DIY Water reservoir chiller

So I am looking at ways to cool my nutrient reservoir. My ideal solution would create a snap-in water temperature regulator that simply uses a temperature probe, 110VAC outlet, and a pair of hoses to connect to any system. Here's what I've got planned so far..

* Controller $38
* Elements $17
* Chilling block $15
* Active heat sinks (x2) $26
* Pump $10
* DC Power supply $35

My plan is to thermal glue three of the elements onto the water chilling block. Then use the two heat sinks to actively cool the reverse side of the elements. I would then mount this chilling reservoir to the side of the nutrient tank, connect the pump to pull water into the cooling block from the resevoir. When the pump is turned on, it would suck water from the top outlet of the chilling block, which would create a reverse pressure system pulling fresh nutrient solution out of the reservoir. The block would be slightly tilted so all the water will drain from the bottom inlet back into the reservoir when the pump is turned off.

Are there any better solutions out there? Any feedback is welcome.

something like this? http://www.bulkreefsupply.com/iceprobe-thermoelectric-aquarium-chiller-nova-tec.html?gclid=CjwKEAjw19vABRCY2YmkpO2OzTsSJAAzEt8s-vlsHrVev-DIhpPTA_mK71fUOT2TEI82-l96pdfr6BoCYJfw_wcB

Peltier elements dont have a lot of cooling power in the end. as long as the room your reservoir is in has reasonably thermal stability, you can just add elements until you hit your target. Insulate the reservoir if it is in a warm room and then just tune your peltier power to hit your target. Assuming that 1/3th of the power input is the cooling efficiency is a good starting point. when you are dealing with larger reservoir or a higher thermal differential then you need to go to a small water pump on both the hot and cold side, a CPU radiator on the hot side and water cooling blocks forming a sandwich for the cool side heat exchange. Your cheap option on the power supply is a computer PS with green bridged to black as the ground and yellow as the positive. Just buy a PS for twice the power demands of the peltier, pump and radiator fans.

-Eskander

Eskander said:

Peltier elements dont have a lot of cooling power in the end. as long as the room your reservoir is in has reasonably thermal stability, you can just add elements until you hit your target. Insulate the reservoir if it is in a warm room and then just tune your peltier power to hit your target. Assuming that 1/3th of the power input is the cooling efficiency is a good starting point. when you are dealing with larger reservoir or a higher thermal differential then you need to go to a small water pump on both the hot and cold side, a CPU radiator on the hot side and water cooling blocks forming a sandwich for the cool side heat exchange. Your cheap option on the power supply is a computer PS with green bridged to black as the ground and yellow as the positive. Just buy a PS for twice the power demands of the peltier, pump and radiator fans.
-Eskander

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Yeah, I'm only looking to take off about 4-6 degrees from the ambient temperature. I was already looking at moving it into a "insulated storage tank" like this one for only $16. Looking at that price, I don't know why I've ever bothered with anything else. The DC power supply I picked out was 500W peak, which I assume is 250W stable. I'm using 3x 65W peltiers.. which is 195W + the pump and stuff which are small change. However, if the insulated tub isn't enough, like you said I can slap more cooling elements on the opposite side of the cooling brick if necessary, but I think this should be enough. If I get a run-away cooling effect on the brick, then I'm definitely going to add the second pump. My thinking with just one is that first off all, the cooling devices like you said aren't packed with power, and since temperatures are only a measurement of averages, pumping a gallon of water water 2 degrees colder is basically the same cooling effect as 2 gallons of water that are 1 degrees colder. Instead of mounting it to the side of the reservoir, I had the idea to install everything into an aluminum hammond enclosure with just the power cord, probe, and hoses hanging out, and the temperature controls mounted on the face of it. That's going to look far more professional, and I can leave it on the countertop.

disratory said:

something like this? http://www.bulkreefsupply.com/iceprobe-thermoelectric-aquarium-chiller-nova-tec.html?gclid=CjwKEAjw19vABRCY2YmkpO2OzTsSJAAzEt8s-vlsHrVev-DIhpPTA_mK71fUOT2TEI82-l96pdfr6BoCYJfw_wcB

Click to expand...

