Ya,
Ever scene I had that problem, I have been on a quest to find economical ways to cool the
nutrient selution. The in-ground reservoir (geothermal reservoir) was the only realistic economical option I found. Just about every other option involves using a lot of electricity, and with $700 electric bills during summer (because of running AC 24/7) adding much more to the bill is not really economical for me. The design works as intended with ease of use in mind. Although I never really finished it. I had planed to build up the above ground portion because I was not able to get the hole as deep as I wanted (too much rock in the ground here). I also never really completed insulating the above ground tubing, and plant buckets that I Had intended to do. But never the less, the nutrient temperature remained pretty constant between 80 and 84 degrees thought the hottest part of the summer (late July and August), and I never added any ice to it at all.
That's about 10-12 degrees warmer than perfect. So despite the fact it could have been better if I didn't get lazy, I think it preformed quite well. I also know next summer I can make it better by not being lazy, and finishing up the details. I also have two new ideas to test next year. Both work on cooling by evaporation, but in different ways. One is relativity easy and inexpensive to build. The other will take some more research, as well as small scale testing and refining in order to see if it's feasible and what it would take on a larger scale.
The first one was built by a guy in Phoenix where they get the same type of daily temperatures we do here (phoenix is about a 4 hour drive), and he clams it works well. He sent me pictures of it with details, but I don't want to post his pics because I never asked if he would mind. But When I build it I will be happy to post all the details of how I did it. Also I may draw up some 3-D pictures to post asap for people if there is any interest.