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Old 12-01-2016, 11:03 PM
GpsFrontier GpsFrontier is offline
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Join Date: Mar 2009
Location: Lake Havasu AZ.
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Hello shillamus,
Sounds interesting, but lower energy bills are only part of being cost effective. The cost of the parts and equipment is a big factor as well. If it takes more than 2-3 grow cycles to break even in cost to buy and run, it's not really cost effective. In other words if it's going to cost you more to grow yourself than it does to buy at the store it's not cost effective. If your going to spend $400 to grow some tomato plants, you better get more than $400 worth of tomatoes from them in the first couple of grow cycles. If not it's not cost effective.

One thing you should keep in mind is that the size of the reservoir (number of gallons) isn't going to play a big part. Temperature differential and BTU capability is. What I mean by that is it's not the number of gallons the reservoir is, it's how much heat you need to remove from it. What works for one guy in AZ (where I live) to cool a 20 gallon reservoir, may also work for someone in Oregon with a 100 gallon reservoir. Why, because here in AZ the day and night time temperatures are much higher and it takes a lot more heat exchange to accomplish the same thing. One person may have a larger reservoir but not need to cool it as much as someone with a smaller one but needs to cool it a lot more.

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Do you chill outdoor systems?
If I plan to grow during the summer months, then yes I plan out how I'm going to cool the nutrient solution before I even start growing. I learned the hard way how important the water temp is the very first year I grew hydroponically. Winter months (Nov, Dec, and Jan) I need fish tank heaters to keep the water from getting to cold. During fall (late Sept to early Nov) and spring (Feb and March) I don't have too much issue with water temps. but summer months (April through September) the water temps will get to high If I don't account for it.

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Do you insulate the reservoirs?
Yes, absolutely. Insulation is the single best method to not only preventing heat transfer (the water from heating up, and/or staying cool longer). But it's also the cheapest in cost to do, and cost nothing in electricity to work. I use Styrofoam sheets, bubble wrap insulation, rolled foam, and even pipe insulation on water feed and return lines and the tubing.

Quote:
Can you provide an example of a chiller you use?
If you read the article I wrote and posted earlier, I have listed every method I know of on how to cool the nutrient solution, as well as went into detail about them.

I focus on being cost effective and prefer to stay away from costly and complicated cooling methods. I rely mostly on geothermal energy methods for larger reservoirs (in ground reservoirs and cooling coils). Smaller reservoirs I can usually get away with using insulation and ice. I even used a small (2-3 gallon) Ice chest I found in the trash as a reservoir for a small water culture system that worked great even in direct sunlight and in 110 degree heat. I just added 8-16 ounces of ice every night and the water stayed cold all day long.

I do have plans to build a reverse swamp cooler to use as a water chiller, but haven't gotten around to it yet. It sounds complicated, but it's not and uses very little electricity (pennies a day). The best part about the reverse swamp cooler in it can also be used for multiple reservoirs at the same time. I can make you drawings if your interested in building one.

Quote:
Do you use any passive cooling from the earth?
I assume you mean Geothermal energy, and as I mentioned that is the main method I use for larger reservoirs. In ground reservoir's and cooling coils.

P.S.
There is one cooling method I tried years ago that didn't work the way I did it, but think it will work if I can work out details of the design. That is using liquid nitrogen. I had poured it directly into the reservoir, but it floated on top and all evaporated before cooling the water even one degree. However if you could pump it through metal coils you could get heat transfer without it evaporating. The main issue is being able to find a pump to pump it without freezing up, or at least finding a way to get it to circulate through the coils. You also need a pressure gauge and automatic pressure relief valve for safety. While liquid nitrogen isn't expensive, how long it lasts would determined if using it would be cost effective or not. But the build was more complicated and costly than I wanted to deal with for experimenting.
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Last edited by GpsFrontier; 12-01-2016 at 11:17 PM.
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