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Lunar Power
An Anonymous Coward cites this article on ABC News, excerpting: "...the world would have access to a limitless power supply. The moon receives 13,000 terrawatts of power from the sun. Harnessing 1 percent of that energy, he calculates, could replace all fossil fuel power plants on Earth."
Yeah, except for that Ozone Layer, which has that whole 'filtering' ultraviolet light part, whereas the moon has no atmosphere.
Yeah, so uh what's so special about the moon exactly? Earth is practically the same distance from the Sun as the moon is distant from the Sun and isn't it a heck of a lot more efficient to just create a local satillite network instead of going all the way to the moon?
Or even better... just have it based, I don't know, on the ground? Once we come up with more efficient solar cells then you're all set...
I recall reading about this.
If the beams are wide enough, they don't represent an immediate danger to anything passing through them.
You microwave oven cooks so well because you have a 1000W output, in a contained space (say a cubic foot) reflecting around so most of the energy is absorbed by what you are heating.
You also need to take into account what they mean by microwave. I think microwave is a general term for everything between 1Ghz and the visible spectrum. (1mm to 30cm wavelength)
Your microwave oven operates typically on 2.4Ghz (yes, in the ISM band) (Yes, that's one reason the ISM band is license free, becuase it's dirty)
At the appropriate wavelength, and over a wide enough area, the effects would be miniscule to anything but an appropriately tuned receiver.
Yes the earth recieves much more then the moon, but...
1. There is weather here, making a project like that demand huge ongoing costs. Rain/Snow/Wind/Erosion are all very powerful forces.
2. People don't want 100 miles of solar panels...anywhere, it doesn't matter if we try to stick them in texas/Arizona, they will still be in somebodies backyard. And those people won't want them there.
3. Power distribution will kill you, a massive project like this in Arizona will really (at the very most) just help North America. And that wouldn't be exactly great PR would it?
4. Building Phase. The building of something like this would require enormous amounts of materials to be shipped somewhere. And that somewhere wouldn't like the 20 semi's going by every 20 minutes.
5. If we don't want the world to stay as it is, 1 Super-Power/100 Little Powers/1,000 Crappy Third world nations where people still die of the plague, something like this needs to be built. We need a worldwide energy distribution net so that third world countries don't feel that to succedde they need to cut down all their trees for power plants and strip mine themselves to death.
6. We have a atmosphere so the efficiency of power per square foot generated would be much lower then it would be on the moon.
I don't see this as a question of "will we?" I see it as a question of "when will we?". There's only so much oil underneath Texas/Alaska/Saudi Arabia folks. Someday there won't be any left that is economically viable to drill for.
Besides, don't we all think that a city on the moon would be cool? That it would help the sciences leap forward? This is the first step guys, if there an economical reason for us to be there, we better pack our bags and go!
On the cow manure idea:
A new 750-kW power plant at Tinesdale Farms in Wrightstown, WI, is the first in the state to be powered by cow manure. The facility uses a "digester" to convert the manure to methane, which is then burned to generate electricity. Ag Environmental Solutions, LLC (Wrightstown, WI) owns and operates the facility, and Wisconsin Gas/Wisconsin Electric is buying the power and selling it to its customers. The manure comes from 1,800 cows at Tinesdale Farms, and it generates enough electricity to power 250 homes -- http://www.achrnews.com/.snippy./
Ever need an online dictionary?
Choosing the appropriate SI prefixes for that amount gives the name "13 petawatts".
Here's the question: did they choose the "tera" prefix to create an impressive number, or because somehow "petawatts" doesn't cut it?
Just for kicks and giggles, I thought I'd try to figure out how much area you'd need to cover to pick up that 1% of energy hitting the moon.
Radius of the moon: 6378.1 km
So the area of a disc of that radius is 1.278e8 km^2.
One percent of that is of course 1.278e6 km^2.
Lets construct our solar panels in a band around the equator, so that at any given time, 1% of the sunlight is being collected.
