at a higher angle, during the morning and afternoon.
   
4. Current solar cells absorb most of the incoming sunlight and convert only about 10-15% of the incoming sunlight into electricity. The rest becomes heat. It is possible to get greater efficiencies; but, the problem doesn't go away. With SPS, only about 5% of the microwave energy becomes heat.
   

[TheWraith]

76. Solar power is about twenty five times more plentiful in space.

The Earth's atmosphere absorbs most of the Sun's energy. Be glad of that--it's what produces heat and wind. But when you're talking about solar cells being maybe 12-15% efficient, you need every advantage you can get. But in space you're talking about a kilowatt per square meter, versus only 200 watts on the surface. Plus, when you don't have to deal with the day/night cycle, that increases productivity by about another five fold.

Unfortunately, building and launching giant solar arrays isn't cost effective, even if you managed to get around the implementation issues of transmitting it back to the Earth.

[scubadude]

71. The inverse square law does not apply to beamed signals.

It applies to point sources that radiate signal equally in all directions.

The perfect example of a beamed source is the laser. It's power is almost
linear across large distances of space. In other words the beam doesn't
spread. At the distances required loss would be negligible.

As far as continuously sunlit orbits they exist. As a matter of fact SOHO,
orbits in ome: http://sohowww.nascom.nasa.gov/

Although this orbit would not be practical for power generation due to it's distance,
near earth orbits are practical and are shadow free almost all the time.

To clear up some misconceptions see: http://en.wikipedia.org/wiki/Space_solar_power

Scuba

[monktonman]

4. How about turning the lights out more often?

Maybe riding the train or bus every once in awhile?
I love how we're all trying to come up with new ways to
solve our energy crisis and blabbing on and on about new emerging
technologies and yadda yadda.
Heres one for you...its called THE FINGER.
Use it to shut the frickin lights off.

[f the letter]

29. ha exactly

god forbid we reduce consumption to help with the lack of energy to consume

[mainegreen]

5. Or, how about solar panels on roofs?

Being that hauling them up a ladder is much cheaper than launching them into space.

[daleo]

9. It would be harder for huge corporations to control the process

I think that's the main point of these over-engineered mega-project ideas. It concentrates power (electrical and political) in a small number of owners.

[eppur_se_muova]

18. DING DING DING We have a winner! And our friendly Defense Forces would be ...

always handy to assist the folks maintaining these satellites, just in case the microwave beam needed a little "retargeting" or something.

[TheWraith]

78. No, it's not. It's actually trying to make solar practical.

It isn't on the ground, so people talk about the possibility of putting it in space where you could get ten or twenty times the productivity.

[KansDem]

32. At least put solar panels on the roofs of automobiles...

Use solar power to power the automobile's air conditioner. That way, the engine should run more efficiently since it would not be powering the A.C.

And when are you most likely to use the A.C.? When the sun's out!

[Lionel Mandrake]

35. Your idea is worth exploring, but

1. Since the A/C compressor cycles on and off, it would make more sense to use the solar array to charge the battery (continuously) and use conventional means to run the A/C.

2. Unless it was streamlined and made part of the body of the car, the solar array would increase drag at high speed, causing a net loss of power. It would be up to the manufacturers to design the solar array into the car.

[skids]

74. Aren't AC compressors mechanically coupled?

...I mean, other than in the Prius.

As far as linked solar/AC goes it's been pointed out that using panels to run thermoelectric seat coolers would be the way forward.

But personally I'm more for an integrated fold-out array for stationary parking lot use. For an EV, the average workday commute is within the ability of an array that fits in a parking space to generate daily. Of course hookups would still be needed for cloudy days.

Plus it keeps the car shaded :-). The Prius looks almost as if a roof panel on tracks could be built to cover either the front or back window, but you're right about aerodynamics, because they are doing all sorts of fancy things with vortexes these days. Look at the odd bends on the roof of the current prius -- those are probably very carefully engineered.

However panels are becoming very flexible these days. To boot the canadian who strapped flat panels on his 02 prius actually got better mileage even with the extra drag, so there's potential there.

[CJCRANE]

81. I recently realized

something that may seem obvious - if cars weren't built out of metal maybe they wouldn't heat up so easily. I don't know the cost implications but surely replacing as many panels as possible with carbon fibre or some other less conductive material would prevent cars from turning into solar ovens in hot climates.

[pitohui]

40. i'm very much in favor of a rooftop distributed method

by having small rooftop panels that serve a home or a small building, we actually would be producing energy without taking away habitat

the outer space idea, i dunno, it smells of boondoggle and big energy with hands out for public funds to me

[truthisfreedom]

46. Check out nanosolar.com

I sure wish they were publicly traded.

