Space-based power

[icarus]

800 gigawatt-hours in first year of operation 2016 ... uh-huh, beamed through the ionosphere no problemo ...

http://science.slashdot.org/article.pl? ... &art_pos=3

If PG&E will sign onto this kind of risky venture could Polywell not get such backing? Seems to me the Navy nature of the project becomes more of an impediment than a help at some point.

[KitemanSA]

If PG&E will sign onto this kind of risky venture could Polywell not get such backing?

I'm pretty sure PG&E would sign a similar agreement with EMC2, but what of it. It provides ZERO backing other than providing a "we got a buyer" statement to REAL investors. With electricity, I don't think there is much doubt of that anyway.

But... it may be something Dolly would want to think about.

[icarus]

Kiteman: you've missed the key point of difference between commercial and govt. operations ... financial incentives to deliver, i.e. a loss in case of non-performance.

clipped from link:
"Solaren's director for energy services, Cal Boerman, said he was confident his company would be able to deliver the power starting in mid-2016, as specified in the agreement. "There are huge penalties associated with not performing," he told msnbc.com. He said PG&E would be "our first client" but was not expected to be the only one."

I'd have more confidence if EMC2 signed up to one of these, ... "money talks, BS walks...", I think is the phrase.

[D Tibbets]

800 gigawatt-hours in first year of operation 2016 ... uh-huh, beamed through the ionosphere no problemo ...

http://science.slashdot.org/article.pl? ... &art_pos=3

If PG&E will sign onto this kind of risky venture could Polywell not get such backing? Seems to me the Navy nature of the project becomes more of an impediment than a help at some point.

The cost would be, well, astronomical
Take ISS as a baseline. How many shuttle missions have been primarily for building the truss system and solar panels for the space station. Lets say it was 4. That means ~ $1.2 billion launch costs alone for mearly a few hundred thousands watts of capacity. Assume lauch costs can be reduced to ~$100 per pound (~1/100th of the shuttle or ~ 1/20th of the best current rockets). That would mean a launch cost of ~ 20 to 30 billion dollars. And, that doesn't include the materials cost, assembly, maintainance, ground station costs, etc. Not to mention risk of damage from orbital debri, possible strong solar flares, system failures ( ISS solar panels and thier pointing assemblies have not been without problems).
So, the start up and operational costs might be > 40 billion dollars (I'm guessing this is a conservative estimate). Compare this to a fission nuclear plant that provides more power at perhaps 1/10th the cost (?) or a coal plant that would be even cheaper (even with the cost of coal figured in). Large ground instillations of solar panels or windmills surely would be much cheaper, even if they only provide 10-20% of thier rated capacity on average.

Without a profound breakthrough in the cost of launching material to LEO (well beyound $100 per pound) these projects have to be speculative at best*.

If maintaining a sufficiently low vacuum is the limiting factor in the Polywell's success, building them in low Earth orbit and beaming the power to Earth might be cheaper than building and maintaining huge solar panel assemblies in space.


*Only things that comes to mind is rail systems or a space elevater, or a Bussard type SSTO Polywell powered system (of course, if the Polywell works, the power generation problem is moot).


Dan Tibbets

[Helius]

In the comments, One guy pointed out that the delivery may be a commitment, but the method isn't; They will end up with 2 or 3 wind "parks".
http://slashdot.org/~TapeCutter

[KitemanSA]

clipped from link:
"Solaren's director for energy services, Cal Boerman, said he was confident his company would be able to deliver the power starting in mid-2016, as specified in the agreement. "There are huge penalties associated with not performing," he told msnbc.com.

Huge to who? To a non-existant company perhaps, enough to end them, but not to PG&E. The point is that PG&E is putting up NOTHING except a promise to buy. I'm pretty sure that any company that makes inexpensive baseload power will get someone to buy it. I am not sure I see any real advantage to this deal. But then I am not a financier!

