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Piping in sunlight question?

Discussion in 'Home Power and Microgeneration' started by David O'Daniel, Apr 28, 2010.

  1. Hi, me again. I posted several things a while back. Got another
    idea/question, if it could work.

    A. For solar energy, including focusing lenses & mirror arrays (that
    Spain & also Israel now, HAVE made work), someone is always shooting
    them down, saying it can't work, it is not always daylight.

    B. Fiber-optics have been around now for years even decads, including I
    believe, piping in light from outside, by I assume some lens, then
    through fiber-optics through a pinhole or straw at least sized hole down
    through the building & then expanded back out into room lighting at lest
    on a limited scale. I assume that this idea never caught on for some
    reason & ppl are still using electricity to run lights in the day time,
    maybe too expensive to build such systems through a building?

    C. So then shouldn't lenses & maybe also mirror arrays focusing
    sunlight, send light from one part of the country/globe through a
    fiber-optic cable or a simple straight hole through a pipe (maybe a
    mirrored/polished interior pipe), to then provide light to areas during
    night?

    It seems that a network could be set up of such systems to then use the
    light to heat water at night to make steam & turn turbines & make
    electricity. And of course in day, use the direct sunlight to do it.
    while other systems ship other sunlight to other parts of the globe
    still in darkness?

    Any flaw in this idea? Other than resistance to new technology & cost of
    building it?

    Thanks in advance for any help.


    Bo
     

  2. My guess is capacity of the fiber optic cable limits the amount of
    power that can economically be transported.

    If you are going to use light energy to make steam you are talking
    about substantial amounts of energy.

    According to a very quick search:

    At atmospheric pressure (0 bar g), water boils at 100°C, and 419 kJ of
    energy are required to heat 1 kg of water from 0°C to its saturation
    temperature of 100°C. An additional 2 257 kJ of energy are required
    to evaporate 1 kg of water at 100°C into 1 kg of steam at 100°C.

    So to turn 0 degree water into 0 psi(gage) steam requires some 2,676
    kj of energy. About 743 watt-hours of energy.

    see:
    http://www.spiraxsarco.com/resource...rinciples-and-heat-transfer/what-is-steam.asp
    for more complete calcs.

    John B. Slocomb
    (johnbslocombatgmaildotcom)
     
  3. Thanks for responding.

    Wouldn't it be a material thing then? If today's fiber optics are
    limited, melt or deform maybe, then maybe the idea of a mirror/polished
    internal surface high-temp resistent steel or whatever material pipe
    instead.

    I always go on the assumption that you can use vast areas, with the use
    of lenses, focusing into such pipes (if not fiber optics), so amount of
    light shouldn't be a problem.

    From when I was first googleing mirror arrays & solar furnaces & fresnel
    lenses, back maybe a decade ago now, it seemed that it didn't take that
    much of an area of sunlight to concentrate, to melt steel. The 3X3'
    Fresnel lens story where they were blasting holes in the sidewalk trying
    to melt a dime & burning holes in steel stop-signs, as an example. So if
    you had the area say over a parking lot or just the roof of a house,
    much less a mall, gathered & focused to shine down a pipe, maybe a
    vacuum filled (aka empty) pipe, then there should be plenty of energy to
    make steam for electricity when it is night on the other end. When it is
    day, just use the focused light on site.

    Arguably, the reducing of at least some of the sunlight shining down on
    a parking lot could help reduce skin cancer from sun exposure. Discussed
    that idea though with my parking lot covered by a canopy of solar
    panels, before.

    Just that shoppers would have to avoid the point where the light is
    being focused to, down into the pipe or whatever system, lest they melt
    their shopping carts, toast their groceries & fry themselves along with
    it. Cost would probably be prohibitive to build the lenses of mirror
    arrays but IF the investment were made & regular maintenance of cleaning
    kept lenses & mirrors clear, there should be little to no other further
    costs. Unless a car crashes into some section perhaps. Probably some
    cost-cutters will use cheap glass rather than lexann or pressure glass
    or whatever & thus be vulnerable to teen vandalism of throwing rocks, I
    suppose.

    Recently, there was some suggestion of putting up floating giant
    sports-stadium-sized discs or umbrellas (I assume inflated) to block out
    (rather than make use of) sunlight, as a suggestion for the global
    warming scare. That will also never be built but I thought that it was
    less likely than my idea and that idea made the news. Granted, I had
    only "heard" of it & hadn't personally seen the news story on it at the
    time.


    Bo
     
  4. Guido

    Guido Guest

    Ever look through thick glass? How it looks green? Now imagine that
    glass being miles thick. The light diminishes into uselessness. The
    reason fiber optic networks work is that at intervals where the light is
    about to become useless for data transmission, they put in a
    relay-amplifier, to boost it. These amps would reduce efficiency in what
    you propose so much as to make it cost prohibitive.
     
  5. <Guido wrote>:
    "Ever look through thick glass? How it looks green? Now imagine that
    glass being miles thick. The light diminishes into uselessness. The
    reason fiber optic networks work is that at intervals where the light is
    about to become useless for data transmission, they put in a
    relay-amplifier, to boost it. These amps would reduce efficiency in what
    you propose so much as to make it cost prohibitive."

    <Bo>: Thanks for responding, Guido. Yes, even in air there is filtering
    down of light. Thus why I was thinking of the tubes being used be sealed
    vacuums, with only the lenses at either ends being direct material.
    Though then the sides would still absorb some of the light energy as
    heat as the light expanded, I suppose.

    So there would be loss unless the light could be focused to a pin-point
    for the full spectrum of sunlight or the reflective surface so efficient
    as to absorb a minimal amount as heat. Also then, the straighter the
    tube, it would seem the less light would hit the sides but that is just
    an assumption & depending on how narrow the light can be focused. Though
    perhaps even if only a limited wavelength could be send for miles in a
    straight line, could it then still be useful on the other end to
    generate electricity or at least use as light directly for such as
    street-lights?

    Perhaps the heat on the tube itself could be made useful, at least in
    winter. Its still an idea in progress and again, probably just
    speculation on an idea that will never really be even considered to be
    built anyways. Just thinking.


    Bo
     
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