HydroPower Plants - Notes, Civil Engineering, Semester Notes | EduRev

Created by: Mohit Garg

: HydroPower Plants - Notes, Civil Engineering, Semester Notes | EduRev

 Page 1


Worldwide, hydropower plants produce about 24 percent of the world's electricity and 
supply more than 1 billion people with power. The world's hydropower plants output a 
combined total of 675,000 megawatts, the energy equivalent of 3.6 billion barrels of oil, 
according to the National Renewable Energy Laboratory. There are more than 2,000 
hydropower plants operating in the United States, making hydropower the country's 
largest renewable energy source. 
 
 
 
When watching a river roll by, it's hard to imagine the force it's carrying. If you have ever 
been white-water rafting, then you've felt a small part of the river's power. White-water 
rapids are created as a river, carrying a large amount of water downhill, bottlenecks 
through a narrow passageway. As the river is forced through this opening, its flow 
quickens. Floods are another example of how much force a tremendous volume of water 
can have.  
Hydropower plants harness water's energy and use simple mechanics to convert that 
energy into electricity. Hydropower plants are actually based on a rather simple concept 
-- water flowing through a dam turns a turbine, which turns a generator.  
 
Page 2


Worldwide, hydropower plants produce about 24 percent of the world's electricity and 
supply more than 1 billion people with power. The world's hydropower plants output a 
combined total of 675,000 megawatts, the energy equivalent of 3.6 billion barrels of oil, 
according to the National Renewable Energy Laboratory. There are more than 2,000 
hydropower plants operating in the United States, making hydropower the country's 
largest renewable energy source. 
 
 
 
When watching a river roll by, it's hard to imagine the force it's carrying. If you have ever 
been white-water rafting, then you've felt a small part of the river's power. White-water 
rapids are created as a river, carrying a large amount of water downhill, bottlenecks 
through a narrow passageway. As the river is forced through this opening, its flow 
quickens. Floods are another example of how much force a tremendous volume of water 
can have.  
Hydropower plants harness water's energy and use simple mechanics to convert that 
energy into electricity. Hydropower plants are actually based on a rather simple concept 
-- water flowing through a dam turns a turbine, which turns a generator.  
 
Here are the basic components of a conventional hydropower plant:  
 
? Dam - Most hydropower plants rely on a dam that holds back water, creating a 
large reservoir. Often, this reservoir is used as a recreational lake, such as Lake 
Roosevelt at the Grand Coulee Dam in Washington State.  
? Intake - Gates on the dam open and gravity pulls the water through the penstock, 
a pipeline that leads to the turbine. Water builds up pressure as it flows through 
this pipe.  
? Turbine - The water strikes and turns the large blades of a turbine, which is 
attached to a generator above it by way of a shaft. The most common type of 
turbine for hydropower plants is the Francis Turbine, which looks like a big disc 
with curved blades. A turbine can weigh as much as 172 tons and turn at a rate of 
90 revolutions per minute (rpm), according to the Foundation for Water & Energy 
Education (FWEE).  
? Generators - As the turbine blades turn, so do a series of magnets inside the 
generator. Giant magnets rotate past copper coils, producing alternating current 
(AC) by moving electrons. (You'll learn more about how the generator works 
later.)  
? Transformer - The transformer inside the powerhouse takes the AC and 
converts it to higher-voltage current.  
? Power lines - Out of every power plant come four wires: the three phases of 
power being produced simultaneously plus a neutral or ground common to all 
three.  
?  Outflow - Used water is carried through pipelines, called tailraces, and re-enters 
the river downstream.  
Page 3


Worldwide, hydropower plants produce about 24 percent of the world's electricity and 
supply more than 1 billion people with power. The world's hydropower plants output a 
combined total of 675,000 megawatts, the energy equivalent of 3.6 billion barrels of oil, 
according to the National Renewable Energy Laboratory. There are more than 2,000 
hydropower plants operating in the United States, making hydropower the country's 
largest renewable energy source. 
 
