Japan Revives Orbiting Solar Idea

I haven’t heard this one for fifteen or twenty years. Energy is to be transmitted to earth by coherent (laser-like) microwave beams. Main environmental impact is cooked geese. Stewart Brand was big on this idea once, or at least his magazine Coevolution Quarterly was, if I recall right.

(This one is h/t Felicia Day‘s tweet stream, of all people. And if you don’t know who she is, you are in luck because you get to watch this.)

Wikipedia has more here.

Comments:

  1. Pingback: Another Week of GW News, December 9, 2012 – A Few Things Ill Considered

  2. JAXA and (a group of engineering scientists at) Kyoto University are seriously pursuing the goal.

    With several searches, I find several links.
    http://www.nature.com/news/2009/091125/full/462398b.html
    http://www.ard.jaxa.jp/eng/research/advancedmrg/amrg-index.html
    http://www.jaxa.jp/article/interview/vol53/index_e.html
    http://www.rish.kyoto-u.ac.jp/space/people/shino/research-spse2.htm

    As for transmission, they have two parallel approaches, one using microwave, another using laser of visible light. They say that in their microwave technology the energy flux density will be at the same order of magnitude as the solar light (1 kW m-2), so the condition of safety will probably be satisfied. But, as I understand, then the area of their receiving antenna will be of the same order of magnitude as ground-based solar collector of similar capacity. I doubt that is can be effective enough to be accepted for mass use.

    Putting solar collectors in space is certainly expensive, but the area needed for this application is much smaller than the area of mirrors that would be needed to reflect away significant portion of solar radiation for the purpose of climate geo-engineering.

    It will produce waste heat on the ground, but its impact on climate will be much smaller than the same amount of energy use by fossil fuel.

    • Kooiti Masuda writes,

      the energy flux density will be at the same order of magnitude as the solar light (1 kW m-2), so the condition of safety will probably be satisfied. But, as I understand, then the area of their receiving antenna will be of the same order of magnitude as ground-based solar collector of similar capacity. I doubt that it can be effective enough to be accepted for mass use.

      There are two reasons why Masuda's doubt doesn't follow from the sentence before it. (1) The conversion efficiency has been shown to be (see Figure 15) much higher for microwaves to DC electricity than for sunlight to DC electricity.

      (2) The 1-kilowatt-per-square-metre areal power density that is mentioned for sunlight is its peak value, not its year-round average. The microwaves are available 24 hours a day, 363 days a year, times the uptime fraction of the orbiting transmitter (it is eclipsed twice a year). This is the second of two factors-of-several in beamed microwaves' favour.

      ... It will produce waste heat on the ground, but its impact on climate will be much smaller than the same amount of energy use by fossil fuel.

      The impact will be smaller than that of any heat engine that dumps its waste heat into the troposphere.


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