I have been making some rough calculations of the efficiency of solar and
nuclear power sources for use on the moon. The initial O'Neill plan called
for the export of 3 million tonnes of lunar material per year. This export
rate is really quite large and it calls for an installed round-the-clock
power capacity, of some 500MW on the lunar surface. A less ambitious plan,
would be an initial base capable of exporting perhaps 200,000 tonnes per
year. This calls for a more modest power capacity of perhaps 20MW round the
clock power. Given that the initial power source will have to be imported
from Earth, which type of power source is likely to be more effective?
Solar PV, Solar thermal, or Nuclear? or maybe a combination of solar and
nuclear power?
The SP-100 space nuclear reactor, would be capable of generating 850Kw,
round-the-clock power, with a core life of 7 years. The complete power
system, including power transmission to base, transformer system, heat
sink, etc, was projected to weigh around 20 tonnes. That gives a total
power output of 42.5 W/Kg. Only a small amount of astronaut work was
thought to be needed. The reactor shielding was provided by the bulk
regolith itself. The astronauts would dig a hole approximately 3 metres
deep and maybe 2 meters wide and place the core at the bottom of the hole.
The set-up could be up and running within 1 week.
On the other hand, solar PV systems can be made extremely lightweight.
Some PV panels mass about 2Kg/M2. The support structure and sun-tracking
equipment is unlikely to weigh much more than 2Kg/m2. A 20% efficient solar
power system, could produce an average round the clock power output of
perhaps 34w/kg. This figure is only 20% less that the specific power of a
nuclear reactor. Critics often argue that the use of solar power systems
would entail importing hugely heavy fuel cells from Earth. This argument
does not strike me as being true. The only base systems that are required
to function during lunar night are life support functions. These could
easily be powered by a small SNAP reactor or RTG. Given the large
development costs and development time-scales of nuclear power systems, it
seems dubious to suggest that nuclear power systems are likely to be more
economic that solar PV systems.
However, all of this assumes that the power sources have infinite
lifetimes. Solar PV systems suffer radiation damage from solar events and
galactic cosmic rays. A solar power system may not survive much longer than
10 years. A nuclear system on the other hand, can be refuelled several
times within its lifetime, so that reactor life is extended to perhaps
20-30 years.
Which system is best? Would it be wisest to assume that a combination of
the two systems would be more appropriate?
Tony
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income streams, from the comfort of your own home.
I have been making some rough calculations of the efficiency of solar and
nuclear power sources for use on the moon. The initial O'Neill plan called
for the export of 3 million tonnes of lunar material per year. This export
rate is really quite large and it calls for an installed round-the-clock
power capacity, of some 500MW on the lunar surface. A less ambitious plan,
would be an initial base capable of exporting perhaps 200,000 tonnes per
year. This calls for a more modest power capacity of perhaps 20MW round the
clock power. Given that the initial power source will have to be imported
from Earth, which type of power source is likely to be more effective?
Solar PV, Solar thermal, or Nuclear? or maybe a combination of solar and
nuclear power?
The SP-100 space nuclear reactor, would be capable of generating 850Kw,
round-the-clock power, with a core life of 7 years. The complete power
system, including power transmission to base, transformer system, heat
sink, etc, was projected to weigh around 20 tonnes. That gives a total
power output of 42.5 W/Kg. Only a small amount of astronaut work was
thought to be needed. The reactor shielding was provided by the bulk
regolith itself. The astronauts would dig a hole approximately 3 metres
deep and maybe 2 meters wide and place the core at the bottom of the hole.
The setup could be up and running within 1 week.
On the other hand, solar PV systems can be made extremely lightweight.
