I like your theory.

I'm not educated in electronics,but I'm a curious person,and electronics have always interested me.

What I was told from friends who do have more knowledge than I do, is that lightning is so powerful that it would blow up your capacitor.Also that it was tried before by various world leading governments.

What I propose is that you would have to build an underground transformer,that would ground most of the energy but charge your capacitors...use the ground as a buffer. ;)