[gateley]

6. Build me up just to let me down. The headline and article are encouraging!

Your practical rebuttals aren't, but sure make sense. :(

It IS positive that there seems to be increased research into alternative energy sources (glass half full).

[TheMadMonk]

60. These practical rebuttals were rebutted 30 years or more ago.

Indeed they read very much like a fundy "disproving" Darwin, or an oil exec taking on Anthropogenic Global Climate Change.

[ewagner]

7. I read about this 18 years ago

If I recall, it would require an number of geosynchronous satellites which would collect the sun's energy through the panels, then convert it to microwave power, then beam/transmit the microwave energy back to earth at a receiving station where it would be reconverted back to electrical energy, rectified (I think that's the right word) and then transmitted through an existing power grid.

Nobody is talking about the environmental effects of that much microwave radiation being transmitted through the atmosphere to a single collection point on the ground..

and...

in 1987 (when I first looked at this) the devices for converting microwave energy back to electrical energy were crude and incredibly inefficient....something like 30% at the time...

nice idea...not terribly efficient compared to other methods and not studied deeply enough at the moment...

JMHO

[slackmaster]

10. Just a nit, but there ARE a few possible continuously-lit orbits

I am thinking of some of the Lagrange points.

Specifically L1, L4, and L5 have both continuous sun exposure and visibility from Earth.

[Lionel Mandrake]

12. Right, but the Lagrange points are all too far away for power transmission.

L1 is a great place for observing the Sun, but it's about 1.5 million kilometers from the Earth.

[slackmaster]

14. A giant Fresnel lens at L1 would be more efficient than photovoltaics

;-)

http://www.owensworld.com/flashgames/play-126.htm

[Lionel Mandrake]

21. A lens at L1 with focal length 1.5 million kilometers?

That would create a real image of the Sun at the position of the Earth. The size of the image would be comparable to the size of the Earth.

[slackmaster]

26. That's why we would only run it at night

;-)

(I've been looking for a segue to use that punch line for several days.)

[Lionel Mandrake]

30. Do I feel tension in my lower extremity?

[Thor_MN]

33. No thanks, I don't want to be an ant with * holding a magnifying glass...

[AllexxisF1]

11. ...

Um...couldn't you just run a really long power cable down to Earth to transmit the energy. I mean really is it that hard.

[Lionel Mandrake]

13. The Skyhook concept would work

if there were a sufficiently strong material. Unfortunately, right now there isn't.

For more info: http://www.nss.org/settlement/L5news/1983-skyhook.htm

[gimberly]

27. Like the 'space elevator'? I prefer rooftops, but why not do both

[CaliforniaPeggy]

19. K&R! nt

[Demeter]

20. Since a land mass the size of Arizona Would power the country

there is no point in going out to space--just cover the Empty Quarter with PV Arrays.

[roamer65]

75. PV arrays in the Southwest and Western US could do it.

Clean energy and it would bring jobs to areas that need them desparately. A generous tax credit to people who put PV arrays on the roof of their house would be good as well.

[TheWraith]

80. That area is far from "empty."

It's desert, yes, but the desert houses its own unique ecosystem. You wouldn't pave over Yellowstone, so why Yuma? It's still a vast amount of environmental destruction.

[brentspeak]

22. Your point about there not being a continuously sunlit orbit is moot

Because the job of the solar panels is to STORE solar energy.

[Lionel Mandrake]

25. I thought the job of the solar panels was to convert light to electricity.

To store energy, you would need some sort of battery. Even on the Earth, there are no batteries big enough to use in conjunction with electrical power grids.

You might consider running hydroelectric generators backward to pump water uphill, but this would involve a major redesign and have all sorts of technical and political problems.

Large amounts of electrical power are generally not stored, but distributed and used immediately.

[haktar]

24. Sorry, both the article and your assumptions are mostly bullshit.

1st.(where you are completly wrong) Technologically it would be possible.
A satellite at (Lagrange point) L1(Like Soho) or L4, L5(stable, but probably too far out) or even in wide enough orbit at L2 would be able to transmit the energy to any point of the Earth continuously (with a little help of additional 3 geostationary reflector satellites ;-) ).