Some PV panels mass about 2Kg/M2. The support structure and suntracking
equipement is unlikely to weigh much more than 2Kg/m2. A 20% efficient
solar power system, could produce an average round the clock power output
of perhaps 34w/kg. This figure is only 20% less that the specific power of
a nuclear reactor. Critics often argue that the use of solar power systems
would entail importing hugely heavy fuel cells from Earth. This arguement
does not strike me as being true. The only base systems that are required
to function during lunar night are life support functions. These could
easily be powered by a small SNAP reactor or RTG. Given the large
development costs and development timescales of nuclear power systems, it
seems dubious to suggest that nuclear power systems are likely to be more
economic that solar PV systems.
However, all of this assumes that the power sources have infinite
lifetimes. Solar PV systems suffer radiation damage from solar events and
galactic cosmic rays. A solar power system may not survive much longer than
10 years. A nuclear system on the other hand, can be refuelled several
times within its lifetime, so that reactor life is extended to perhaps
20-30 years.
Which system is best? Would it be wisest to assume that a combination of
the two systems would be more approapriate?
Tony
Sign up for FREE and learn how to use your computer to create multiple
income streams, from the comfort of your own home.
One concept worth considering is bootstrapping. Perhaps the first mission
could be a solar cell factory.
hollroa@...
Please respond to
ssi_list
I have been making some rough calculations of the efficiency of solar and
nuclear power sources for use on the moon. The initial O'Neill plan called
for the export of 3 million tonnes of lunar material per year. This export
rate is really quite large and it calls for an installed round-the-clock
power capacity, of some 500MW on the lunar surface. A less ambitious plan,
would be an initial base capable of exporting perhaps 200,000 tonnes per
year. This calls for a more modest power capacity of perhaps 20MW round the
clock power. Given that the initial power source will have to be imported
from Earth, which type of power source is likely to be more effective?
Solar PV, Solar thermal, or Nuclear? or maybe a combination of solar and
nuclear power?
I have been reading through NASA litterature on space nuclear reactors.
The SP-100 space nuclear reactor, would be capable of generating 850Kw,
round-the-clock power, with a core life of 7 years. The complete power
system, including power transmission to base, transformer system, heat
sink, etc, was projected to weigh around 20 tonnes. That gives a total
power output of 42.5 W/Kg. Only a small amount of astronaut work was
thought to be needed. The reactor shielding was provided by the bulk
regolith itself. The astronauts would dig a hole approximately 3 metres
deep and maybe 2 meters wide and place the core at the bottom of the hole.
The setup could be up and running within 1 week.
On the other hand, solar PV systems can be made extremely lightweight.
Some PV panels mass about 2Kg/M2. The support structure and suntracking
equipement is unlikely to weigh much more than 2Kg/m2. A 20% efficient
solar power system, could produce an average round the clock power output
of perhaps 34w/kg. This figure is only 20% less that the specific power of
a nuclear reactor. Critics often argue that the use of solar power systems
would entail importing hugely heavy fuel cells from Earth. This arguement
does not strike me as being true. The only base systems that are required
to function during lunar night are life support functions. These could
easily be powered by a small SNAP reactor or RTG. Given the large
development costs and development timescales of nuclear power systems, it
seems dubious to suggest that nuclear power systems are likely to be more
economic that solar PV systems.
However, all of this assumes that the power sources have infinite
lifetimes. Solar PV systems suffer radiation damage from solar events and
galactic cosmic rays. A solar power system may not survive much longer than
10 years. A nuclear system on the other hand, can be refuelled several
times within its lifetime, so that reactor life is extended to perhaps
20-30 years.
Which system is best? Would it be wisest to assume that a combination of
the two systems would be more approapriate?
Tony
>>>>One concept worth considering is bootstrapping. Perhaps the first
mission
could be a solar cell factory.>>>>
For space based engineering two factors dominate the cost of a system (1
Development costs (2) Launch costs, in that order. I suppose that we would
eventually use a lunar solar cell factory in any event. The question is,
will it be (1) light enough to compete with imported solar cells, initially
(2) Can it be developed in a reasonable amount of time (5 years), for a
reasonable amount of money ($1billion) (3) Will the production rate of
installed power capacity be great enough? We would want to build up a
capacity of 20Mw of installed power, within a few years. This amount of
power would permit 100,000t/year export rates and the large scale
production of SPS power systems.
