can't we develop a device which combines both sound and solar energy for power production?
this is as follows... we produce electricity through different sources like hydropower, wind mill , thermal and ofcourse nuclear reactions. so won't it be feasible to produce electricity through sound? the output current which we get from a loud horn of a train would not be able to generate a power or 1/100 of a watt. but i guess a lot can be done by utilising the vibrations. also the sound is available on every corner of the earth and therefore there is no problem for the source. if we can somehow combine this so produced power with that of the solar energy, then there can be greater chances of power output. and through this process though minimum energy is generated, this can be replaced in many appliances like the batteries in a watch, or as a battery for the artificial pacemakers.