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NSSO on Space Based Solar Power

samzenpus posted more than 6 years ago | from the it-is-always-sunny-50-miles-up dept.

Space 198

apsmith writes "About a year ago some of the people at the US National Security Space Office began looking into space-based solar power (SBSP) as a technology in the near-term strategic interests of the United States. At first the participants were skeptical, and the "phase 0 study" went along with no official funding. In a rather innovative move, they organized the study as a series of internet-based (bulletin-board and email) discussions, with the wordpress site open to the public, and a closed experts-only discussion using Google Groups. Initially expecting only a dozen or so interested parties, the discussion grew to include over 170 people with past expertise and interest in the issues. The final report was released Wednesday morning; it provides an excellent broad-brush review of the status of SBSP, showing immense potential, but also a number of challenges that appear only surmountable with a strong government commitment to the project. The big question is where it goes from here — NASA? DARPA? The new ARPA-E? Or something new? I was able to attend the press conference, which included Buzz Aldrin in an announcement of a new alliance to push for implementing the recommendations of the report."

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198 comments

dream on there is plenty of oil (-1, Troll)

Anonymous Coward | more than 6 years ago | (#20934447)

Oil is not a fossil fuel.
Look up abiotic oil.

http://tinyurl.com/ymcxyg [tinyurl.com]

Re:dream on there is plenty of oil (0)

Anonymous Coward | more than 6 years ago | (#20934521)

Yes, and here are some other myths debunked.

there IS plenty of abiotic oil & buzz is a lia (-1, Flamebait)

Anonymous Coward | more than 6 years ago | (#20935383)

Oh yes, it's a myth because "bermuda-triangle.goatse" said so.

BTW, Buzz Aldrin is a coward, a liar and a thief who sucker-punches truthseekers.

Yay!!!111!!!!!!!!eleven!!!!!!!1111!! (0)

Anonymous Coward | more than 6 years ago | (#20935879)

Yay, let's be cunts and mod every challenging idea as "flamebait" even when you have no fucking idea what the motiviation of the original poster is.

Let's pigeonhole every controversial idea into one of two slashdot ghettoes in order to stifle the flow of information, and let's pat ourselves on the back for our Orwellian law enforcement.

Let's be proud of our complete and total subservience to the herd mentality.

Ok, someone explain it to me (4, Insightful)

iamlucky13 (795185) | more than 6 years ago | (#20934509)

How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency, and then receive the beamed power at (optimistically) 50% efficiency, meanwhile creating the navigational hazards of the power beams and still requiring distribution from receiving stations rather than simply generating it via panels at the point of use?

Don't get me wrong, I'm all for finding ways to utilize space, but I don't see how this is even remotely economical, especially at our current technology levels.

Convince me.

Re:Ok, someone explain it to me (1)

Marxist Hacker 42 (638312) | more than 6 years ago | (#20934545)

How about the same concept as the space elevator? All you have to do is get those carbon nanotubes to conduct electricity....

Re:Ok, someone explain it to me (3, Informative)

TripMaster Monkey (862126) | more than 6 years ago | (#20935041)

Actually, carbon nanotubes ("buckytubes") are quite good conductors of electricity [azom.com] .

So that problem's solved...leaving only the original problem of manufacturing enough defect-free tubes in enough industrially-significant quantities to make the skyhook in the first place...

Re:Ok, someone explain it to me (1)

geekoid (135745) | more than 6 years ago | (#20934555)

How about a series of mirrors to reflect in an orbit that keeps the side of the earth away from the sun lit up? then you could use standard solar panels.

heh

Re:Ok, someone explain it to me (1)

Kadin2048 (468275) | more than 6 years ago | (#20935611)

How about a series of mirrors to reflect in an orbit that keeps the side of the earth away from the sun lit up? then you could use standard solar panels.
That would not be a good idea. Lots of biological organisms -- including humans, but a lot more critical ones -- really don't like having direct sunlight 24/7. Lots of plants will just refuse to go into seed, for instance.

Re:Ok, someone explain it to me (3, Funny)

B3ryllium (571199) | more than 6 years ago | (#20936189)

At least it would ward off that dreaded Global Cooling disaster we've all been hearing about.

Re:Ok, someone explain it to me (2, Insightful)

apsmith (17989) | more than 6 years ago | (#20934601)

Saves on transmission and storage.

No weather, and a clear view (no atmosphere at all in the way).

That gives you a factor between 5 and 10 over on-the-ground systems to start with.

If you really lose 50% in transmission *and* 50% in receiving the case is harder to make - most estimates seem to have higher numbers for overall system end-to-end efficiency, but of course nobody's buit one yet.

Re:Ok, someone explain it to me (2, Interesting)

modecx (130548) | more than 6 years ago | (#20935497)


If you really lose 50% in transmission *and* 50% in receiving the case is harder to make - most estimates seem to have higher numbers for overall system end-to-end efficiency, but of course nobody's buit one yet.


Actually, I'm quite sure someone has built an earth bound a set of devices capable of comparable beam energy density to a proposed orbit power system. IIRC, the efficiency of the receiving antenna can be around 90%, not sure about that of the transmitter.

Personally, I'm sure an array of heat engines could provide more power density than currently comparably priced solar panels, it's silly to pass them up.

Re:Ok, someone explain it to me (1, Interesting)

QuantumG (50515) | more than 6 years ago | (#20934627)

Seeing as you seem to be a big fan of this 50% you speak of.. here's another one for you: at night, solar panels on the ground receive no sunlight whereas, get this, in space they do. Now, whereas I'm plenty doubtful of your claims to the use of 50% I'm pretty certain of the almost 50% split between day and night.

Of course, I'm more of the belief that solar power satellites will not be practical until we have off earth resources to build them from and, as such, low tech heat exchange designs are a better solution than high tech solar panels as we might actually have a chance of making low tech stuff in space in the near term.

Re:Ok, someone explain it to me (1)

Cecil (37810) | more than 6 years ago | (#20934629)

There is no nighttime in space, nor any clouds, nor any seasons, nor any atmosphere. Solar panels in orbit deliver full power 24 hours a day 7 days a week 365 days a year with no need for fuel or maintenance. And they don't have to be, and probably shouldn't be, in orbit. Inject them into an orbit between Venus and Mercury, or closer still. Solar radiation falls off with the square of the distance. The closer we get them to the sun, the more power they will generate, by orders of magnitude.

