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alternative to solarcellss - dish? heat gathering dish?

Discussion in 'Home Power and Microgeneration' started by ...D., Aug 24, 2004.

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  1. ...D.

    ...D. Guest

    I just saw a segment on a hybrid hydrogen car on "screen savers", and it was
    mentioned and shown an alternative to using solar energy over photovoltaic -
    it just looked like a big satellite dish. All it does I think is gather heat,
    and this powers something that makes your hydrogen fuel from water -

    OK, does anyone know what this technology is called so I cam look further into
    it? The company said they were just now starting to make these things and
    that they are cost effective, much better than even today's panels - and I got
    the impression it would become very cheap in a few years..

    ...D.

    P. S. as a side note the hydrogen hybrids were 1 mil a year ago to make, this
    years 100 thou, next year cheaper, and in a couple of years cheaper to make
    than regular because less moving parts..
     
  2. Try "solar thermal hydrogen". I did a quick google search and found
    things like these...

    http://www.re-co2.com/REfocus Article - RECO.pdf
    http://www.redrok.com/hion96.htm

    Anthony
     
  3. One alternative to PV that seems promising is solar-fired Stirling
    engine driving electrical generator.

    For a parabolic reflector / Stirling example under development, see:

    http://www.sunmachine.de

    I've seen another plan for trough-reflector / Stirling / generator
    combinations and the outfit was predicting twice the overall
    electrical output / insolation efficiency of PV, but I can't put my
    hands on a link right now.

    I'm glad this stuff is looking good and all, but speaking selfishly,
    my problem is generating power when the sun *isn't* out. My PV system
    is fine, what I need is wood-fired Stirling.

    But that's me, the frozen Canuck.

    -=s
     
  4. ....
    You might look into the possibility of storing the solar hot as 100C water,
    then using a low temperature difference engine to get the power out. A
    slightly more complex system would use the very hot focus of the solar
    concentrator and atmospheric to produce power, then use the power to pump
    heat from a mixed fluid system with fresh water packets that can transition
    to ice and back, into a 100C stratified tank. Reversing the heat pump, or a
    separate heat engine then gets it out, and you do not have the loss of
    simply collecting it at 100C rather than 300-500C where more of the energy
    is available. A thermal storage battery.
     
  5. Interesting thoughts Fred, but again, my problem is power when the sun
    don't shine. I'm already fully equipped to store a week's worth of
    juice with the PV/battery setup. But for two or three socked-in weeks
    in December, say, I need something that isn't solar-powered, at least
    not directly, or I'm gonna need a lot of storage.

    Over time I'll be evaluating wind options here, but as I'm burning
    wood to stave off the -20 to -40 C temps in the winter anyway, when
    insolation is scarce and even sunny days are short, it seems a shame
    not to cogenerate a few watts to keep the paycheque generating
    apparatus (a.k.a. notebook) fired up.

    I don't need a lot. One kWhr / day, on average, would be utterly
    luxurious. Half of that -- I'd still be laughing.

    The solution at present is to burn a tankful of dinosaur juice once in
    a while, which is convenient and easy. I just don't happen to like
    that solution.

    -=s
     
  6. You are missing the core of this. Well, one core anyway. By setting the
    temperature difference at 100C, ice on bottom and 100C water on top, we have
    a thermal version of a battery. This stores a lot of energy. You just need
    to build a relatively efficient heat engine to use it. Common processes use
    a low boiling point liquid and construct a steam engine using say butane
    under pressure, water under vacuum, things like that. A sterling engine
    would work well, but you need a pretty big one to work with this small
    temperature difference. And there are other simple engines you could
    investigate.
     
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