But: (and there you are absolutely correct) Transforming the energy into microwaves and receiving it on Earth would have an efficiency that's only laughable. It would only be a cash cow for some corporations. (Ok; and a runaway satellite hit by a micro meteorite would have a good chance to cook thousands or even millions of people, you're right again). And if i remember correctly, even the L1 Point is about 5 million kilometers out and L2 is not much nearer,(and forget about the 157 million kilometers for L4 and L5). if you want to focus the beam to a small enough area to actually use it, good luck. So this stuff is pure Science Fiction. While not technologically impossible, it can never compete economically against Earth based solar plants, that could already be competitive.(At least if you count in, that for current power plants earnings are privatized, but environmental costs are socialized)
So, while it would be possible, it is a bullshit idea, because it it is much cheaper and more efficient(even with the not too great sun elevation crossection) to build conventional solar power plants on Earth.

[Lionel Mandrake]

28. How would you transmit the energy from L1 to a geostationary satellite?

As I said before, L1 is about 1.5 million kilometers from the Earth. What part of the electromagnetic spectrum would you use to transmit the energy over this distance? I can't think of a way that would be technologically feasible at any wavelength, but maybe you can.

[haktar]

36. That would be actually the easiest part

The natural spectrum. To create usable energy you need a difference in entropy, be it heat, potential energy, etc. To create energy to retransmit in any form, you would need to radiate away the excessive energy to create a potential cliff, which is actually difficult in space. You can't cool it down with cooling of water evaporation, you would have to radiate it away. And if you then transmit the converted energy in any spectrum you would have the conversion losses again on earth. It would be much easier to focus the energy on earth and use the earth environment like rivers and seas to create the cooling). So the theoretical solution would be -> Big mirrors in space and a rather conventional power plant on earth.
But: while you might get a little less of 2 Gigawatt of energy per square kilometer in orbit around L2 (sun elevation is always around 90 degrees) and you only might get about 400 megawatt per square kilometer on earth (sun elevation changes and there is a night too ;-) ) at 100 % efficiency, a satellite the size of several square kilometers is rather hard to build, a even bigger plant on earth is manageable.
So my conclusion is - a solar power plant is buildable and payable(even competitive) on earth, but while it may theoretically be buildable in space it will never be payable. (and don't forget, only L4 and L5 are stable, for L1 and L2 you need fuel to stay in orbit, decreasing dramatically the lifetime of your satellite, not even counting the acceleration the reflected sunlight would cause, which would probably blow the satellite out of orbit within hours)

[Lionel Mandrake]

44. How do I say this politely?

You haven't answered my question because you haven't understood it. "The natural spectrum" is not an answer. Possible answers would be microwaves, millimeter waves, IR, visible, UV, X-rays, etc. To transfer power from one spacecraft to another, you would need to pick one of these types of electromagnetic radiation. Pick one, and I'll tell you why it won't work.

Entropy is not the huge problem you make it out to be. The space environment is very far from being in thermal equilibrium. Thermal design of spacecraft using louvers, paint, and other low-tech methods is routine.

It is not "much easier to focus the energy on earth and use the earth environment like rivers and seas to create the cooling". Using "big mirrors in space" makes no more sense than transmitting microwaves to the Earth for electrical power.

Lack of stability at L1 is not a significant problem. Existing spacecraft inhabit so-called Lissajous orbits near but not exactly at L1. Stationkeeping requirements are modest - not " decreasing dramatically the lifetime of your satellite".

The acceleration of reflected (or absorbed) sunlight would not "blow the satellite out of orbit within hours". It's a familiar, small perturbation to the orbit. No problem at all.

The real problems, which you haven't grasped, include the need for unprecedented accuracy of the ff in the spacecraft at L1:
1) attitude determination and control, and
2) pointing of whatever structure (antenna or telescope) transmits the power.
A slight angular error would cause the beam to miss the appropriate part of the spacecraft in geosynchronous orbit. Plug in the numbers, if you know how, and you'll see that I am right.

[haktar]

83. There is no need to say it politely !

I told it the smart-ass way :-)
But, contrary to your assumption, i did understand it. The easiest way to ->receive<- the energy on earth would be somewhere between millimeter waves and microwaves. But, converting solar radiation into microwaves and transmitting it to earth with a maser would cause intense conversation losses. These losses would have to be radiated away, because you don't have the option for cooling with water evaporation like on earth. In space your only option is to radiate it away via a black body radiator with a big enough surface.(that's the entropy cliff i talked about the smart-ass way :-) ) if you consider, it costs about 6000 Euros per kilogram to put anything into a near earth orbit, the costs alone for putting the transmitting maser into L1 or preferable an orbit around L2 (sun elevation always at 90 Degrees) with the matching cooling unit would be astronomical. If we talk giga- or tera-watt, It's impossible to handle the conversion losses in space at an reasonable price. So, self unfolding tin foil reflectors wouldn't have the conversation losses and are actually light enough to be send into space even in the square mile size necessary. And ok, you've got me, I didn't calculate the needed precision. An direction error of an arc-second at L1 (1.5 million kilometers out, another of my memory errors, i looked it up) would cause an error of about 7 Kilometers on earth. (i apologize to prefer doing this calculation in metric units). For a Civil application in the tera-watt scale this is actually precise enough.

