Enough to heat the core, create a magnetic field, and possibly make the planet rotate. A miniscule amount compared to what is available.
If it’s so massive why aren’t we harvesting it?
Because most of our energy 'capture' is based on an itsy-bitsy teeny-weeny part of the Electro-Magnetic Spectrum, and even that we are inefficient at converting.
Has this theory been published anywhere?
Probably. It seems obvious.
What do you think generates the ozone, and what creates the 'hole' in it ?
Your obvious theory needs refinement. The moon had a molten core when formed and had a magnetic pole yet it went cold. Mars had a molten core and magnetic pole when formed and went cold. Where did that energy go?
As for ozone, you could easily google hundreds of sources that explain that ozone forms when oxygen molecules are split by ultraviolet radiation. The ozone hole is obviously due to the expiration of the DuPont patents on first generation chlorofluorocarbon refrigerants. ; )