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Harvesting solar power in space and sending it back to Earth

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Re: Harvesting solar power in space and sending it back to Earth

#51

Post by Gravityloss »

jacques_chester wrote: post #28
vacri wrote: post #8

Earlier quoted context omitted.

http://en.wikipedia.org/wiki/Water_window It doesn't have to be absorbable by water to interact with biological matter.

Digging into it some more, it looks like I was wrong. The studies use 2.45Ghz, which is also used in most microwave ovens. The actual offsetting design element is that energy is received over a large area -- 10km^2 -- so that at any one point the radiation that a human or other living creature would receive would be below the safe threshold. Goddamit I hate being so confidently wrong.

"The functional principle of a microwave oven is not related to the resonance frequencies of water, and microwave ovens can therefore operate at many different frequencies. The resonance frequencies of water are about 20 GHz, which would be much too large to penetrate common foodstuffs. Microwave ovens work on the principle of dielectric heating.[88]"

https://en.wikipedia.org/wiki/List_of_common_misconceptions#...

From Hacker News a couple weeks back.

Re: Harvesting solar power in space and sending it back to Earth

#52

Post by jacques_chester »

Gravityloss wrote: post #51
jacques_chester wrote: post #28

Earlier quoted context omitted.

Digging into it some more, it looks like I was wrong. The studies use 2.45Ghz, which is also used in most microwave ovens. The actual offsetting design element is that energy is received over a large area -- 10km^2 -- so that at any one point the radiation that a human or other living creature would receive would be below the safe threshold. Goddamit I hate being so confidently wrong.

"The functional principle of a microwave oven is not related to the resonance frequencies of water, and microwave ovens can therefore operate at many different frequencies. The resonance frequencies of water are about 20 GHz, which would be much too large to penetrate common foodstuffs. Microwave ovens work on the principle of dielectric heating.[88]" https://en.wikipedia.org/wiki/List_of_common_misconceptions#... Fr…

It's like a rabbit hole, constructed out my errors.

Re: Harvesting solar power in space and sending it back to Earth

#53

Post by wffurr »

jlebrech wrote: post #38
dnautics wrote: post #9

Earlier quoted context omitted.

What if instead of solar panels, you put up big mirrors, and instead of earth you have them orbit far closer to the sun? Btw, great quote.

yes, and shuttling antimatter batteries back to earth.

And people get scared of "giant solar death rays" from beaming solutions for power transmission. Anti-matter batteries sound terrifying.

Re: Harvesting solar power in space and sending it back to Earth

#54

Post by zxcdw »

tripzilch wrote: post #47
willyt wrote: post #40

Earlier quoted context omitted.

Why would you put solar panels up there? Why couldn't you just focus the energy into a beam and point it towards earth like space based mirrors for one of these solar power stations[0] where sunlight is focused on a 'boiler' which generates steam for a conventional turbine. I've no idea if the physics works out but i'd be interested to hear from someone who does. [0] http://en.m.wikipedia.org/wiki/PS20_solar_power_to…

well, first thing that comes to mind is, with that anyone that builds a device that focuses a large amount of solar energy into a tight beam aimed at the Earth, I'll have a hard time believing that's going to be used for some benevolent energy-harvesting purpose. And even if it is intended to, what will be the accuracy of this beam? what's to say some orbital junk won't crash into it and "oops" scribble a nice kilome…

I'd be surprised if most didn't think of this at some point when reading the original article, let alone when talking about concentrating huge energies from space in general.

That said, perhaps people don't consider it feasible, as in, "not in MY world". Sounds dystopian sci-fi and so on.

Re: Harvesting solar power in space and sending it back to Earth

#55

Post by angersock »

jacques_chester wrote: post #30
kokotko wrote: post #7

"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…

The thing is that in the time when solar orbital was first discussed, solar panels sucked and oil was super-expensive. I think the O'Neill designs were based on concentrating mirrors and turbines. He claimed it could pay for itself within a standard utility company's financial planning horizon of 30 years. And then oil prices went back to normal. The real conceptual competitor at the time -- in fact, it's still the r…

But nuclear is evil and not cleantech.

