how impractical is water cooled LEDs

[TropTrea]

Yes I would say it is feesable but question the Cost and practicality. Lets look at the basics. I have several 40 gallon frag tanks on LED's and the best results of both Color and Growth are under the following LED's.
10 Watts of Neutral White LED's
8 Watts of Near UV LED's 420nm
15 Watts of True Blue 470nm LED's
30 Watts of Royal Blue 455 nm LED's.

Light distribution on the 40 breeder tank is a big area with a shallow tank. You want at least 4 different point sources if your keeping the lights close to the surface. If you raise them so they are at least 30" from the substrate than you need to increase the wattage to account for the added distance. But two more powerful light sources would be more viable then.

Four groups with a total of 63+ watts would mean about 16 watts per pight point. That would easily be handle by one of the collers you listed. Provided you fcan fit the desired LED's combination on the Cooler.

Going with 2 light sources would mean at 32 watts per light source and preferable closer to 50 watts with the added distance the light needs to travel. Again this is peobably hitting the near limit of the heat sink however will you have enough space on it to mount everything?

For cooling I see it being very simple where for each cooler have a small submergable pump with a pre-filter on it to pump the water. With a 40 gllon tank you want at least 1000 gallons total flow so with 4 units you only need a pump that will run about 250 gallons per hour. The question is with the small tubing what is max you can flow through the water cooled heat sinks?

On the ergonomic sense is the power used to pump the water through the piping going to cost less than the amount f heat that the will saved from the heater?

 

[TropTrea]

Wow read through the posts that poped up while I was writing mine. Pulled through some added ideas from them. Yes copper is a no no with salt water but I do not see a big issue with alumnium. So rather than the small CPU fans using a heat excanger made of of smething like 1"X 3" Tubed Alumnium. Getting the endswelded closed and putting in nipples for 1/2 tubing on opposite sides. Now you can easily pump 1000 gallons per hour through the unit provided it is prefiltered.

Now you have a heat sink of say 3" X 30" Which would be enough room to mount up to 90 3 Watt LED's. Since you won;t need that much light your in good shape. Now on a rough estimate you may have 60 Watts of LEd's with 45 watts of heat generated. I the transfer in 50% effecient then you would have the equiveent of a 22 watt heater in the tank at all time. That would give you normaly about a 0.5 degree increase in temperature each hour up to the point where evaporation nalances the cooling of the added heat.

 

[7808]

ive had bare aluminum hanging over my tank for years, it looks uneffected. althought it's not constantly in direct contact with sw. i like your idea of getting some 1x3 aluminum square tube welded shut at the ends with some npt bungs, i thought of the same thing. wish i had a tig welder to play with.

you could also run a heat exchanger in your sump that you could circulate fresh water through. ends up sounding like too much complicated business

 

[Sander_Bos]

good info. i guess someone would just have to try it. i did find some crazy high priced water cooled LED lights designed for aquarium use, but nothing that used tank water.

like this one for $1200:uhoh3: http://www.bluemoonaquatics.com/BMA_P100.php pretty cool though

Well, it's funny that this topic pops up, because I was actually planning on making a water cooled LED fixture, in combination with some other functions....

That LED bulb is actually very cool, indeed expensive, but we can maybe come up with a cheaper solution.

 

[7808]

that could defineatly be build way cheaper, the only fancy part is all the custom made acrylic and spendy connectors, oddly they didnt even have a custom temp display made, it shows cpu and hdd lol

 

[Gorgok]

Wow read through the posts that poped up while I was writing mine. Pulled through some added ideas from them. Yes copper is a no no with salt water but I do not see a big issue with alumnium. So rather than the small CPU fans using a heat excanger made of of smething like 1"X 3" Tubed Alumnium. Getting the endswelded closed and putting in nipples for 1/2 tubing on opposite sides. Now you can easily pump 1000 gallons per hour through the unit provided it is prefiltered.

Aluminum is 'okay' in saltwater until it has a charge in it, like a harbor or tank with pumps/powerheads in it... Electric charge plus conductive water makes corrosion happen fast. Aluminum is actually used as a sacrificial anode to protect other metals on boats because it corrodes so fast under these conditions...

Also, a box with water is a bad waterblock. Just like air cooling, metal fins should be used to increase the area that contacts the cooling fluid (air, water, whatever) otherwise you get minimal heat transfer and the rest of it is effectively insulated by the surface layer of the fluid.