 
 
When watching a river roll by, it's hard to imagine the force it's carrying. If you have ever 
been white-water rafting, then you've felt a small part of the river's power. White-water 
rapids are created as a river, carrying a large amount of water downhill, bottlenecks 
through a narrow passageway. As the river is forced through this opening, its flow 
quickens. Floods are another example of how much force a tremendous volume of water 
can have.  
Hydropower plants harness water's energy and use simple mechanics to convert that 
energy into electricity. Hydropower plants are actually based on a rather simple concept 
-- water flowing through a dam turns a turbine, which turns a generator.  
 
Here are the basic components of a conventional hydropower plant:  
 
? Dam - Most hydropower plants rely on a dam that holds back water, creating a 
large reservoir. Often, this reservoir is used as a recreational lake, such as Lake 
Roosevelt at the Grand Coulee Dam in Washington State.  
? Intake - Gates on the dam open and gravity pulls the water through the penstock, 
a pipeline that leads to the turbine. Water builds up pressure as it flows through 
this pipe.  
? Turbine - The water strikes and turns the large blades of a turbine, which is 
attached to a generator above it by way of a shaft. The most common type of 
turbine for hydropower plants is the Francis Turbine, which looks like a big disc 
with curved blades. A turbine can weigh as much as 172 tons and turn at a rate of 
90 revolutions per minute (rpm), according to the Foundation for Water & Energy 
Education (FWEE).  
? Generators - As the turbine blades turn, so do a series of magnets inside the 
generator. Giant magnets rotate past copper coils, producing alternating current 
(AC) by moving electrons. (You'll learn more about how the generator works 
later.)  
? Transformer - The transformer inside the powerhouse takes the AC and 
converts it to higher-voltage current.  
? Power lines - Out of every power plant come four wires: the three phases of 
power being produced simultaneously plus a neutral or ground common to all 
three.  
?  Outflow - Used water is carried through pipelines, called tailraces, and re-enters 
the river downstream.  
 
 
 
The shaft that connects the turbine and generator 
 
 
 
The water in the reservoir is considered stored energy. When the gates open, the water 
flowing through the penstock becomes kinetic energy because it's in motion. The amount 
of electricity that is generated is determined by several factors. Two of those factors are 
the volume of water flow and the amount of hydraulic head. The head refers to the 
distance between the water surface and the turbines. As the head and flow increase, so 
does the electricity generated. The head is usually dependent upon the amount of water in 
the reservoir. 
 
 
 
Page 4


Worldwide, hydropower plants produce about 24 percent of the world's electricity and 
supply more than 1 billion people with power. The world's hydropower plants output a 
combined total of 675,000 megawatts, the energy equivalent of 3.6 billion barrels of oil, 
according to the National Renewable Energy Laboratory. There are more than 2,000 
hydropower plants operating in the United States, making hydropower the country's 
largest renewable energy source. 
 
 
 
When watching a river roll by, it's hard to imagine the force it's carrying. If you have ever 
been white-water rafting, then you've felt a small part of the river's power. White-water 
rapids are created as a river, carrying a large amount of water downhill, bottlenecks 
through a narrow passageway. As the river is forced through this opening, its flow 
quickens. Floods are another example of how much force a tremendous volume of water 
can have.  
Hydropower plants harness water's energy and use simple mechanics to convert that 
energy into electricity. Hydropower plants are actually based on a rather simple concept 
-- water flowing through a dam turns a turbine, which turns a generator.  
 
Here are the basic components of a conventional hydropower plant:  
 
? Dam - Most hydropower plants rely on a dam that holds back water, creating a 
large reservoir. Often, this reservoir is used as a recreational lake, such as Lake 
Roosevelt at the Grand Coulee Dam in Washington State.  
? Intake - Gates on the dam open and gravity pulls the water through the penstock, 
a pipeline that leads to the turbine. Water builds up pressure as it flows through 
this pipe.  
? Turbine - The water strikes and turns the large blades of a turbine, which is 
attached to a generator above it by way of a shaft. The most common type of 
turbine for hydropower plants is the Francis Turbine, which looks like a big disc 
with curved blades. A turbine can weigh as much as 172 tons and turn at a rate of 
90 revolutions per minute (rpm), according to the Foundation for Water & Energy 
Education (FWEE).  
? Generators - As the turbine blades turn, so do a series of magnets inside the 
generator. Giant magnets rotate past copper coils, producing alternating current 
(AC) by moving electrons. (You'll learn more about how the generator works 
later.)  
? Transformer - The transformer inside the powerhouse takes the AC and 
converts it to higher-voltage current.  
? Power lines - Out of every power plant come four wires: the three phases of 
power being produced simultaneously plus a neutral or ground common to all 
three.  
?  Outflow - Used water is carried through pipelines, called tailraces, and re-enters 
the river downstream.  
 
