Since our Residential Power Generator's can easily be adapted for salt water application 
imagine the amount of salt water available to us on the Earth's surface.
 

Estimates vary, but somewhere between 70 and 75 percent of the Earth's surface is water-covered. 
But water also exists in the air as water vapor and in the ground as soil moisture and in aquifers. 
The RPG is a  device which could run indefinitely on the virtual limitless 
hydrogen found in salt water.