Treating the band as approximately a rectanle, so I don't have to think too hard, 1.278e6/6378.1 = 100.18 km
Now this stripe on a flat disc needs to be translated back to a band on the surface of a shpere. Approximating that band as a cylender, with hight 100.18km, and radius as that of the moon, we get approximately 4.0e6 km^2. For reference, thats tad less than half the size of the United States (9.629e6 km^2).
But why:
use photovoltaic
ship power back from the moon?
This was examined back in the 70s and there's a set of even better solutions. Two samples:
1) Put the actual collectors/generators in sync orbit:
Much shorter distance to ship the power.
Much greater surface area than the moon.
Negligible gravity (just tidal and station-keeping forces).
Alternatively: Use the L4 or L5 points - same distance from the Earth but still has the low-gravity and improved surface area factors.
Mine the moon for the bulk of the material, but use a catapult to launch it to orbit. (For L5 there's an orbit using one of the other L points as a lens that requires very little delta-v to perform the final injection, so the catapult does essentially all the work.) Smelt and construct it in orbit.
2) Build a STEAM plant on the ground and launch the pieces into sync orbit, where they're assembled. (Most of 'em go in reusable unmanned heavy-lifters. Much cheaper than the shuttle.)
Steam has the advantage that you don't need to do a lot of fancy processing. Just a turbine, mirrors, pipes, generators, condensers (a flat plate painted black at right angles to the sun or behind the collector mirror, with some more plumbing attached), and a trick microwave transmitter (plus an antenna farm in the desert.) You don't need much water, and it goes around and around without leaking out for decades or more, like the freon (or whatever) in a household refrigerator.
Tesla could have done it (except he'd have used VLF radio for the power feed, at considerable loss).
These proposals and several others were examined in detail by the L5 society (founded by the same Keith Henson who is now in Canadian exile over the Scientology thing).
NASA did a study on number 2, and came to the conclusion that it was too expensive. The L5 society then studied NASA's study and found an error: They'd done it in two steps:
- Design a plant.
- Design a set of vehicles to lift the parts.
The heavy-lift vehicle was sized to lift the largest single part, which was the turbine wheel, which was enormous, making the vehicle very expensive. But it turns out it was enormous only because the plant designer had gone for efficiency with no thought to the launch issue. By sacrificing 10% efficiency the turbine could be reduced to the size of the next largest part, which would enable a much smaller and cheaper rocket to do the job.
With the (unofficial) revised estimates, amortized over enough plants to feed the rate of growth of US power demand at the time, the total capital investment was a bit over a trillion bux. Sounds like a lot. But in fact it was cheaper than building any of the earthbound alternatives for the same capacity. (Fossil fuel and nuclear were both expensive - though nuclear wasn't yet politicized out of affordability - and the remaining options such as water, tidal, wind, biomass, etc. couldn't hack the demand.)
Of course that's without even considering that the fuel is free.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Most of the Sun's energy is released between 225nm and 3200nm (UV, just outside visible spectrum, through IR, quite a bit farther oustide the visible spectrum). The upper atmosphere absorbs most frequencies up to about 320nm (thank you, ozone layer). The lower atmosphere (i.e. clouds, humidity) absorbs a great deal of the energy above about 1100 nm.
The idea of having collectors on the moon is that on Earth the bulk of the Sun's spectrum is absorbed by the atmosphere. The moon has no atmosphere (ok, a negligble atmosphere). The entire spectrum can thus be collected, coverted to a narrow band frequency that has relatively low levels of absorption by the atmosphere, and beam it to Earth. Also, becuase the energy could be sent in a relatively narrow beam, the energy is easier to harnass without requiring sophisticated methods for focusing the beam (i.e. it's a lot easier to kill an ant with sunlight focused through a magnifying glass than it is to let unfocused sunlight to burn it).
Actually, all you're doing is moving the focusing aparatus to the moon. But, on the moon, it gets to focus light that has not been filtered by the atmosphere. Thus, the resulting yield will be higher than if the same operation is conducted in the Sahara Desert.
