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  1.  
    Overview
    http://en.wikipedia.org/wiki/Solar_power_satellite

    A freebie summary from 2013 from IEEE (without their help :)
    https://www.academia.edu/4875442/Wireless_Power_Transmission_Technologies_for_Solar_Power_Satellite

    Global power consumption
    http://en.wikipedia.org/wiki/World_energy_consumption

    That's about 20 PWh annually, so a good target accounting for growth (Asia, then Africa) and for efficiency at 30% conservatively, means we need a global system for the next 50 years capable of annually providing ~100 PWh. That's an average global power requirement of ~10 TW and a peak power of ~50 TW, with a good margin. There is little point in building something expensive without a generous margin built in for future proofing. That figure represents ~10 KW/person worldwide, 24/7/365.

    The reaction force due to a 50 TW beam is ~150 kN. A 1 metric ton satellite would experience a reaction acceleration of ~15 gee. Thus, from a station-keeping perspective, we need to use multiple satellites. Fortunately, we need to do this anyway in order to achieve global coverage. This is where launch costs come centre stage; total launched mass to provide 50 TW worldwide with reaction accelerations pegged at 0.015 gee is going to be ~1000 metric tons. [Note that using inert mass from the Moon or asteroids will at some future point make this a lot more economical. Fortunately, orbital parameters are insensitive (to first order) to the mass of the orbiting body.]

    To grab our 50 TW from the sun at earth orbit requires a 100% efficient square collector 200 Km on the side. This is excessive. Better would be beamer tech closer to the sun, to take advantage of the increased solar intensity. For example, to collect 50 TW at Mercury orbit would require a 100% efficient square collector 80 Km on the side. Still big, though.

    Looking out to SpaceX and Skylon predictions for launch costs, we can assume ~$2K/Kg, so the system will cost ~$2B to launch. That's a nice low number, considering what is achieved. This represents a launch cost of $40K/GW. For comparison, the direct cost of a new coal or nuclear power plant ranges from $3B/GW to $6B/GW (not including the full cost to the environment from CO2 emissions or storage of spent nuclear fuel, respectively).

    All that remains is to price up the cost of the devices themselves, and their rectenna ground stations. Over to you...
  2.  
    "And if you look quickly, out of the right side of the saucer, you can get a glimpse of Dirt, the legendary home of humans. Nobody lives there any more. When they used up their Moon and the ocean tides stopped, they pretty much all died off, and then the nanopsych plague finished off the rest."
  3.  
    •  
      CommentAuthorAngus
    • CommentTimeAug 7th 2014
     
    Eggs. Basket.
  4.  
    Quite so. Ergo SPS
    •  
      CommentAuthoraber0der
    • CommentTimeAug 8th 2014
     
    Why not put the solar cells on the ground. Would be easier to reach for maintenance etc.
  5.  
    Advantages

    The SBSP concept is attractive because space has several major advantages over the Earth's surface for the collection of solar power.

    There is no air in space, so the collecting surfaces could receive much more intense sunlight, unobstructed by the filtering effects of atmospheric gasses, cloud cover, there is no night, dust to be cleaned, clouds and other weather events. Consequently, the intensity in orbit is approximately 144% of the maximum attainable intensity on Earth's surface.[citation needed]
    A satellite could be illuminated over 99% of the time, and be in Earth's shadow a maximum of only 72 minutes per night at the spring and fall equinoxes at local midnight.[28] Orbiting satellites can be exposed to a consistently high degree of solar radiation, generally for 24 hours per day, whereas the average earth surface solar panels currently collect power for an average of 29% per day.[29]
    Power could be relatively quickly redirected directly to areas that need it most. A collecting satellite could possibly direct power on demand to different surface locations based on geographical baseload or peak load power needs. Typical contracts would be for baseload, continuous power, since peaking power is ephemeral.
    Elimination of plant and wildlife interference.


    You might read the links...
    •  
      CommentAuthorAngus
    • CommentTimeAug 8th 2014
     
    Save me the trouble and also recite the downlink loss budget.
    •  
      CommentAuthoraber0der
    • CommentTimeAug 8th 2014
     
    I can imagine all that, but having this stuff up there seems to be a major show stopper, at least until we have the infrastructure (launch capability on short notice, permanent human presence in space, fast deployment of human servicing crews etc.).

    The ground based solar(+wind etc.) harvesting tech is much cheaper to build and maintain. The distribution of wealth around the globe is also a nice side effect.
  6.  
    I tried
    •  
      CommentAuthoraber0der
    • CommentTimeAug 8th 2014
     
    When you spend so much on a single project there are much more things to consider than pure theoretical efficiency. A decentralized ground based approach seems to be much more practical now.

    SPS is a nice idea but I don't think it is the solution to our immediate challenges. It's a long term project that needs a lot of R&D to be successful.

    Maybe we should try train-based solar first. :p
  7.  
    It seems to me that if you know that, statistically speaking, an extinction-level event will happen to your planet, but you can't know when, the time to start working on mitigating measures is urgently "already".
  8.  
    Posted By: aber0derWhen you spend so much
    I assume you know this amount. What is it, based on what sources?
    •  
      CommentAuthoraber0der
    • CommentTimeAug 8th 2014
     
    Posted By: Andrew PalfreymanWhat

    Certainly more than solar etc. without a space program. How much? Sources? I don't know.

    Let's be optimistic and take the cost of the ISS and multiply by 4. 600 bn USD.
  9.  
    Let's discuss celebrity underwear instead
    •  
      CommentAuthoraber0der
    • CommentTimeAug 8th 2014
     
    Space based celebrity underwear?
    •  
      CommentAuthoraber0der
    • CommentTimeAug 8th 2014
     
    OK, divide it by 16 (years) and we have 37 bn per year.
  10.  
    And that has to do exactly what with Sandra Bullock's zero-g brassiere?
    • CommentAuthorLakes
    • CommentTimeAug 8th 2014
     
    Does it make her boobs weightless?
  11.  
    You mean the opposite of a double mastectomy, which renders a woman's weight boobless?