Cooling and Powering 2000w of LEDs?

Discussion in 'The Projects Forum' started by berry1, Sep 18, 2014.

  1. berry1

    Thread Starter New Member

    Oct 17, 2013
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    Hi guys

    I want to build a 2000w led light unit consisting of 20 x 100w high power led chips.

    My question is what would be the most cheapest way to cool 20 x 100w led chips? steel u pipe?
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    More like copper pipe which has water running through it. Cheapest would be dumping them in a vat of oil, but they would make much light that way would they.
    On a more serious note, 2kW is a vast amount of power, you will need a huge aluminium heatsink. Do you mind using fans to help with the cooling, or is noise a problem?
    How big are the modules and how closely do you need to space them? Do you have a datasheet?
     
  3. berry1

    Thread Starter New Member

    Oct 17, 2013
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    Funny you should say that because i was researching mineral oil for cooling i was thinking a large custom built glass tank with the led chips siliconed to the bottom face down so the light passes through the glass i wouldn't think the glass would restrict to much light but it would probably be pretty impractical just thinking of all ways to cool the set up.

    Fans to help with cooling is no problem but i cant go much over 30db for each fan most fans seem to be under this so that shouldn't be much of a problem.

    I need to fit all 20 modules in a 8 x 8 foot square if possible not really limited for space providing they fit in that size space roughly i could do say 20 individual units and just wire them together to split the cooling up? but even a single 100w high power led would need a fair amount of cooling.

    The information i have on the leds i was planning to use is 100w chips cool white - input voltage DC 32-36V - Current IF 3500MA - lumen 6,000 - 7,000.

    Thanks for the help :)
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    No more info on them? That will be quite hard to design properly, you need at least some thermal data on them to pull this off. At least junction to case thermal resistance and maximum junction temperature, or something along those lines. How big is each module? You might try finding something similar that has a datasheet and going from there.
    Also note that from what you describe these modules are just a string of leds attached to a metal pcb, so each will need some form of current regulation, preferably a switching controller with that amount of current.
     
  5. berry1

    Thread Starter New Member

    Oct 17, 2013
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    This is the same leds i was planning to use is this much more help?

    http://szgmled.en.alibaba.com/product/657156206-0/high_power_100w_led_with_data_sheet.html

    Its the heat sink im worried about as the kind of heat sink needed to cool the amount of leds i want to build would be very expensive.

    Thanks
     
  6. #12

    Expert

    Nov 30, 2010
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    Those are calculating at 36V x 7A = 252Watts each. They appear to come with a heat sink, but you're going to need a fan for each one to get enough velocity in the air to strip away the boundary layer. 20 x 252W = 5040 watts or 17,202 BTU's. That's a ton and a half of air conditioning to cool those 140 amps of current!!! :eek:

    Let's see...BTU = 1.08 CFM dt (in Fahrenheit)
    17202 = 1.08 CFM 54F = 295 CFM
    If you allow the exiting air to be 30C (54F) above ambient, the gross fan that empties the air from all the little fans would be about 300 CFM. You can forget 30 db if you use only fans. Back to the drawing board with the copper pipes and water pump using a fan driven radiator out of a 12000 BTU air conditioner.

    Of course, this is only one way to look at the problem.

    If you're not gong to drive these LEDs balls out, you can adjust the math accordingly.
     
  7. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    They say it has 8°C/W, so if you run them at the stated 200W the LEDs will be 1600°C hotter than the heatsink. So much for chinese bogus numbers.
    If this were per LED it would make a bit more sense - the picture shows 20x12LEDs, that makes for 0.83W per led and 6.6°C temperatire rise.
    So lets say you need to dissipate 100W, and you want the LEDs run at no more than 100°C, with ambient temperature of 40°C. That means you need to have heatsink that has thermal resistance of around (100-6-40)/100=0.54K/W with the fan running. The heatsink will be a bit larger than than the chipitself, I´d guess about 120x120mm, but it should be doable.
     
  8. #12

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    'scuse please, Kubeek. Datasheet says 75C max operating temperature.
     
  9. kubeek

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    Sep 20, 2005
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    Yes I noticed that, but I took it for another bogus number that had something to do with the ambient tempearature of the discrete leds. Might be wrong though..
     