Obviously it's not economical yet, or it would've been done already. But it has potential.

Re:Ok, someone explain it to me (2, Insightful)

timmarhy (659436) | more than 6 years ago | (#20934765)

just how do you propose to get the electricity back to earth from venus.

how do you propose we maintain them from that distance? yes, solar cells aren't this eternal source of power people think they are. expect to need to do rolling replacments every 10 years atleast, if not more under those conditions.

Re:Ok, someone explain it to me (1)

TooMuchToDo (882796) | more than 6 years ago | (#20934973)

Robot equipment would perform the maintenance, powered by the array itself. When not working (although, they would probably ALWAYS be working), the robotic equipment would charge. Think of them as an army of advanced Roombas.

Re:Ok, someone explain it to me (1)

UncleTogie (1004853) | more than 6 years ago | (#20935077)

Robot equipment would perform the maintenance, powered by the array itself.

...and how will the robots create a new solar panel if a panel is damaged?

Think of them as an army of advanced Roombas.

Are they able to repair themselves, and if so, where do they get spare parts?

As far as the idea is concerned, I'd not mind if they can do it cleanly. The S-G power delivery methods I'd heard of so far have been microwave-based; anyone think there'd be any impact to global warming?

Re:Ok, someone explain it to me (0)

Anonymous Coward | more than 6 years ago | (#20935375)

> The S-G power delivery methods I'd heard of so far have been microwave-based; anyone think there'd be any impact to global warming?

None at all. Next question?

Re:Ok, someone explain it to me (1)

fredklein (532096) | more than 6 years ago | (#20935763)

how will the robots create a new solar panel if a panel is damaged

1) Over-size the array, so a few dead/damaged panels wouldn't matter.
2) Have a stock of spares. Robots cut bad panel loose, push into sun, slap spare panel into place.
3) We could ship up a stack of spares every so often.

Re:Ok, someone explain it to me (1)

Nefarious Wheel (628136) | more than 6 years ago | (#20935213)

just how do you propose to get the electricity back to earth from venus.

Interesting hard SF treatment of this in a fairly old set of novels. They were talking of communications, but the same rules apply. I recommend "The Complete Venus Equilateral" by George O. Smith.

Re:Ok, someone explain it to me (3, Interesting)

Lloyd_Bryant (73136) | more than 6 years ago | (#20935001)

There is no nighttime in space, nor any clouds, nor any seasons, nor any atmosphere. Solar panels in orbit deliver full power 24 hours a day 7 days a week 365 days a year with no need for fuel or maintenance. And they don't have to be, and probably shouldn't be, in orbit. Inject them into an orbit between Venus and Mercury, or closer still. Solar radiation falls off with the square of the distance. The closer we get them to the sun, the more power they will generate, by orders of magnitude.
First off, putting them somewhere other than Earth orbit is silly - yes, you can get more energy from the Sun, but how do you transmit it to Earth? The microwave (or whatever) beam will also fall of with the square of the distance.

And how exactly do you keep the power beam locked onto the target, when the target is on a sphere rotating once per day?

Putting them in equatorial geostationary orbits is *much* simpler. You'll lose a small amount of generating time each day (while the station is in Earth's shadow), but if you schedule as much of your maintenance as possible during this time, the effect is minimal.

And maintenance *will* be required, for the foreseeable future. Someday we may be able to build solar cells that don't need to be periodically replaced, but not today.

Furthermore, it's been noted that Earth orbit is "halfway to anywhere in the solar system" (attributed to Heinlein). So we'll need serious orbital capability to build these things, regardless of where we put them.

Point source vs. directed beam. (2, Informative)

melstav (174456) | more than 6 years ago | (#20935671)

First off, putting them somewhere other than Earth orbit is silly - yes, you can get more energy from the Sun, but how do you transmit it to Earth? The microwave (or whatever) beam will also fall of with the square of the distance.

Actually, no.

Light intensity from the sun drops off at the square of the distance because the sun radiates as a point source in all directions.

If you put your collector array closer to the sun, you collect significantly more sunlight. Then you use that energy to power a laser. If you can keep that beam tightly focused, you won't have much loss in the beam at all.

Re:Ok, someone explain it to me (2, Informative)

CrimsonAvenger (580665) | more than 6 years ago | (#20935895)

Putting them in equatorial geostationary orbits is *much* simpler. You'll lose a small amount of generating time each day (while the station is in Earth's shadow), but if you schedule as much of your maintenance as possible during this time, the effect is minimal.

No. An equatorial orbit only goes into Earth's shadow during two short periods a year, near the Equinoxes. Off the cuff, I think the sats will be able to enter Earth's shadow once daily for about three weeks every Equinox.

The rest of the time, the axial tilt of the Earth is enough to keep the sats in light 24 hours a day.

we will indeed need serious orbital capability (2, Informative)

alizard (107678) | more than 6 years ago | (#20935943)

meaning mainly, lower launch to orbit costs. Doing this not only gets us power, it gives us a platform for space industrialization.

Because you don't need batteries... (4, Informative)

Goonie (8651) | more than 6 years ago | (#20934635)

There are several advantages space solar power has:
  • higher intensity sunlight than even a cloudless day, 24 hours a day
  • you've always got direct sunlight, so you can use cheap mirrors to focus the light on a very expensive but efficient solar cell (you can do this on Earth as well, but it doesn't work as soon as you get clouds)
  • No need for backup power. That's worth a lot of money.
  • The ground based gear is much smaller and lighter than equivalently-powerful terrestrial solar panels. This is a big advantage for the military, who are the proposed initial customers.

I'm skeptical too, but it's not quite as crazy as it sounds.

The difference between... cannot go wrong (3, Interesting)

cumin (1141433) | more than 6 years ago | (#20934767)

Douglas Adams - "Mostly Harmless"
- The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair.

Lets build in some redundancy shall we? (Just in case.)

I think you covered the list pretty well but corrosion is also a factor that space should mitigate. Well, mostly aside from the wandering bit of space debris.

