How Japan Plans To Build Orbital Solar Power Stations

the_newsbeagle (2532562) writes "Solar power stations in orbit aren't exactly a new idea — Asimov set one of his stories on such a space station back in 1941. Everyone thinks it's a cool idea to collect solar power 24 hours a day and beam it down to Earth. But what with the expense and difficulty of rocketing up the parts and constructing and operating the stations in orbit, nobody's built one yet. While you probably still shouldn't hold your breath, it's interesting to learn that Japan's space agency has spec'd out such a solar power station."

Comments

If you're just beaming it down to earth anyways

[mark-t]

why not just collect it from the ground in the first place?

What's going to make collecting energy on the ground from a satellite more efficient than collecting it from the sun?

Re:If you're just beaming it down to earth anyways

[Maury Markowitz]

> why not just collect it from the ground in the first place?

Exactly.

> What's going to make collecting energy on the ground from a satellite more efficient than collecting it from the sun?

In theory you don't have night, so you get twice as much hours of sunlight. Add "cosine error" and the lack of weather, and you're up to five times.

But then you have to throw away half on the way down to the earth. And then the panels last half as long in space. So in the end it's a *very* small *theoretical* advantage.

Which is, of course, utterly wiped out by the cost of launch. And everyone knows this. But the guys proposing these things are not power companies, but space companies. As is the case here, it's JAXA, the Japanese space agency. Everyone outside the space field is completely aware of the fact that this is an utterly ridiculous idea.

Re:If you're just beaming it down to earth anyways

[alexander_686]

2 reasons.

First, you don’t have to worry about your power going out at night. These things are so far away that the earth’s shadow will rarely fall on the array.

Second, in theory cells in space should be more efficient then cells buried underneath the atmosphere. I am not sure if they can overcome the practical problems to make it actually more efficient.

Side note – the US military is also looking at this. Beaming power to remote locations could be more efficient then hauling fuel. Power could be beamed to drones, giving them unlimited endurance.

Re:If you're just beaming it down to earth anyways

[Maury Markowitz]

> First, you don’t have to worry about your power going out at night

But that's not a problem we actually have. Baseload power is currently selling for 2 to 3 cents, peak power is up into the 20's. No one is going to build a space-o device to provide something we have trouble giving away.

> cells in space should be more efficient then cells buried underneath the atmosphere

Actually, the opposite is true. Cells, silicon ones anyway, are more efficient under the air. It has to do with their band gap.

> Beaming power to remote locations could be more efficient then hauling fuel

The problem is that all you're doing is replacing the array of solar panels with an array of dipoles. The increase in energy density is about 50%, so you need a field that's almost as big as normal PV. There's really no advantage here.

Re:If you're just beaming it down to earth anyways

[gstoddart]

What's going to make collecting energy on the ground from a satellite more efficient than collecting it from the sun?

Probably the ability to do it for more hours than you would have daylight?

If there exists an orbital path which can see the sun 24 hours/day, and that same orbital path lets you see the receiving stations, say, 18 hours/day ... you get more access to sunlight than you would otherwise.

Besides, it has the added benefit that if your neighbors get a little uppity, you let your mirrors slide a little off course and get a little more tightly focused ... bam, instant death ray. And, that's where the real money is. ;-)

Re:If you're just beaming it down to earth anyways

[ubergeek2009]

The power will be transmitted as microwaves, which aren't scattered by the atmosphere as easily as visible light.

Re:If you're just beaming it down to earth anyways

[DerekLyons]

A satellite in geosynchronous orbit is in daylight essentially 24/7/365. A solar panel on the ground.... isn't.

That being said, this is about as newsworthy as yet another Bennet Hazelton bloviation. Solar power sats have been spec'd out by any number of agencies or organizations with the engineering chops to do so, and they all come a cropper on the same issue - it's simply too goddam expensive to boost the satellite's components into orbit.* Even SpaceX's most fevered dreams of how low they can reduce the costs ends up being too expensive by a wide margin. Not to mention that even adding another 9 or two to the current dismal reliability** of space launchers not only vastly increases the cost, but due to the number of launches required still means you're almost certain to lose at least one of your payloads.

* No, building out asteroid or lunar mining technology isn't much help due to the immense cost of doing so.

** On average, somewhere between .94 and .96 for mature launchers.

Re:If you're just beaming it down to earth anyways

[mark-t]

The article.

Mirrors in orbit would reflect sunlight onto huge solar panels, and the resulting power would be beamed down to Earth.

Re:If you're just beaming it down to earth anyways

[Bengie]

I would not want to be a bird or in an airplane if I passed under this satellite. They'll have to make sure they have some really good fail-safes in place in case it pivots any. I've played SimCity 2000, I've seen what a microwave power plant can do.

Re:If you're just beaming it down to earth anyways

[MetricT]

It's not a completely stupid idea, just a mostly stupid idea.

But it might make financial sense for powering McMurdo Base, for instance. The cost of hauling diesel down there is almost as ludicrous. Remote outposts and stuff.

Or if your government decided to send a small team of special forces into hostile territory, that would be a convenient way to provide them power. And you could use "cheap solar power for everyone" as good cover for launching something.

Re:If you're just beaming it down to earth anyways

[Mr D from 63]

Isn't there a bit of irony in the idea, in a time of global warming attributed to greenhouse capture of solar heat, to capture even more solar energy and send it to earth? A large amount of that energy will be dissipated as heat eventually.

In the end, it seems like a cost prohibitive pipe dream.