Where you made a mistake:

Only L4 and L5 (for a satellite mass below 1/20 earth mass) are stable due to centrifugal forces. In L1 a Lissajous orbit isn't stable beyond a timescale of a few month, you would need a ->lot<- of fuel to keep that orbit with a structure the size of a city.

Don't get me start laughing. The ratio the impulse of sunlight imposes on a conventional satellite may be ignorable, but we talk about a surface/mass ratio several powers of 10 higher. Ok, i didn't calculate it, and i admit, i 'don't know if it blows such a satellite out of orbit within minutes, hours or days. but i beg you, don't force me to calculate it, i'm confident the satellite will be out of orbit in a ->short<- time.

L1 is not a geosynchronous orbit
A Geosynchronous orbit would have the following disadvantages.
It would have Eclipses two times a year for several days. Because of earth's gravity gradient, a satellite this size would self stabilize to a position fixed relatively to earth. To stabilize it pointing toward the sun, you would have to rotate it . Because of that your transmitter must be steerable to all directions or you would loose additional time in transmitting the energy. So 24/365 in that orbit ? no way!
This would have military applications but i can't think of any payable civil application.


But, Why do we fight? We agree it's impossible (or in my case, unplayable) for civil use in the gigawatt or tera-watt scale needed, while military applications in the megawatt scale are probably coming :-( .
And (ok, i admit, i am green) -<civil>- power plants can be build at a fraction of the price on earth.

[Turbineguy]

34. But your argument makes it

a good idea to Bush:

1. Cooking large numbers of people (OK, maybe the wrong ones, but these things happen)
2. Privatized profits, socialized costs (I smell another tax cut on the way)
3. The fact that it will never work is not an issue (look at Iraq)
4. The fact that it is ridiculously expensive and inefficient to even attempt (see item 2).

[Barrett808]

31. No continuously sunlit orbits?

I believe there are:

However certain orbits exist, passing just a few degrees from the poles, whose planes are rotated by the bulge of the Earth by exactly one rotation per year. Such "sun synchronous" orbits, can be made to always face the Sun, or always go through midnight. The DMSP satellites have such orbits (the picture here, of the aurora above the Great Lakes, was taken by one of these satellites; note Florida at bottom right), and so did Magsat.

http://www.phy6.org/stargaze/Sorbit.htm

Whether the rest of the plan holds up is another question, but keeping the solar collector sats in the sun isn't a problem.

[Lionel Mandrake]

37. sun-synchronous orbits are not continuously sunlit.

These LEOs are generally used to keep the sun as high in the sky as possible during one half of each orbit. The other half of each orbit is eclipsed (no sunlight).

You could design a sun-synchronous orbit to keep the sun as near the horizon as possible. The S/C would be sunlit day after day at the equinoxes but would be eclipsed part of each day in other seasons. At solstice, the elevation angle of the sun would oscillate between +23.5 and -23.5 degrees (with respect to the horizon).

[SyntaxError]

53. You seem to know your stuff... Is it from work, study or both? (or perhaps google & wikipedia :P )

[Lionel Mandrake]

57. All of the above.

[TheMadMonk]

38. Sorry, but what you think you know isn't quite right.

You have several misconceptions based on incomplete knowledge.

1. There are any number of quasi geo-syncronous orbits which have only brief periods of eclipse at intervals of up to half a year. These can be considered continuously sunlit for the purpose of the exercise.
   
   Further from the ground beneath they appear to mark out a figure 8 in the sky. This addresses your objections in your points 5 & 6. The receiver array can be easily situated to "see" the transmitter continuously.
   
2. irrelevant
   
3. Just plain wrong.
   
4. Microwaves yes, but not broadcast as you seem to be envisioning. MASERs would be used for transmission. These have a dispersion measured in hundreds of meters over the distance from here to the moon. Dispersion from geosynchronous orbits is minimal and easily contained within the size of the receiver array.
   
5. Actually the physical size of the receiving array is limited in it's minimum size by the acceptable Earth surface energy density. Which is chosen to prevent frying birds or aircraft which might fly through the beam. This would be disastrous if the receivers were as expensive as silicon solar cells, but the 30% efficiency quoted elsewhere is for a bent piece of wire and a diode rectifier, and IIRC a dipole can double this to almost 60%. The price of paving over entire square kilometers would be less to that of a coal or gas fired power plant of similar capacity. Nor would the land beneath be lost as it could be safely used for growing crops.
   