I haven't RTFA, probably won't, but I'd like to throw in the additional suggestion we look into Von Neumann devices to build most of the components on a lunar base. (Earth first, and strip-mine the moon later.)

Re:Ok, someone explain it to me (5, Informative)

Jubedgy (319420) | more than 6 years ago | (#20934719)

Portability and extensibility. The sun provides, about 1367 W/m^2 in space (courtesy, Space Mission Analysis and Design third edition, page 432) and about 250 W/m^2 on the Earth's surface (FTFA). In any case...

Portability:

By using an orbital energy collection system, you can simply re-route the beam to any place on the planet within the system's FOV...done right, you can get full 4*pi sr coverage of the Earth 24/7. Design a portable ground station, and you can provide power to a disaster area that has been removed from the rest of the power grid (paraphrased directly FTA).

Extensibility:

If, once in place and a standard orbital collection platform design has been established, more power is required, simply launch the spare unit. Proper formation flying techniques (something currently at about the cutting edge of orbital design) should allow the new unit to 'hook in' to the system to boost the amount of available power. This may be in the article, I have not finished reading it yet.

The LISA mission provides a pretty good overview of how I see the entire system distributing power from the collectors to the emitters (the things that will transmit the power down to the surface), though I may be totally off base from what the authors have in mind. The LISA mission will consist of three satellites forming an equilateral triangle with leg lengths of 5 million Km shooting lasers at each other. Last time I checked, anyway.

It is currently not economical, nor is it really achievable yet. I encourage you to at least browse through the article as it does discuss some of your questions in a more cogent manner than I have.

Re:Ok, someone explain it to me (5, Informative)

QuantumG (50515) | more than 6 years ago | (#20935203)

The sun provides, about 1367 W/m^2 in space (courtesy, Space Mission Analysis and Design third edition, page 432) and about 250 W/m^2 on the Earth's surface (FTFA).
Hmm.. the first number is correct, but we don't have 100% efficient solar panels and won't any time soon (if ever) so you've gotta down rate that.

The second number, however is totally wrong. If you're going to talk about what "the sun provides", i.e., the theoretical 100% efficiency solar panel, then you get a figure of about 1000W/m^2 on the Earth's surface. You could say it is more like 800W/m^2 when you take cloud cover into consideration.. and then there's the fact that you only get that during daylight hours, so halve it to get 400W/m^2 but that's still a lot more than 250W/m^2. It *feels* like someone is downplaying the possible efficiency of solar panels on the Earth's surface vs the same solar panel in space in order to make their argument stronger. As you took that figure straight from the article, I'll give you the benefit of the doubt, but that's what it sounds like.

It's still a heck of a lot of difference though. You're talking nearly 3.5 advantage to putting your solar panels in space over leaving them on the ground.. but there *are* losses to transmitting the power as microwaves through the atmosphere, and there is the astronomical cost of launching anything into space.

Whenever I hear people talk about solar power satellites I'm reminded of the episode of Seinfeld where they stock the mail truck with bottles to collect the 5c deposit in the adjacent state. If you can get a free ride you might be able to make solar satellites work, but you've still gotta crunch a lot of numbers first, and no-one has done that successfully.

Re:Ok, someone explain it to me (1)

apsmith (17989) | more than 6 years ago | (#20935773)

250 is the average across Earth's surface, per unit surface area. If you were able to keep the array pointed directly at the sun all day long, you'd get 500 (1/2 of 1000, since half the time is still night-time). But that takes extra equipment, additional expense on the local side, and requires extra ground-area one way or another (that's a long shadow you're casting near sunries/sunset).

Re:Ok, someone explain it to me (1)

m2943 (1140797) | more than 6 years ago | (#20936051)

250 is the average across Earth's surface, per unit surface area.

Solar cells on earth aren't exposed to an "average" per unit area, you put them in the places where they work best, like high, cloudless deserts, and you steer them.

1/2 of 1000, since half the time is still night-time

And solar cells in orbit around the earth move through the earth's shadow. You can't put them into geostationary orbits (too crowded), and further out is expensive. Maybe we could build stators.

If you were able to keep the array pointed directly at the sun [...] But that takes extra equipment

That problem is even worse for any kind of orbital power generation. Let's not even get into all the crap you need for cooling and repairs.

Re:Ok, someone explain it to me (1)

QuantumG (50515) | more than 6 years ago | (#20936063)

Actually, geostationary orbits is exactly where they intend to put them.

Re:Ok, someone explain it to me (1)

m2943 (1140797) | more than 6 years ago | (#20936085)

Actually, geostationary orbits is exactly where they intend to put them.

Well, it ain't gonna happen: that space is too valuable and too crowded.

Re:Ok, someone explain it to me (2, Informative)

QuantumG (50515) | more than 6 years ago | (#20936113)

Ya know, I think you should probably put down the crack pipe.

It's space, dude.

The orbit is 264,869 km around.

Re:Ok, someone explain it to me (1)

Dr. Spork (142693) | more than 6 years ago | (#20934729)

In space, nobody needs to wash those things. I'm not trying to make a joke; dirt is a serious issue when we're talking about gigantic, fragile surfaces.

Another advantage is that the array could be pointed directly at the sun permanently, whereas on Earth, you need to keep swiveling it.

Re:Ok, someone explain it to me (1)

timmarhy (659436) | more than 6 years ago | (#20934869)

you do release there's lots of things flying about in space? what about the tiny meteor shower that we get every 50 years?

Re:Ok, someone explain it to me (1)

ScrewMaster (602015) | more than 6 years ago | (#20935337)

Who cares? We're probably just talking thin-film reflectors here. If they get enough holes punched in them that power output drops too much, just have your maintenance robots unfurl some more.

Re:Ok, someone explain it to me (1)

timmarhy (659436) | more than 6 years ago | (#20935981)

and when you run out? the point i'm trying to impress on people here is that installations of this size require constant maintenance, it's in space it's expensive to do. it's a significant cost that must be addressed.

idunno, it just seems like a massively complex, expensive solution to something we don't have a problem with, and won't have a problem with in the forseeable future.

by all means reasearch, and if they can make it work and make economical sense, great. i'll remain skeptical until they solve the launch and maintenance issues.

