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Help with old solar thermal engine

Discussion in 'Home Power and Microgeneration' started by no spam, Mar 27, 2007.

  1. no spam

    no spam Guest

    Long story looking for a short answer.

    Many years ago I read a book that had a design for an interesting solar pump
    and I was wondering one has plans for one or can help me make up my own.
    And as always I'm looking to go as cheap as possible.

    The pump used a closed double acting cylinder. When one end was heated the
    gas inside expanded which pushed the rod. This rod action did a couple of
    things:

    1) It moved the mirror(s) so that the sun was moved to the opposite end of
    the cylinder to restart the cycle.
    2) It moved a second rod in a second cylinder which pumped water.
    [IIRC, the original used the weight the mirror assembly to help pump the
    water]

    I know this is probably an inefficient way to do it as well as being a very
    low pressure, very low volume and possibly noisy pump but I only need 15 to
    20 gal per day for my animals. If I could get more volume out of it I could
    use it as a start for a 'geothermal' AC for my house.

    I'm having some problems figuring out how to build it. The first problem is
    the 'heat' cylinder. Any ideas how to build one or where I might be able to
    find something used I could 'adjust' to work? I don't think a standard
    pneumatic cylinder would work because of the temperatures it would be
    exposed to.

    The next problem is what gas to use. I think the original used freon or
    propane. Would the new stuff (132a??) work?

    Then there's the fact that the mirror will have to track the sun so that the
    focal point will remain on the cylinder. I was thinking a trough type
    parabolic mirror that would slide on a track. This would pretty much
    eliminate the need for the mirror to have to be reaimed throughout the day.
    The problem I see with this is because the mirror would slowly slide down
    the cylinder causing the temp on both sides of the cylinder to equalize and
    stop the engine. That means I would have to have some kind of 'tipping
    point' so that once the cylinder reaches a point the mirror moves all at
    once.

    Thanks for any help.
     
  2. Morris Dovey

    Morris Dovey Guest

    no spam wrote:

    | I'm having some problems figuring out how to build it. The first
    | problem is the 'heat' cylinder. Any ideas how to build one or
    | where I might be able to find something used I could 'adjust' to
    | work? I don't think a standard pneumatic cylinder would work
    | because of the temperatures it would be exposed to.
    |
    | The next problem is what gas to use. I think the original used
    | freon or propane. Would the new stuff (132a??) work?
    |
    | Then there's the fact that the mirror will have to track the sun so
    | that the focal point will remain on the cylinder. I was thinking a
    | trough type parabolic mirror that would slide on a track. This
    | would pretty much eliminate the need for the mirror to have to be
    | reaimed throughout the day. The problem I see with this is because
    | the mirror would slowly slide down the cylinder causing the temp on
    | both sides of the cylinder to equalize and stop the engine. That
    | means I would have to have some kind of 'tipping point' so that
    | once the cylinder reaches a point the mirror moves all at once.

    I have a web page showing a bit of a current project to develop a
    liquid-piston Stirling (fluidyne) powered pump at the link below. The
    current plan is to build the engine and pump using off-the-shelf 4"
    CPVC. The only moving parts will be air, water, and check valve
    mechanisms.

    The web page shows construction and testing of a parabolic trough, but
    the high temperatures (724F) tend to melt the engine plumbing. It
    appears that a same-area flat plate collector may solve that problem
    as well as allowing the pump to run (more slowly) on hazy or light
    overcast conditions.

    I'm not sure if this is close to what you want, but it may provide a
    few ideas that you can use.

    I just recently added a short video of one of our early test fluidynes
    running (with an electrical heat source) to show how simple these
    critters can be.

    BTW, the fluidyne runs silently - and the only noises from the pump
    will be the soft "click" of the check valves and the gurgle of
    water...
     
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