   Further to the frying problem: The microwave frequency in a microwave oven is deliberately chosen to resonate with and heat water and thus cook the food. This would be the worst possible frequency for transmission through the atmosphere, which contains considerable amounts of water vapour. The frequency chosen would be carefully chosen for minimum adsorption in the atmosphere.
   
6. addressed
   
7. For the most useful orbits the microwave beam may be steered to anywhere but the polar regions, albeit with some loss off efficiency as the angle becomes more oblique.
   
8. addressed
   

And the price of putting the solar arrays up there might not be as high as one might think. There is a VERY experimental propulsion system based on utilising the focused energy of a microwave beam from above to ionise and accelerate air molecules past the vehicle. Ironically it appears that the ideal shape is essentially a flying saucer with a parabolic dish in the upper surface.

Getting the first few (tens?|Hundreds? of) megawatts of solar panels in space wouldn't be cheap, but once in place, This starter/seed could boostrap an entire orbital renaissance, lifting larger and larger payloads as the power station expanded, until the price to orbit would be dollars per kilogram. IF of course the flying saucer idea pans out.


Outre and futuristic as the idea sounds, it has actually been within our technological grasp to do this since the early 1970's. Only the "flying saucer" is a more recent refinement which woul,d if it works, reduce the cost of implementation by orders of magnitude.

[haktar]

43. Sorry, but what you think you know isn't quite right

While a geosynchronous orbit with a few degrees inclination is nearly continuously in the sunlight there are eclipses two times a year. While these eclipses last only a for several minutes they occur for a period of several days.
There is no such thing as a harmless radiation in the Gigawatt scale. Independent of the frequency something always will absorb it. if i use a energy density definitely harmless, it is below the energy density of the natural sunlight. Then i could use the sunlight directly.
So, i send an antenna the size of a town , a generator the size of a few blocks and a black body radiator the size of a few blocks into space to generate electricity at an efficiency of at most 50 % ,only to transfer it into microwaves at an efficiency of about 5 % with an maser( ok i forgot the second block size black body radiator for the maser) to send it to earth at an harmless energy density that forces me to build a receiving structure on earth the size of a town. Ok i admit, its possible, but what has occam's razor to say about it?

[TheMadMonk]

73. Whattever efficiency at 2.5 x surface energy densities.

And near 100% duty cycle (No day/night). So we've already 5 times as many KW/hrs to play with at our source.

Transmission, reception and conversion to AC is roughly 50% efficient. (It would appear that I'm stuck with Klystrons (and dishes for focusing) or suchlike if you're right about the efficiency of MASERs.)

But whatever the specific technical solutions at each stage of the process, The final result is 250% more energy available to the end user for a given size collector array. Nor is there any need for batteries (or some other energy store) to "smooth" the supply over nights and overcast days.

Direct conversion of sunlight on the surface is problematical in many ways: Location; Transmission losses in lines; Massive overkill in necessary storage capacity to cater for nights, weather and seasons. And even then the threat of power rationing; Engineering FOR weather; Land usage; A mind boggling toxin load; and More.

Orbital generation addresses all of these problems in full or to a major degree.

The new printable solar cells that "should" be in production sometime "soon" would make orbital platforms even more attractive.

As for beam density, at the right frequency, a kw or more per square meter would not be problematical. But far lower densities remain quite ecconomical since the receivers are so simple and cheap.

Oh and the vast majority of waste or lost microwave energy can be reflected back into space. The little added to Earth through atmospheric adsorption is negligible. So we don't even have to worry about that particular "pollution" problem.

The sole question is economics and the blokes who should know say that orbital power is potentially viable. I happen to think they're being cautious. Because one thing about us is they were creatively lazy. If there's an easier way to do something them it's pretty much a given we will find it. And the best way to start looking for the easy way is to start doing it the hard one.

[Lionel Mandrake]

47. Let's plug in some numbers

to get an order of magnitude estimate of the size of the receiving array.

Let's say the frequency is 3 GHz, so the wavelength is 0.1 meter. This may not be optimal, but it has the right order of magnitude. If the frequency were much higher, the beam would be significantly attenuated by water in the atmosphere. If the frequency were much lower, the ionosphere would be a problem.

Let's say the transmitting antenna has a diameter of 100 meters. The main lobe of the antenna pattern then has an angular width of (0.1 meter)/(100 meters) = 1/1000 of a radian (one milliradian).

If the propagation distance is 22000 miles (i.e., geosynchronous), then the size of the receiving array must be at least 1/1000 of this distance, or 2.2 miles. It actually must be somewhat larger to account for pointing errors, imperfect antenna pattern, and oblique incidence. So let's say 3 miles is the diameter of the receiving array.

