
Building solar farms above the clouds - rmason
https://news.cnrs.fr/opinions/solar-energy-aims-for-the-sky-0
======
jws
I just did the math, it works out!

What we need to do is move the aluminum reduction cells into floating solar
powered processing units which drift around the world receiving aluminum oxide
from drone craft and deliver refined aluminum back to them.

It will take 59 kilojoules per kilogram to raise the ore to 6km, times the
inefficiency of the craft, lets say a number less than 10. Plus, aluminum
oxide is only about half aluminum so another 2, lets call it 1 megajoule per
kilogram of aluminum in round numbers.

Refining aluminum oxide into aluminum takes 54 megajoules per kilogram of
aluminum! (according to a number I found on the internet and most probably
read correctly).

That makes the energy to raise the aluminum negligible. So forget about how to
transmit electricity down from the solar pelagic behemoths drifting lazily
around the planet, just use them to refine aluminum.

Ships of aluminum oxide will cruise out to the behemoth orbitals and track
them while they exchange their cargo for refined aluminum.

Presumably a sufficiently clever person will find areas in the Pacific ocean
where the behemoths can lazily circle by gently pushing themselves from
eastward to westward currents using altitude variation which is easy by
controlling how much inventory is onboard, but also by how much waste heat you
put into your gas bags. Sure, once in a while they will be blown away on
longer excursions, that will take them offline until they can get back over
another drone supply ship.

This is the future science fiction has been promising me!

------
Animats
Solar in space is only about 2x more effective per unit area of solar panel
than solar on the ground, after you deduct transmission losses. The costs, of
course, are much higher. The enthusiasm for hydrogen as energy storage is
misplaced. Electricity to hydrogen to electricity is maybe 40% efficient.
Lithium batteries are 80% - 90% round trip.

In any place that needs air conditioning, solar power is very effective. Peak
load and peak solar panel output line up nicely, and little storage is needed.
Keep it simple.

~~~
m-i-l
Some countries don't get much sunshine though, e.g. the UK only gets sun
around 30% of the daytime according to
[https://en.wikipedia.org/wiki/Climate_of_the_United_Kingdom](https://en.wikipedia.org/wiki/Climate_of_the_United_Kingdom)
.

~~~
cmsmith
Spain isn't that much farther away than outer space.

~~~
CapitalistCartr
We can't beam energy from Spain to elsewhere via microwaves, though. And it
still gets dark at night in Spain.

~~~
notahacker
It gets dark in the stratosphere too, and the UK already has a power grid
connecting it with the Spanish power grid which doesn't rely on 20km cables
into the sky...

~~~
CapitalistCartr
The parent post was about outer space, not the stratosphere. And that method
uses microwave transmission, not cables.

~~~
dogma1138
Outer space gets dark too you not sure which orbit will get you 100 sun time
solar synced orbits still get 50% night time. Maybe some geosync high polar
orbit but then you have issues with transmition. Space solar makes very little
sense you only get twice the solar power at 50% efficiency rate at best.

------
sevensor
How are these things supposed to stay aloft? They need to lift:

1) Themselves

2) The solar panels

3) Fuel cells

4) 20km of tether and cable

The idea seems really neat, but I'm an engineer and I want to see the math.

Edit: And how about that tether? What's the wind load going to be like? How is
it moored? What is it made of?

~~~
djKianoosh
why tether? why not let the balloon charge a battery, and have drones carry
the battery back to earth when full, and vice versa...

~~~
Jedd
Good question. The winds up there are _really_ strong.

Tethering also lets you wind the appliance back to the ground even when
(especially when) it's faulty.

