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Cheap Peltier air conditioner?

Discussion in 'Hobby Electronics' started by Gregory Toomey, Sep 6, 2003.

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  1. **Points:
    1) It would not be cheap. A small air con delivers around 1,500 watts of
    cold air with less than 1,000 Watts of input power. A typical Peltier device
    delivers less than 30 Watts of cold air, with more than 30 Watts of input
    power. You'll need *a lot* of Peltier devices, *a lot* of heat sinks and *a
    lot* of power.
    2) Peltier device generate their heat around away from the cold bit. It
    will require heroic methods to shift the heat away.
     
  2. Arpit

    Arpit Guest

    THink about it, an average 2 hp air conditioner pumps 1400 watts. say
    your pelters pump 80 watts each, you need 18 to match that. At 20
    dollars each thats only about 400 dollars. BUT each one will draw
    about 7 amps at 12 volts. So your elelctricity charges will be very
    large. YOu can power them by 9 good computer power supplies, if you
    find a trash bin full of them, your ok, but otherwise expect to pay at
    least 30 dollars new. Plus you'll need to give them a resistor to load
    the 5 volt rail. THen theres the problem of getting rid of 1400 watts
    YOud need a huge ugly black heatsink arrangement, which would be
    expensive, or a more elegant solution would be to use lots of computer
    amd or p4 cpu coolers. naturally these would be poking out your wall.
    And would be really noisy and whiny. Youd need pretty much the same
    thing on your side too, to cool the room. FInally comes switching.
    PEltiers dont like to be switched at low frequencies so youll need to
    build something to drive themm at a few kilohertz. Welll, rather, 9
    things, each capable of 18 amps. SO the minimum price list

    Peltiers: 360 dollars
    Tools to cut holes in your wall: 300 dollars
    CpU coolers: 540 dollars
    Total: 1200 dollars

    More realistic cost list
    Pelters: 630 dollars
    Power supplies: 450 dollars
    Resistors: 5 dollars
    Coolers: 1080 dollars
    Driver circuitry: 270 dollars

    Total: 2435 dollars
     
  3. I've only seen these devices in the past year, though the effect was
    discovered over a century ago. Maybe more research is needed, just like
    superconductors/fuel cells/solar panels. Consumers would buy a 500 watt
    device with a simple fan that sits in a window, provided it costs less to
    manufacture than an evaporative air conditioner.
    Just mount it in a window with the hot end outside.

    gtoomey
     
  4. Uncle Al

    Uncle Al Guest

    Peltier coolers have low efficiency and are unsuited to moving large
    amounts of heat. They are good for quiet spot cooling and maintaining
    the temp of a well-insulated volume. One ton of air conditioning
    might barely do a nice home for 24 hours in the summer - the energy of
    melting one ton of ice at 80 cal/gm or 80 million calories. One
    cannot imagine a Peltier cooler that large - or its electric bill.

    Peltier CPU coolers are not even suitable for (admittedly crappy)
    Intel Pentium IV's and their 30-50 watt heat outputs. You would need
    a 100-250 watt cooler. What cools the cooler's hot side?

    A Ranque-Hilsch vortex tube won't do it either - too inefficient, too
    noisy. A freon refrigerator is engineering and thermodynamic heaven
    on Earth. Safe and cheap, too. That is why Luddite Enviro-whiners
    hate it so. They violate the Enviro-whiner holy trinity: Expensive,
    shoddy, deadly. ("Shoddy" was the first recycled wool back in
    Industrial Revolution days. How good do you think it was?)
     
  5. Uncle Al

    Uncle Al Guest

    You do it. Watch the thing melt before your eyes. The cold plate and
    hot plate of a Peltier cooler are separated by about 3 mm - and for
    good reason. Do you know how a Peltier cooler works?
     
  6. Rod Speed

    Rod Speed Guest

    Not cheap to run, anyway.
    They've been around for years now,
    not uncommon with camping eskys etc.
    'more research' wont help, the current ones do close
    to whats theoretically possible and thats nothing like
    the running cost you get with a true airconditioner.

    Basic physics that no 'research' can change.
    What matters is the running cost, not the purchase price.
    Pity about the electrical power required to provide useful cooling.
     
  7. Yes, but I'm no expert at thermodynamics. There are a number of small
    Peltier refrigerators (mainly for vehicle use) so I thought an air
    conditioner would be possible.

    gtoomey
     
  8. Dissipating the heat should be possible.

    For comparision, modern CPUs put out >60 Watts. With a heatsink, the CPU
    fan only consumes about 1 Watt. Some CPUs are even passively cooled.


    gtoomey
     
  9. Arpit

    Arpit Guest

    Yep, Even a portable air conditioner beats them.
     
  10. Russ

    Russ Guest

    I think what you are missing is the reason behind using both heat pumps and
    evaporative air conditions - they both exploit physical principles for
    efficient cooling - that is, they remove more heat than they require to run.

    Peltiers are inherently inefficient, and are thus a poor choice, except for
    specific applications where their simplicity and size make them appropriate,
    such as esky heater/coolers.

    Russ.
     
  11. I was thinking along the same lines. There is probably a market for a
    cheaper (and proably quieter) window unit. If you can just get away with
    fans & heatsinks I think there would be a big market.

    gtoomey
     
  12. Rod Speed

    Rod Speed Guest

    Or even basic physics either.
    The difference is that with a small fridge, you only have to pump
    out what leaks in thru the insulation. Doing a whole room is completely
    different and you basically have to pump a lot more heat, and peltier is
    hopeless for that. If you want cheap, evaporative is the way to go unless
    its very humid. Otherwise there is no substitute for real airconditioning.

    You should have noticed that while peltier is used for
    fridges in vehicles, it aint used to cool the vehicle itself.
    They use a real airconditioner for a reason.
     
  13. Rod Speed

    Rod Speed Guest

    Pity the running cost is much worse than a real airconditioner.

    And if water is available, you might as well just cut to
    the chase and have an evaporative air cooler instead.

    Which just happens to be what is done.
     
  14. Rod Speed

    Rod Speed Guest

    Nope, because of atrocious running costs.

    If you want quieter, you just use a split system.
    You're wrong, because of the running cost.
     
  15. DarkMatter

    DarkMatter Guest

    It would be nice if the smart folk, like you would extend those
    brains to being smart enough to trim the irrelevant parts of your
    reply away. DUH!

    You put down one idiot's remarks, replying to one sentence, yet your
    stupid ass STILL quoted the entire tripe post. You need to get more
    clues than those you have chosen to embrace, boy.
     
  16. **I don't think so. It has been explained to Mr Toomey the reasons why
    Peltier devices are completely unsuited to air conditioning, yet he keeps
    asking the same questions, in different ways. It can be very frustrating.
     
  17. Ian Stirling

    Ian Stirling Guest

    Anyone know what's happening with thermal diodes?
     
  18. With somebody offering to make a prototype ...

    gtoomey
     
  19. **A fool and his money......
     
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