There must be a great deal of convection from the heat rising from the streets and roofs of cities. Surely someone could figure a way to harness it.

Masbury: hadn't thought of that but you are right - especially in summertime. And that made me think about wind tunnel effect on streets with lots of tall building. Out in LA, California the ocean breeze is funneled into what becomes, in effect, a wind tunnel otherwise known as Wilshire Blvd and the Miracle Mile. Buildings there could take advantage of wind effects. And then there is Chicago! Grin. I'll find some folks to pass ideas along to - thanks.

All these little gadgets reminds me of someone trying to make ends meet until their ship comes in. As our technology grows we will need a source of power that exceeds our needs. I doubt wind or other quick fixes will do that.

Thermal efficiency is needed in all devices. Thermal recovery technology is needed. Perhaps the kinetic energy of gravity will be the wave of the future.