Re:Ok, someone explain it to me (1)

ScrewMaster (602015) | more than 6 years ago | (#20935309)

Another advantage is that in space, immensity can be bought very cheaply, once you have the infrastructure in place to build it. Put it this way: how much of every terrestrial structure is devoted to supporting said structure against Earth's gravity? The answer: most of it.

Plus which, as others here have pointed out, in space solar power is something.

Re:Ok, someone explain it to me (5, Insightful)

lgw (121541) | more than 6 years ago | (#20934803)

How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency
It's better because now you have a hugely powerful microwave cannon in orbit that can fry anyone you need it to. Thinking about an orbital power station other than as a weapon is probably misguided. This is probably a feature for the "National Security Space Office".

Not likely (1)

WindBourne (631190) | more than 6 years ago | (#20935683)

As china showed (and USSR, as well as America), it is easy to shoot a small sat out of the sky. Now put something of that size, and it is literally shooting at the broadside of a barn. And the brilliant pebble approach would work nicely for this.

TO be honest, years ago, I thought the same thing, but if you think about it, we can simply use a nuke power plant on the ground and beam the energy to a set of sats to send the power. Just make the main receiver be at geo over USA, and then from there beam it around. The nice advantage of that, is that does not have to be just 1 power plant in America. It can be any where on the globe.

Re:Ok, someone explain it to me (1, Informative)

Anonymous Coward | more than 6 years ago | (#20934981)

Well, it may not be economical yet, but it is certainly worth investigating.

First, such a plant is unlikely to use photovotaic cells at the space end. A good old fashioned steam turbine plant can give an efficiency of around 50-60 % for the initial conversion of solar heat to electricity. The hardest part of this is actually the radiator to get rid of the waste heat.

Next, the conversion to microwave energy is pretty efficient...I don't have any up to date figures for magnetrons but something approaching 90% should be attainable.

Now, the bit that always mystifies people....the path loss. Provided the frequencies chosen are in a suitable window with no atmospheric absorbtion, there is virtually no path loss. For those familiar with the usual sorts of path loss seen in radio systems, that is very counterintuitive. The reason for it is that the sending and especially the receiving antennae are both large enough that all the power sent is intercepted by the ground antennae. To put it another way, the antennae are operating in the near field. That means that the inverse square law does not apply.

There will of course be resistive losses in both antennae, and power conversion losses in the ground equipment.

Finally, just to deal with the "microwave death beam" worry. The size of the sending antennae determines how tight the beam delivered to the ground can be. It will be immediately obvious to a ground based scope if the system has been built with the capability of delivering a dangerous power intensity to the ground. Since in doing so it is radiating a microwave signal at high power, it is also effectively saying "here I am, shoot me down" such that a missile could home on it without needing to turn on its own radar. This would make it a single use weapon, which, considering the capital cost, would make such use unattractive.

Re:Ok, someone explain it to me (1)

TripMaster Monkey (862126) | more than 6 years ago | (#20935121)

The hardest part of this is actually the radiator to get rid of the waste heat.

Actually, that part is simplicity itself. All that is needed is an array of radiator fins, positioned behind the collector mirror. In the perpetual shadow behind the collector, things are going to get very cold, and any waste heat can easily be bled off there.

Re:Ok, someone explain it to me (1)

Daniel Dvorkin (106857) | more than 6 years ago | (#20935191)

In the perpetual shadow behind the collector, things are going to get very cold, and any waste heat can easily be bled off there.

That depends on what your definition of the word "cold" is ... there's no conductive loss in vacuum, which means all the heat needs to be bled off by radiation. There's a reason we use (partial) vacuum as an insulator here on Earth.

Re:Ok, someone explain it to me (1)

TripMaster Monkey (862126) | more than 6 years ago | (#20935297)

Granted, but you're going to face that problem wherever you try to get rid of your waste heat.

Basically, if you're using a steam-engine type of generator to produce your power, you're tapping into the energy of a temperature differential you're creating. Using the occluded space behind the mirror as your low point increases that differential considerably. Also, even though the only mechanism a radiator fin can lose heat by is radiation, that difficulty can be surmounted by simply increasing the surface area of the fin, and in zero-gee, fairly gigantic structures can be constructed without excessive regard for their structural integrity (a fact we'll already be counting on in the construction of the mirror).

Re:Ok, someone explain it to me (0)

Anonymous Coward | more than 6 years ago | (#20935545)

As the original AC, yes, the radiator is simple enough in principle, but in space I think we can paraphrase Clausewitz in saying that everything is very simple, but the simplest things are very difficult. Of the main components...mirror, heat exchanger, turbo generator, microwave generation and antennae, and the waste heat radiator, I think the waste heat radiator is probably the hardest. I don't think it is a show stopper, but we are certainly going to need some serious heavy lift capabilities to get a decent sized plant into orbit.

Overall my own opinion is that this is a more promising technology than fusion, not least because we know that all the processes involved work

Re:Ok, someone explain it to me (1)

TripMaster Monkey (862126) | more than 6 years ago | (#20935597)

As the original AC...

Ahh...I'm glad you returned. I have a question.

Given the potentially huge range of temperatures we're talking about here (potentially millions of degrees in the focus of the mirror, only a few degrees above absolute zero in the shadow of the mirror), what sort of material were you considering for the heat transfer? You made a reference to "steam engines", suggesting water as a possibility, but considering the temperatures involved, might not another substance prove to be more suitable?

Just wondering if you have considered this possibility...

Re:Ok, someone explain it to me (0)

Anonymous Coward | more than 6 years ago | (#20935829)

I suppose I should create a login again...used to have one about 6 years back!
The limiting factor for temperature range is going to be what the materials can stand rather than what is attainable. The working fluid must of course be considered as one of the materials involved. The ice-water-steam substance is surprisingly good for something so cheap and non toxic. Mercury has been used for combined cycle plants, eg a mercury cycle for the high temperature end and water/steam at the low temperature end. If really low temperatures can be attained then there might be a case for using something with an even lower boiling point for a bottoming cycle. (eg the remaining heat in the steam is used to boil something like a refrigerant, which condenses at an even lower temperature. If the reachable condensing temperature is low enough, you could use something like nitrogen.

