Renewable Energy

I have many ideas floating around in my head a lot of the time, but I thought I should make my first blog page a repository for a large class of these ramblings. Below is a list of various sources of free and renewable energy sources. The catch, however, is that they are 1) not usually thought about, and 2) not necessarily easily harvestable. Please leave me comments and feedback, and especially new ideas, if you want!

Down-Elevators (Potential energy): Every time I take an elevator up in a building, I always feel a little guilty demanding all of the energy that has to go into pushing the elevator car (not to mention me) up to my destination. And then, when I ride back down, I wonder if there is some way to recoup the potential energy that I stole being so lazy! It would be great convert the potential energy that is given back as wasted friction (that I very much appreciate) used to slow the descent into a more constructive use.