Do you think these numbers are reasonable? If not, feel free to change the parameters.

[TheMadMonk]

51. MASERs are NOT radiating antenae.

Different rules of propagation apply. Not that it really matters since that is about the size receiver array we want to avoid the "cooking" problem anyway.

[Lionel Mandrake]

56. You still need an antenna, and it will still have an antenna pattern.

A MASER is to microwaves what a LASER is to light. It produces a very monochromatic signal, but it doesn't change the laws of physics. If you think my estimate doesn't apply to microwaves produced by a maser, you are sadly mistaken.

Would you be happy with a transmitting antenna diameter of approximately 100 meters? That actually is feasible, but not easy to build.

[TheMadMonk]

63. If that's what it takes.

The "antenna" for a MASER is a resonant cavity/waveguide.

I would have no problem with a 100m (or even larger) dish if that were the only way it could be done.

One major problem with doing it this way is that it put all the energy through one "aperture" creating a bit of a heat concentration problem, because no system is perfect and there are always losses.

With modern electronics the simpler solution is to array a large number of small (relatively speaking) transmitters to create a much larger artificial aperture. Furthermore, such an artificial aperture can do tricks that would make MC Escher's eyes water. With a minimum of properly spaced transmission elements, the wavefront can be shaped to arrive "face on" to the receiver elements whatever their latitude. Add more elements and a sufficiently sophisticated control algorithm and the beam can be split and "focused" on multiple receiver arrays scattered across an entire continent. Even shape the wavefront to generate polyphase alternating current at a properly configured receiver without auxiliary equipment.

The entire system is technologically feasible and has been with ever improving refinements for decades. It's been the economics which has always stood in the way.

[LongTomH]

66. Sorry, guy! No one is talking about Masers!

The 1970's study discussed the use of klystron or magnetron tubes like the ones used in radar. The more recent studies are of all solid state transmission systems using 'power transistors.'

Refer to my post below:
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=102&topic_id=3024804&mesg_id=3026709

[BearSquirrel2]

42. Star Wars Again ...

This is just more Star Wars malarky. They need to demonstrate some real prototype systems before we can take this seriously. They have to demonstrate the effectiveness of the transmitter and collector as well as their ability to effectively aim the beams.

In order to become even remotely effective at power generation, you would effectively be creating a death ray weapon. Perhaps thats why people are really bringing up the subject.

[TheMadMonk]

45. Yes and no. It has some potential as a strategic weapon...

...but tactically it's just not all that useful. As a battlefield weapon (frying armies from orbit) it would have zero effect on any vehicular units, and troops could protect themselves with a tinfoil umbrella.

Strategically it might be used to direct weather, causing flood or drought in a target area, but it would be fairly obvious what was going on, and several nations have the capacity to make powersat space confetti.

Not to say that safeguards aren't needed, but the potential for harm is not as high as you fear.

Transmission and reception HAVE been demonstrated. And the aiming precision needed is far far less than is routinely used with space telescopes and communicating with distant probes.

[SyntaxError]

54. So you're saying that the militaries of the world should start arming themselves with tinfoil hats?

:P

[TheMadMonk]

59. tinfoil coolie hats maybe.

:P backatcha. Gotta protect those shoulders doancha know?

It could be used as a weapon, but it would be a very clumsy one. And one that is very easily neutralised.

[BadgerLaw2010]

67. Low wattage thermal weapons are also awful useless against humans. We have too much water.

Compare someone wading through constant kilojoules of thermal energy from a building fire to someone "wading" through constant kilojoules of kinetic energy.

[Doctor Cynic]

48. Does this remind anyone else

of that 007 movie about North Korea secretly controlling a mirror in space?

[Sirveri]

49. This is the only feasable long term solution we have.

All other solutions rely on energy supplies that have fixed supply. The Sun, while not technically infinate, has a large enough supply to ensure we would not need to worry about energy resources for an incredibly long time. Land based solar is subject to weather disruption, however I do still support it. Ultimately however solar sattelites will be required due to our outpacing the requisite land area required to generate the electrical power we will need.

To answer your bullet points. Orbits do not need to be sunlit all the time, one simply needs to set up a network of sattelites so as to produce a continual feed. They also do not to be low orbit, as one could use relay sattelites as part of the solsat network. Current power transmission models are designed around microwave transmission tech, however research could produce refinements in transmission capabilities causing them to have less diffusion over distance and greater accuracy, or to not rely on microwave at all.

