Hydroelectric Power Intro

Hydroelectric power is a form of sustainable energy that is produced by harnessing the power of flowing water. The power is generated by channeling the flow through a turbine which rotates a generator and creates the power. The most common location for instillation of a hydroelectric power plant is at a dam. The water develops potential energy while it is stored in the reservoir behind the dam and is then gravity feed through extremely large steel pipes into the turbine. The pipes used are referred to as penstocks. In large-scale power plants, the penstocks can easily reach up to 30 feet or more in diameter. As the jet of water exits the penstock and encounters the turbine, its kinetic energy is converted into mechanical energy and used to rotate the turbine. The turbine rotation is then used by the generator to generate electrical energy.

After the water flows through the penstock it encounters a turbine. There are two main types of turbines used in hydroelectric power plants: impulse and reaction. The Kaplan turbine is a reaction turbine and is ideal for applications where there are large flow volumes present with only a small head. A Kaplan turbine has blades which resemble the blades on a propeller and as the water flows over them, the pitch of the blades causes the turbine to spin. Many Kaplan turbines have blades with pitches that can be adjusted according to the amount of flow going through. An example of a Kaplan turbine can be seen in Figure 1. An example of an impulse turbine is the Pelton turbine. The Pelton turbine is ideal for lower flow, high head applications. Run by the force of a jet of water impacting it, the Pelton turbine is governed by Newton’s second law. As the jet of water hits the cup, the change in energy in imparted onto the wheel causing it to rotate. The direct impact of the water onto a flat surface of the turbine can create unwanted vibrations in the system. There are several ways to address this including staggering the cups or having them stick out to one side. The most efficient way to prevent this vibration is by introducing a splitter in the middle of the cup to smoothly direct the water jet. The Pelton turbine section shown in Figure 2 is a good example of these center splitters.

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