Re: Harvesting solar power in space and sending it back to Earth

#56

Post by primitur »

schiffern wrote: post #41
kokotko wrote: post #7

"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…

>solar panel is on-orbit, you get twice the solar energy - assuming that it is out of Earth's shadow Not quite. When compared to stationary panels (which beat trackers economically, so they should be the baseline), space-based power harvests π (yes, pi) times as much sunlight due to lack of cosine loss, plus there's the bonus of reduced reflective loss. Atmospheric and weather loss is avoided entirely. I would estima…

>>>It's an interesting niche tech, but spaceflight is just so expensive that I doubt it'll ever be viable.

Harvest the energy in space. Microwave it to the wing-surface receivers of ultra-light high-altitude gliders which use the energy to stay aloft.

Use the gliders as a platform from which to deliver rockets.

Re: Harvesting solar power in space and sending it back to Earth

#57

Post by icegreentea »

This blog likes to crush various energy schemes with math and physics.

http://physics.ucsd.edu/do-the-math/2012/03/space-based-sola...

Honestly, reading through his stuff is almost depressing. But as long as he sticks to the physics stuff, it's pretty hard to argue - all the math and sources are there.

The planned proposal claims that they can use some nifty beamforming to get good microwave transmission. It appears that the proposed technology will reduce the weight to diameter size of the transmitter, but Do The Math's calculations should still more or less be in the right magnitude.

Re: Harvesting solar power in space and sending it back to Earth

#58

Post by justincormack »

jacques_chester wrote: post #30
kokotko wrote: post #7

"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…

The thing is that in the time when solar orbital was first discussed, solar panels sucked and oil was super-expensive. I think the O'Neill designs were based on concentrating mirrors and turbines. He claimed it could pay for itself within a standard utility company's financial planning horizon of 30 years. And then oil prices went back to normal. The real conceptual competitor at the time -- in fact, it's still the r…

Oil prices went back to "normal" for a bit but have since gone back up. This chart http://inflationdata.com/Inflation/Inflation_Rate/Historical... is out of date, but we are roughly back at the 1980 peak in real terms again (Brent was $113 last time I looked, US prices are probably slightl lower).

Re: Harvesting solar power in space and sending it back to Earth

#59

Post by oakwhiz »

jacques_chester wrote: post #52
Gravityloss wrote: post #51

Earlier quoted context omitted.

"The functional principle of a microwave oven is not related to the resonance frequencies of water, and microwave ovens can therefore operate at many different frequencies. The resonance frequencies of water are about 20 GHz, which would be much too large to penetrate common foodstuffs. Microwave ovens work on the principle of dielectric heating.[88]" https://en.wikipedia.org/wiki/List_of_common_misconceptions#... Fr…

It's like a rabbit hole, constructed out my errors.

s/out/out of/ :-)

Re: Harvesting solar power in space and sending it back to Earth

#60

Post by jacques_chester »

justincormack wrote: post #58
jacques_chester wrote: post #30

Earlier quoted context omitted.

The thing is that in the time when solar orbital was first discussed, solar panels sucked and oil was super-expensive. I think the O'Neill designs were based on concentrating mirrors and turbines. He claimed it could pay for itself within a standard utility company's financial planning horizon of 30 years. And then oil prices went back to normal. The real conceptual competitor at the time -- in fact, it's still the r…

Oil prices went back to "normal" for a bit but have since gone back up. This chart http://inflationdata.com/Inflation/Inflation_Rate/Historical... is out of date, but we are roughly back at the 1980 peak in real terms again (Brent was $113 last time I looked, US prices are probably slightl lower).

Absolutely, but in the meantime solar panels have improved enormously also. The third part of the equation is launch costs, which haven't really fallen at all.
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