I have to say, I am biased towards lunar manufactured solar-PV systems.
Creating the power supply out local materials has a certain elegance of
design. The question is whether or not it can compete with imported solar
or imported nuclear power sources.
Tony
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income streams, from the comfort of your own home.
I have to say, I am biased towards lunar manufactured solar-PV systems.
Creating the power supply out local materials has a certain elegance of
design. The question is whether or not it can compete with imported solar
or imported nuclear power sources. I think that the original NASA studies concluded that locally produced solar cells could not compete with imported solar arrays in the initial days of the program. At the initial stages, no manufacturing on the lunar surface whatsoever was assumed. But past a certain point, when it was time to expand the facilities on the moon, only then was local manufacturing from native materials suggested; chiefly of mass driver components, and presumably their PV power supplies as well. On the other hand, David Criswell and some others seem to think that manufacturing of at least low-grade PV cells on the moon should be a snap. In the original space manufacturing studies, I know that in the early days there was that buried nuke you mentioned. Then past a certain point it was gone, and there were only solar arrays. I think by that point it was assumed the mass-driver would only be operational during the lunar day. Whether the elimination of the nuke was simply an acknowledgement of the political difficulties in launching it, or due to some trade-off analysis, I can't say.
Mike Combs
Tony,
Solar Power Satellites was about a 1% loss each year.
Tom M.
TomM@...
Date: Thu, 5 Jul 2001 08:25:02 -0500
I think that the original NASA studies concluded that locally
produced solar cells could not compete with imported solar arrays in
the initial days of the program.
==============
Is the surface of the Moon the best place to put a power supply for a
lunar base ?
I submit that the answer is NO.
The best place to put the power source, be it solar, nuclear or
whatever, would be at the Earth-Moon L1 libration point. This is
40,000 kilometres from the luanr surface (about the same as GEO to
Earth).
It is a lot cheaper to place objects at L1 than it is to put them into
lunar orbit, let alone soft land them on to the Moon.
The power can be beamed from L1 there to the lunar surface.
We still need to soft-land components for rectennas on to the Moon, but
these weigh a lot less than PV arrays, the power per kilogram
soft-landed figure of merit would be a lot better, perhaps an order of
magnitude.
L1 is unstable, so some minimal stationkeeping is required, electric
propulsion and/or solar sailing would suffice.
Another advantage, L1 is in continuous sunlight, so a PV array there
would have 24/7 illumination. Whereas the surface of the Moon has a 14
day night time when no solar energy can be produced. That further
doubles the figure of merit for a lunar rectenna versus a PV array.
Cheers,
CR.
> [snip] Is the surface of the Moon the best place to put a power
supply for a lunar base ? [snip] The power can be beamed from L1 there
to the lunar surface. [snip] <
less underneath can be in sunlight all the time.
++JohnWheeler
>
> > [snip] Is the surface of the Moon the best place to put a power
> supply for a lunar base ? [snip] The power can be beamed from L1 there
> to the lunar surface. [snip] <
>
> Or, a big, dumb mirror (BDM) can be put in L1 and a lunar base more or
> less underneath can be in sunlight all the time.
>
First, we need to focus the energy into an area only a few kilometres
across at most, this requires precision in the mirror surface to within
about 1/10th ( 0.1 ) of a wavelength, aka "tenth wave" precision. The
longer the wavelength, the easier this is to do. Getting 0.1 wave
precision at optical wavelengths is extremely difficult. Doing it at
microwave frequencies is much much easier.
Second: the conversion efficiency from optical light to electricity is
rather poor, at best 20%, more likely 10 to 15 %. Microwave covnersion
efficiencies are much higher, 90ish %. The figure of merit we need to
achieve is maximum electricity delivered for minimum weight soft landed
on the lunar surface. Microwaves will be better than optical light by
at least an order of magnitude.