
Scientists are working on space-based solar panels - ogezi
http://www.businessinsider.com/space-based-solar-panels-beam-unlimited-energy-to-earth-2015-9
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eloff
You can see why Elon Musk thinks the economics of space based solar is
untenable. I think his argument is sound.
[http://www.youtube.com/watch?v=gVgM2BlMczY](http://www.youtube.com/watch?v=gVgM2BlMczY)

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JoeAltmaier
tl;dw: I recall he mentions the losses due to multiple format conversions
(light:electricity, electricity:laser, laser:electricity). But these losses
get smaller as technology improves. And the 24X7 advantages pretty much make
up for that. Ground-based solar has the disadvantage of 'night'.

Further, ground-based stations require land, damage ecosystems, are eroded by
weather, are vulnerable to politics. Stations near cities (where the energy is
needed) have political hurdles (eminent domain, right of way).

Orbital solar has its own problems. But it can be expanded at will, with no
political problems.

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eloff
Even assuming that you can get the conversion loss low enough that you're
coming out ahead due to not having night or clouds, you're still only
marginally producing more power. The cost is you have to launch all of that
equipment into orbit. That doesn't even begin to justify marginal
improvements. The whole thing is wildly optimistic and not grounded at all in
economic realities. It would take space elevator type costs of space launch to
even consider this. And if you have that, then you have cables to the ground
and you can stop worrying about conversion.

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JoeAltmaier
That's a leap. Its 10X better solar flux out there in vacuum than on the
ground. Gonna take a lot of losses to cancel that.

And its not a matter of total cost - its payback period. It keeps transmitting
for decades after being built. We plant forests, reclaim ocean, terrace
mountains - with an outlook of 20 to 100 years, and call it good business. Why
not orbital solar?

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eloff
I would say it's you who is making a leap here. [http://physics.ucsd.edu/do-
the-math/2012/03/space-based-sola...](http://physics.ucsd.edu/do-the-
math/2012/03/space-based-solar-power/)

~~~
JoeAltmaier
Guy starts out with fakery to make ground-based work better. Transmitting
thousands of miles on land is far worse proposition than he makes out - cable
losses are great. Can't use anything as efficient as a laser, because air and
dirt.

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marwann
So this is basically how satellites already work, except the energy would be
sent back to Earth through microwaves. What would be the room taken on Earth?

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jeremysmyth
It says in the article: Rectenna arrays up to six miles in diameter.

Interestingly, the article also suggests that this could be useful for remote
applications that would have difficulty getting supplied with diesel or other
fuels:

    
    
        "An advantage for the military, as well as civilians, 
         would be that they could build receivers at remote 
         operating bases and locations where it is 
         logistically difficult and incredible costly to 
         deliver diesel fuel."
    

I find it hard to see how setting up a 6 mile diameter rectenna array is any
easier than setting up a diesel supply route except in the most specific
circumstances (e.g. mountain-bound plateau inaccessible by road intended for
long-term station that can be supplied initially by a long chain of
helicopters providing the array components).

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JoeAltmaier
Half of the trillion(s) spent in the Mideast wars, was spent on hauling diesel
fuel. For air-conditioning tents. And it is never finished - have to keep
hauling forever. For any protracted conflict, you only have to build an array
once.

However a true disadvantage to arrays would be, a geostationary energy farm
would transmit optimally to land directly under it - the air is thinnest.
Steering the laser to remote places would lose efficiency as it traversed
oblique slices of atmosphere at odd angles.

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norea-armozel
Likely you'd need relay sats to beam the energy as microwave then down to the
best groundstation location. This isn't an optimal solution I think since it
would require sats that could change their orbit to link up (even if you had
them setup their initial orbits as a grid it still would require adjustments).

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JoeAltmaier
Maybe a ring of relay sats around the planet? With relatively infrequent
changes in energy switching (as ground stations are built) a static setup
could be formed. Then just modulate the beams (day/night demand flux).

For the original plan, there's no actual requirement to steer the beam. A
station isn't so large that one city couldn't consume the whole capacity. So
still a reason to build the thing.