 
 
The shaft that connects the turbine and generator 
 
 
 
The water in the reservoir is considered stored energy. When the gates open, the water 
flowing through the penstock becomes kinetic energy because it's in motion. The amount 
of electricity that is generated is determined by several factors. Two of those factors are 
the volume of water flow and the amount of hydraulic head. The head refers to the 
distance between the water surface and the turbines. As the head and flow increase, so 
does the electricity generated. The head is usually dependent upon the amount of water in 
the reservoir. 
 
 
 
 
Pumped-Storage Plants 
There's another type of hydropower plant, called the pumped-storage plant. In a 
conventional hydropower plant, the water from the reservoir flows through the plant, 
exits and is carried down stream. A pumped-storage plant has two reservoirs:  
? Upper reservoir - Like a conventional hydropower plant, a dam creates a 
reservoir. The water in this reservoir flows through the hydropower plant to create 
electricity.  
? Lower reservoir - Water exiting the hydropower plant flows into a lower 
reservoir rather than re-entering the river and flowing downstream.  
Using a reversible turbine, the plant can pump water back to the upper reservoir. This is 
done in off-peak hours. Essentially, the second reservoir refills the upper reservoir. By 
pumping water back to the upper reservoir, the plant has more water to generate 
electricity during periods of peak consumption. 
The Generator 
The heart of the hydroelectric power plant is the generator. Most hydropower plants have 
several of these generators. The generator, as you might have guessed, generates the 
electricity. The basic process of generating electricity in this manner is to rotate a series 
of magnets inside coils of wire. This process moves electrons, which produces electrical 
current. Each generator is made of certain basic parts:  
? Shaft  
? Excitor  
? Rotor  
? Stator  
As the turbine turns, the excitor sends an electrical current to the rotor. The rotor is a 
series of large electromagnets that spins inside a tightly-wound coil of copper wire, called 
the stator. The magnetic field between the coil and the magnets creates an electric 
current.  
   
 
 
 
Page 5


Worldwide, hydropower plants produce about 24 percent of the world's electricity and 
supply more than 1 billion people with power. The world's hydropower plants output a 
combined total of 675,000 megawatts, the energy equivalent of 3.6 billion barrels of oil, 
according to the National Renewable Energy Laboratory. There are more than 2,000 
hydropower plants operating in the United States, making hydropower the country's 
largest renewable energy source. 
 
 
 
When watching a river roll by, it's hard to imagine the force it's carrying. If you have ever 
been white-water rafting, then you've felt a small part of the river's power. White-water 
rapids are created as a river, carrying a large amount of water downhill, bottlenecks 
through a narrow passageway. As the river is forced through this opening, its flow 
quickens. Floods are another example of how much force a tremendous volume of water 
can have.  
Hydropower plants harness water's energy and use simple mechanics to convert that 
energy into electricity. Hydropower plants are actually based on a rather simple concept 
-- water flowing through a dam turns a turbine, which turns a generator.  
 
Here are the basic components of a conventional hydropower plant:  
 
