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Thread: Creative Cooling Solutions?

  1. #21
    jesse's Avatar
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    Jan 2011
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    Quote Originally Posted by TheFury View Post
    Then I stumbled on this guy:

    It's an electric cooler that uses a Peltier device to bring the temperatures inside the container down to about 40 degrees below ambient, which for all but the hottest months of summer means it'd stay within 10 degrees of freezing in the ice box. It uses less power than a 40-watt light bulb, and it's quiet.
    Does anyone have any thoughts on this cooler?
    OMG! If this thing is quiet, then you are deaf.

    And how can it use "less power than a 40-watt light bulb" while it is manufacturer rated 4 amps at 12 volt = 48 watt? See here:

    BTW: You will need an additional AC/DC adapter to operate that box with mains supply.
    Such thermoelectric peltier coolers make a lot of noise with their fan. And they provide only little cooling power compared to their power consumption.

    Thermoelectric cooling is inefficient, the cooling power is about 2/3 of the electrical power consumption, so if such a device consumes 48 W, it will provide roughly about 48*2/3= 32 W cooling power.

    If you intend to create a heat exchanging device from this box and your growing chamber, you could pump water to and fro, need an aquarium pump with about 5 W and this already is a new heating device in your circulation. Substract 32 W - 5 W and there will be a total of 27 W of cooling power that arrives in your growing chamber.

    How good is the insulation of your growing chamber? How low can the temperature go with just 27 W of cooling power?

    On the other side: Compressor coolers can easily provide 2/3 more(!) cooling power than they consume as electrical power. So a 48 W compressor cooler provides roundabout 48*1,666 = 80 W of cooling power. Reduce by 5 W for the pump are 75 W remaining.

    So from 48 W of electrical power input you can have either 27 W of cooling power with a peltier cooler or 75 W of cooling power with a compressor cooler. Pretty much different, isn't it? Efficiency is much higher with compressor coolers!

    Unfortunately, compressor coolers are more expensive and (in most cases) louder than thermoelectric coolers. And the cooling power range starts with compressor coolers where it ends for thermoelectric coolers.

    But long speech, short point: I doubt that a thermoelectric cooling box provides enough cooling power to lower the temperature in a growing box by a significant amount.

  2. #22
    Oh, the humanity!! TheFury's Avatar
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    Thanks for all that detail! Yeah, the insulation in my grow rack consists of nothing more than a few mylar blankets and a shower curtain. I'll definitely have to maintain a cool breeze all day.

    I never really intended to use the thermoelectric cooler as a source of cold air... I just wanted to use it in a modified version of Reaper's setup on p.1 to keep the cooling fluid (water & ice) from heating up as quickly as it would without input from the cooling device.

    However, if I can snag a cheap mini fridge, I might just do that.

    Does anyone have ideas specifically about the heat exchange mechanism? What sort of options are out there, besides the home made "redneck AC" devices that consist of fans with copper tubing wrapped around them?

    Also - my grow rack has three shelves. I achieve lowland conditions on my top shelf for 10 months out of the year, which is awesome. In July and August, it's quite a bit hotter than LL. I was planning on pumping cool air into the lower shelf to get closer to intermediate/HL conditions on my BOTTOM shelf, about 4 feet below my top shelf. I'm hoping the low temperature might bleed up (across two light fixtures and two levels of plants) into my top shelf to take the edge off the summer heat. Any physicists here care to refute this??

    Sorry for writing a novel here... lots to think about, which for me means lots to ask about!

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