The concept makes perfect sense. It's not a logical kludge. However, I still have yet to see any sensitivity analysis conducted on the effects of adding additional energy to what is effectively a closed system. In other words, at least burning fossil fuels is harnassing energy already collected and stored by Earth. Adding energy that normally would not reach the Earth might force the system out of balance. Of course, the additional energy added to the system might be negligble compared to the energy transmitted directly to the Earth and the energy coming from our core (radioactive decay in our core? it's been a while...). I'm really curious to know how sensitive the Earth's system is to the addition of external energy sources.
--Be human.
The generators would then convert the energy into harmless microwave beams, which would be aimed at collecting stations on Earth
Apparently this dude has never put a marshmallow in his microwave oven.
You misunderstand the technology.
The household microwave oven uses K-band microwaves. These were chosen because they're strongly absorbed by water, resulting in very efficient heating of most foods. (There are several ranges of frequencies that do that. But K band is absorbed about the right amount to cook food through rather than frying the surface or mostly passing right through.) Microwave ovens also have a very high energy density because the microwaves bounce back-and-forth and build up until they're absorbed by the food (or the transmitter magnetron, which is why they burn out if you run them too long when empty).
The "microwaves" proposed for space solar power downlinks are MILIMETER waves - chosen because they're easy to handle and go RIGHT THROUGH water without being strongly absorbed. That's mostly so they'll go through humidity and clouds without major loss - though it helps that birds don't get cooked either.
At the downlink rectenna farm the milimeter wave energy density is similar to the energy density of sunlight to maybe three times that. But the rectenna is MUCH more efficient than a solar panel at turning it into electricity. And the rectenna intercepts very little light. You can graze cattle under it.
Even if there were an issue with the waves if they hit something ELSE (and for some stuff there is - it would heat up as if a heat lamp was shining on it), aim is not a problem. That's because the downliink is a synthetic-aperture system driven by a pilot beam from the rectenna site. The pilot signal is the only thing keeping the thousands of individual transmitters in phase. So if it's lost the beam defocusses. Most of it misses the planet entierly and the rest becomes nothing more than an annoying milimeter-band radio noise.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Somehow nobody has yet linked to Criswell's original article, which was published in the current issue of the Industrial Physicist, put out by the American Institute of Physics, a highly respected research physics organization in the US.
:-)
In other words, Criswell is no crackpot; this is a realistic plan. Read the article. I don't entirely agree with him - I think lunar materials could more effectively be used to construct orbiting solar power satellites - launch from the lunar surface can be very cheap using electromagnetic railgun technology, and in orbit you can get sunlight 100% of the time, not 50% (with solar incidence angle effects to worry about too). But Criswell's scheme is one of the most promising options, and should be considered seriously.
How soon could this be done? Essentially all the technology is in place - the scheme could benefit from some further developments of robotics, but a first launch date of 2010 is not unrealistic, and we could have power from the Moon before we would see anything from ANWR
Energy: time to change the picture.
well, I am the AC from #3395157 that you sent over here. while i applaud your desire to do something feasible, and to do it now, you don't seem to realise that while you might not want to pave death valley for environmental reason solar panels themselves are environmentally damaging. aside from mining the materials necessary to build them, their production creates a variety of highly toxic compounds. so unfortunately increasing our production of solar cells will still be bad for the environment. part of the appeal of doing it on the moon is that no one really cares about that, there, yet.
that said a great site is futureenergies.com for alternative energy.
No, because Luna does not rotate away from Sol. Luna's rotation and orbit times are exactly the same, something like 28 1/2 days. So the same side of Luna always faces Sol.
The 20-40 lunar power bases would be stationed at the east and west edges of the moon so one or the other would always be sunlit as the moon travels around the Earth. Earth-orbiting satellites and mirrors could also help aim the beams towards the terrestrial antennas.
And if you'd bothered to read the article...
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(^.^)
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not quite an analog pussy, just a cat that plays with vinyl