ABSTRACT
It is fitting to begin our discussion of the various kinds of renewable energy with the sun—the medium-sized star that symbolizes life, power, strength, force, clarity, and, yes, energy. The sun nourishes our planet. Solar energy is a green/renewable resource because it is continuously supplied to the Earth by the sun. When we consider the sun and solar energy first, we quickly realize that there is nothing new about green energy. The sun was the first energy source; it has been around for at least 4.5 billion years. On Earth without the sun there is nothing—absolutely nothing, zero. There is the old 5-5-5-thumb rule that guides the essence of life on Earth. That is, we commonly state that one cannot survive a lack of breath (oxygen) after five minutes; we must have water available to drink in five or fewer days; and we need food to eat in five weeks or less to stay alive. All this is true, of course, but without the sun the 5-5-5-rule has no validity—without the sun nothing related to life has validity—without the sun there is nothing: no air, no water, no food, and no life.
