It depends what you mean by "solar energy." Humans have always used solar energy in some sense: to warm themselves, to grow food, etc. However, I'm assuming that's not really what you mean (although it is important to realize that all energy on earth, with the exception of nuclear fission and geothermal, is ultimately driven by the sun's energy -- even fossil fuels, which after all were plants that grew with sunlight millions of years ago). Solar power has been used directly in various forms for over 100 years.
Group items matching
in title, tags, annotations or url
5More
Where does wind energy come from? - Alternative Energy - 0 views
« First
‹ Previous
61 - 80 of 143
Next ›
Last »
Showing 20▼ items per page