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View Diary: Solar Energy Cheaper than Coal? (351 comments)

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  •  Well, obviously the solar "fuel" (2+ / 0-)
    Recommended by:
    SarahLee, AnnCetera

    isn't stored!  Anymore than windpower or tidal power is stored. All renewable/sustainable forms of energy must be converted into electricity before they can be transported or stored.  

    But we can't stick with coal forever.

    "The extinction of the human race will come from its inability to EMOTIONALLY comprehend the exponential function." -- Edward Teller

    by lgmcp on Tue Dec 18, 2007 at 04:58:33 PM PST

    [ Parent ]

    •  Storage methods (2+ / 0-)
      Recommended by:
      Dallasdoc, lgmcp

      The obvious answer to you is to use PV cells to charge batteries. This technology is available now to recharge small cells like those used in MP3 players and cellphones. Tiny amounts sure but think of all the power used by those chargers in wall sockets, especially when they are accidentally left in the wall all the time and most do not have automatic cut-offs.

      On large commercial scales, some solar heat generating stations are starting to use salt as a heat store to be drawn on after the sun goes down thus extending the generating day.

      One of the better solutions for home use is not to go the PV route entirely but to replace heating boilers with combined heat and power units. These can use wood pellets. They really only become most efficient if you can sell back your excess electricity to the grid and this is one thing that should be mandatory for all power companies.

      •  Batteries wear out (1+ / 0-)
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        there's a limited number of recharge cycles before most batteries fail. One of the challenges for battery electric vehicles is getting batteries that have enough recharge cycles.

        Old fashion lead-acid batteries and nickel-iron batteries are fairly easy to recycle back into new batteries.  

        Flow batteries don't suffer from that sort of wearout and have a much longer life. But they need storage tanks and pumps, adding to their complexity and cost.

        The amount of power going into portable rechargeable devices is only a small fraction of the total power consumed in the typical household or business. I don't think there's any real Earth-saving gains there.

        •  Supercapacitors (2+ / 0-)
          Recommended by:
          lgmcp, wondering if


          This is an intriguing technology, thousands of times more capacity than a conventional capacitor. From the article, a conventional capacitor the size of a D-cell battery would have a capacity measured in microfarads, while a supercapacitor of the same size would have a capacity of sever farads.

          They have very fast recharge times, which would be great for electric cars. Another huge advantage over batteries is that these capacitors can be charged millions of times - no having to dispose of batteries.

          The downside is that, at the current time, they hold less energy than does a battery so you would need a larger array of supercapacitors. But the technology is improving.

          It is the job of thinking people not to be on the side of the executioners.

          by A Citizen on Tue Dec 18, 2007 at 10:03:30 PM PST

          [ Parent ]

          •  low power density (1+ / 0-)
            Recommended by:

            much less than batteries.  The current front-runner, the recent nanotube based designs, are expected to reach 25% the density of batteries, and just possibly might reach half that of batteries.

            Another important thing is that the voltage off a capacitor drops as soon as you pull power out, and continues to drop; the voltage off a battery is relatively constant until it gets near full discharge. The dropping voltage makes using capacitors a bit more complicated than batteries.

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