[MSimon]

800 GWh = a 91 MW plant operating 24/7 365.

That is a trivial amount of power. Esp for a $40 bn outlay. To be cost effective the cost of the whole contraption would need to be no more that $7
a watt. Better $1 a watt.

So let us see @ $1 a watt the cost would need to be $100 million. Certainly no more than $700 million. So the cost is between 50 and 400 times too much.

[MirariNefas]

If the mass efficiency of solar cells goes up, launch costs can meet it half way. Thin film solar may not be efficient in watts per cubic meter, but its quite good at watts per gram. One company has apparently developed a thin film capable of 4300 watts per kilogram in space conditions
(http://www.nrel.gov/pv/thin_film/docs/u ... 4wcepc.pdf). Solaren is hoping for "four or five" launches of 25 tons each - at 4300 watts per kilogram, that would translate into 430 to 537.5 megawatts.

We can assume that an array with power beaming antennae and support structures won't actually reach 4300 watts/kilogram, but if we assumed something more like 1000 watts/kilogram, we'd still be getting 100-125 megawatts from those launches. Lets assume automated deployment can make expensive spacewalk construction obsolete, and that launch costs are the dominant cost driver here. Space X founder Elon Musk has stated that launch costs of $1,100/kg are achievable with his Falcon 9 rockets (http://en.wikipedia.org/wiki/Space_x), so that would mean about $1.10 per watt, at a total cost of $110 to $137.5 million. If we assumed instead it took five launches to get a 91 megawatt satellite, that would be $1.51 per watt. Assuming development and construction costs double that, it'll still be in the competitive range.

Do I actually think it'll work out to be so economical in the next 7 years? No, because my faith in SpaceX is limited and I don't know much about construction and development costs. But I think it has a shot, and accusations of $40 billion price tags aren't waranted. I bet it'll be better than wind or earth-based solar power in the long run, however it works out.

[D Tibbets]

My earlier post was carefully researched and thought out... err, sort of.

After the above post I looked a little deeper. This link goes into detail, giving some optimistic counter arguments to a pessimistic assesment that it refers to. One key point is that $1000 per KW is needed. Current space solar systems are quoted as being ~$750,000, so conciderable improvement is needed in weight efficiency and launching costs.

http://space.alglobus.net/papers/FetterResponse.html

Lots of developement costs befor practical deployment is needed. Also, any power satallite would need to be launched to GEO or above (like a Lagrange point), not low Earth orbit, if you want to stay out of Earth's shadow for more than half of each orbit. This would considerably increase launch costs.

Part of the proposed very light solar arrays launch costs would be absorbed by the more realistic cost of ~ $2,400 per kg (~$1,100 per pound) than the $100 per pound I assumed. Another concern of a lower efficiency but much lighter solar array would possibly be the solar sail effect. Keeping a large array on station against possibly as much as a pound or two (?) of solar wind pressure would recuire additional structure/ mass/ engines which would partially offset the low mass of the light weight solar arrays. Weather this is significant, I don't know, but it is something else to scratch your head about.

Also, (another nonresearched speculation) if the weight of a current technology stallite - with a very large solar array capable of producing 1 MW and beaming it to Earth was 75% solar panels and 25% other structure, then reducing the weight of the solar panels to almost nothing would only reduce the weight of the satallite to 1/4th of it's original weight.



Dan Tibbets

[MirariNefas]

Lots of developement costs befor practical deployment is needed. Also, any power satallite would need to be launched to GEO or above (like a Lagrange point), not low Earth orbit, if you want to stay out of Earth's shadow for more than half of each orbit. This would considerably increase launch costs.

Yes and no. Yes, getting to a Lagrange point is optimal. No, it doesn't need to be directly launched there. Remember that each launch contains a large amount of power generating capacity. One way of moving something in space with a minimum of mass is an ion drive or similar thruster. What do these need most? Power. Yes, adding an ion drive decreases useful payload mass, but nowhere near as much as a launch straight to GTO. Instead of halving the payload mass, we might be cutting it by 10% or so.

