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."

Comments

At What Cost?

[Galahad2]

It currently costs $10,000 to get 1 lb of material into orbit. How much would it take to get it to the moon? One hell of a lot.

It's going to be a heck of a lot cheaper to burn money to make power than use the moon for a long, long time.

Re:Doesn't the earth receive more?

[Anonymous Coward]

Yeah, except for that Ozone Layer, which has that whole 'filtering' ultraviolet light part, whereas the moon has no atmosphere.

Harmless, my eye!

[swankypimp]

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.

Re:Harmless, my eye!

[mindstrm]

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.

Re:Harmless, my eye!

[The Mayor]

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.

uuh

[dmiller]

You don't take photovoltaic cells to the moon, you build a factory on the moon and make the cells there. Just about everything you need is there: water, minerals and even some things that you don't find that often on Earth.

This is probably as far beyond our immediate capability as getting to the moon was to people of the 1940's - just a matter of time, money and will. The latter seems to be the most lacking.

That's not limitless

[SecretAsianMan]

... a limitless power supply. The moon receives 13,000 terrawatts ...

Gosh darn it, that sounds like a limit to me.

Re:doesnt seem economical

[slackergod]

Total nonsense?
Sure, you could pursue fusion.
But we may not get fusion. Should we wait
for the PERFECT energy source while we rely on
the bad ones, unstead of using a better one,
while we pursue the goal of fusion, which
(while theortically realizeable) doesn't even
have a timetable associated w/ it?

Furthermore, sure, the short-term costs would be
large, but what are the costs for building and planning a new nuclear reactor?

Solar cells on earth? We have clouds. We have day and night. The moon (thanks to an astronomical quirk) has permanent day and night. Much better
efficiency that we can get. Store it there.
Send it over, microwave style, when the terran
receiver is in place.
Or bounce it off a satellite.

Just because you can conceive of better long term ideas, why should we not pursue a better short term idea, rather than stick to one that's actually harming us?

-Slackergod

Re:At What Cost? -- Why waste trees?

[x-empt]

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./

But sync orbit is better.

[Ungrounded Lightning]

You don't take photovoltaic cells to the moon, you build a factory on the moon and make the cells there.

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.

Re:Oh. My. God.

[greenius]

> The answer, of course, is to use less energy period

Using less energy is not a solution.

The future of humans can not survive by staying on earth. The only way to get to the next level of development required for interplanetary and insterstella travel will require huge amounts of energy compared to what we have on Earth. The sun is pumping out loads of wasted energy into space. The sooner we can start the technology development to grab some of this energy then the sooner we can expand off this planet and increase our chances of survival.