? Dam - Most hydropower plants rely on a dam that holds back water, creating a 
large reservoir. Often, this reservoir is used as a recreational lake, such as Lake 
Roosevelt at the Grand Coulee Dam in Washington State.  
? Intake - Gates on the dam open and gravity pulls the water through the penstock, 
a pipeline that leads to the turbine. Water builds up pressure as it flows through 
this pipe.  
? Turbine - The water strikes and turns the large blades of a turbine, which is 
attached to a generator above it by way of a shaft. The most common type of 
turbine for hydropower plants is the Francis Turbine, which looks like a big disc 
with curved blades. A turbine can weigh as much as 172 tons and turn at a rate of 
90 revolutions per minute (rpm), according to the Foundation for Water & Energy 
Education (FWEE).  
? Generators - As the turbine blades turn, so do a series of magnets inside the 
generator. Giant magnets rotate past copper coils, producing alternating current 
(AC) by moving electrons. (You'll learn more about how the generator works 
later.)  
? Transformer - The transformer inside the powerhouse takes the AC and 
converts it to higher-voltage current.  
? Power lines - Out of every power plant come four wires: the three phases of 
power being produced simultaneously plus a neutral or ground common to all 
three.  
?  Outflow - Used water is carried through pipelines, called tailraces, and re-enters 
the river downstream.  
 
 
 
The shaft that connects the turbine and generator 
 
 
 
The water in the reservoir is considered stored energy. When the gates open, the water 
flowing through the penstock becomes kinetic energy because it's in motion. The amount 
of electricity that is generated is determined by several factors. Two of those factors are 
the volume of water flow and the amount of hydraulic head. The head refers to the 
distance between the water surface and the turbines. As the head and flow increase, so 
does the electricity generated. The head is usually dependent upon the amount of water in 
the reservoir. 
 
 
 
 
Pumped-Storage Plants 
There's another type of hydropower plant, called the pumped-storage plant. In a 
conventional hydropower plant, the water from the reservoir flows through the plant, 
exits and is carried down stream. A pumped-storage plant has two reservoirs:  
? Upper reservoir - Like a conventional hydropower plant, a dam creates a 
reservoir. The water in this reservoir flows through the hydropower plant to create 
electricity.  
? Lower reservoir - Water exiting the hydropower plant flows into a lower 
reservoir rather than re-entering the river and flowing downstream.  
Using a reversible turbine, the plant can pump water back to the upper reservoir. This is 
done in off-peak hours. Essentially, the second reservoir refills the upper reservoir. By 
pumping water back to the upper reservoir, the plant has more water to generate 
electricity during periods of peak consumption. 
The Generator 
The heart of the hydroelectric power plant is the generator. Most hydropower plants have 
several of these generators. The generator, as you might have guessed, generates the 
electricity. The basic process of generating electricity in this manner is to rotate a series 
of magnets inside coils of wire. This process moves electrons, which produces electrical 
current. Each generator is made of certain basic parts:  
? Shaft  
? Excitor  
? Rotor  
? Stator  
As the turbine turns, the excitor sends an electrical current to the rotor. The rotor is a 
series of large electromagnets that spins inside a tightly-wound coil of copper wire, called 
the stator. The magnetic field between the coil and the magnets creates an electric 
current.  
   
 
 
 
 
Hydrologic Cycle 
Hydropower plants take advantage of a naturally occurring, continuous process -- the 
process that causes rain to fall and rivers to rise. Every day, our planet loses a small 
amount of water through the atmosphere as ultraviolet rays break water molecules apart. 
But at the same time, new water is emitted from the inner part of the Earth through 
volcanic activity. The amount of water created and the amount of water lost is about the 
same.  
At any one time, the world's total volume of water is in many different forms. It can be 
liquid, as in oceans, rivers and rain; solid, as in glaciers; or gaseous, as in the invisible 
water vapor in the air. Water changes states as it is moved around the planet by wind 
currents. Wind currents are generated by the heating activity of the sun. Air-current 
cycles are created by the sun shining more on the equator than on other areas of the 
planet.  
Air-current cycles drive the Earth's water supply through a cycle of its own, called the 
hydrologic cycle. As the sun heats liquid water, the water evaporates into vapor in the 
air. The sun heats the air, causing the air to rise in the atmosphere. The air is colder 
higher up, so as the water vapor rises, it cools, condensing into droplets. When enough 
droplets accumulate in one area, the droplets may become heavy enough to fall back to 
Earth as precipitation. 
The hydrologic cycle is important to hydropower plants because they depend on water 
flow. If there is a lack of rain near the plant, water won't collect upstream. With no water 
collecting up stream, less water flows through the hydropower plant and less electricity is 
generated. 
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