Red neck Geothermal cooling

I am living off grid in a 10 by 20 foot shack I built, with minimal solar and no cooling. I am trying to rig up enough cooling to take the edge off with 100 degree weather coming.

I have seen a video where a guy was running a 80 watt 12 volt automobile radiator fan, and a low wattage 12 volt water pump, using a 120 watt solar panel without a battery or charge controller. Just a pump and fan wired direct to a solar panel. When a cloud passes the fan and water pump slow down and then return to full strength in full sunlight. He was pumping water from a 5 gallon bucket with a couple of ice blocks, to a transmission cooler with the fan blowing through the tranny cooler. He was getting great results.

Usually in geothermal systems 8 to 10 foot ditches are dug and water line is placed forming a closed loop system. I was thinking about burying a 2000 gallon water tank hoping the ground temps would help keep the water cool instead of trying to dig 400 foot of trenches to lay water pipe in. I don't know if a water tank would have enough surface area to dissipate enough heat. But a 3/4 inch water pipe can't be alot of surface area either. I would have much more cool water to draw from.
Since this system would only run when the sun was hitting the solar panel using a 3 gallon per minute pump, say 6 hours of sun during the summer that just over 1000 gallons pumped. So half of the water would be cycled every day with 18 hours between use to cool down for another 6 hour day of use.

Does anyone think this might help cool 200 square feet enough to help or am I missing something. I have a extra 200 gallon tank and a 150 watt solar panel that are currently unused. Let me know if this goes against the laws of physics or something I'm missing. Thanks.

I hear you. The current heat wave up here has been killing me.

First thing first: There is nothing redneck about what you propose. It's what all the cool kids are doing. Massive downtown buildings on the Great Lakes are doing this to reduce their energy footprint. New urban developments are doing this using drilled well systems. Even better: properly engineered, with heat pumps, it can work for cooling in summer and heating in winter.

Looking at potential "gotchas" in your play, three things come to mind: insulation, soil temperatures at depth, and wear-and-tear on electrical equipment.

Insulation comes first. Insulation almost always trumps complex heating/cooling solutions, both for cost and effectiveness. Do whatever you can to create passive systems that knock the problem down to size.

Soil temperatures are a big deal in the calculations. I vaguely recall that temperature maps are available for many areas. Basically, it will give you the data to determine what depth and radiative surface area is needed to add/subtract X number of BTUs/kJs. If you have a well, you can get some rough numbers by lowering a thermometer.

Direct drive from solar panels can work, but it's a tricky proposition because it's really hard on electric motors and can reduce their life quite a bit. The windings in motors overheat on voltage that is too high AND too low. If a PV panel is feeding a motor but the voltage is too low to start motion, the windings are effectively a toaster. The insulation on the windings will degrade. Pumps and fans are designed with the cooling flow of water or air in mind. So, heads-up.

Final thought: If you have access to large volumes of water, evaporative cooling is quick and simple. It might give the added kick needed to keep you comfortable while you work on the bigger picture. Cooling 200 sq. ft. is entirely do-able.

My 2c.

I have seen a video where a guy was running a 80 watt 12 volt automobile radiator fan, and a low wattage 12 volt water pump, using a 120 watt solar panel without a battery or charge controller. Just a pump and fan wired direct to a solar panel. When a cloud passes the fan and water pump slow down and then return to full strength in full sunlight. He was pumping water from a 5 gallon bucket with a couple of ice blocks, to a transmission cooler with the fan blowing through the tranny cooler. He was getting great results.

Sounds pretty redneck to me!

I think it's a good idea. Basically the same idea as a "Port-A-Cool" fan right? I do think how well it will work and the effect you will get will depend a lot on location.

I live in a very humid area, so I didn't want to do evap cooling. I understand about heating or burning up the motor and pump. I was thinking about doing as a trail run and if it worked adding a charge controller and battery. At 10 foot of depth,  last summer 100 degree temps, the ground temp was 65 degrees.

Yes, think blowing air over a water cooled radiator. I am going to add a porch on front of my shack and thought why not bury my extra 2000 gallon water tank then build the porch over top. Fill it with extra rainwater and try to cool things off a bit. But on the cheapest budget I can.

It's obvious you've done your homework. Kudos!

Evap cooling can be an outside process too, if you have the water.

What's your insulation situation? And, any chance of adding heat reflective layers to your roof? Potential huge impact.

I have r-13 in the walls. The floor is just soil that was rototilled and cement added then moistened and tamped, about 6 inches thick. The roof is r-19 inside and 2 inches of salvage foam over the osb outside with tin on top. This is my shed/workshop I'm living in until I finish building my ferrocement/aircrete dome.