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easy, DIY solar powered AC for small room??

Discussion in 'Electronic Design' started by AA, Aug 6, 2012.

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  1. P E Schoen

    P E Schoen Guest

    Here are 60W Peltier cooling plates for $4 each with free shipping. 200
    BTU/hr. 25 of them would (should) give you a 5000 BTU/hr A/C for under $100.
    http://www.ebay.com/itm/320899431129
    "Watt" a deal! How do they do it?

    These are more believable (and complete units with heat sinks). $38 each for
    70W or 170 BTU/hr. They are selling 24 pieces for $35/each. So for $840 you
    would have a nice 4000 BTU/hr A/C. I don't know the efficiency, but it's
    probably a lot better than going through a solar power inverter and then an
    AC motor and compressor.
    http://www.mpja.com/Peltier-Cooling-Assembly-Larger/productinfo/15513+PM/

    Paul
     
  2. amdx

    amdx Guest

    I'm curious if this concept could be pushed further, with modern
    material and technology. Just to throw out an idea, a very well
    insulated room with a pipe running in the center of the room vertically
    to the ceiling, then horizontally to the outside down to the ground then
    back to the center of the room. Circulate a liquid through the pipe. On
    the outside the pipes use the evaporation concept to cool the liquid
    which circulates to the center of the room. The pipe/evaporation
    scheme would be duplicated as many times as required for the room.
    I wonder if the liquid could be self circulating just by temperature
    difference alone. Are there materials that could be used for the
    evaporative sheets that are more efficient.
    In the end it's a swamp cooler, but we don't want the evaporated
    moister inside the room, we do want the cooled liquid
    in the pipe circulated into the room.
    Your ideas welcome.
    Mikek
     
  3. mike

    mike Guest

    Dias Analytic
    https://www.google.com/search?num=1....0.0.0.182.182.0j1.1.0...0.0...1c.boGF2uLShRo

    has a process that uses a membrane to suck moisture out of the air
    without condensing
    it or changing the temperature. Then they put the air thru a swamp
    cooler to
    cool the air and put the moisture back.
    A year ago, they had the DoE interested enough to give them a bunch of $$$$.
    But the steady decline in stock price suggests that things may not have gone
    so well since.

    If you have a hot area and a cold area, you can move the heat from one
    area toward the other.
    Normal technology requires some kind of heat exchanger.
    The problem is that the hot area is typically higher in elevation
    than the cold area. Efficient heat exchangers, like heat pipes,
    work better moving heat upward. That requires some motive power
    to reverse that process.

    I've made some heat exchangers for a heat recovery ventilator using
    copper pipe and freon. The pipes work amazingly well. Problem
    is getting the heat from the air into the pipe with stuff you can build
    in your garage. Suggestions welcome.

    For air to air exchange, DIY units made out of Coroplast give a lot
    of bang for the buck. Would be interesting to try to make an air to
    water one.
    Would take a LOT of caulk to patch up all the leaks. Or just use a car
    radiator.

    Bottom line is that your best investment is insulation. If you have
    EXCELLENT insulation, simple schemes like pumping water around have
    a better chance of working, but the amount you save is small.
    Do the math. Takes a LOT of water to mediate the daily temperature
    change, even if you do have the right climate for it.

    If you do the math, it's likely that anything you do with retail cost
    parts isn't cost effective. It then becomes a hobby exercise in what
    you can do with what you have on hand or available for free.
     
  4. mike

    mike Guest

    The problem has two loosely coupled parts, so let's separate them.

    1)How do I cool the bedroom?
    If you need to move heat from one place to a hotter place,
    it's hard to imagine anything more cost effective than the air
    conditioner he already has. Peltier is a very bad solution for
    anything without severe restrictions...like cooling something
    that puts out no power to very cold temperatures...thermal imaging...
    or something that can't have any moving parts. Yes, sometimes it's
    handy to be able to drink warm pop in the car instead of hot pop,
    but it ain't efficient.

    If you have a heat sink at a colder temperature, you may be able
    to do something with a heat exchanger.

    2)How do I power it cost-effectively with solar?
    You don't!
     
  5. P E Schoen

    P E Schoen Guest

    "Jeff Liebermann" wrote in message
    There are personal cooling vests and suits:
    http://www.veskimo.com/liquid-cooled-microclimate-vest.html
    http://en.wikipedia.org/wiki/Liquid_Cooling_and_Ventilation_Garment

    You could probably make chilled water and circulate it through tubing and
    thermally conductive pads placed on various parts of the body to feel
    cooler. Sort of the reverse of a diving heater:
    http://www.patcoinc.com/aqua_heaters.html

    Paul
     
  6. Martin Brown

    Martin Brown Guest

    And that is even true for off grid provided that there is some
    relatively easy way to carry a suitable battery to and from the site.

    Wind turbines are a little bit better - you might at least hope to get
    enough electricity out of one of them on a good day to power A/C though
    there is still a very hefty capital investment to do so.

    Best you can do for a small room is put a scacrificial thin shade layer
    on the sun facing walls and follow the sorts of ancient building codes
    with verandas and shutters to keep heat out during the day. Cacti and
    termite mounds demonstrate most of the requisite engineering tricks.

    Using modern advanced insulating materials like aluminium foil backed
    bubble wrap and the equivalent in thick glass fibre insulation you can
    prevent a lot of heat getting in from the roof space. Preventing the
    heat getting inside is better than struggling to remove it later.

    Regards,
    Martin Brown
     
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