Tethering also lets you obtain power throughout the 12+ hours of power
generation per day.

~~~
djKianoosh
Maybe the balloons could be autonomous as well, rising/falling depending on
conditions, and also falling to an acceptable elevation for the drones to
reach them efficiently :)

------
acd
It seems easier to put solar power in deserts Mojave desert, Sahara and
transport the power via high voltage direct current which has low tranmission
loss.

[https://en.wikipedia.org/wiki/High-
voltage_direct_current](https://en.wikipedia.org/wiki/High-
voltage_direct_current)

It should also be possible to put solar power high on mountains in areas where
they place observatories that is no cloud cover.

------
gozur88
The fuel cell part is a bit dodgy. It would make more sense to include a
little hydrogen bottle on the tether if extra H2 is needed to top of the
balloon.

And there's no point to storing power in the air like that - it's better fed
to the grid when the sun is shining to be stored at the grid level. Generating
hydrogen just isn't a very efficient way to store power.

------
mhandley
If you're going to use huge tethered balloons, why use PV? You've got the
benefit of strong predictable winds up there, 24 hours a day, so once you've
bought into the cost of tethered aerial power, wind seems a better bet.

------
aaron695
More junk science designed by artists?

Wind I can see making sense since at high altitudes, it's more constant.

Creating and storing the hydrogen in the balloon triggers a strong, this is
just fluff. We can't really even do this on the ground.

They are inventing two new technologies we yet don't have?

I going to go with, it'll be better covering the other 98% of roof space with
solar first. And get wind powered balloons going for night time use if you're
going down this route.

------
lordnacho
I live in the mountains just a few hundred meters above sea level. It's often
clear here when it's cloudy in the valley. There must be other places like
this where you could put the panels, without having to resort to balloons?

------
viacoffee
Although it has always been a good idea for something like this. I'd be
surprised if the FAA allowed such a thing to happen. It would have to be a
permanent NOTAM, and in an already existing no-fly zone for personal aircraft.

~~~
eric_h
Save you folks a google:

A Notice to Airmen (NOTAM or NoTAM) is a notice filed with an aviation
authority to alert aircraft pilots of potential hazards along a flight route
or at a location that could affect the safety of the flight.

NOTAM - Wikipedia, the free encyclopedia
[https://en.wikipedia.org/wiki/NOTAMWikipedia](https://en.wikipedia.org/wiki/NOTAMWikipedia)

------
Htsthbjig
Oh, yeah, and give me shadows in the land.

I hate the idea because it has the potential for abuse: If it works it means
blocking the sky for those under. Like making clouds to artificially rain on
your land, while not raining where it used to rain.

Sun is one of those fantastic things that is free. Free until someone has the
idea to appropriate it.

Problems to aircraft makes this idea non practical near population centers,
where energy is consumed. It is possible in the ocean.

~~~
oska
The shadow from a balloon six kilometres up is basically non-existent. When
was the last time you noticed a shadow from an overflying jetliner cruising at
that height?

------
davnils
Isn't it easier to modify the weather in an area populated with PV?

~~~
blacksmith_tb
Modify it how? We have some fairly blunt instruments like seeding clouds to
modify weather, but those wouldn't be of much use here. Of course, it seems a
lot more straightforward to build solar farms in Arizona or Algeria, though
transmission is still a problem. Possibly they could be used to generate
hydrogen for synthesizing fuels...

~~~
davnils
True, seem to be harder to go the opposite way.

Something noteworthy: China plans to halt rain for Olympics -
[http://www.latimes.com/world/la-fg-
rain31jan31-story.html](http://www.latimes.com/world/la-fg-
rain31jan31-story.html)

------
Findeton
What kind of danger would this kind of thing pose to airplanes?

~~~
bigiain
I was making this argument in another thread yesterday.

The fact that aviation currently assumes it has exclusive right to all
airspace does not mean things have to be (or even should be) that way.

The vast majority of commercial air traffic file flight plans and flys along
well know routes.

There's currently outcry about drone pilots "flying in dangerous manner for
airplanes/helicopters", but it seems to me that nobody ever agreed that the
occasional police or news helicopter flying over my local park was
automatically reason to ban flying drones/kites/rc-aircraft there _ever_.

Same here, just because general aviation has had un-contested access to the
sky and the freedom to assume they're entitled to unimpeded safety
_everywhere_, is not something we've ever chosen - it's just "the way things
have always been", which isn't necessarily "the way things should stay".

If someone comes up with a technical way to make tethered balloons work as a
reliable and cost-effective renewable energy source - I personally don't think
that "but it might impose a safety risk to airplanes who want to fly there" is
a good enough reason to not allow them to try.

There's is (I suspect) a great "safety risk" to flying your Cessna or
gyrocopter over, say, Area 51 or Groom Lake or The Whitehouse, why shouldn't
pilots have the responsibility to avoid tethered-balloon electricity plants as
well? Surely the net benefit to society of a few GW of renewable energy is way
more than the ability of civilian pilots or news choppers to have unlimited
access to all airspace at all times for no reason?

