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Energy of Moving WaterStudent Guide
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Energy is ound in diferent orms, such as light, heat, sound, and
motion. There are many orms o energy, but they can all be put into
two categories: potential and kinetic.
Potential and Kinetic Energy
Potential EnergyPotential energy is stored energy and the energy o position.
Potential energy includes:Chemical energy is energy stored in the bonds o molecules. Fossil
uels such as coal, oil, and natural gas contain chemical energy
that was stored in the remains o ancient plants and animals rom
which they were ormed millions o years ago.
Biomass is any organic material (material that was once living
materialsuch as wood or corn) that can be used as a uel.
Biomass contains stored chemical energy, produced rom the sun
through the process o photosynthesis.
Energy of position. A rock on top o a hill contains potential
energy because o its position. I a orce pushes the rock, it rolls
down the hill because o the orce o gravity. The potential energy
is converted into kinetic energy until it reaches the bottom o thehill and stops.
Stored gravitational energy. The water in a reservoir behind a
hydropower dam is another orm o potential energy. The stored
energy in the reservoir is converted into kinetic energy as the water
ows down a large pipe called a penstock and spins a turbine.
The turbine spins a shat inside the generator, where magnets
and coils o wire convert the kinetic energy into electrical energy
through a phenomenon called electromagnetism. This electricity
is transmitted over power lines to consumers who use it to perorm
many tasks.
Kinetic EnergyKinetic energy is energy in motion; it is the motion o
electromagnetic and radio waves, electrons, atoms, molecules,
substances, and objects. Forms o kinetic energy include:
Electrical energy is the movement o electrons. The movement o
electrons in a wire is called current electricity. Lightning and static
electricity are other examples o electrical energy.
Radiant energy is electromagnetic energy that travels in waves.
Radiant energy includes visible light, x-rays, gamma rays, and radio
waves. Light is one type o radiant energy. Energy rom the sun
(solar energy) is an example o radiant energy.
Energy makes change; it does things or us. It moves cars along the road and boats on the
water. We use it to bake cakes in the oven and keep ice rozen in the reezer. It plays our avorite
songs on the radio and lights our homes. Energy helps our bodies grow and allows our minds
to think. Scientists dene energy asthe ability to do work or the ability to make a change.
What is Energy
POTENTIAL TO KINETIC ENERGY
HILL
KineticEnergy
PotentialEnergy
HYDROPOWER DAM
RIVER
SWITCHYARD
view from above
MAGNETSCOPPER COILS
ROTATINGSHAFT
1. Water in a reservoir behind a hydropower dam ows through a large intakescreen, which lters out large debris, but allows sh to pass through.
2. The water travels through a large pipe, called a penstock.
3. The force of the water spins a turbine at a low speed, allowing sh to passthrough unharmed.
4. Inside the generator, the shaft spins coils of copper wire inside a ring ofmagnets. This creates an electric eld, producing electricity.
5. Electricity is sent to a switchyard, where a transformer increases the voltage,allowing it to travel through the electric grid.
6.Water ows out of the penstock into the downstream river.
GENERATOR
GENERATOR
TURBINE
RESERVOIR
IntakeDAM
PENSTOCK
DETA
IL
1
2
3
4
5
6
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Thermal energy is the internal energy in substances; it is the
vibration and movement o the atoms and molecules within
substances. The more thermal energy in a substance, the aster the
atoms and molecules vibrate and move. Geothermal energy is an
example o thermal energy. Thermal energy is sometimes calledheat.
Sound is the movement o energy through substances in
longitudinal (compression/rareaction) waves. Sound is produced
when a orce causes an object or substance to vibrate; the energy
is transerred through the substance in a longitudinal wave.
Motion is the movement o objects and substances rom one place
to another. Objects and substances move when a orce is applied
according to Newtons Laws o Motion. Wind is an example o
motion energy.
Law of Conservation of EnergyThe Law o Conservation o Energy is not about saving energy. The
law states that energy is neither created nor destroyed. When we
use energy, it does not disappear; we change it rom one orm into
another. A car engine, or example, burns gasoline, converting the
chemical energy in the gasoline into useul motion; some o the
energy is also converted into light, sound, and heat. Solar cells
convert radiant energy into electrical energy. Energy changes orm,
but the total amount o energy in the universe remains the same.
Energy EciencyEnergy eciency is the amount o useul energy produced by a
system compared to the energy input. A perect energy-ecientmachine would convert all o the input energy into useul work,
which is impossible. Converting one orm o energy into another
orm always involves a loss o usable energy. This is called a
conversion loss and is usually in the orm o heat. This waste heat
spreads out quickly into the surroundings and is very dicult to
recapture.