But the determining factor would be whether it is better to use a more complex plant, or simply make the mirror and radiator a little larger to get the required power with a lower thermodynamic efficiency. The efficiency is no great concern in itself, the important factors would be the total weight required in orbit and the maintenance. My own opinion would be to start out with a plant using simply a steam cycle at the sort of temperatures and pressures we can readily attain in existing earthbound plant. Once the concept is proved, you can look at refinements. Could be a refit if you kept the initial design open enough.

Re:Ok, someone explain it to me (1)

QuesarVII (904243) | more than 6 years ago | (#20935539)

The hardest part of this is actually the radiator to get rid of the waste heat.

Why think of it as waste heat at all? Why not generate even more power from it? There are electricity generation methods that work off of a temperature differential.

Think of a peltier cooler working in reverse.

Re:Ok, someone explain it to me (0)

Anonymous Coward | more than 6 years ago | (#20935795)

If you don't cool part of the structure it will eventually all come to the same temperature and there won't be any differential to generate electricity from. Remember, there's no air to conduct heat away, the only differential available is between parts of the spacecraft.

Re:Ok, someone explain it to me (1)

mikelieman (35628) | more than 6 years ago | (#20935303)

Ok, consider this:

The infrastructure developed to implement this project is pretty much the infrastructure needed to leave earth and visit other places on a regular basis.

You get the Electricity, and Access to the Universe is gravy.

Re:Ok, someone explain it to me (1)

Iftekhar25 (802052) | more than 6 years ago | (#20935433)

Economic feasibility is admitted as a hurdle, but technologically, they seem pretty confident. From TFA (formatted for easy reading):

FINDING: The SBSP Study Group found that SpaceBased Solar Power is a complex engineering challenge, but requires no fundamental scientific breakthroughs or new physics to become a reality.

SpaceBased Solar Power is a complicated engineering project with substantial challenges and a complex tradespace not unlike construction of a large modern aircraft, skyscraper, or hydroelectric dam, but does not appear to present any fundamental physical barriers or require scientific discoveries to work. While the study group believes the case for technical feasibility is very strong, this does not automatically imply economic viability and affordabilitythis requires even more stringent technical requirements.

Also

[...] Advances (since 1970s) have included
  • improvements in PV efficiency from about 10% (1970s) to more than 40% (2007);
  • increases in robotics capabilities from simple teleoperated manipulators in a few degrees of freedom (1970s) to fully autonomous robotics with insect class intelligence and 30100 degrees of freedom (2007);
  • increases in the efficiency of solid state devices from around 20% (1970s) to as much as 70%90% (2007);
  • improvements in materials for structures from simple aluminum (1970s) to advanced composites including nanotechnology composites (2007); and many other areas.

Here's the explanation. (1)

Ungrounded Lightning (62228) | more than 6 years ago | (#20935469)

You're off on several items:

How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency, and then receive the beamed power at (optimistically) 50% efficiency, ...

First: It isn't necessarily panels. Steam plants work just fine, and are much cheaper to build and lift.

Second: There's 7 times the power per square foot available up there due to lack of atmospheric attenuation and the 24/7 nature of sunlight in space, compared to the atmosphere-and-weather-compromised equivalent of 5 or so noontime-hours-worth you get on the ground.

Third: As of the '60s they could already do > 90% DC in at orbit to DC out on the ground, using masers and TWT amplifiers in orbit and schottky diode based rectennas on the ground, not the 25% you consider optimistic. (Vacuum tubes are EASY when you don't need to pump air out of them and can heat the cathodes with focussed sunlight...) ... meanwhile creating the navigational hazards of the power beams and still requiring distribution from receiving stations rather than simply generating it via panels at the point of use?

The power beams are not a navigational hazard. You can fly right through them - as can birds. You can also sit on the ground where they're strongest - grazing cattle under the rather lacy rectennas (assuming you put 'em up on grazing land rather than, say, some sterile hunk of rocks and sand.) This is accomplished by picking the right band for the beam - in the millimeter range - where it passes right through water (clouds, birds, people, ...) rather than being strongly absorbed (like the K-band microwaves used in ovens, which are tuned to one of water's absorption bands.)

The distribution grid is already there and very efficient. It's eminently suitable for taking power from a few rectennas located in remote regions and distributing it to cities, towns, and rural consumers across the country. What's your gripe with it?

The L5 society investigated and was pushing this a half century ago, and this is what they came up with back then. Some things have improved since. But they didn't really NEED to improve in order to make it practical.

Re:Ok, someone explain it to me (1)

Spy Hunter (317220) | more than 6 years ago | (#20935583)

I think it's worth noting that our current space efforts (ISS, moon and mars bases) are not remotely "economical" either. If we must spend billions of tax dollars on space missions, I think they would be better spent doing something that might conceivably free us from oil dependency and benefit the entire human race here on Earth, than on a manned Mars mission (for example). The main practical benefit to the human race of a Mars mission, if there is one, is as a step toward mining and colonization of Mars and eventually even interstellar travel, but those goals are even farther away than space-based solar power, if they are even feasible.

In my part of the world we get no direct sunlight (0)

Anonymous Coward | more than 6 years ago | (#20935645)

In my part of the world we get no direct sunlight for part of the year, so we'd need some monster sized batteries.

Re:Ok, someone explain it to me (1)

ShieldW0lf (601553) | more than 6 years ago | (#20935705)

You can put up as many solar panels as you want, floating in space, aimed at the sun. No need to clutter up the landscape of earth. It scales up until the point you've got a Dyson Sphere,

Then you transmit the power from the small panels to an space station in a geostable orbit around earth.

Then you transmit the power from the space station to a matching ground installation on the earths equator.

Then you transmit the power from there around the earth using whatever method is best.

The strengths of such a system are that you can scale your solar collections out endlessly, eventually aiming to farm space for materials to build more instead of shipping them from earth, while having a single transmission line to earth for it all. No more need of terrestrial power generation.

This is the way towards a future of continued growth for the human race. All global efforts should be dedicated to the achievement of this goal.

Re:Ok, someone explain it to me (1)

jollyreaper (513215) | more than 6 years ago | (#20935731)

How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency, and then receive the beamed power at (optimistically) 50% efficiency, meanwhile creating the navigational hazards of the power beams and still requiring distribution from receiving stations rather than simply generating it via panels at the point of use?

