How about the potential between the ionosphere and the Earth's surface? We see amazing displays of that potential with severe weather. But that potential exists 24/7/365 everywhere on Earth regardless of whether you can akctually see it arcing. Seems so obvious a potential vast, unlimited and safe energy source that I'm surprised that no one has patented the idea for backyard units? I'll bet there's enough brain power on this board for us to design a backyard box that taps into that omnipresent energy potential!