chosen based on their particular application and the height of standing water—referred to as "head"—available to drive them. The turning part of the turbine is called the runner. The most common turbines are as follows: Pelton Turbine A Pelton turbine has one or more jets of water impinging on the buckets of a runner that looks like a water wheel. The Pelton turbines are used for high-head sites (50 feet to 6,000 feet) and can be as large as 200 megawatts. Francis Turbine A Francis turbine has a runner with fixed vanes, usually nine or more. The water enters the turbine in a radial direction with respect to the shaft, and is discharged in an axial direction. Francis turbines will operate from 10 feet to 2,000 feet of head and can be as large as 800 megawatts. Propeller Turbine A propeller has a runner with three to six fixed blades, like a boat Propeller. The water passes through the runner and drives the blades. Propeller turbines can operate from 10 feet to 300 feet of head and can be as large as 100 megawatts. A Kaplan turbine is a type of propeller turbine in which the pitch of the blades can be changed to improve performance. Environmental Issues and Mitigation Current hydropower technology, while essentially emission-free, can have undesirable environmental effects, such as fish injury and mortality from passage through turbines, as well as detrimental effects on the quality of downstream water. A variety of mitigation techniques are in use now and environmentally friendly turbines are under development. Electric Utility Net Generation of Electricity(Based on 1998 total kilowatt hours generation) Electric Utility Net Generation by Renewables(Based on 1998 total kilowatt hours generation) Diversion hydropower - channels a portion of the river through a canal or penstock, but may require a dam. The project below, The Tazimina project in Alaska, did not require a dam. Impoundment hydropower - ...
