Slide 14 of 14
Here’s a modern example of how energy is “collected.” Like virtually all “renewable” energy resources, the energy collected by windmills like these started out deep inside the Sun as nuclear potential energy, which was converted to radiant energy and eventually to sunlight that heats the Earth’s surface. The sunlight heats the Earth’s surface, expanding the lower atmosphere -- in effect creating gravitational potential energy by lifting the cooler, higher atmosphere. Just like Atwood’s machine, the kinetic energy of the winds is converted from that gravitational potential energy when the now heavier, upper atmosphere falls, lifting up the warmer, lower atmosphere.
But let’s face it, this is not “renewing” anything; this energy is literally a windfall: Collecting energy from the wind is like picking up a few coins that were accidentally dropped in the street and putting them in our pockets.