Here are 3 examples of what GamerXR72 was talking about:Direct conversion of light to electricity: http://en.wikipedia.org/wiki/Photoelectric_effect e.g.: calculators in elementary schoolDirect conversion of heat to electricity: http://en.wikipedia.org/wiki/Thermoelectric_effect e.g.: any digital thermometerDirect conversion of mechanical stress to electricity: http://en.wikipedia.org/wiki/Piezoelectricity e.g.: any digital scaleThe reason these methods are appealing is that there is only one conversion from the input energy to create an electric current. You don't have to burn it, generate mechanical energy, convert it into an electromagnetic field, and then harness that field to drive a current. You also aren't creating significant wasteful byproducts, like heat, water, pollution, ash, radiation, etc.Unfortunately, these methods for energy capture are not economical on a large scale at this time.