I was thinking of setting up a base underground. Sunlight is obviously not found down here so I cant use solar panels. I could run some cables down but this is a lot of trouble since I wanted to set this up very deep underground and don’t want to be tied down. If I bring downwind turbines, will they generate power underground?
Yes, wind turbines will work underground. They do not seem to work as well as they do on the surface and seem to only work in areas where there are natural caves. You can check out this guide for a tunnel-digging machine which makes use of wind power and batteries to power a vehicle to dig below the surface of a planet.
It would be best to work on obtaining the materials you need to start building the RTG. This will be the answer to all of your power-related issues below the surface of the planet.