Technologies and Facilities
There are three types of hydropower facilities: impoundment, diversion, and pumped storage; some include dams, and some do not.
Impoundment systems are the most common type of hydroelectric power plant which uses a dam to store river water in a reservoir. When water is released from the reservoir it flows through a turbine which activates a generator to produce electricity.
Diversion also known as a “run-of-river” facility, channels a portion of a river through a canal or penstock to utilize the natural decline of the river bed elevation to produce energy. A penstock is a closed conduit that channels the flow of water to turbines. A diversion does not necessarily need a dam to be productive.
Pumped Storage known as pumped storage hydropower (PSH) works like a battery. The facility is able to store the electricity generated by other power sources like solar, wind, and nuclear. The facility stores energy by pumping water from a reservoir at a lower elevation to one at a higher elevation. When the electricity is needed, the water is released back to the lower reservoir and turns a turbine to generate electricity.
Types of Hydropower Turbines
The two main types of hydropower turbines are reaction and impulse. The type of turbine used for a project is dependent on the height of standing water and the flow of water over time at a site. Other factors include how deep the turbine must be set, turbine efficiency, and cost.
Reaction turbines generate power from the combined forces of pressure and moving water. A runner is placed in the water stream and the water is allowed to flow over the blades. Reaction turbines are used for sites with lower standing water and higher flows and are the most common type used. Reaction turbines include Propeller, Francis, and Kinetic.
- Propeller Turbine – has a runner with three to six blades. Water is constantly contacting all of the blades. The different types of propeller turbines include Bulb, Straflo, Tube, and Kaplan.
- Francis Turbine – the first modern hydropower turbine invented by a British-American engineer James Francis. The Francis turbine has a runner with fixed blades in which water is introduced above the runner and then falls through causing the blades to spin.
- Kinetic Turbine – generate electricity from kinetic energy of flowing water. Kinetic turbines can operate in rivers, channels, tidal waters, or ocean currents and can make use of existing structures such as bridges, tailraces, and channels.
Impulse turbines use the velocity of water to move the runner. The water stream hits each bucket on the runner and because there is no suction on the down side of the turbine, the water flows out the bottom. These turbines are used for high standing water, low flow applications and the two main types are Pelton and cross-flow.
- Pelton Turbine – has one or more free jets discharging water into an aerated space and impinging on the buckets of a runner.
- Cross-flow Turbine – drum-shaped and uses an elongated, rectangular section nozzle against curved vanes on a cylindrically shaped runner. The water flows through the blades twice.
Updated by Erin Bennett, June 2022
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