Filtered or not eventually you will grow something in the box, then you have all sorts of issues, from losing flow to further insulating the walls. Lack of flow, thick growth and a rapidly heating LED could cook something off the walls. Once flow returns because that cooked thing died and released it gets pumped back into the tank as special soup it may not be too good...

 

[sleepydoc]

Several comments-
First - Water is more conductive (to heat) and carries more heat than air which is why most engines, etc are water cooled. The problem is water cooling adds significantly more complexity, expense and opportunity for failure (leaks, pump failures, corrosion, etc.)

As others have alluded, the theoretical maximum power saved by using the heat from the LEDs would be on the order of 40 watts, minus the power used by the water pump. For argument's sake, a maxi jet 1200 uses about 20 watts, so you're down to 20 watts. Where I live, electricity is about $0.10/kwh. If the lights are on 12 hours a day. This works out to about $10/year in potential electricity saved. This ignores the fact that during the summer you may actually have to turn off the system because of excess heating of your tank.

Now there's the issue of corrosion. As others have mentioned, aluminum is not inert. The absence of visible corrosion of an (? anodized) piece of aluminum above a tank cannot be applied to the current application. Aluminum in constant contact with salt water will corrode. The rate depends on charges, etc. Corrosion has several potential detrimental effects - first, a layer of corrosion would likely inhibit heat transfer, reducing the efficacy of your cooling system. Second, it may also reduce flow or lead to complete failure, depending on system design. Finally, there is evidence of aluminum toxicity to corals. (see http://www.advancedaquarist.com/2003/7/chemistry) I do not know about fish, but a system such as this has the potential to increase the aluminum levels several orders of magnitude. I don't know if there is any data on toxicity of those levels to reef inhabitants (vertebrate or invertebrate.) To my knowledge, most chillers use Ti heat exchangers instead of Al because of this.

The final issue is reliability. If you depend on a home-made system to cool your lights and a pump goes or clog occurs because of a snail, algae, etc, you risk burning out your LED fixture, or worse yet, a leak in the plumbing drains your tank, floods your living room, kills your livestock and burns out your circulation pump that ran dry.

To summarize, it may be technically feasible, but the benefits become almost negligibly small next to the potential risks.

 

[reefergeorge]

I use to build very large battery chargers.This one would push 3000 amps. In the pic you can see the water cooled SCRs. Even the cables are watercooled and it's all pumped back into a Cadillac radiator. I know its not exactly the same, but the theory is the same.

 

[FullBoreReefer]

good info. i guess someone would just have to try it. i did find some crazy high priced water cooled LED lights designed for aquarium use, but nothing that used tank water.

like this one for $1200:uhoh3: http://www.bluemoonaquatics.com/BMA_P100.php pretty cool though

"With so much available light, high performance cooling fans were designed to eliminate any over heating of the*P100*and a temperature guage was added to safely monitor temperature..."

That's from the link you mentioned. Was there something else that mentioned the water cooling?

 

[Gorgok]

I actually think that fancy pendant in the link uses a premade CPU heatsink that can be had from newegg or whatever, then its dressed up in 'fancy' crud around it to make it look like they put effort into it. Just a case of dress-up...

The heatpipes is probably what they are mistakenly calling water cooling. They do indeed contain a liquid, but its hardly water cooling.

 

[TropTrea]

Going back a few years on my job we had issues with blowing out transistors on an almost predictable schedule. On the original design we had extremly large finned heat sinks. Our interm design was to putting large cooling fans under the units which were located directly over air conditionong duct. This worked better than the original design however air conditioning is not on constantly and if the transistors were stressed when the air conditioning was off we had the problem again. The final fix was using a special designed heat sink that was basicly a series of tubes welded to an alumnium plate. We then pumped pressurized refregerant to the tubes like the A frame in an air conditioning unit. The condesnor pump was regulated by temperature sensors on the plate that kicked in the pump when the plate temperature exceeded 40F and the unit was operational. In two years after the final fix we did not have one reported transistor failure.

LED cooling does not have to be this drastic. We were running roughly 1,500 Watts through this bank of transistors. Even simple free air cooling of LED's without even fans usualy is suffecient with less than 5 square inches of surface area per watt. It is only when your using some of the multicip combinations that now go as high as 200 Watts that require elaborate cooling. On a 40 gallon tank 80 watts if LED's would be roughly the most anyone would require unless they had them located several feet above the tank.

Going back to my original idea allumnium and copper are the most frequently and economical materials for a liquid cooling system. Copper is imediatly eliminated with corals and several people gave reason to eliminate alumnium. However the sustem still could be built as a closed loop system with the bottom of the tank holding coils of tubing that is pumped to the LED cooling system. With enough lenght even plastic tubing could be used for most of this. But the issue remains what do you use for the material the LED's are mounted on that will absorb the heat.