A typical coal-red plant converts about 35 percent o the energy
in the coal into electricity. The rest o the energy is lost as heat. A
hydropower plant, on the other hand, converts about 95 percent o
the energy in the water owing through the system into electricity.
Most transormations are not very ecient. The human body is a
good example. Your body is like a machine, and the uel or yourmachine is ood. The typical body is less than ve percent ecient
at converting ood into useul work such as moving, thinking, and
controlling body processes. The rest is lost as heat. The eciency o
a typical gasoline powered car is about 15 percent.
ENERGY TRANSFORMATIONS
Chemical Motion
Radiant Chemical
Chemical Motion
Electrical Thermal
EFFICIENCY OF A POWER PLANT
BOILER
STEAM LINE
TURBINE
CONDENSERFEED
WATER
GENERATOR
SWITCHYARD
ELECTRICITY
TRANSMISSION
FUEL BURNING
ELECTRICITY GENERATION
12
3
45
FUEL SUPPLY
How a Thermal Power Plant Works
1. Fuel is fed into a boiler, where it is burned to release thermal energy.
2. Water is piped into the boiler and heated, turning it into steam.
3. The steam travels at high pressure through a steam line.
4. The high pressure steam turns a turbine, which spins a shaft.
5. Inside the generator, the shaft spins coils of copper wire inside a ring of magnets.This creates an electric eld, producing electricity.
6. Electricity is sent to a switchyard, where a transformer increases the voltage,allowing it to travel through the elect ric grid.
ost thermal power plants are about 35 percent ecient. Of
the 100 units of energy that go into a plant, 65 units are lost as
one form of energy is converted to other forms. 35 units of
energy are produced to do usable work.
100 units ofenergy go in
THERMAL ENERGY
MOTI ON EN ERGY
35 units ofenergy
come out
6
Fuel Sources
Petroleum Coal Natural Gas Uranium Biomass
CHEMICAL
OR NUCLEAR
ENERGY
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Sources of EnergyWe use many diferent sources to meet our energy needs, all o
which have advantages and disadvantages. Some are cheap;
others are expensive. Some contribute to global warming; others
are pollution-ree. Some are limited in their supplies; others areabundant. Some are always available; others are only available part
o the time.
Energy sources are classied into two groupsrenewable and
nonrenewable. In the United States, most o our energy comes
rom nonrenewable energy sources. Coal, petroleum, natural gas,
propane, and uranium are nonrenewable energy sources. They
are used to make electricity, heat our homes, move our cars, and
manuacture all kinds o products.
They are called nonrenewable because the reserves o the uels
are limited. Petroleum, or example, was ormed millions o years
ago rom the remains o ancient sea plants and animals. We cannot
make more petroleum in a short time.Renewable energy sources include biomass, geothermal energy,
hydropower, solar energy, and wind energy. They are called
renewable because they are replenished by nature in a short time.
Day ater day, the sun shines, the wind blows, the rivers ow, and
plants grow. Heat rom inside the Earthgeothermal energyis
continuously made by the radioactive decay o elements in the
Earths core.
We can harness this renewable energy to do work or us. We use
renewable energy sources mainly to make electricity.
U.S. ENERGY CONSUMPTION BY SOURCE, 2008
PETROLEUM 37%Uses: transportation,
manufacturing
COAL 22.6%Uses: electricity, manufacturing
NATURAL GAS 23.5%Uses: heating, manufacturing,
electricity
URANIUM 8.5%Uses: electricity
PROPANE 1%Uses: heating, manufacturing
Source: Energy InformationAdministration
BIOMASS 3.9%Uses: heating, electricity,
transportation
HYDROPOWER 2.5%Uses: electricity
GEOTHERMAL 0.4%Uses: heating, electricity
WIND 0.5%Uses: electricity
SOLAR 0.1%Uses: heating, electricity
NONRENEWABLE
RENEWABLE
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Electricity must be generated quickly to meet the changing demand
o consumers. Large amounts o electricity, however, cannot be easily
stored. Power plants that can easily change the amount o electricity
they can make, such as hydropower plants, are very important.
As we use more technology, the demand or electricity continues to
grow. In the U.S. today, more than 40 percent o the energy we use is
in the orm o electricity. This amount is expected to rise and poses
many challenges or the nation, with no easy answers.
Global climate change is one important issue to consider when
discussing electricity production. Most U.S. electricity is produced
by ossil uels, which when burned emit greenhouse gases. Should
ossil uel plants be required to reduce emissions? Should we build
more nuclear power plants? Can we reduce demand by cutting
back the energy we use? Can renewable energy sources meet
rising demand? How much are consumers willing to pay or a
reliable supply o electricity, or a cleaner environment, or ecient
technologies? These questions will only become more important.
