Space-Based Solar Power

a public discussion sponsored by the Space Frontier Foundation

Space Solar Power Meets Wikipedia…

Posted by Coyote on July 8, 2007

The Evil Dr Mankins introduced me to Wikipedia a couple of months ago. Naturally, I felt like an idiot because apparently this has been a huge Internet phenomenon over the last few years that I just missed. What can I say? I’ve been distracted by reality lately.

But I’ve discovered that Wikipedia can be a wealth of information and misinformation…and the innocent might not know the difference.

Please take a look at Wikipedia’s page titled Space Power Satellite.

Is this information or misinformation? Would this serve as a sufficient primer on the subject of space solar power? What edits can we make to improve this page for everyone’s benefit?

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10 Responses to “Space Solar Power Meets Wikipedia…”

  1. Edawg said

    How bout throwing in the the social and political benefits of the ssp?Like how profits and spinoff tech can be fed back into the system to adress social security issues and make America the top exporter of high technology!?

  2. Des Emery said

    Wikipedia gives short shrift to Space Solar Power, Coyote, but is generally a somewhat dry source of information and conservative by nature. You’ll note that it proposes four necessary conditions for the enabling of space solar power, and makes the fourth condition dependent upon the depletion of fossil fuels. That to my mind is happening now, and we are suffering Global Warming as a consequence, imminent Global Warming to boot. Terrestrial solar power is a stop-gap temporary solution, but space-based solar energy can fill the bill. I still see it as necessary for a fast development for your project to enlist other aid, such as a university like McGill in Montreal which has a team working on a Space Elevator. Removing a big impediment like the cost of a rocket to get construction into space seems to me to be a move required by that expense.

  3. Greetings, I am one of the co-authors of the Wikipedia SPS article, my Wikipedia user name is CFRJLR which is the account I use on most systems. I put quite a lot of work in to clarifying and enchaining the article, and I added a ton of links and references, since the article was flagged by the WP community as “lacking sources”.

    I also restructured the article, and I introduced better structure to the discussions of various competing forms of energy, which previously was an amorphous mess. I introduced a heading for each major competitor, and then itemizing “advantages” and “disadvantages” under each

    I think it is a pretty darn good primer myself, and is objective, considering all aspects of the issues involved.

    If you disagree.. feel free to edit the article and/or participate in the article’s discussion page .. that is what WP is all about.

    I also create similar pages on luanrpedia.org and citizendium.org

    Those two sites offer advantages over WP in a couple of respects.

    Lunarpedia.org has fewer restrictions than WP, and allows “original work” (WP does not).

    Citizendium requires users to show their real identities, and expertise (WP does not).

  4. Think big, think cheap:

    For economy of scale, why bother with orbiting new satellites? The moon is a natural satellite with raw materials available for building at hand.

    For power generation, generally a themal differential is needed. The earth’s deep ocean is an accessible thermal sink which eventually radiates most of its energy back to space at night. The moon receives a tremendous amount of solar energy on its surface, which could be redirected to select points on earth with a massive array of identical steerable mirrors. Set up a steam turbine and reject the waste heat to deep ocean water.

    O.K., so the moon is only “lit” 14 days of 28, double impoundment hydro-electric facilities could store energy during those 14 days by pumping water “uphill”, and release it as needed.

    Most of this is 1930s technology… the first working facilities could be built by 2030, and I’d wager that there’s enough real-estate on the moon to power today’s population many times over.

    Clever folks could also set up secondary (orbiting) reflectors at lagrange points to pick up power from the farside of the moon, reducing the need for local energy storage from 14 days to 20 hours (more in cloudy areas).

    Just a thought.

  5. Follow-up thought: if you think nuclear weapons are the ultimate strategic deterrent, think about having control of this reflecting system.

  6. Vernon Nemitz said

    Even though it is expected that much of the materiel needed to make solar power satellites will come from the Moon, the Earth still MUST have an inexpensive means to acess space. Too much infrastructure needs to be put into place, transported from Earth, before the Moon can be an easy resource base. One way that is considered to be relatively inexpensive to operate (if not to build) is known as an “electromagnetic launcher”. It has a problem with the Earth’s atmosphere, but that problem has a solution, which is described here: (consider this to be a pilot (pilot plant”). If it is decided that a prototype should be built first, then that can be very useful, too, as described here: On removing space debris.

  7. Coyote said

    Joemerchant: I don’t want to pump the Earth’s atmosphere with reflected white sunlight as that would significantly increase our heat budget…and I don’t want any unnecessary accusations of trying to build a weapon.

    That said, you raise an interesting issue…going to the Moon and using its resources. I have discussed this with many space lawyers who are telling me that the current treaties prevent or forbid anyone from using the physical resources of the Moon for any capital venture. Great bunch of laws, huh? “Look, but don’t touch.” We probably need to redress this in the international venues.

  8. Coyote: If there’s a feasible project with this kind of benefit (“carbon free” energy), I suspect the laws could be amended easily with proper greasing of the controlling palms (locate power stations in the concerned countries, give assurance of mutual control – non weapon use, etc.)

