Turning moon into a solar panels

Question

In the year 2115 A.D. we have managed to cover the entire surface of the moon with cheap and flexible solar panels and have them bathe in the day, the energy collected will be stored at a lunar power station. My question is

1. can such scheme powers the entire electronics on Earth and
2. assuming the power is delivered via beam where on Earth is a good place to erect an antenna to receive the beam with minimum interruption? If possible
3. what kind of material candidate would serves my story, I'm looking at able to manufacture in vast quantities and economical material.

Answer 1

Delivering energy at a distance requires something like a very tightly focused microwave beam, or a laser. There are several issues here:

1. All the energy is being fed through the Earth's atmosphere, which will heat up under the energy beam. This will cause several effects, including thermal "blooming" which could defocus the beam, or even a breakdown of the atmosphere if the energy intensity of the beam is too great (the air will "explode" into plasma, which is opaque to the energy beam and block reception downrange). Considering the energy usage of Earth is measured in Terrawatts, even splitting the beam into multiple smaller beams will still create hotspots in the atmosphere, severely affecting the weather.

2. Assuming issue one is dealt with, the area around the receiver is going to be quite dangerous. Humans are (generally) smart enough to avoid areas marked with danger signs, air corridors will be clear of the beams and so on, but animals and plants are not so sensitive to warning signs. Birds, insects and animals will wander into the beam path and be fried. Birds and insects in particular will be a problem as their carbonized bodies will be falling onto the receiver, reducing efficiency and possibly causing electrical short circuits. The task of maintaining the receiver will be difficult, since technicians and robots will have to be protected from the beam, or the beam shut off for downtime to fix things.

3. Because the beam will be travelling for greater than a light second to get from the Moon to the Earth, the focusing lens or array will have to be quite huge to focus the beam to a reasonable size on Earth (see 1), and the receiver will be jumbo sized as well. This puts a lot of land area out of bounds, and the energy conversion will always be less than 100%, meaning the ground below the beam will become hot or irradiated with microwave or laser radiation, not so great for plants or the rest of the ecosystem in the area. As well, the energy will have to be transmitted from distant receivers to the customers, so a large and elaborate power grid will grow around the receivers.

4. Because the Moon orbits the Earth, no receiver will be in view of the Moon 24/7, which makes baseline power difficult. The energy from the Moon not only has to be received, but also either stored or somehow "wheeled" through the grid to the customer. In theory, high capacity superconducting power cables could be strung along the equator to link all the receivers together, so as long as one is energized, power can flow around the ring to all the customers on Earth. This also highlights another issue; most of the customers in the First World are not on the Equator, but in the Northern and Southern hemispheres. The beam would be most efficient if it passes through the atmosphere at an almost vertical angle, not at an acute angle (see point 1).

Some of the other possible solutions are equally alarming, such as using the energy to send buckets of lunar dust down the gravity well to be captured by huge magnetic decelerators and converted to electrical energy (eventually there will be a lot of moon dust in Earth orbit). The high amount of solar energy could also be used to create anti matter, which is a very high density form of energy storage. Only a truly insane person would want to send large amounts of antimatter to Earth, much less Earth's surface.

Frankly, I see the best use of generated energy in space to be in space. Beaming energy to friendly receptors on spacecraft provides power without the spacecraft lugging around a heavy nuclear reactor or acres of solar cells. Space industry can also use large amounts of energy for refining regolith into it's constituent elements, manufacturing and agriculture in space.

Answer 2

As @Thucydides says, beaming energy to the Earth's surface is quite problematic. A way around this is to have a series of Space Elevators, perhaps a minimum of three, each of which has a receiver which is set up to be a target for the moon's energy beam.

The transmitter on the moon is programmed to switch between these: as the moon orbits the earth and the earth rotates, it will periodically shut off the beam, target a different receiver, then reactivate the beam. If there were two transmitters, this could be done without any downtime.

The receivers on the elevator tops convert this energy (transmitted as laser or microwave or whatever) into electricity, use some of it to charge up the batteries which power the elevator operation, and send the excess down cables to the earth. In this way, the moon is powering some Space Elevators and providing energy to the earth's surface.

Since the coordinates of the beam between the moon and the receivers are 100% predictable, it's easy to manage a "no fly zone" around the beam paths, in order that spaceships using the elevators don't get accidentally zapped by the beam.

It could also be managed so that the moon only ever beamed to a elevator top which was angled well away from the Earth, so that if there's some problem and the beam misses the receiver, it won't zap the earth. This might require a larger minimum number of elevators. It might also be a good idea to make the elevator currently getting the beam not be open to elevator traffic, again just in case of accidents.

This image

gives an idea of the relative scales involved, and looking at this you can see that you could get away with just three elevators, to meet the requirement of always being able to beam to one which wasn't in line with the earth.

Answer 3

For #3, and the reason to built it on the moon and not in free orbit, consider factories that mine the lunar regalith and produce solar power cells to pave behind.

So you want something that is made from the loose material on the surface, for the most part.

There are three broad approaches to solarvoltaic generation:

• metal
• semiconductor
• organic

So what elements are present in the loose material on the surface of the moon?

Automation trumps efficiency of the units. Quasi-living nanotechnology that grows in fields like weeds on the Maria, even if only producing a small yeild, would trump high efficient silicon panels that are laboriously produced.

I like the idea of competition in a story. Tried-and-true moving factories making old-technology panels, vs. "farmers" of electric grass, trying to get the overhead of manual involvement down to the point where it pays.

Assume superconductors to move the story along.