The Pelton wheel is a water impulse turbine. It was invented by
Lester Allan Pelton in the 1870s. The Pelton wheel extracts
energy from the impulse of moving water, as opposed to its
weight like traditional overshot water wheel. Although many
variations of impulse turbines existed prior to Pelton's design,
they were less efficient than Pelton's design; the water leaving
these wheels typically still had high speed, and carried away
much of the energy. Pelton's paddle geometry was designed so
that when the rim runs at ½ the speed of the water jet, the
water leaves the wheel with very little speed, extracting almost
all of its energy, and allowing for a very efficient turbine.
The water flows along the tangent to the path of the runner.
Nozzles direct forceful streams of water against a series of
spoon-shaped buckets mounted around the edge of a wheel. As
water flows into the bucket, the direction of the water velocity
changes to follow the contour of the bucket. When the water-jet
contacts the bucket, the water