HYDROPOWER 101

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This page of Hydro Industry FAQs offers a wealth of information about the industry to the online hydropower community, including definitions, resources, professional and business development and more.

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How does a hydro turbine work?

A hydraulic turbine is a mechanical device that converts the potential energy contained in an elevated body of water (a river or reservoir) into rotational mechanical energy. Turbines can be either reaction or impulse types. The turbine type indicates the manner in which the water causes the turbine runner to rotate.


What is the difference between a reaction turbine type and an impulse turbine type?

A reaction turbine operates with its runner fully flooded and develops torque because as a reaction to the pressure of water against the blades of the turbine.

An impulse turbine operates with its runner in the air (not submerged in water) and converts the water’s pressure energy into kinetic energy using a jet that shoots water onto the runner buckets to develop torque.

FURTHER READINGQ&A: The Choice between Reaction and Impulse Turbines, Hydro Review, Volume 16, No. 1, February 1997, pages 89-91.


What is a Francis turbine?

A Francis turbine is a reaction-type turbine having a runner with a large number of fixed buckets, usually nine or more, to which the water is supplied in a whirling radial direction. It can be designed for operating heads ranging from 50 to 2,000 feet.

The Francis turbine was invented by James Bicheno Francis, a pioneer in early waterpower development. 

FURTHER READING“Francis and His Turbine,” Hydro Review, Volume 8, No. 1, February 1989, pages 24-28.


What is a Kaplan turbine?

A Kaplan turbine is the most common type of propeller turbine, in which the angle of the blades to the flow can be adjusted. This type of turbine is most frequently used in the low- to moderate-head range.

The Kaplan turbine was invented by Dr. Viktor Kaplan, an Austrian engineer.

FURTHER READING“Viktor Kaplan and the Adjustable-Blade Propeller Turbine,” Hydro Review, Volume 8, No. 6, December 1989, pages 38-45.


What is a Pelton turbine?

With a Pelton turbine, the energy of water is converted through nozzles into high-velocity jets of water that drive a turbine by virtue of the forces of the water jets on buckets attached to the turbine wheel. This impulse-type turbine is generally used for high-head applications.

Lester Allen Pelton invented this turbine.

FURTHER READING“Lester Pelton and His Water Wheel,” Hydro Review, Volume 8, No. 5, October 1989, pages 22-26.


I’ve heard a pump can be used as a turbine to generate hydroelectricity. How does this work?

Running a pump in reverse to operate as a hydro turbine to generate electricity is sometimes feasible. Standard pumps are available to use as turbines with capacities as large as 2 MW at small hydro plants, but the most usual installations are a maximum of about 500 kW per unit.

FURTHER READING“Using Pumps as Hydroturbines,” Hydro Review, Volume 9, No. 5, October 1990, pages 52-61.