Yes I will agree this is more of a can it be done project than a truely return on your investment project. But ome times for most hobby tinkerers doing something no one else has cone is the biggest reason for a project.

 

[sfsuphysics]

If you were to try and build a system that is as energy efficient as possible, regardless of the cost, these are the steps I would go to for a water cooled LED system

1) Closed system, do NOT use the tank water, have a titanium coil as a heat exchanger, and fluid moving around but do not use tank water under any circumstances. You can still get the waste heat to heat your tank, yeah it'll be more expensive, but the risks mentioned above with corrosion are not a factor.

2,3,4) Air cooling as backup for the LEDs, an electric heater as back up for the tank, a controller that can handle all the logic.
Air cooling is in case tank doesn't need to be warmed anymore but lights are still on
Heater is in case tank needs to be heated but lights not on.
Controller is to manage everything, so if the tank is too warm but lights are on it'll power the fan to cool the LEDs and turn off the pump to the water cooler, if lights off but heating necessary then it'll power the heater and make sure the pump doesn't come on (so you don't cool your tank), if lights on but temperature too low it'll throw the heater on as backup...

So it is feasible to do it, but you already got a heater, air cooled LEDs, do you really want to add that layer of complexity to a tank just so you can feel good about saving a few kWh a year?

 

[TropTrea]

I think the above by sfsuphysics is a little over kill. I do agree with the closed looop but I do not think you need to use titanium. The Cooled Plate that the LED's are mounted on could be alumnium, or even copper since it will be above the water and not in contact with the tank water.

The heat transfer coil in the tank could be very simple and made completly out of a thin walled plastic. It is just a matter of having the coils on the bottom of the tank and making the coils large inough. This system would be simular to what you have in hot water heated floors. The warm water is pumped into the coils.

Now the issue is finding the plate with cooling for mounting the LED's on. with a 40 breeder tank I would recommend a size in the range of 30" X 12". This could easily be made. With Alumnium you would have to find someone with Alumnium welding experience. But if you went with copper you could almost solder the entire Plate copper tubing to it.

 

[7808]

i wouldnt go as far as to use controllers and all that unless i really NEEEDED to do water cooling and was transfering alot of heat.

if i were to do it, to try it, i would buy cheap ebay aluminum cpu blocks, or build an aluminum single block, for multiple 10-20w multichips, coil of maybe 1/4" stainless steel tube in my sump (think brake line/ice machine line), and a small pump closed loop freshwater. or i would do a fine mesh screen y strainer and use tank water, but pretty sure this would end up getting gunked up and loosing lots of effciency after a couple months. maybe. probably would have to end up pumping some vinigar or somthing through them every few weeks

if it ended up raising the heat too much in my tank, thats where i would scrap it for fans

 

[mussel and hate]

Stainless steel will corrode in saltwater, it's merely a question of time.

If you want to make a ghettoriffic simple WC system then how about an elevated tank with a slab of aluminum affixed to the bottom pane with thermal epoxy. LEDs go on the downside of the Al slab. The Al slab is your heatsink which in turn dumps heat through the glass into your water(I know glass is a poor thermal conductor). Center this monstrosity over top your display and plumb it for recirculation with a standpipe to avoid siphoning in a power failure.

Simple, cheap and maybe even effective...

 

[TropTrea]

I would not put any metal in the tank at all. If you get some thin walled Plastic tubing and run enough lenght of it through the tank you will get enough of a heat transfer.

But as far as steel corroding in salt water I would say it depends on the composiotion and grade. There are virtualy hundreds of steel compounds with different metals and ratios on the market. I'm sure there i one that would not react with salt water. However it would probably not be inexpensive.

 

[kgk]

After spending years building watercooled PC rigs, my gut reaction says this is fraught with danger. There are so many really bad failure scenarios. What happens when the cooling pump stops working? Etc. Water cooling rigs take maintenance.

 

[TropTrea]

After spending years building watercooled PC rigs, my gut reaction says this is fraught with danger. There are so many really bad failure scenarios. What happens when the cooling pump stops working? Etc. Water cooling rigs take maintenance.

You just have to think of all the possible failure modes and create a saftey check around each of them. Pump failure could be taken care of with either a flow sensor, or possibly at high temperature cut of on what ever the LED's are mounted to.

My concern would be leaks between a fresh water plumbing system and the salt water piping. Could salt water get into the system and eventualy cause clogs?