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Building solar farms above the clouds

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Re: Building solar farms above the clouds

#11

Post by cmsmith »

m-i-l wrote: post #8
Animats wrote: post #5

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. P…

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 .

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

Re: Building solar farms above the clouds

#12

Post by undersuit »

sevensor wrote: post #10

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?

They are energy collectors, I would assume you use some of that energy to heat the air in their balloons.

I'm more interested in how you optimally position the solar cells, would a sphere really be the best or would a pontoon dragging in the wind give a better chance for the solar panels to receive optimal light? You probably don't want that 20km tether to be twisted too many times either.

Re: Building solar farms above the clouds

#13

Post by feelix »

m-i-l wrote: post #8
Animats wrote: post #5

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. P…

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 .

It also doesn't need much air conditioning. And when it does, it's because the sun is out.

Re: Building solar farms above the clouds

#14

Post by [deleted] »

Shivetya wrote: post #7
Animats wrote: post #5

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. P…

Lithium batteries are not portable, hydrogen can be. With sufficient solar power generation that forty odd percent efficiency would become a non issue.

[deleted]

Re: Building solar farms above the clouds

#15

Post by sevensor »

undersuit wrote: post #12
sevensor wrote: post #10

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?

They are energy collectors, I would assume you use some of that energy to heat the air in their balloons. I'm more interested in how you optimally position the solar cells, would a sphere really be the best or would a pontoon dragging in the wind give a better chance for the solar panels to receive optimal light? You probably don't want that 20km tether to be twisted too many times either.

Interesting point about placement --- seems like a dense array of these would be at risk of getting tangled. And then there's the risk of the tether / cabling becoming a conduit for electrostatic discharge. Of all the engineering issues here, I think tethering is the most problematic.

Re: Building solar farms above the clouds

#16

Post by CapitalistCartr »

cmsmith wrote: post #11
m-i-l wrote: post #8

Earlier quoted context omitted.

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 .

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

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

Re: Building solar farms above the clouds

#17

Post by 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!

Re: Building solar farms above the clouds

#18

Post by codecamper »

Animats wrote: post #5

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. P…

Hydrogen could be handy for heating. The efficiency would be higher too, since what you want is heat & you get all of it by simply burning it.

You could collect it in North Africa and distribute to Europe in the winter.

Re: Building solar farms above the clouds

#19

Post by 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

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

Re: Building solar farms above the clouds

#20

Post by djKianoosh »

sevensor wrote: post #10

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?

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