Another concern of a lower efficiency but much lighter solar array would possibly be the solar sail effect. Keeping a large array on station against possibly as much as a pound or two (?) of solar wind pressure would recuire additional structure/ mass/ engines which would partially offset the low mass of the light weight solar arrays. Weather this is significant, I don't know, but it is something else to scratch your head about.

A Lagrange point is just a mathematical point where two forces balance. If a little bit of another force is added to the equation in one direction, you just need to place the object a bit farther in the other direction where gravitational forces compensate. It's a bit more math, but the satellite won't know the difference. The only problem I can see is that the force might not be constant, as with solar flares or varying solar maxima. This might require some extra fuel on the ion drives for occassional stationkeeping, but it's not like it'll be constantly thrusting against pounds of solar wind.

Also, (another nonresearched speculation) if the weight of a current technology stallite - with a very large solar array capable of producing 1 MW and beaming it to Earth was 75% solar panels and 25% other structure, then reducing the weight of the solar panels to almost nothing would only reduce the weight of the satallite to 1/4th of it's original weight.

Yes, that's why I didn't assume we'd actually reach 4300 watts per kilogram total for the satellite. I don't actually know what a reasonable minimum for structural mass is, but in zero gravity, I suspect we're not talking about giant I-beams.

You raise some good points, and I think skepticism is healthy here. I don't actually think this company can acheive something economical in the next 7 years either. But renewable energy is currently subsidized at considerably higher than $1/watt, and it's only expected that the first prototype system be considerably more expensive than subsequent ones (where development costs are spread out and economies of scale drive down launch costs). So I think there's reasonable hope for a system which is a good proof of concept in the next decade, which can be expanded into something economical and widely useful in the next two or three decades. Which will all be moot if Polywell is developed in the next two decades, but hey, why put all your eggs in one basket?

[icarus]

The biggest unproven in all this is the magical "beaming the power back to earth" fantastical technology ... or is that fantasy tech.?

It doesn't exist, hasn't been developed or proven for GEO to surface ... the ionosphere and atmosphere are not layers significant radiation powers just "beam through" magically, that's why we're able to live on this ball of rock, relatively close to a massive, fusing ball of gas.

But hey, if it's "green" and "renewable" and "sustainababble" then .gov will throw money at it forever ... or until people stop paying taxes for madcap schemes.

[pfrit]

When you look at the size and number of lifts, it may be useful for them to use the "Free" or cheap methods for moving their satellite to GEO. Tether drives and solar sails(no brainer here) to boost to GEO or the low fuel routes (really slow changes using minimal fuel and paths made by the sun and moon). As far as station keeping, the issue of the sail is a net bust. The light pressure cancels itself out over the whole orbit. I wonder if you could do station keeping by simply capturing less light at different times in orbit and let the light pressure push you where your drift has taken you.

On a different issue, why do you assume that they would deploy cells for their total area? If I was designing this, I would use mylar (Really light) and reflect the light to my high efficiency solar cells. They have passed 40% efficiency now. Use a few m^2 of cells and several hundred m^2 of mirrored mylar. Much lighter plant for the same output.

[pfrit]

Yes, getting to a Lagrange point is optimal.

No, a Lagrange point would be BAD. From the earth, Lagrange points move through the sky in orbit. Your plant would be beneath the horizon 12 hrs a day

[pfrit]

Actually, by using mylar, you could reduce the hardware costs as well. Imagine letting a sheet bell out and put the solar cells at focus of the shape. You would have minimal support weight (> zero however) in the reflector and only truly support the solar cells. Much lighter. The engineering would be much more complicated.

[MSimon]

If I was designing this, I would use mylar (Really light) and reflect the light to my high efficiency solar cells.

That gets you the problem of heat dissipation. Always a problem in space for concentrated sources.