I am trying to determine how much energy can be, in ideal circumstances, harvested from piezoelectric crystals that draw pressure from being buried in roadways. To start, we found a basic fact on Wikipedia; http://en.wikipedia.org/wiki/Piezoelectric "...a 1 cm cube of quartz with 2 kN (500 lbf) of correctly applied force can produce a voltage of 12,500 V." Using what means and understanding we possess, we determined so far that; -that the average wheel on a car would be roughly 5 kN -that .20m of a wheel touches the ground on average with an area of 0.034m^2 Now based on my understanding of piezoelectricity, I am not sure as to whether time would have to be factored in as well or not. So basically if we could come up with some kind of a unit measurement/equation to determine how much voltage a 1 cm cube of quartz would put off with the force of the average vehicle going at an average speed, we could then extrapolate that to conclude exactly how much power could be generated from a roadway of any given length and thus the overall energy potential of piezoelectricity as a whole. Overall, we'll have one more sound fact to give hope to the world that could be. But I seem to have taken this equation as far as I can on my own at the time, so I need someone's help. Anything at all would be greatly appreciated.