How does alternative energy work?

How do alternative energy sources work?

• Answer:

  Most of them operate on exactly the same principle that fossil-fuel energy sources work.  Something is exerted to turn a magnet inside a coil of wire, or a coil of wire inside a magnet. This converts the mechanical energy that turns the thing into electrical energy. In a fossil fuel generator, you burn the fuel to heat water, which pushes steam through a turbine to turn the generator. For a wind turbine, it just uses the wind to turn gigantic fan blades to turn the generator. For hydroelectric, the water falling through the dam turns the turbines. For solar-thermal, an array of mirrors collects and concentrates sunlight to heat a target, which heat can boil water and turn a turbine. The only one that's really different in the fundamental mechanism is photovoltaic.  Photovoltaic utilizes the http://en.wikipedia.org/wiki/Photoelectric_effect inside a p-n junction (diode), where light pops electrons out of the depleted region of the p-n junction where they are collected at the terminals, generating a voltage and current.