Microwave power transmission on the lunar surface

Assuming a lunar settlement uses solar power for all their energy
needs, the biggest problem is how to store power during the 328 hour
lunar night. If the solar panel 'farm' supporting the settlement were
split into three farms, evenly spaced around the circumference of the
moon, total power production would be relatively constant. This would
require greater production of solar cells than a single farm would use
but would eliminate the need to store energy for 14 days. Since the
cost to build and send the solar cell manufacturing system to the Moon
would probably far outweigh the operating costs, I expect even doubling
the total number of solar cells would be cheaper than building and
shipping a separate energy storage system to the Moon.

Rather than running cable around the Moon, would it be possible to
design wave-guides to carry the power efficiently as microwaves over
the 1000s of km between solar farms? How many would be needed and how
large might they need to be?

wrote in news:1138043278.690113.127830
@g44g2000cwa.googlegroups.com:

Rather than running cable around the Moon, would it be possible to
design wave-guides to carry the power efficiently as microwaves over
the 1000s of km between solar farms? How many would be needed and how
large might they need to be?

Three reflectors in orbit ought to do the job. Possibly
not a simple flat panel but a passive antenna array?

--Damon

wrote in message
oups.com...
Assuming a lunar settlement uses solar power for all their energy
needs, the biggest problem is how to store power during the 328 hour
lunar night. If the solar panel 'farm' supporting the settlement were
split into three farms, evenly spaced around the circumference of the
moon, total power production would be relatively constant. This would
require greater production of solar cells than a single farm would use
but would eliminate the need to store energy for 14 days. Since the
cost to build and send the solar cell manufacturing system to the Moon
would probably far outweigh the operating costs, I expect even doubling
the total number of solar cells would be cheaper than building and
shipping a separate energy storage system to the Moon.

Rather than running cable around the Moon, would it be possible to
design wave-guides to carry the power efficiently as microwaves over
the 1000s of km between solar farms? How many would be needed and how
large might they need to be?

Well, if we are building them on Earth and sending them up in rockets, and
their quite remote from the lunar settlement, and using microwave beam
transmission, then probably we should put them into lunar orbit and use the
long lines of sight that gives to beam them to a few receiving stations
close to the settlement. This would work particularly well if the settlement
was at a lunar pole, which is a common scenario.

Why not put the power sat at L1, and microwave or laser the power to
where it's needed?

I think waveguides need to be either far above the horizon, or very
numerous. But I think cable could well be economical, espeically if
manufactured in-situ.

wrote:
Why not put the power sat at L1, and microwave or laser the power to
where it's needed?

That's an alternative to explore. Satellites might be more expensive
than surface structures, especially because lunar satellites would need
lots of fuel for station-keeping. A satellite could be in nearly
continuous sunlight, but it might be harder to keep it in continuous
line of sight to a surface base. A tall tower at a polar base might be
one approach, I guess.

I think waveguides need to be either far above the horizon, or very
numerous. But I think cable could well be economical, espeically if
manufactured in-situ.

This is confusing. Where I come from, a "waveguide" is essentially a
hollow aluminum tube with microwaves inside. Whether waveguide would
be more economical than solid cable, considering the need for power
conversion at each end, isn't clear, but at first glance the idea
doesn't seem ridiculous.

The simplicity of a waveguide is why I proposed using microwaves in the
first place. As for conversion efficiency, I think that 90% overall
efficiency of electricitymicrowaveselectricity has been
demonstrated. I'm betting that the mass of aluminum needed for
waveguides would be a lot less than for cable. Also, the lunar
landscape is not a nice flat table; stringing cable over mountains and
ravines over 1000s of kilometers could be a lot more dangerous and
difficult than flying a ship to a few dozen spots to set up waveguides.
But this whole idea hangs on how large the waveguides would have to be
and how widely spaced they could be (assume they'd be atop
reasonable-sized towers or convenient mountains). Can any EEs provide
some numbers for waveguide size and spacing requirements?

wrote:
The simplicity of a waveguide is why I proposed using microwaves in the
first place. As for conversion efficiency, I think that 90% overall
efficiency of electricitymicrowaveselectricity has been
demonstrated. I'm betting that the mass of aluminum needed for
waveguides would be a lot less than for cable. Also, the lunar
landscape is not a nice flat table; stringing cable over mountains and
ravines over 1000s of kilometers could be a lot more dangerous and
difficult than flying a ship to a few dozen spots to set up waveguides.
But this whole idea hangs on how large the waveguides would have to be
and how widely spaced they could be (assume they'd be atop
reasonable-sized towers or convenient mountains). Can any EEs provide
some numbers for waveguide size and spacing requirements?

You don't mean "waveguides," which as I wrote earlier are essentially
hollow aluminum tubes. The word you want is either "relay" or
"reflector," depending on whether you intend them to be active or
passive.

If you are thinking about a polar base, what you might want to consider
is (say) three power stations spaced equally in longitude and far
enough from the lunar pole that at least two of them are always in
sunlight. Then put your transmit and receive antennas on hills and/or
tall poles so each station transmits directly to the base; no relays
needed.

Anybody care to calculate the latitudes and heights that would be
needed?