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You Are My Sunshine
Solar Panels in Outer Space

One of the perks of life in the era of accelerated technological advancement is reading stories like this one. Researchers at a Japanese firm are working on harnessing the power of the sun…from outer space. IEEE Spectrum reports:

[S]pace-based solar power could at last become a reality—and within 25 years, according to a proposal from researchers at the Japan Aerospace Exploration Agency (JAXA). The agency, which leads the world in research on space-based solar power systems, now has a technology road map that suggests a series of ground and orbital demonstrations leading to the development in the 2030s of a 1-gigawatt commercial system—about the same output as a typical nuclear power plant.

Here’s how JAXA envisions this plan might work: Satellites in geosynchronous orbit could use photovoltaic solar panels to generate electricity, which would then be converted into microwaves beamed back to collecting stations on earth, and then finally converted back in to electricity. Simple, right?

JAXA has set its sights on getting this system up and running in just 25 years, but given solar energy’s terrestrial track record, you’ll forgive us if we’re skeptical. This project requires strong, durable, extremely light-weight materials. It needs a mechanism which the satellite could use to focus these microwaves continuously on the right spot. (Note: We aren’t talking about a superweapon waiting to fall in the hands of a supervillain. The microwaves “wouldn’t even be intense enough to heat your coffee.”) And, of course, it needs funding—lots and lots of funding—because launching things in to space isn’t cheap.

There’s plenty that could go wrong here, but this kind of outside-the-box—or outside-the-planet—thinking is what we’ll need to meet the growing energy needs of humanity in a sustainable fashion. Space-based solar power solves one of its ground-based cousin’s biggest problems: intermittency. On earth, solar panels can’t produce electricity at night, but in geosynchronous orbit, these panels could produce power “nearly 24 hours a day.” It may be more fiction than science at the moment, but a near-constant supply of renewable energy is certainly a dream worth chasing.

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  • William Nevins

    Actually, this is not a particularly new idea–I recall hearing about it during the energy crises of the 70’s. What is new (one hopes) is that this Japanese has the funding to carry it out… Assuming that they really do. More likely they are publicizing the idea in the hope go getting funding. I wish that

  • Jim__L

    “because launching things in to space isn’t cheap.”

    One interesting solution to this problem is to use near-Earth asteroids (like the one NASA is talking about hauling back to Earth) to recover dozens (or hundreds) of times more mass than you launch.

    Producing solar power satellites out of this material has some interesting manufacturing challenges associated with it, but these are hardly beyond human ingenuity. There are actually some talented people working on the problem right now.

  • Breif2

    “in geosynchronous orbit, these panels could produce power ‘nearly 24 hours a day.'”

    I’m in general agreement with the post, but an instant’s thought about the word “geosynchronous” should be enough to realize that the above statement is self-evidently preposterous.

    • Jim__L

      Satellites in geosynchronous orbit are in direct sunlight at all times, with the following exceptions:
      – When eclipsed by the Moon
      – When eclipsed by the Earth

      Geosat batteries are typically scaled to provide power to the satellite through both events in a row — a bit over 90 minutes.

      These happen during “eclipse season”, which is around the equinoxes; due to the Earth’s axial tilt, having an orbit directly over the equator only results in being in Earth’s shadow when the line between the Earth and Sun is near perpendicular to the line of Earth’s axis of rotation.

      So, for nine months out of the year, the satellite is in full sunlight pretty much all the time; for about a month and a half every summer and fall, they have outages for as much as 94 minutes (usually less) once a day.

      (If this is still too imprecise, please Google “geosynchronous satellite eclipse season” and check out Intelsat’s page on the subject.)

      • Breif2

        First, thanks to Jim for taking the time to try to clear things up.

        Second, I completely retract my previous comment, which was based on poor assumptions on my part regarding celestial geometry, and apologize for the original scoffing and the accusation of imprecision.

        • Jim__L

          To be fair, the article doesn’t go into much detail, and the above details aren’t well known outside of the industry.

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