The ice probe is what actually inspired me to do this, because it's sooooo over priced. It's like a $20 component, I don't care about being able to make a profit, so for the same price I'm going to get more than just a 45W cooling element. What I'm going to end up with is something more like this except using peltier cooling instead of compressed gas.

I'm hoping it will be able to shave off 2 degrees from the reservoir solution per hour while it's running. So like Eskander mentioned, insulating the reservoir would probably be enough to bring me across the finish line if I can't get enough out of it. I'm hoping once it hits it's target temperature the insulated cooler will only raise the solution about 1 degree every 4-8 hours depending on lighting conditions. I am still debating putting it on the UPS, but my goal is that this thing only has to run like 2-3 hours a day on a normal day, because my UPS is only 1KW. I'm not sure how much value there is to stabilizing the water temperature for 8 hours, if it means my pumps only have 8 hours of backup battery instead of days. That might sound silly, but I travel often and leave my system running automatically when I'm gone. My UPS isn't to avoid waking up in the morning to drooping plants, it's to avoid coming home from some trip to a complete crop failure.

If you are going to use the small elements and have a metal reservoir than you can make this exceedingly simple. Simply stick the elements to the reservoir and then stick passive heat sinks to the other side. It isn't possible to get runaway cooling with these. They have a maximum differential vs ambient that they can't pass unless you stack them. I recall it being 20C but it has been a while. Regardless, they'll never actually do that in an application like this. In testing I did a while back a single element stuck between a really good active heat sink and a water chilling block managed to cool a gallon in an igloo thermos about 15F when run non-stop. The element was around 230W at 15.5v so 150W at 12v and ultimately 50W of cooling minus the thermal output of the .3A 12v pump.

If you need more power than that, a real 12V PS going to be the way to go. Hacked computer ps are only cost effective at a very low level. You can drive these at their rated max full time without issue: https://www.amazon.com/dp/B00D7CWSCG/ref=psdc_1161760_t1_B01IMOS20A so you could run 5 of these: https://www.amazon.com/Vktech-TEC1-12706-Thermoelectric-Cooling-Peltier/dp/B00IKDL22O/ref=sr_1_1?s=pc&ie=UTF8&qid=1478006546&sr=1-1&keywords=Peltier and you'd end up with 120w of cooling for $40 or with two PS, 240w for $60. If you passively cool with something like: http://www.ebay.com/itm/1-Pcs-Aluminium-Radiator-Heatsink-Heat-Sink-40mm-x-40mm-x-20mm-/172259203841?hash=item281b72db01:g:WOwAAOSwhOVXdLx0 then you can just stick on more elements until you get the amount of cooling you want and there are very few things that can fail...

The second you add pumps to circulate through chilling blocks, active heat sinks, a PID controller and thermocouple you exponentially increase the likelihood that something will fail.

I wouldn't bother putting that on the ups. Getting slightly warmer for a few hours won't kill anything and the power demands are kinda high.

When you insulate the reservoir, you might look at the reflective foam board. Havinging the reflective outside on its own will make a big difference on light heating. You can stick that to anything with construction adhesive and then use aluminum tape on the corner. Pretty easy to make it fairly professional looking.

-Eskander

Eskander said:

If you are going to use the small elements and have a metal reservoir than you can make this exceedingly simple...

When you insulate the reservoir, you might look at the reflective foam board. Having the reflective outside on its own will make a big difference on light heating. You can stick that to anything with construction adhesive and then use aluminum tape on the corner.

-Eskander

Click to expand...

