looking for a geothermal valve

I've learned one bit in about 2 hours of internet searching, which I want in the design;

"self actuating" which means, the on/off switch is a thermal mechanical function and doesn't require electrical power.

So I want a 2-way, 3-inch, self actuating (closes as the temperature goes above about 40 F) thermovalve  

It seems such a thing would be a somewhat common cold storage construction component, but I didn't see any larger diameter, "common outdoor air temperature" stuff anywhere.  Looking in the wrong place?

I've got a small ~8'x8' earth integrated root cellar that's almost done.  It's got a small thermal well, or a 3" polypipe that comes in at floor level, goes straight into the ground about 40", and then "U" right back up to the floor.  There's then a vent pipe in the roof.   When it was warmer the cold air flowing out at floor level was obvious to a hand held in front of the external pipe opening.  I wasn't sure with the length of 3" pipe and temperature difference but there's some decent air flow in the set up.

I was thinking I'd manually open the floor pipe when it gets colder and leave it closed otherwise, but having an actual valve is going to cool the earth much more effectively without my time.

Anybody know where one can find such a thermovalve?

I am interested in the idea.
I found this:
https://www.g-rau.de/fileadmin/user_upload/G.RAU_Produkte_ThermischeAktoren_210x297mm_EN_180521_Ansicht.pdf

There are thermostatic valves for radiators that might work:
https://en.wikipedia.org/wiki/Thermostatic_radiator_valve
I don't know if they exist for 3" pipe.

There are  also thermally activated actuators  used to open and close greenhouse vents.
They could be fitted to a pipe plug instead of  a greenhouse window.

I know of several versions that open above 40, greenhouse and crawl space vents are the most common, but can’t think of any that work the other way.

I agree it should be possible to rig one to work backwards and adapt to a 3” pipe, but surely there must be something easier.

John, I just cannot work out what is happening, can you explain it again please?