Hello MontyJ,
I don't know how much new construction you have near you, or what the construction standards are in Mexico. But here in lake havasu there are new houses going up all the time. Here they wrap the whole house in Styrofoam and chicken wire before applying the stucco. If you catch them before they through out the scraps you can probably get some good size pieces of Styrofoam (as well as plywood or OSB).
I don't think you understand what I'm referring to when I say a reverse swamp cooler. Also your stuck on BTU's, and you cant compare BTU's to how it works because it simply doesn't apply. If you want to increase the cooling power of the reverse swamp cooler, you simply increase the reverse swamp cooler reservoir size (water volume). It can be as big as a small pool or spa if you wanted. You could even use your fountain as the reverse swamp cooler reservoir, and just sit your
nutrient solution reservoir in the cool water.
Also the reverse swamp cooler concept only needs enough energy to run a small fan and water
pump. Depending on the wattage output of your solar setup, you should easily be able to run it, as well as the other pumps and timers on solar power.
As you have already noticed, it takes a lot of electricity and time to freeze enough ice to even begin to keep up. Not to mention that everything in the freezer begins to thaw, and the ice cream is the first to melt. Or the fact you need to dump ice in the reservoir 2-3 times a day. Also keep in mind that the larger your reservoir is (and you already know it's too small) the more ice it will take to cool it down.
I know people are often confused by the term "reverse swamp cooler" I use to describe it. They tend to think of how a typical swamp cooler works, and think of it in terms of it that way. They don't really understand the the "reverse" part of the statement/concept. You don't need to go out and buy a swamp cooler (or compare BTU's). I have decided that within the next month or so I will put together a working model to explain how it works, and how to use it to cool a nutrient reservoir that I will post on my website.
Although there are literally hundreds of different ways to build one, the concept of how it works is always the same. The idea is to use the cool water coming out of it, not the air (hence the reason I call it "reverse"). I created and attached a drawing of one like I plan to build using 4 inch ADS or PVC tubing. You can also always change the configuration to include more than one cooling pad tube for more cooling pad surface area. The design's are endless, but the concept is simple, and the cost to build and run is minimal. I already have many fans and water pumps I can use, I just need some tubing and connectors, and cooling pad. If I built it from scratch buying everything I needed, I could probably build it for about $50 to $80 depending on the pump and fan I decided to go with.
Cost here in USA, and energy use (based on 9.8 cents per kilowatt hr):
Electricity Cost Calculator
6 inch inline duct fan about $30 and (42 watts) 10 cents to run 24 hours
8 inch inline duct fan about $35 and (78 watts) 18 cents to run 24 hours
10 inch inline duct fan about $45 and (132 watts) 31 cents to run 24 hours
9 inch high velocity fan from walmart about $16 (96 watts) 23 cents to run 24 hours
500 gph, 8.7 foot head height fountain pump (I already have) about $40 (42 watts) 10 cents to run 24 hours
Costs per month
6 inch fan, 10 cents x30= $3.00
8 inch fan, 18 cents x30= $5.40
10 inch fan, 31 cents x30= $9.30
9 inch high velocity fan, 23 cents x30= $6.90
fountain pump 10 cents x30= $3.00
Even if I used the 8 inch inline duct fan, it would still only cost me less than $10 a month to run the reverse swamp cooler 24 hours a day all month long, and only use about 110 watts. Almost the same as a 100 watt light bulb. I'm guessing your solar system could handle that.
P.S.
If I remember correctly, you said that you are renting, so I never considered geothermal energy for you because it look like the ground is brick or tile. So I didn't think you would be able to dig there. But in case it is an option I also have design plans to use geothermal energy to keep the nutrient solution cool. Thanks for reminding me though. If your interested, you will need to e-mail me so I can send you the design plans for them. I cant post a link because I don't have them uploaded to the website yet, and it will take me a couple weeks to get them posted (with everything else I need to do first). Also the forum doesn't allow attaching text or pdf. files to posts, or in private messages. So I can only send them by e-mail right now. But thanks for reminding me, I need to get them uploaded to the website ASAP. The Geothermal energy design doesn't require a secondary reservoir, and only takes the electricity of one water pump. Depending on how much you run your system, it may not even take extra water pump, or even use any extra electricity to run through it.