    Every energy source has weapon potential, and the “big” modern ones will of course have potential in abundance.

    As to the heat budget, again look to the scale: the earth receives direct sunlight on 50% of its surface, for us to build reflectors equivalent to 0.1% of the earth’s surface would be an astounding project. With much of the heat being rejected into deep ocean water, I suspect cloud cover would increase and over-compensate for any warming effects, but really, you’d need to cover 10,000 square miles with mirrors before you’d have any measurable effect at all. If it gets to be a problem, we could orbit a “sun shade” at a sunward lagrange point to compensate, just a big (thin), dumb sun blocking umbrella…. any energy generation solution, whether it’s breaking chemical bonds formed with solar energy over millions of years, releasing nuclear energy, or otherwise, will involve increasing the planet’s “heat budget” – I think people underestimate the scale of the night-side radiator. The real problem with greenhouse gas is that it reduces the efficiency of heat radiation to space.

    I like the lunar mirrors because you could mass produce them, thousands or millions made at whatever scale is most practical / economical, and there’s no reason they can’t all be identical, they just need to be “pointed” at the currently active receiving station(s), which could be selected in real-time based on relative location, weather, local demand for energy, available storage capacity, etc.

    O.K. – lunar dust might be a problem – but tall towers should be relatively easy in lunar gravity, and I imagine an electrostatic generator could address the dust issues on a local scale for stationary objects.

    The real trick is building with local materials, and that’s going to be a long road no-matter what, possibly 50-100 years. It’s hard to get old lawmakers to care about their grand-children.

  9. Neil Cox said

    Here is part of the Joemerchant post with some changes and my comments. Yes, the cost per kilowatt hour typically decreases if you think big, unless you think so large that you get an unpleasent surprise.

    For economy of scale, why bother with orbiting new satellites? The moon is a natural satellite with raw materials available for building at hand.

    For power generation, generally a themal differential is needed. The earth’s deep ocean is an accessible thermal sink which eventually radiates most of its energy back to space at night. The moon receives a tremendous amount of solar energy on it’s surface, which could be redirected to select points on earth with a massive array of identical steerable mirrors. Set up a steam turbine and reject the waste heat to deep ocean water.
    Me: The beam will spread too much, unless we can first collumate the sunlight. Balloon mirrors in earths atmosphere, might be close enough to a giant steam boiler on Earth, that we could live with the beam spread.
    O.K., so the moon is only “lit” 14 days of 28, double impoundment hydro-electric facilities could store energy during those 14 days by pumping water “uphill”, and release it as needed.
    Me: I understand impoundment, but “double”?
    Most of this is 1930s technology… the first working facilities could be built by 2030.

    Clever folks could also set up secondary (orbiting) reflectors at lagrange points to pick up power from the farside of the moon, reducing the need for local energy storage from 14 days to 20 hours.
    Me: Why 20 hours?

  10. Neil Cox said

    Here is what wikipedia says about collimatated. Note, I spelled it wrong in post 9:

    Collimated light is light whose rays are parallel and thus has a planar wavefront. The word is derived from `Co-linear’ and implies light that does not disperse, even over an infinite distance. Light can be collimated by a number of processes, for instance to project a beam on a parabolic concave mirror with the source at the focus. Collimated light is sometimes said to be focused at infinity. A simple way to test a beam for proper collimation is the shearing interferometer. In reality a perfectly collimated beam with no divergence cannot be created due to the fundamental limitations of diffraction, but in practice sufficiently low-divergence beams are considered collimated.

    Laser light is normally automatically collimated because it is formed in a chamber between two such mirrors, in addition to being coherent. This is indicated by the ‘pencil beam’ of laser projectors, with very little angular spread.

    The light from stars can be considered collimated (for almost any purpose) because they are so far away. Due to its relatively large appearance on the sky, the light from the sun deviates about half a degree to all directions when compared to a point source in the same position, giving approximately collimated light.

    A perfect parabolic mirror will bring parallel rays (from a star) to a focus at a single point. Spherical mirrors are easier to make than parabolic mirrors and they are often used to produce approximately collimated light.
    To produce usefully collimated light, the light source must approximate a point; that is, it must be small relative to the optical system, like the image of the star formed by a mirror.

    The necessary tradeoff is that, since the luminosity of most sources is small, such an optical system cannot produce much optical energy. Lasers are a notable exception to this general rule.
    Me: As the artical infers, collimation from the sun is adequit for mirrors a few kilometers from the photovoltaic panels or other energy receiver. A honeycomb structure, painted dull black inside, should make a reasonable collimator. The only collimator I have seen had 2 centimeter square cells, about 100 of them, so the light traveled about 3 centimeters through the cells. Perhaps a several square kilometer collimator could have simular geometry with billions of cells and be cooled by a fluid, if there was a use for the low grade heat. Otherwise cooling is unnecessary, unless the light was concentrated before collimating. I’ll guess that such a collimator converts about 70% of the sunlight to heat, so several square kilometers would yield perhaps two gigawatts of collimated sunlight. Neil

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