Not going to happen

[Maury Markowitz]

The numbers don't work. Period.

http://matter2energy.wordpress.com/2012/03/17/the-maury-equation-redux/

Re:Not going to happen

[Maury Markowitz]

> The Japanese don't have a Nevada to put vast solar arrays into

It is important to note that the safely limits for microwave radiation is about 10 mW/cm^2. It is widely assumed that this number would be increased for a SPS system, and the baseline figure is 23 mW/cm^2. That compares to about 90 to 110 mW/cm^2 for "bright direct sunlight" under AM1.5 to AM1 conditions.

Let's examine the numbers. The article speaks of a collector "3 kilometres long". Let's assume, for the math, that this is the diameter of a circular collector, so that would be pi x 1500^2, or about 7 million square meters. In Japan, which is just about exactly AM1.5, that's 900 W/m^2, so that's 6.3 GW of power falling in that area. If covered with conventional panels with an arial efficiency of 16%, which is common these days, then this array using ground-mounted panels would generate 1.8 GW of power.

Now how much power is their design supposed to generate? 1 GW.

So you see the problem Now admittedly the *daily* energy produced would be about 24 GWh for the SPS and about 10 to 16 GWh for the solar panels (the upper limit assumes trackers). But I think you will agree that the small increase in size needed to cover that gap in total production, assuming you even want that (no one wants power at night, we're sleeping) is never ever ever ever going to cost less than the satellite. Even in Tokyo!

> but the energy received from the sun in space is stronger before it is weakened by passing through the atmosphere

About 25%, which is mostly reflection and scattering. Some of that you get back as diffuse blue-sky radiation. Overall it's much smaller than you might think - you can see the sun after all, think about what that actually means. Offsetting this is the drop in efficiency of the cells due to the spectrum, which is from 16 to 14%. This makes up a good chunk of what's left. In the end, it's pretty much a wash, maybe a few percent, at best.

> Your Insolation numbers seem to indicate a 6 hour day on earth with a 24 hour day in space

Those numbers include EVERYTHING. And I mean EVERYTHING, I mean everything from direct sunlight to diffuse sunlight to reflections off snow to dust on the panels to clouds in the sky to whether or not its cloudier in the morning or afternoon where you live to losses in the wiring to reflections off the glass on the front. If you can think of a loss mechanism, its accounted for in there.

> the mirrors wouldn't degrade at the rate the panels do

Go read the wiki article on space debris (which I basically wrote) and look at some of the images. Are you still so sure?

Trust me, I've looked at this issue six ways to Sunday. It cannot possibly work.

SimCity 2000?

[VorpalRodent]

If there's anything I've learned from video games, it's that this is a bad idea.

Re:Blofeld-San's new proposal approved

[Joe_Dragon]

Just trun on no disasters and it will be fine.

Corn fields?

[Hamsterdan]

Just imagine if they aim that thing at corn fields? I can see the headlines, major city destroyed by popcorn tsunami...

They should put it at L5

[karlandtanya]

Words: Bill Higgins and Barry Gehm c. 1978
Music: "Home on the Range"

Oh, give me a locus where the gravitons focus
And the three-body problem is solved,
Where the microwaves play down at three degrees K
And the cold virus never evolved.

CHORUS: Home, home on LaGrange,
Where the space debris always collects.
We possess, so it seems, two of man's greatest dreams:
Solar power and zero-gee sex.

We eat algae pie, our vacuum is high,
Our ball bearings are perfectly round.
Our horizon is curved, our warheads are MIRVed,
And a kilogram weighs half a pound. CHORUS

You don't need no oil, nor a tokamak coil,
Solar stations provide Earth with juice.
Power beams are sublime, so nobody will mind
If we cook an occasional goose.

INTERLUDE (to Oh, What A Beautiful Morning)
All the cattle are standing like statues.
All the cattle are standing like statues.
They smell of roast beef every time I ride by,
And the hawks and the falcons are dropping like flies...

I've been feeling quite blue since the crystals I grew
Became too big to fit through the door.
But from slices I sold, Hewlett-Packard, I'm told,
Made a chip that was seven foot four. CHORUS

If we run out of space for our burgeoning race
No more Lebensraum left for the Mensch,
When we're ready to start, we can take Mars apart
If we just find a big enough wrench. CHORUS

I'm sick of this place, it's just McDonald's in space
And living up here is a bore.
Tell the shiggies "Don't cry," they can kiss me goodby,
'Cause I'm moving next week to L4!

Re:But what does an actual physicist think?

[Virtucon]

While I agree with your comments I do have to point out that it's nice to set goals and to think out of the box when it comes to new ideas. Back in the 1960s we had this President that set a goal for the US in reaching the Moon, which we did. People need goals and objectives to strive for otherwise they become hopeless derelicts like Cliven Bundy.

Re:Blofeld-San's new proposal approved

[jcomeau_ictx]

_Dark Rivers of the Heart_ by Dean Koontz. the sat is nicknamed Godzilla and a programmer, Ellie, has a backdoor into it. great book.

Re:Satellites have eclipses

[Teancum]

The cost of sending 10 metric tons to LEO and about 5 metric tons to GEO is claimed by SpaceX to be slightly under $60 million USD, or about $6k/kg. That seems to be at least a competitive price (few companies say they can beat SpaceX on launch costs). From this figure, sending 10000 metric tons to GEO would be something like $120 Billion. Some cost savings could definitely happen, although the reusable Falcon 9 with all parts being reused on multiple flights is still about $7 billion each, or dropping that price down to about $14 Billion.

Regardless, a guy who knows the figures for the solar power industry, Elon Musk, who also happens to own a spacecraft launching company as well as a completely separate solar panel manufacturing company (in the form of Solar City) has repeatedly said that spaced based solar power for terrestrial consumers makes absolutely no sense and is something he refuses to become involved with because he thinks it will be a financial disaster if anybody tries to get one going.