71–80 of 83 posts
"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…
Seems to me that a significant advantage of 'space solar' is that you can ditch a significant amount of ground based distribution infrastructure. Transformers are pretty efficient but lose about 2% per step up/down[1], power lines are another 1-4%/100 miles[2], then you have losses related to storage since you can't turn solar on/off at will like you can with hydro or fired plants. If a single solar sattelite [multip…
Woah there. Exactly how much power would each of these hypothetical satellites provide?
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Who cares about the efficiency when solar panels weigh over 50 kg per kW? Even at SpaceX prices, the cost of launching a solar panel into space is hundreds of times the cost of the panel. If your alternatives are "buy 500 panels and put them on the ground" and "buy one panel and put it in space," why the hell is anyone even remotely considering the second option?
Wasn't the original concept for SPSS (at least in O'Neils The High Frontier) to build them out of mined asteroid materials? At that point the cost of the proposal is disconnected from the cost of launching the panels. I've heard many analyses of that which do suggest the economics of it is inevitably atrocious for ground-launched SPSS. Cost numbers for asteroid mining vary by a couple orders of magnitude though, whic…
Doable? Sure. But you have to make a lot of panels before it pays off.
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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…
Quite unintuitively, you can't really focus light from the sun to a long distance, since the sun is not a point source. Basically, you can't exceed the power per steradian of the sun with mirrors. So you would have to fill a large portion of the receiving end's sky to transmit any real power. Which means the mirrors would have to be really close (like they are in heliostats) or if they're far away, they would have to…
This is something I've wondered about. It seems like one should be able to make a counterexample by focusing an enormous area on a tiny one. Is it just because due to "fuzzy focus," the concentrated focus volume unavoidably grows as the mirror size grows?
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Solar energy is actually nuclear energy.
All energy is actually nuclear energy. (Of course Earth-based nuclear power doesn't have the entire mantle of the sun as radiation shielding. So there's that…)
Geothermal is in part latent residual heat of formation, which is arguably either kinetic or gravitational energy again. Some is _also_ the result of radioactive decay, though I don't have the precise breakdown.
I suppose there might be some ways of tapping planetary or stellar magnetic fields, which aren't directly caused by nuclear power.
Similarly energy systems based on collapsed stars (white dwarves, neutron stars, black holes) would not be directly driven by nuclear processes.
But yes, your point generally stands: most available energy on Earth is largely ultimately derived from nuclear reactions.
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Wasn't the original concept for SPSS (at least in O'Neils The High Frontier) to build them out of mined asteroid materials? At that point the cost of the proposal is disconnected from the cost of launching the panels. I've heard many analyses of that which do suggest the economics of it is inevitably atrocious for ground-launched SPSS. Cost numbers for asteroid mining vary by a couple orders of magnitude though, whic…
So now instead of launching panels, you're launching a panel factory . Actually you're launching their entire supply factories too (mining, high-purity silicon boule manufacturing, wafer cutting, smelting metals for busbars and backing, etc). None of this has been done in microgravity before. Everything will need mass optimization, and you need provisions for maintenance and repair on all these systems. Doable? Sure.…
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Concentrators have problems. If you use them with solar panels, then your panel will heat up and its efficiency will drop. Maybe lifetime as well. If you use a thermoelectric generator, you then have wearing mechanical low efficiency systems on board. In both cases you need to reject heat, which is hard in space. They also require precise pointing. There's also the problem of beaming the power to earth. If you're in…
Yep, after writing all that I realized that heat rejection is going to be a problem. Dissipating 8.4 MW is no easy feat in orbit. At that point the balance of system probably shifts to thin film PV. There would need to be a lot of advancement in that area before such a project becomes practical. >What about beaming between satellites? You'd need a laser for that. I was picturing a microwave rectenna, actually.
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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.