I haven't read more than the 1st page of this thread, but I just want to say that I get a hard on thinking about putting up a pole barn near a spring fed pond/lake where I could run the geothermal heat pump.
I'm sure I'd still have to air cool the lights, but that's no problem.
If this is what gives you a woodie, then you're one sick puppy, lol. I'm telling yer girlfriend!
Yes, this would totally be the ideal setup! Then the cost of cooling falls to the power needed to run your pump. I would still run a closed system where the working fluid is never exchanged with either your nutes or the lake.
What about running geothermal piping outside your house during the winter. This would at least allow for cooling in the winter without exchanging any grow room air, and would be an easy install with no digging.... Might even be able to rig it to a hot water heater for the summer.
Hell yes this would work! Be damned sure you're running glycol so your lines don'd freeze.
In fact, when I free up a little time and capital I plan to do exactly this to reduce my cooling cost over the winter. The water cooled website sells a box that looks an awful lot like an AC condenser that sits outside. Instead of running freon through it, just run water. As long as air temps outside are below maybe 55 degrees it should work well enough to keep your actual chiller from having to work as much, and possibly not at all. I would keep the chiller in the water circuit so that as temps change, it would take up the slack. Maybe you could set up a thermal switch; send water outside whenever temps fall below the threshold of 55 degrees, and bypass it if temps are too high.
I confess an unfamiliarity with the finer points of geothermal and heat pump design. From what I've seen, the water temps in my chiller setup don't change a great deal so in order to extract the heat, you'd have to concentrate it somehow. How efficient this would be, and whether it would save any money are questions I would need to get answered. That's something I don't know much about.
The nice thing about a chiller setup that's cooling room air and hydro nute water is that it's one system, not several different ones. Keeps things simple. For now, there's no good reason to stop passing air through the vented hoods. If I had access to unlimited free cold that might change, for this reason:
In another thread, I'm discussing the merits of a light rotator system I've used off and on for the last 20 plus years. The design is very sensitive to the type of reflector the light is mounted in, and closed box vented hoods are not the best solution. Open adjust-a-wing style hoods are much better, for reasons I go into some detail about in the other thread (Advanced Techniques and Problems, 'built my own light rotator, wanna see?'). No vented hoods means getting the heat out another way, and geothermal or lakewater cooling makes a lot of sense here.
One more consideration: If you decide to use lake water, be aware of a phenomenon known as the thermocline. This refers to the fact that water likes to layer itself by temperature, warmer on top, cooler down deeper. Every lake's thermal profile is different, but in general, if you want to access good cold water, you're gonna need to get at least a dozen feet down. I can see a sizeable car radiator , mounted horizontally on a frame that holds it up off the bottom a couple feet. The fact that warm water is passing through the radiator would create a natural current as cooler water rises through the core to replace the warm water rising off it. This may or may not be enough, as the temperature difference is only a few degrees...
