@Mike, if you know of any good engineering books/materials going over the earth battery, please post here. I have not seen any. All I have seen is very rough numbers from the Citrus in the Snow guy, and soil temperature profile normals. The Citrus in the Snow guy uses something like 4 to 8 pipes running something like 200' to get the temp to stabilize. I would use plastic underground, and try to use stainless above. I have read people using perforated pipe underground so that any condensation will leak out.
Derating the estimated 100A @90C capacity of 2-2-4 aluminum SER wire is a very good idea. Also use niloc (or whatever it is called -- which keeps the connections from oxidizing). Your electrician shoud do that, but know that if you are in a place that will allow you to do your own wiring to read through the code books and comply with at least the residential standards, if not the commercial ones. Like I tell people "every sentence of the code book represents someone being injured, maimed, or killed". Following the code is not just the law, it is a VERY good idea. Also, run another separate ground wire (unless the 2-2-4 is shielded). Also, go ahead and wire up the an extra outlet circuit (or a special outlet near the door for 240V and 120V). You never know when you need to run an extra fan, emergency heater, water pumps, welder, etc. It is easy to wire up when you are starting, and a pain later. Also, make sure that the ground and commons are *not* tied together in the breakout panel, but *are* in the main panel where you took the power from -- tying both can create a ground-loop. Oh yea, and this is likely very important also, use GFI's where it makes sense, but know you should not use them on circuits with GFI's...
Before putting in a inflation fan (that will const constantly), try just installing a wax-filled vent piston (see: https://www.amazon.com/Univent-Automatic-Solar-Vent-Opener/dp/B0083IZG0A
for a good one that would work close to the ground, but I would look for one that can be set to open near 90 or so for a vent near the apex). Once you know what can be done with passive means, you know what you have to operate actively.
I probably forgot a dozen things off the top of my head, but this should be a decent start. Hope this is a good start.