Don't get me wrong, I'm all for finding ways to utilize space, but I don't see how this is even remotely economical, especially at our current technology levels.

Convince me.
The best ideas aren't solar panels in space, they're solar mirrors for heat turbines. You ever see that tower in the desert surrounded by mirrors? Up at the top they have a fluid that gets super-heated by the mirrors and it turns a turbine. Heating a fluid and letting it turn a turbine is the oldest form of power generation we have, it's just updating the heat source to solar.

So the idea is that you put something like this in space and beam the power down with microwaves. At the moment, this sort of device generates more power per pound than solar cells.

This sort of idea was originally proposed in Dr. O'Neill's "The High Frontier." That book also included cylindrical space habitats that were the inspiration for the Babylon 5 station.

Beyond the Orange-Bellied Parrot (2, Interesting)

Nefarious Wheel (628136) | more than 6 years ago | (#20934525)

It's not really a bad idea, provided there are no orange-bellied parrots in the way. The real fun is when you have to explain to greenies that yes, it's really solar power, and yes, it's also thermonuclear.

I like the idea of a separate organisation dedicated to this technology, as it's clear none of the existing organisations can do it. Set it in motion, get it done before the bloat sets in. Also like the idea of the solar-electric HEO ferry -- anyone have a link to an artist's perception of it (a real one I mean)?

Re:Beyond the Orange-Bellied Parrot (2, Interesting)

RyanFenton (230700) | more than 6 years ago | (#20934969)

Indeed - and because of the potential for unparalleled amounts of energy that are possible with more and more direct forms of solar energy extraction, new things become possible. Dark matter-based energy storage systems and/or weapons become closer to practical, matter fabrication factories manipulating atoms using nuclear interactions (think renewable nuclear fuels), all kinds of uses for the astounding amounts of energy we can't practically transport directly back to earth, but have flowing out at all times. New kinds of engineering and uses for high-energy physics.

That's the enormous potential lying just out there, and also something that almost justifies the apprehension that one can feel about nuclear weapons. Dark matter weapons would be to a nuclear weapon as a nuclear weapon is to fireworks. Of course, that's the same kind of problem that exists with any kind of space travel - anyone can get ahold of a big enough rock and manipulate existing forces send it towards anyone else to pose the kind of threat that would also make a joke of existing nuclear weapons.

But we can't stop threats - they come from nature just as much as they do from man. Learning how to face such danger is much more valuable than refusing to ever touch such ostensibly 'dangerous' forces. And I'd much rather have 10, then 100, then thousands of earths able to start up, rather than stagnating ourselves just to force this one earth to hold our entire future potential. Of course, that isn't the real choice we have either - in almost everyone's ideals, we should care for ourselves, care for eachother, and expand to be a peaceful force of diverse enlightenment rather than spending all our resources on war and revenge. We should care for our world, while we embrace the dangerous potential around us, so that we can grow to a point where the potential danger doesn't have to be so terrifying.

Ryan Fenton

Re:Beyond the Orange-Bellied Parrot (1)

RyanFenton (230700) | more than 6 years ago | (#20935157)

Oops - meant anti-matter, not dark matter. Hate it when I make mistakes like that.

Ryan Fenton

Re:Beyond the Orange-Bellied Parrot (1)

Nefarious Wheel (628136) | more than 6 years ago | (#20935327)

"I think we should stop targeting Cheyanne Mountain now."

"Why?"

"It isn't there any more"

-- "The Moon is a Harsh Mistress", Robert A. Heinlein.

Yep, lots of energy up there, and you don't have to produce it, just sort of funnel it. Large concentrating reflectors are quite easy to maintain in microgravity, just lots of metallised mylar film with supporting struts made of alfoil. Oh, and a guidance system of some sort. Some time back there were a few designs for manufacturing these as they unrolled from stock in an orbiting space widget (I remember the photos, but not the reference -- sorry). I was thinking of these when I first thought of ice lasers, but Jerry Pournelle said I could do it just as easily with silicon. I still think ice would be easier, as the water supplies in the solar system (mostly Saturn's rings) would require less time overall in fusion purification, and the minor difference in melting points given the ambient shade temperature in space are probably negligible. Not as many interesting by-products, though.

bring in Zaph Brannigan (1)

User 956 (568564) | more than 6 years ago | (#20934527)

The big question is where it goes from here -- NASA? DARPA? The new ARPA-E? Or something new?

By "something new", I'm sure you mean the formation of D.O.O.P.

Hey, libertarians! (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#20934533)

Guess what? Our government is itself a product of the market system. Cities like New York, London, and San Francisco are successful precisely *because* of their enormous governments--they compete for capital, talent, and prestige against cities with small, ineffectual governments that are unable to effectively lure and corral said capital, talent, and prestige. And as goes the city, so go city-states and nations: Somalia, being a libertarian paradise, is a rather unpleasant place to live for non-ideologues. Somalians, those who can, vote with their feet and leave.

Now go suckle Ayn Rand's rotten tits some more and leave the rest of us alone, you stupid fucking Paultards.

Re:Hey, libertarians! (1)

spykemail (983593) | more than 6 years ago | (#20934669)

So inefficiency is the key to success? Right... that's why my Libertarian Manifesto says "smaller government," as in, wasting less trillions of dollars. That's opposed to not wasting any money at all - see? Even idealists are willing to compromise.

Re:Hey, libertarians! (0)

Anonymous Coward | more than 6 years ago | (#20935455)

Great job identifying a troll and feeding it immediately!

Oh, come on, mods. (0)

Anonymous Coward | more than 6 years ago | (#20935475)

Even as a Randroid libertarian I found that post hilarious.

Stop modding provocative posts down. Your Orwellian sanitary impulses are spoiling the environment here.

a number of challenges (0)

Anonymous Coward | more than 6 years ago | (#20934611)

but also a number of challenges that appear only surmountable with a strong government commitment to the project.
Yoo hoo, Blackwater!

What they didn't know... (0)

Anonymous Coward | more than 6 years ago | (#20934619)

Initially expecting only a dozen or so interested parties, the discussion grew to include over 170 people with past expertise and interest in the issues.

