So I've been brainstorming this idea for a couple months and I wanted to see what everyone thought out there. This seemed like a good post to submit my ideas.
My concept includes the following parts:
Used mini-fridge
Copper pipe and copper "U" connectors
20 - 30 gallon insulated cooler (the kind you use to bring your beer to games or parties)
2 inline water pumps
icebox reflector cooler
http://www.gchydro.com/Ice+Box.html
Decent fan for the icebox
bulkheads
1-quart ziplock freezer bags
PVC pipe (and adapters if needed)
Vinyl tubing
First, build a stacked grid using the copper pipe and "U" connectors (you'll have to sweat the pipes) to occupy the space in the mini-fridge. Basically sweat the pipes using the "U" connectors to build a grid going back and forth. Once you've made the grid the width of the inside of the fridge, use a "U" connector going up and down to start another level of pipe. In the end the entire inside of the fridge should be copper piping.
Take some of the ziplock bags and fill them with water. Set these on top of a lot of the piping throughout the grid, but not enough to block the air-flow inside the fridge (leave some space in between the bags), otherwise you'll only chill the areas where the air can get to.
Drill two holes in the fridge and four in the cooler for the bulkheads. One of the holes in the fridge should be at the highest point and the other at the lowest.
With the PVC pipes and connectors, connect the cooler to an inline water pump and then to the highest bulkhead on the mini-fridge. The bulkheads on the fridge should be connected to the copper pipe inside.
Connect the lowest bulkhead on the mini-fridge to the return bulkhead on the cooler (gravity return).
Connect PVC to the other water pump on the cooler and then the water pump to the vinyl tubing. This will go to the icebox. Connect the return on the icebox to the last bulkhead on the cooler.
The icebox and fan should be mounted on the hood and should be exhausting the hot air past the icebox. This should provide cooling for the growroom. You don't want to chill the air going into the hood as hot air would still be exhausting out of the hood past the light. We want to cool the room more than the light. I don't know if blowing cooled air (probably with condensation) across an HID light at well over 1000 degrees would be such a good idea. I could be wrong though.
Multiple iceboxes, a larger cooler, and a larger fridge could be used for larger growrooms.
So it works like this...
The cooler is filled with purified water.
The water pump between the cooler and the fridge pushes water to the highest point on the fridge. The water goes through all the copper pipe. The ziplock bags help the fridge stay cold as water absorbs 4 times the heat almost 20 times faster than air and because they would be sitting on the copper piping, he pipe would be able to dissipate the heat from the water more quickly. So the bags full of water sitting on the pipes should work much better than if it was just air inside the fridge trying to absorb the heat coming from the pipes. The water is returned to the cooler via gravity since the water is pumped to the highest point and drained at the lowest.
The second pump sends chilled water to the icebox. The fan blowing air across the icebox will cool the growroom just like an air conditioner.
Some things to consider:
Instead of using more expensive inline pumps, the water may stay cool enough to absorb the heat being produced by the pumps if submerged pumps are placed in the cooler. But, it would probably mean your fridge would run more often to compensate.
The fridge, cooler, and icebox should probably be close to the same level to keep the water circulating enough to cool it down.
Actual "Chillers" can be used instead of a mini-fridge, but they seem to start at the $400 range so it's probably cheaper to convert a mini-fridge. Plus, if your chiller goes out that's an expensive piece of equipment to replace. If the mini-fridge goes out you can replace it for less than $100 if you look around.
The larger the cooler the more efficient it should be as changing the temperature in a large body of water takes significantly longer than a small amount of water. It would take longer to chill initially but once it's chilled it take a lot to warm it up any.
The fridge should be in another room. My design would have the fridge in the garage and pass the pipe through the wall into the growroom where the cooler sits. The mini-fridge is a heat exchanger. If you have your heat exchanger in the same room you're trying to cool, you are defeating the purpose. The fridge should be able to dissipate the heat it's exchanging. If the room where the fridge resides in is hot then the fridge will not be able to get rid of the heat. I would have fans blowing across the coils on the fridge when it's hot to help cool it.
You might be able to get away with a single water pump going from the cooler to the icebox and then to the fridge, but I imagine the pump would have to be fairly powerful because the water needs to move quickly.
Here are a couple reasons I would use two pumps instead of one:
The pump going from the cooler to the fridge can be set to run incrementally (like once an hour) to cool chill the water. You would want the water circulating the entire time the light is on though. The system may be efficient enough to where the pump doesn't have to run 100% of the time.
Before the lights turn on for the day, the water could be pre-chilled without having to run it through the icebox.
What does everyone think of this concept?