http://physics.about.com/cs/experiments/a/260303_4.htm 

The Kelvin Water Dropper

What You Will Need To Build Your Own

Did you know that you can build a very simple high voltage generator which has no moving parts and is powered by the energy of falling water? By dribbling water through empty tin cans, thousands of volts can be “magically” generated.

The water dropper was named for its inventor, the Baron Kelvin (1824-1907). A professor at Glasgow University (from 1846), Baron Kelvin also made important contributions to experimental electromagnetism and theoretical thermodynamics. With James Joule, he discovered the Joule-Kelvin effect. His name is also given to the unit of the absolute temperature scale, the kelvin.