What they didn't know was that one of those 170 was an Anonymous Coward... [evil grin]

What is the point of putting it in orbit? (1)

HornWumpus (783565) | more than 6 years ago | (#20934663)

Terrestrial solar power is approaching $1/peek watt, at which point it will be economic.

What are the current costs per kg to get to LEO?

Benefits: doubled power due to no atmospheric loss, approximately quadrupling average power generation as you can expect to run the cells at peek power full time.

Costs: lift cost, shorter lifetime of the cells and attitude control system of the satellite (which feeds back on lift cost), power transmission loss.

Short of building a space elevator, or making the cells on orbit or on the moon I don't see that working out to a net benefit. I can't justify any of those as reasonable assumptions.

forget LEO (1)

Dr. Spork (142693) | more than 6 years ago | (#20934799)

I'm pretty sure that the plans are to build these things in geosynchronous orbit, so the satellite doesn't move relative to its receiving station - which would be some equatorial platform floating somewhere between the US and Africa.

Re:What is the point of putting it in orbit? (1)

timmarhy (659436) | more than 6 years ago | (#20934887)

$18,000 USD/kg is the cheapest i've heard of.

if it's geosynchronous, you still have night time to deal with, since *shock* the earth will block the sun on you.

what makes you think your power production will double out in space suddenly. solar panels are operating at their limits under the measley solar rays we get here on earth.

Re:What is the point of putting it in orbit? (0)

Anonymous Coward | more than 6 years ago | (#20935257)

idiot. solar insolation is at least 6 times greater on average in space. as for your comment about geo. clearly you are an idiot. the shadow is microscopic.

Re:What is the point of putting it in orbit? (1)

WhiplashII (542766) | more than 6 years ago | (#20935359)

if it's geosynchronous, you still have night time to deal with, since *shock* the earth will block the sun on you

You're not thinking in orbital distances - the Earth only blocks it for a few minutes, at local midnight. Most power usage is during the day, so this would have very little impact. (Needs some design - such as getting power from another sattelite half a time zone away, but not a hard problem).

Given: GEO orbit is 35,786 km up, the Earth is 6,400 km in radius, the sun is 150,000,000 km away. Set the problem up this way, make a triangle with one point at the sun and the other points on the GEO orbit curve. The triangle barely touches the Earth on each side - so if you draw a line through the Earth, you make a smaller triangle with exactly the same angles/side length ratios as the bigger one. That is the relationship you use to answer this question.

So [150,000,000 km] divided by [2 * 6,400 km] is the same as [150,000,000 km + 35786 km] divided by X, where X is the distance the GEO sattelite travels in the shadow of the Earth. Since the sun is so freaken far away, obviously X is approximately 12,800 km (about the diameter of the Earth). Since the GEO orbit is 224850 km in circumference, and it has a 24 hour period, GEO orbit is about 9,370 km/hr - so the sattelite is in at least some shadow for 82 minutes. But this analysis has ignored the fact that the sun is not a point source (among other things), so it is actually less than that.

So power generation starts dropping off at about 11:20 PM local time, hits zero at about 11:45 or so, comes back at 12:15 or so, and it totally back up by 12:40. Not really that bad.

Re:What is the point of putting it in orbit? (1)

timmarhy (659436) | more than 6 years ago | (#20935809)

how do you propose we transmit power for 35,786 km.... you simply aren't going to be able to with conventional technology.

Re:What is the point of putting it in orbit? (1)

indrax (939495) | more than 6 years ago | (#20935507)

When you're on earth, the earth fills up half the sky.
When you are 26,000 miles away, it is much smaller.
When you are orbiting at roughly seven times its radius, and matching the tilt of it's axis, it almost never gets in the way of the sun. You are usually well above or well below the plane of it's orbit.

Similarly, We very rarely shade the moon.

Re:What is the point of putting it in orbit? (1)

m2943 (1140797) | more than 6 years ago | (#20936069)

What are the current costs per kg to get to LEO?

In LEO, you lose half the benefit because half the time, the devices are in earth's shadow.

Too much junk up there already (-1, Troll)

obeythefist (719316) | more than 6 years ago | (#20934747)

What, they have satelites and space shuttles up there and now they want to put a sun up there as well? Won't it burn the satellites and the shuttle? Did they think about what that would do to the GPS systems that people use in their cars? How are people going to find their way around?

Also, what about global warming? Sure, it'll reduce carbon emissions, but that extra sun will make everything down here even hotter! They didn't think about that! No, putting a sun up in earth orbit for space based solar power is just a dumb idea.

Re:Too much junk up there already (0, Troll)

Anonymous Coward | more than 6 years ago | (#20934903)

umm... is this meant as a joke or are you being serious?? ...God, I hope it's a joke.

Just use the light (0)

Anonymous Coward | more than 6 years ago | (#20934773)

How much power do we use for outdoor night lighting? Think of all those street and parking lot lamps.
How much could this demand be reduced by simply reflecting sunlight down to the night side of the Earth?
The satellites could be nothing but big steerable mirrors. No energy conversion would be needed.

I would say the same. (1)

emj (15659) | more than 6 years ago | (#20934781)

showing immense potential, but also a number of challenges that appear only surmountable with a strong government commitment to the project.


If I needed funding for my project I would say the exact same thing, especially if I had 170 other highly skilled fanboys to back up my idea.. ;-) Now it is a very cool idea, but there are alot of cool idea out there..

more intense sunlight? (1)

timmarhy (659436) | more than 6 years ago | (#20934847)

People here keep claiming that the more intense sunlight will result in high power generation, but i'm skeptical of this.

solar cells here now aren't capable of extracting more then 35% of the light that makes it to earth now, so they won't do any better in space.

the only type of solar generation that will produce more power in space due to the more intense soalr rays will be some form of mirror heating, and that present a whole bunch of other problems.

i'm also curious as to how they will keep the solar array in a sationary orbit? if it's not, you will still end up with the problem of night time

There's more important hurdles to get over before we do anything like this. namely making exiting the earth's atmosphere cheap and safe.

Re:more intense sunlight? (0)

Anonymous Coward | more than 6 years ago | (#20935083)

well the thinking behind why putting a solar array in orbit would yield more power is that the sun outputs a large chuck of it energy in the uv spectrum much of which gets blocked by the atmosphere. since there far more energy in the upper UV band it would make sense to try tapping it. although i have no idea if in the end it would make sense economically.
   

