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What will be the best renewable source of energy in 2050?

As of now, we have Wind, Water, Solar, Geothermal, and many more. But as our technology changes and diversifies, do you think we will use completely different sources?

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    Jul 27 2012: Solar panels in space, that broadcast the power down to earth by laser beam. The energy is limitless, and the ecological cost is practically zero.

    Aeronautical engineers have discussed this idea in various formats since the 1940s, and most of the technology currently exists. Note that solar panels in space are twice as efficient as ones on the ground, because there is no night time in space. Also, due to zero gravity, the panels can be built orders of magnitude larger than anything that could be built on the ground.

    If a secondary energy source was needed for some reason, I think the next best source will be liquid thorium fluoride reactors (http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor).
    • Jul 27 2012: Until you lose targeting and send a multi-megawatt beam across the land scape, setting fire to cities, fields, etc. You could do it in radio waves, but then you'll invisibly microwave everyone.

      I think small-scale, sub-critical nuclear reactor like the Toshiba 4S or wave reactor are the ways to go.
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        Jul 27 2012: It doesn't work that way, Jason. The beam is too weak to physical harm to anything, much like the microwave relay stations that dot the countryside now. In fact, the laser beams might very well be in the microwave spectrum.
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          Jul 30 2012: If you are taking solar energy over say 1 square kilometer and converting that into a beam that is10m across. You are talking about an energy density of about 10000 times that of sunlight. It doesn't matter what the frequency is, that level of energy per square metre is lethal.
          Microwave relay stations are only harmless because they are very low power. If you climb to the top of a television braodcast tower while the signal is on it will kill and then cook you, and that's just a communication signal, not a power source!
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        Jul 27 2012: Here's the Wikipedia link regarding space-based solar power, which I forgot to include in my original post.

        http://en.wikipedia.org/wiki/Space-based_solar_power
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          Aug 2 2012: On the Wiki page the energy density of the beam is 1/4 that of normal sunlight. So why go to the trouble of using PV to make electricity and converting that to microwave when you could just use a mirror to reflect the sunlight down to PV on Earth. This would be much cheaper and just as effective. Also if the beam is only as energy dense as sunlight the recievers would have to take up the same space as Earthbound PV for the same energy output. You may aswell cover the area with PV instead and put mirrors in space so the PV works at night.
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      Jul 27 2012: This assumes that we are working off of a grid. I would like to conceptulize that any device requiring power will generate it's own power.

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