Geothermal, Magnetic, Wind, Water and... anytime an extra-terrestrial's been involved with native peoples here on Earth, there has been the 'free energy' technology they bring with them and may or may not bestow any benefits of which upon the natives.
In the last 100 or so years we have seen many free and near free technologies get suppressed. From Victor Schauberger to Joseph Newman. There are so many now! Because the main stream media is so controlled, most won't find out through that venue the rich history of free energy machines and inventors.
Assassinations have taken place. Made to look like something else of course but plenty of inventors have died mysteriously coincidentally after coming up with something highly 'disruptive' to the globalists.
It does not have to be an invention. I can be over ideas. Look at how suppressed even the notion of 'enlightenment' is by the main stream media.
I have several worthwhile video's below for you to enjoy. I will be adding many more, links too Give me some time to fill this page in more.