In time, solar sat tech will be the only viable power source, unless a future advance yields a way to overcome entropy or produce zero point energy. Solar sats will at least give us enough viable time to advance to that point. In addition it is the only currently feasible solution to peak energy supply. Overcomming peak energy will allow us to divert more resources to overcomming peak food and peak water. Lets think long term, and with less fear, new technology is a good thing, how it is used is the thing to worry about.

[Lionel Mandrake]

50. We'll have to agree to disagree.

I don't think microwaves from satellites make much sense. There are other sources of power that will last for a very long time, such as wind, photo-voltaic (on the ground), hydroelectric, geothermal, and maybe water waves. Nuclear fusion may eventually become useful. Nuclear fission with fuel recycling (breeding) would last for centuries.

All of the more exotic energy sources would be unnecessary if we could stop producing so many babies. The planet is grossly overpopulated with humans, and it's getting worse every year. The planet is sick, and we are the disease. But that is a topic for another thread.

[Sirveri]

72. I'm not really disagreeing.

But I do think that ultimately we will need solar sats. Yes, Fission with breeder and reprocessing COULD last a very long time. However due to anti-reprocessing laws in the US, we can't take advantage of it. Also other fission fuel cycles such as the thorium cycle which Rickover and other began to explore in the sixties were never taken anywhere even though they showed great promise. Thorium cycle would enable power generation without serious risk of proliferation. Iran could actually develope a nuclear program that wasn't actually used to make bombs!

However when all is said and done, fission fuels might last 300-400 years based on projected energy demand growth rates. In addition we would need time to transition. Can wind and land solar work? Maybe, they surely can't hurt. EROIE plays a big part in it though, how much energy do you use creating and maintaining those wind and solar farms compared to the return? I honestly need to do more research myself on the subject to truly speak in an educated manner on it. Sadly other items in my personal life have taken a forefront on my plate over peak oil and other energy related issues. But it is still my belief that ultimately we will need solar sats due to requiring the remaining terran land mass for food generation and habitation. This isn't a near future need but a far flung requirement, perhaps 500+ years in the future depending on how we manage our energy sources and respond to the comming peak oil crisis. I see all energy production research as necessary for the future growth of the species however.

That and I really liked the comic book Transmetropolitan and how they lined mercury with solar panels and turned it into a super huge power generator to beam energy back to earth.

[Freddie Stubbs]

52. A Dyson sphere is the only way to go

[SyntaxError]

55. Couldn't we just build a large power plant around the sun and string some power-lines back to earth?

It sounds easier and a little bit more feasible.

[Lionel Mandrake]

58. No, we couldn't.

You're kidding, right?

[SyntaxError]

61. No, why would I kid about such a thing...

ahem, yes I was kidding.

[LongTomH]

64. Let me argue for Space Solar Power!

There's a great body of research data on solar power satellites, going back to the 1970's NASA/DOE study. I hate to have to tell you this; but, your "inconvenient truths" may be inconvenient; but, they're not true!

Taking your objections one at a time:

1. There is no such thing as a continuously sunlit orbit.

This hardly matters. The geosynchrous orbit considered in most solar power from space (SSP) studies has, at most, a one hour 'blackout' during spring and fall. The blackouts would come around midnight when power loads are relatively low. That could be made up with grid power from areas where the solar power satellite is not in shadow.

2. Even if there were, it wouldn't help.

Huh? Actually, see number 1 above.

3. The least impractical orbit for this hair-brained scheme (see comment #5) would be sunlit about half the time.

Nope! See number 1!

4. The power would have to be be sent to the earth as microwaves, which would spread out to cover a large area of the earth's surface. That entire area could only be used as a receiving antenna. Anyone entering the area would be cooked.

This is a bit of distortion and disinformation that was widely circulated during publication of the '70s study. Actually, the 'rectenna' would only be about 6 miles by 7 miles. See the Solar Power Satellite art gallery at the Space Studies Institute website.

The intensity of the microwaves would only be about 30 mw per square centimeter; far below the intensity need to cause short term bodily damage. Check out Gerard K. O'Neill's article on the SSI main page.

5. To minimize the area of the receiving antenna, the satellites would have to be in low earth orbit, where they orbit the earth in about 90 minutes. Each power generating satellite could transmit power to a particular antenna for only a few minutes during each 90 minute orbit.

Ooops! See number 1 for this too!

6. To ensure that the satellite would pass over the receiving station during every orbit, the station would have to be either on the equator or at one of the poles.

Nope. Most of the studies have been for an equatorial orbit at geosynchrous altitudes.

The Russians did do a study of solar power satellites in high, polar orbit - the so-called "Molniya" orbits. The Russians have put some of their communications satellites in these orbits to reach areas above the Arctic circle.

