
How Japan Plans to Build an Orbital Solar Farm - austinz
http://spectrum.ieee.org/green-tech/solar/how-japan-plans-to-build-an-orbital-solar-farm
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cvbncvbncgbc
Elon Musk's opinion the concept( not this one in particular though ).

[http://youtu.be/J_af0ow1__E?t=43m12s](http://youtu.be/J_af0ow1__E?t=43m12s)

Let me tell you one of my pet peeves: space solar power. Okay, the stupidest
thing ever. If anyone should like space solar power, it should be me. I got a
rocket company and a solar company. I should be really on it, ya know. But
it's like, super obviously, not going to work because, ya know, if you have
solar panels - first of all, it has to be better than having solar panels on
Earth, so then you say, okay, solar panel is on-orbit, you get twice the solar
energy - assuming that it is out of Earth's shadow - but you've gotta do a
double conversion. You've gotta convert it from photon to electron to photon,
back to electron. You've got to make this double conversion, so, okay, what's
your conversion efficiency? Hmm. All in, you're going to have a real hard time
even getting to 50%. [The solar cells are better.] It does not matter, put
that cell on Earth then. See, that's the point I'm making. Take any given
solar cell, is it better to have it on Earth, or is it better to have it on
orbit? What do you get from being in orbit? You get twice as much sun - best
case - but you've got to do a conversion. You've got to convert it the energy
to photons - well, you have incoming photons that go to electrons, but you -
you've gotta do two conversions that you don't have to do on Earth, which is
you've got to turn those electrons into photons and turn those photons back
into electrons on the ground, and that double conversion is going to get you
back to where you started, basically. So why are you bothering sending them to
bloody space. "I wish I could just stab that bloody thing through the heart."
BTW - electron to photon converters are not free and nor is sending stuff to
space. Then it obviously super doesn't work. Case closed. You'd think. You'd
think case closed, but no. I guarantee it's gunna come up another ten times. I
mean, for the love of God.

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anateus
He's ignoring one constraint: land area. You need to put those panels
somewhere. This approach let you perform the concentration somewhere you
aren't renting real estate. For an extremely dense island nation like Japan
this actually makes a lot of sense.

Now, this doesn't refute the issues Musk is bringing up here, but he isn't
taking consideration of this factor at all.

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chc
Is this actually easier for an island nation than, say, floating solar panels
in the surrounding waters? I assume Japan must see some benefit to space, but
I'm having trouble working out just what it is.

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pokstad
What about the ecological effect on plant/plankton life in the ocean blocked
by these floating panels? Assuming the cost of producing solar panels
eventually comes down and we can cover large areas of the ocean, won't it take
a toll?

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BrandonMarc
Another ignorant question ... so you have a massively powerful microwave beam
pointed at a certain spot of your nation. What happens when it misses? Passes
over the inhabited land that's infinitesimal fractions of a degree away from
the target?

From 36000 miles, a few miles is a rounding error. Must take some huge
tolerances to keep the beam pointed in the right place.

Is this even dangerous, or am I off base? I know they're nervous about nuclear
since Fukishima, but unless I'm mistaken there's similar risks with this
option.

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puls
I can't believe nobody has mentioned this yet: exactly this was one of the
standard disasters in SimCity 2000, where "microwave" was one of the power
plant types.

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HCIdivision17
Thanks for saving me the trouble.

Microwave tech was awesome and cost effective until the first time the
satellite got out of alignment and burned half the city down. I've been
terrified of the idea ever since: you just can't make a weapon like that fail
safe, and if you _do_ manage, then your throughput is too low to make it worth
it.

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worldsayshi
What you possibly could do is to not have a single emitter but loads of them
for each collector. So that a single satellite getting out of alignment would
be harmless. Many emitters would need to get out of alignment pushing the beam
in the same direction for it to be harmful.

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resu
Wouldn't a structure this large be inevitably hit by debris, whether from our
own junk or stuff from elsewhere in space?

They'd need a gundam squadron to protect it too.

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grecy
I was also wondering about the shadow it would cast...

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thret
I'm sure someone here will do the math, but short answer is that it wouldn't
produce a noticeable shadow. Too small, too high.

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cvbncvbncgbc
The apparent size of the structure in the sky, is on the order of three
magnitudes smaller compared to the size of the moon.

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csense
It seems like the article discusses the challenges of building large
structures in space.

Maybe the large-scale building techniques developed for this application would
be useful for building large space stations. Space would be a lot cheaper if
our spacecraft didn't have to use huge amounts of fuel to get out of earth's
gravity well, which logically implies production [1] and refueling facilities
in space using resources that don't have to be brought from Earth.

Which will probably be bigger structures than the ISS, which means the
technology to build large structures in space is something which will be
useful for reasons beyond solar power.

[1] At first, the spacecraft itself will probably be built on earth, and fuel
will be the only thing produced in space.

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danielweber
I really really want to see the numbers on this.

1\. How much mass are they putting into orbit?

2\. How much is it costing them to put that into orbit?

3\. How much energy will that generate?

4\. How long will the solar cells last?

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jessaustin
I don't think there are many power plants on Earth that function unattended
and maintenance-free for very long. It will be nice if transport to space will
be commonplace enough 25 years from now that sending a regular rotation of
maintenance techs will be feasible.

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e12e
Pfft forget about using this for mere electrical power. Boil the sea to make
it rain!

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Fando
This idea reminds me of the ION cannon from Command & Conquer.

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spiritplumber
Death ray. Mwhahaha.

