Texas
1. Near Nacogdoches.... no bedrock
2. 10'+ depth earth is stable 70 degree temp +/- 5 degrees in our area
3. difference between need and want I guess . this would give me approx 500 cf storage
4. anything that last longer with dry, dark, cool storage from garden veggies to LTS freeze dried canned goods
5. not Staying down there at all. just storing and retrieving... minutes per usage
Norwesco Bruiser Single Compartment septic tanks are one piece moulded plastic. Designed reinforced to be buried w/o filling full of water. Mainly wondering it would defeat the purpose to have surface air being drawn down into and environment that should already be cooler due to surrounding ground temp at 10' depth. Water table around 25' down in my location.
The fan would be mounted at the bottom of the hot air evac vent pipe down n the tank. The power wire would be fed up the vent to a solar panel on the surface.. Sun shine, fan works... no on/off. forcing the air in the tank up and out the top and resulting in the intake vent drawing in the outside surface air into the tank.
BUT in our summers that air may be at a higher temp than the air in the tank 10' below ground. I am just starting to think this through now and solve the problem foreseeing any drawbacks. Maybe install a on/off switch on the fan, turning it off in the summer and on in the winter? IDK maybe I am overthinking this... I tend to do that sometimes. It is the curse of my profession
PS the cost is excavating and filling the hole ( 1 day on excavator) and the two 1500 gal plastic septic tanks. Solar would probably be less than $150// too old for the do-it-yourself route