Accepted Answer
The only widely-accepted activity of that sort is the universal habit of operating our bodies on the solar energy stored in plants.Other than that, the availability of free solar energy in the forms of real-time wind and radiation is still not used to any great extent, as a percentage of worldwide energy demand. By and large, energy consumers are still a lot more comfortable with the chemical energy stored in wood, coal, and rotted dead dinosaurs.
Suggested Answer
solar power is one, humans eat plants and plants make food by using the sun and the sun is a source of all energy