7. Most of the demand for electricity is at mid-latitudes.

So, what else is news? Most of the demand for communications is at mid-latitudes and satellites in equatorial orbit have no problem serving them.

The rectenna complex at a mid-latitude location will be an ellipse. The microwave beam will spread into an ellipse, just like a flashlight beam coming in at an angle. Check out the Space Studies Institute Solar Power Satellite gallery again.

8. Therefore, the electricity would have to be transported over long distances in locations where construction and maintenance would be difficult, expensive, and not under any one nation's control.

You're battin' a thousand here, cousin! See 1, 6, and 7 above. By the way, it would be great if the SPS complex was under international rather than national control.

For those who want more information try:
The Wikipedia page for Solar Power Satellites.
The Space Studies Institute website.
The report of The Space Solar Power Conference sponsored by the Space Frontier Foundation.
Here's an article calling for A renaissance for space solar power.
Finally, a report from NASA's Fresh Look Study on SPS.

Names, and words, to Google with:
solar power from space
space solar power
Peter Glaser
Gerard K.O'Neill
Seth Potter

[ozone_man]

69. 30 mw/cm2 is safe if it's sunlight.

I'm not sure about that level of RF energy. It would probably depend on the frequency, but I don't think I'd want to be working as an RF energy collector maintenance crew.

The biggest problem I have is with the militarization of outer space, which this may migrate to. For example the development of RF weapons encircling the planet. I just have a bad feeling about it. Keep energy local and energy use local. As much as possible anyway. The more separate energy production and energy use are, the less sensitive we are to environmental impacts or aware of military dangers.

I feel that solutions to our energy and environmental needs should be met on the Earth. We have to change our way of thinking and consumption away from the growth model and move toward a sustainable model. Live within our means. Develop renewable power on Earth. There is plenty of wind, solar and tidal power on Earth that we don't have to encircle the planet with solar collectors. And other renewable forms will be discovered and perfected as we spend more on R&D. This must be a priority of a Democratic administration.

Part of changing our consumption model is focusing more on energy efficiency instead of energy consumption. We've made a start on it by increasing appliance efficiencies (e.g., energy star compliance), but we have to go beyond that. And part is in controlling our population growth. We can't support 6 or 7 billion people, and we're still growing. I hear the economists talk about GDP growth and shudder. When will we stop growing? Because the more we grow, the less room there is for nature. Nature is shrinking at an inverse rate to our growth and consumption.

If we discover a perfect energy source, dirt cheap and nonpolluting, it won't save us from our own growth. Instead it will increase our growth until we consume the planet in other ways. So, both a sustainable energy model and a sustainable consumption (zero growth) model are required for the planet. Leave outer space to exploration and wonder. Earth is where it's at. :)

[LongTomH]

70. You wouldn't want to go camping on top of a rectenna.......

....but, it wouldn't be harmful in the short term. Actually the studies assume that there would be an 'exclusion zone' around the rectenna; within a mile of the edge of the rectenna, the level falls off to the lowest level allowed internationally. That's the European standard: 1 mw per square centimeter. The Europeans only allow that for a 1 hr exposure, so you'd really want the fence out further.

The growth issue is a complicated one. Even if we were to halt both economic and population growth, the energy to support our existing population has to come from somewhere!

For the record, I do support all forms of renewable energy, including terrestrial solar, wind, wave, etc. And I would never suggest we depend on one single energy form ever again. I just think the SPS should be kept as an option.

[Barrett808]

68. You can read the report here:

http://spacesolarpower.files.wordpress.com/2007/10/final-sbsp-interim-assessment-release-01.pdf

Seems pretty compelling to me.

[TheWraith]

79. To be technical, there are (almost) continuously sunlit orbits. The moon has one.

You're right that the practical problems are pretty substantial. Frankly, though, I think that the problems with orbit and retransmission are probably the fixable ones. The biggest issue is construction and deployment. Even if you assume that you can improve solar efficiency by ten fold by being out in space, you're still talking about needing collector areas 5,000 square miles in size just to supply the United States. That's a square 70 miles on a side. Unless we could design some kind of lightweight photovoltaic fabric, or design a process for mass producing smaller satellites by the tens of thousands, we'd never be able to build--and, particularly, launch--enough capacity to be worth it. We'd need some kind of self-replicating factory robot.

I don't blame Aldrin--he and others are rightly trying to get people interested in space again. But if we're going to exploit space for energy, we'd be better off extracting Helium-3 from the lunar regolith for use in a Polywell-type fusion reactor. One ton of He3 would let us generate as much energy as a dozen fission reactors do in a year.