  10. #12

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    At least Berry has some math to work with. This is the kind of project that takes several thinks to arrive at a conclusion.
     
  11. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Any way you cut it you need to get rid of 2000 watts. I would rethink water. If your a do it yourselfer you might be able to solder some copper plate to some copper pipe (several rows) and use like a transmission radiator and a fan to get the heat away. The cost of the heat sinks will break the bank otherwise. I've helped a couple of people do this with big electronic loads.
     
  12. #12

    Expert

    Nov 30, 2010
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    If the array of copper pipes is large enough, just circulating some anti-freeze solution through them might be enough to radiate the heat just from the copper pipes.

    Here's a number: 1/2 inch bare copper pipe at 180 F (82.2 C) radiates 56 BTU per hour per linear foot.
    2000 watts times 3.413 BTU/Watt = 6826 BTU
    6826 BTU/56 BTU/ft = 122 feet of pipe.

    82C is out of range for the datasheet limit on the LEDs, so you have to adjust for that.
    The ambient temperature is assumed to be 70F for the radiating number, so if you radiate into a closed space, this method will fail.

    Holy smoke, number twelve! Where do you come up with this stuff??? :eek:
    Air conditioning is all about thermodynamics. :p
     
    Last edited: Sep 18, 2014
  13. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    umm.. what are you trying to do with 2000W of LEDs?
    Hope you don't mind going blind.

    Someone is WAY out of their league.
     
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  14. #12

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    Meh. Even if this project never gets built, discussing it is very educational. :)
     
  15. mcgyvr

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    Oct 15, 2009
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    Sure.. Some more details from the OP would be nice too.. Now its just 99% speculation..
    More about the physical space constraints/db constraints would help.. If this is going in an 8x8 room vs a small area in a warehouse ,etc... Why a 30db limit.. Thats forcing him into to water cooling..
    Not to mention WHY 2000W of LED in a 8x8 area.. Thats FAR more than anyone would EVER need for an area like that unless you are attempting to duplicate the sun for a solar panel experiment..
    What color does he need/color temp? ,etc...etc...

    Heck I can tell him that he can get 100W LEDS on ebay for as little as $5-10 each.. Not to the 40-80 as quoted in that site.. Thats far overpriced.. Not to mention that link is for a company that makes a wide range of those and doesn't specifically call out one in particular..

    Personally I HATE discussing problems when you only have 10% of the information.. I will just walk away all the time when that happens..
    Heck this could be for over a large aquarium and the use of materials like copper would be a serious NO-NO as it could kill everything in the tank.
     
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  16. Experimentonomen

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    Feb 16, 2011
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    Maybe look at how the commercial LED jumbotrons are cooled, the larger ones i think reach toward 2-3kW total. Though they use thousands of regular leds, rather than your few big 100W ones.

    What is this for anyways ?
     
  17. tcmtech

    Well-Known Member

    Nov 4, 2013
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    If it was me I would mount everything to a pair of 4' x 8' 1/4" thick aluminum sheets. Given the 128 sq foot passive radiation surface should be more than enough to keep that heat down.

    At worst some simple ducting and one average sized box fan blowing on the back side of the setup would easily dispate that kind of power.
     
  18. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Flat plates make horrible heatsinks.. They lack the surface area that a proper finned/pin heatsink has.. And natural convection cooling is all about surface area..
    Not to mention the weight associated with a 1/4" sheet of aluminum..
     
  19. #12

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    Nov 30, 2010
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    Most of us don't have 4 foot by 8 foot sheets of aluminum! :rolleyes:
     
  20. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    I mounted some 1.5 W LEDs for under cabinet lighting on Cu strips mounted to Al light ga channel which averages about 4.4 sq in / W. LED about 120 deg F, chanel at edge bairley warm.
    OP's about the same, 4.6 sq in / W. Maybe if 100 W modules were mounted on 20, .o62 Cu, 6 X 8 in. in turn mounted on 4, .o5 in, Al U channels, 2 X 16 X 2 in. & 8 ft long would be sufficient?? There would be 5 in spaces between chanels to keep heat sinks from making a heat trap with bottom of tank.
     
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