At the end of the penstock there is a turbine propellor, which is turned by the moving water. The shaft from the turbine goes up into the generator, which produces the power. Power lines are connected to the generator that carry electricity to your home and mine. The water continues past the propellor through the tailrace into the river past the dam. By the way, it is not a good idea to be playing in the water right below a dam when water is released! As to how this generator works, the Corps of Engineers explains it this way: "A hydraulic turbine converts the energy of flowing water into mechanical energy.
A hydroelectric generator converts this mechanical energy into electricity. The operation of a generator is based on the principles discovered by Faraday. He found that when a magnet is moved past a conductor, it causes electricity to flow. In a large generator, electromagnets are made by circulating direct current through loops of wire wound around stacks of magnetic steel laminations.
These are called field poles, and are mounted on the perimeter of the rotor. The rotor is attached to the turbine shaft, and rotates at a fixed speed. When the rotor turns, it causes the field poles the electromagnets to move past the conductors mounted in the stator.
This, in turn, causes electricity to flow and a voltage to develop at the generator output terminals. Demand for electricity is not "flat" and constant. Demand goes up and down during the day, and overnight there is less need for electricity in homes, businesses, and other facilities.
For example, here in Atlanta, Georgia at PM on a hot August weekend day, you can bet there is a huge demand for electricity to run millions of air conditioners! But, 12 hours later at AM Hydroelectric plants are more efficient at providing for peak power demands during short periods than are fossil-fuel and nuclear power plants, and one way of doing that is by using "pumped storage", which reuses the same water more than once.
Pumped storage is a method of keeping water in reserve for peak period power demands by pumping water that has already flowed through the turbines back up a storage pool above the power plant at a time when customer demand for energy is low, such as during the middle of the night. The water is then allowed to flow back through the turbine-generators at times when demand is high and a heavy load is placed on the system.
The reservoir acts much like a battery, storing power in the form of water when demands are low and producing maximum power during daily and seasonal peak periods. An advantage of pumped storage is that hydroelectric generating units are able to start up quickly and make rapid adjustments in output. They operate efficiently when used for one hour or several hours.
Because pumped storage reservoirs are relatively small, construction costs are generally low compared with conventional hydropower facilities. Water is everywhere, which is fortunate for all of humanity, as water is essential for life. Even though water is not always available in the needed quantity and quality for all people everywhere, people have learned to get and use water for all of their water needs, from drinking, cleaning, irrigating crops, producing electricity, and for just having fun.
Dams can be made of earth or concrete the latter is the most common one. Spillways : They release part of the impounded water without passing through the turbines; water can then be used for irrigation purposes. They are located on the main wall of the dam and can be at the top or at the bottom. Most of the water goes into a plunge pool at the toe of the dam, to prevent scour damage by the falling water.
Water intakes : they let in the impounded water towards the turbines through a penstock. Water intakes have gates to control the amount of water that reaches the turbines and grids to filter out any debris such as trunks, branches, etc.
Powerhouse : it houses the hydraulic and electrical equipment turbines, generators, transformers and the service area with control and testing rooms. It has inlet and outlet gates to ensure the equipment area can be dry in case of repairs or disassembling equipment.
Turbines : they harness the energy of the water that goes through them to rotate around a shaft. There are three main types of turbines: Pelton, Francis and Kaplan turbines propeller type. The photo on the right shows the Alexander Hydroelectric Plant on the Wisconsin River, a medium-sized plant that produces enough electricity to serve about 8, people. Let's say that there is a small dam in your area that is not used to produce electricity.
Maybe the dam is used to provide water to irrigate farmlands or maybe it was built to make a lake for recreation. As we explained above, you need to know two things:. Now all we need to do is a little mathematics. Engineers have found that we can calculate the power of a dam using the following formula:. To get an idea what kilowatts means, let's see how much electric energy we can make in a year.
Since electric energy is normally measured in kilowatt-hours, we multiply the power from our dam by the number of hours in a year. The average annual residential energy use in the U. So we can figure out how many people our dam could serve by dividing the annual energy production by 3, So our local irrigation or recreation dam could provide enough renewable energy to meet the residential needs of people if we added a turbine and generator. Note: Before you decide to add hydropower to a dam, have a hydropower engineer review your calculations and consult with the local resource agencies to be sure you can obtain any permits that are required.
Book Navigation. How Hydropower Works Hydropower plants capture the energy of falling water to generate electricity. Parts of a Hydroelectric Plant Most conventional hydroelectric plants include four major components see graphic below : Dam.
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