Re:more intense sunlight? (1)

apsmith (17989) | more than 6 years ago | (#20935103)

Well, if average sunlight falling on Earth's surface is 250 W/m^2 and average in Earth orbit is 1400 W/m^2, then 36% of 250 is a lot less than 36% of 1400. That's the difference there.

The main proposed orbit is geo-stationary; these are very rarely shaded (for about 1 month of the year a satellite there gets about an hour's worth of shade every day, the rest of the year it's clear).

Inexpensive space launch is definitely one of the technical challenges. The report calls for large-scale development and deployment of reusable launch vehicles and development of inexpensive orbital transfer vehicles (solar electric space tugs) to handle the launch challenge. A lot of people think it can be done, but nobody's succeeded yet obviously.

Re:more intense sunlight? (1)

timmarhy (659436) | more than 6 years ago | (#20935839)

my point is what makes you think the solar panel will generate more power with more light? they don't catch all the energy that falls on the earth, so more in space won't make a difference. your 160 watt panel on earth is still only going to be a 160 watt panel in space...

Re:more intense sunlight? (1)

Ironsides (739422) | more than 6 years ago | (#20935123)

People here keep claiming that the more intense sunlight will result in high power generation, but i'm skeptical of this.solar cells here now aren't capable of extracting more then 35% of the light that makes it to earth now, so they won't do any better in space.

On earth, you get ~250w/m^2, is space, you get 4-5 times as much. So, a solar cell in orbit at the same efficiency will produce 4-5 times as much power. It's not that they are more efficient, it's that they are getting more sunlight->more power.

the only type of solar generation that will produce more power in space due to the more intense soalr rays will be some form of mirror heating, and that present a whole bunch of other problems.

A) not it isn't. B) Such as?

i'm also curious as to how they will keep the solar array in a sationary orbit? if it's not, you will still end up with the problem of night time

A satellite in orbit will receive 100% of the sunlight for a far greater period of time than a satellite on earth. Further, a satellite in orbit will receive light for well over 70% it's orbit. So, put a couple satellites in geostationary and just point a few of them sideways. Enough sufficiently spread out will allow you to cover your base load at night as they will be in the sunlight even if the area they are beaming to is in night. This is the same way the moon reflects light to earth for 99% of the time, albeit the moon is a lot further out.

There's more important hurdles to get over before we do anything like this. namely making exiting the earth's atmosphere cheap and safe

It doesn't have to be cheap, just cheap enough to make it worthwhile. As to safe, we are shipping up a machine. It just needs to get there. Also, once a proof of concept is done, then all it takes is to wait for delivery to get cheap enough and it will be done. One might as well test it prior to it being "cheap enough" to see if it is worth while.

It is a gun, a really big gigawatt class gun. (2, Insightful)

forgotenpasswerdmoro (955491) | more than 6 years ago | (#20935011)

A big beam, needs a big mirror. Be it microwave, infrared or visible light it's a huge gun in orbit, untouchable by IEDs and lesser nations. It doesn't even need to work that well, just 10 x amplification from nominal and any spot on earth is unlivable. Or operate as a great psychological weapon when a given region is bathed in light 24 hours a day. It is a very bad idea, like SDI was a bad idea, like the further militarization of space is a bad idea.

Re:It is a gun, a really big gigawatt class gun. (1)

TripMaster Monkey (862126) | more than 6 years ago | (#20935393)

Unless you could change the focal length of this mirror at will, I doubt the reflected light itself would be of any use as a weapon. Of course, the microwave or laser beam used to transmit the power to earth may be a different story, but there's an interesting refutation of that possibility here [slashdot.org] .

Besides which, I think it would be probably that the economic advantage of having this power would outweigh taking it offline willy-nilly to terrorize lesser nations...we can terrorize lesser nations quite adequately already.

Quote from Alpha Centauri (0)

Anonymous Coward | more than 6 years ago | (#20935311)

From the game Alpha Centauri:
Planet's Primary, Alpha Centauri A, blasts unimaginable quantities of energy into space each instant, and virtually every joule of it is wasted entirely. Incomprehensible riches can be ours if we can but stretch our arms wide enough to dip from this eternal river of wealth.
CEO Nwabudike Morgan "The Centauri Monopoly"

Won't happen until one world, united. (2, Insightful)

tygt (792974) | more than 6 years ago | (#20935371)

Face it, we're already concerned about relying on an unstable Middle East for our energy.

We're certainly not going to rely on a very fragile orbiting setup which is a sitting duck to anyone with a decent missile/launch vehicle.

Re:Won't happen until one world, united. (1)

timmarhy (659436) | more than 6 years ago | (#20935959)

bullcrap, it's certainly a harder target then a power plant on the ground is. they will have to build multiple arrays, one shot won't take it out.

President Camacho Has a PLAN (1)

Baldrson (78598) | more than 6 years ago | (#20935647)

El Presidente Dwayne Elizondo Mountain Dew Herbert Camacho has a PLAN to save AMERICAH!

He'll pick a bunch of SMART guys and they'll solve our ENGERNY problems and they'll do it all in ONE WEEK or he'll... uh... he'll uh... give them MORE TIME and MORE MONEY because its REALLY REALLY HARD to solve our ENGERNY problems! And then if they don't do it before they die then... uh... he'll pick some MORE SMARTER GUYS and let THEM solve our ENGERNY problems!

Nothing like incentives [geocities.com] !

let me get this straight (1)

m2943 (1140797) | more than 6 years ago | (#20935979)

The US is proposing to put devices capable of aiming megawatt beams into orbit? And who exactly will control this?

And the justification for this seems rather dubious, too. Capturing solar power in space has no obvious overall advantage over capturing it on the ground.

Weapon? (1)

sc0ob5 (836562) | more than 6 years ago | (#20936025)

I'm actually a little concerned that something like this could be used as a weapon. Beaming high amounts of energy at certain targets could cause serious damage. Fortunately these guys don't have funding. As much as I like the idea of solar power at least with nuclear the area for potential damage is quiet limited, unlike something that orbits the Earth. Kinda reminds me of the Futurama episode where the sun shade burns through the auditorium.
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