Yeah, if you click on any of the parts they all have links to amazon. You can simply click it all and add it to your cart if you want to replicate the design. I'll be posting the step-by-step "how-to" video once everything is put together and I get all the performance data validated. As far as the foam board, that's actually a really good idea. I was going to just repurpose my existing reservoir to a bloom chamber hydro which has better temperature regulation than my veg closet and switch to a 40L igloo cooler for $16. Since my reservoir is in a framed cabinet, I can just pull off the sides and fill the gaps between the framing with foam board and reassemble. Nice pick on the power supply, I had the weather resistant when I was planning on having the PS external to the unit, but now that I'm throwing everything into a case this is definitely an easy money saver. I'll try them both and if they both work I'll return the bigger one. I'll update the list below to also show the parts I had laying around that I recycled into this. I'll update with the hammond box once I get everything assembled and figure out the dimensions and configuration for the correct internal airflow. I'm also going with the dual pump configuration by default, simply for redundancy in the event of a single pump failure, the system will continue to function.

I'll keep the parts list below updated and then update the main post when everything is finished.

* Controller $38
* Relay Heatsink $6
* Elements $17
* Chilling block $15
* Heat Sink $7
* 40mm Fan (2) $15
* Pump (2) $20
* DC Power supply $18
* Power Switch/Fuse $6
* Power Cord $5
* 16 AWG wire $5
* 16 AWG Wire connectors $6
* Rubber feet $3
* Epoxy $4
* Thermal paste $7
* Exterior DC $3

So your config will be a sandwich that goes air-cooled heat sink, peltiers, water block, pelters, air-cooled heat sink and you are going to put the pumps in a push pull configuration for redundancy? That will probably be ok but not very efficient. Those heat sinks are usually used in server racks and they rely on lateral air flow in the case as well as down from the mounted fans.

You could use a radiator and dial up the efficiency quite a lot at the expense of a more complex system. https://www.amazon.com/AGPtek®-Aluminum-Exchanger-Radiator-Computer/dp/B00CFDS3JA/ref=sr_1_1?rps=1&ie=UTF8&qid=1478124538&sr=8-1&keywords=cpu+radiator&refinements=p_85:2470955011 You'd end up needing three of the water cooling blocks to sandwich the and some Y adapters and more pumps...

If you are using an insulated cooler rather than a metal box then a cold finger design is a hell of a lot simpler. Stick the elements to the end of an aluminum bar like this: https://www.amazon.com/Aluminum-Rectangular-Unpolished-Extruded-Thickness/dp/B000H9FZ1I/ref=sr_1_2?ie=UTF8&qid=1478126434&sr=8-2&keywords=aluminum+square+bar+1+1/2 and drop the bar through the top of the cooler. Stick on big passive heatsinks and then power it up. No moving parts.

-Eskander

Edit: That bar wouldn't give you much breathing room. Going to 1.75" would let you stick one on the top and on on all four sides. https://www.onlinemetals.com/merchant.cfm?pid=1119&step=4&showunits=inches&id=999&top_cat=60

So the heat exchange will basically be the water block as the heat source, transferring heat to the peltier. The peltier will transfer its heat to a heatsink, which will then be cooled by a fan and exhausted from the unit. The math looks good as far as this design, but if I need a contingency I think what I'm going to do is make it into a two-stage cooling system and use a radiator and fan as stage 1 using something like this https://amzn.com/B00CFDS3JA and then the peltier cooling block as stage 2. It seems I can no longer edit my earlier posts, I'll just finish in word and post once I'm finished putting it all together.

Great ideas in this thread, I'm in the process of building a controller myself, I have most of the coding done and it's working like a boss so far!

I was thinking of adding cooling to the microcontroller as well, I have an old dorm fridge sitting around and was thinking of plumbing in a copper coil by drilling a hole in the fridge and running the water through there to chill it. The plan is to 'stick it to the chiller man' by spending $300 on copper tube and another $500 on tools, I'll show those Nazi capitalist pigs!

Living near a college town I have an inexhaustible supply of dorm fridges that can be acquired with $20-$25 every May.

Anyway, looking forward to hearing the results of your experiment!

Peace,
Z

Zekie said:

The plan is to 'stick it to the chiller man' by spending $300 on copper tube...

Click to expand...

I wouldn't ever use copper in the reservoir. Copper is highly toxic to plants and reactive enough in nutrient solution that it will corrode and leach metal into solution. Aluminum is fine as a cooling loop and is usually cheaper than copper.

https://www.amazon.com/Allstar-ALL40180-Diameter-Aluminum-Coiled/dp/B006K8JJ1C/ref=sr_1_2?ie=UTF8&qid=1478191793&sr=8-2&keywords=aluminum+tubing

If you want to do a super lazy fridge conversion, you can drill two holes in the side of the fridge, pass a few loops around inside and then drop a short loop through the nutrient tank. Add a small pump to a vertical PVC pipe reservoir and mount them on the side of the fridge. Insulate the tubing anywhere it is open air or it will drip condensate everywhere. You can run RO water or RO with water wetter and leave it as a closed loop system. When it comes to temp control, just set it to max cool and then plug it in through a controller like this:

https://www.amazon.com/WILLHI-WH1436A-110V-Temperature-Controller/dp/B00V4TJR00/ref=sr_1_5?ie=UTF8&qid=1478192883&sr=8-5&keywords=temperature+controller

Keep It Simple Stupid!

-Eskander

Eskander said:

I wouldn't ever use copper in the reservoir. Copper is highly toxic to plants and reactive enough in nutrient solution that it will corrode and leach metal into solution. Aluminum is fine as a cooling loop and is usually cheaper than copper.

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Totally forgot about that, plus aluminum way way cheaper! +1 to you!

For the prices you're looking at I'd almost say just covert a small window ac. Wouldn't be surprised if it was more efficient from a power usage perspective too.

Shugglet said:

For the prices you're looking at I'd almost say just covert a small window ac. Wouldn't be surprised if it was more efficient from a power usage perspective too.

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Yeah, the price adds up quickly when you build this way.. it's unfortunately the expensive and unavoidable "product development" process. If I want to build 10 of them, I can get all the parts for about $145 a piece... right now I'm at $215 in parts. Maybe if there is enough interest I can put together some $150 build kits as a group buy or offer them assembled for $200. There's a few advantages to this system running everything at 12VDC versus a system with 110VAC compressors, besides the fact this can heat or cool as opposed to just cooling. I'm sure if someone wanted a compressor system there is at least one already on the market. I'll be interested to see how product testing goes once I get something together. I think there's a compelling argument to "set your temperature, stick the two hoses in your tank, and find a small space within 10 feet to store it"

Tell, you what. I actually have enough spare parts to toss together the cold finger design I'd mentioned with two 150W elements. I'll set it up this weekend and let you all know what it can manage in my cloner. It is running a little warmer than I'd like anyway. I don't think it'll be more than a few degrees difference but you never know.

-Eskander

TeamSuperman said:

Yeah, the price adds up quickly when you build this way.. it's unfortunately the expensive and unavoidable "product development" process. If I want to build 10 of them, I can get all the parts for about $145 a piece... right now I'm at $215 in parts. Maybe if there is enough interest I can put together some $150 build kits as a group buy or offer them assembled for $200. There's a few advantages to this system running everything at 12VDC versus a system with 110VAC compressors, besides the fact this can heat or cool as opposed to just cooling. I'm sure if someone wanted a compressor system there is at least one already on the market. I'll be interested to see how product testing goes once I get something together. I think there's a compelling argument to "set your temperature, stick the two hoses in your tank, and find a small space within 10 feet to store it"

Click to expand...

Ive always just found peltier chips to be (in general) terrible at this particular application. Plus they are extremely inefficient from the start.

I hope it works for ya though.

Yeah... the passive heatsink thing is obviously not the way to go. Core was only a little cool with the heatsinks around 30F over ambient. I'll try again with some spare active heat sinks once I have the mounting hardware.

-Eskander

Ended up with a device that really was only good at heating water. Talk about disappointing.

You sure you didn't reverse the polarity?

-Eskander

Yeah, I set it up to work in both directions. The cooling performance was way worse than the heating performance. I was able to remove a few degrees in cooling, but I was able to heat like 20 gallons up by 60 degrees.

I think the way a peltier works to cool is that you need to exhaust the heat outside of your grow area. Like a wall or tent divides the cold side and hot side. If they are in the same space you are using watts which is energy (heat). To help dissipate more heat you could use a heat sink with a small pc fan blowing over it