A Mysterious Force
What exactly is the orce we call electricity? It is moving electrons.And what exactly are electrons? They are tiny particles ound in
atoms. Everything in the universe is made o atomsevery star,
every tree, every animal. The human body is made o atoms. Air and
water are too. Atoms are the building blocks o the universe. Atoms
are so small that millions o them would t on the head o a pin.
Atomic StructureAtoms are made o smaller particles. The center o an atom is called
the nucleus. It is made o particles called protons and neutrons
that are approximately the same size. (The mass o a single proton is
1.67 x 10-24 gram.)
Protons and neutrons are very small, but electrons are much, much
smaller1,836 times smaller, to be precise. Electrons move around
the nucleus in orbits a relatively great distance rom the nucleus. I
the nucleus were the size o a tennis ball, the atom with its electrons
would be 1,250 eet in diameterthe size o the Empire State
Building.
I you could see an atom, it might look a little like a tiny center
o balls surrounded by giant invisible clouds (or energy levels).
Electrons are held in their levels by an electrical orce. The protons
and electrons o an atom are attracted to each other. They both carry
an electrical chargea orce within the particle.
Protons have a positive charge (+) and electrons have a negative
charge (). The positive charge o the protons is equal to the negative
charge o the electrons. Opposite charges attract each other. When
an atom is neutral, it has an equal number o protons and electrons
The neutrons carry no charge and their number can vary. Neutrons
act as a glue to hold the nucleus together.
The Nature of Electricity
Electricity is diferent rom primary energy sources; it is a secondary source o energy, which
means we must use another energy source to produce electricity. Electricity is sometimescalled an energy carrier because it is an ecient and sae way to move energy rom one place
to another.
ATOM
proton neutron
nucleus
electron
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ElementsAn element is a substance composed o atoms that have a given
number o protons. The number o protons is an elements atomic
number and determines the elements identity.
Every atom o hydrogen, or example, has one proton and one
electron. Every atom o carbon has six protons and six electrons.
The atomic mass o an element is the combined mass o its
protons, neutrons, and electrons. Atoms o the same element may
have diferent numbers o neutrons, but they will all have the samenumber o protons. Atoms o the same element that have diferent
numbers o neutrons are called isotopes o that element.
ElectronsThe electrons usually remain within a well-dened region at a
relatively constant distance rom the nucleus. These well-dened
regions are called energy levels. Within various energy levels,
there are areas o diferent shapes, called orbitals, where there is a
high probability that the electrons will be ound. The energy level
closest to the nucleus can hold a maximum o two electrons. The
next level can hold up to eight. The outer levels can hold more, but
the outermost level that contains electrons can hold no more thaneight.
The electrons in the energy levels closest to the nucleus have a strong
orce o attraction to the protonsthey are stable. Sometimes, the
electrons in the outermost energy level are not strongly held. These
electronsvalence electronscan be pushed or pulled rom their
energy level by a orce. These are the electrons that are typically
involved when chemical reactions occur.
MagnetsIn most objects, the molecules are arranged randomly. They are
scattered evenly throughout the object. Magnets are diferent
they are made o molecules that have North- and South-seeking
poles. Each molecule is really a tiny magnet.
The molecules in a magnet are arranged so that most o the North-
seeking poles point in one direction, and most o the South-seeking
poles point in the other direction. This creates a magnetic eld
around a magnetan imbalance in the orces between the ends o
a magnet. A magnet is labeled with North (N) and South (S) poles.
The magnetic eld in a magnet ows rom the North pole to the
South pole.
Electromagnetism
A magnetic eld can produce electricity. In act, magnetism andelectricity are really two inseparable aspects o one phenomenon
called electromagnetism. Every time there is a change in a
magnetic eld, an electric eld is produced. Every time there is a
change in an electric eld, a magnetic eld is produced.
We can use this relationship to produce electricity. Some metals,
such as copper, have electrons that are loosely held. They can be
pushed rom their valence shells by the application o a magnetic
eld. I a coil o copper wire is moved in a magnetic eld, or i
magnets are moved around a coil o copper wire, an electric current
is generated in the wire.
ELEMENT SYMBOL PROTONS ELECTRONS NEUTRONS
Hydrogen H 1 1 0
Lithium Li 3 3 4
Carbon C 6 6 6
Nitrogen N 7 7 7
Oxygen O 8 8 8
Magnesium Mg 12 12 12Copper Cu 29 29 34
Silver Ag 47 47 51
Gold Au 79 79 118
Uranium U 92 92 146
SEVERAL COMMON ELEMENTS
BAR MAGNET
LIKE POLES
OPPOSITE POLES
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Producing ElectricityA generator is an engine that converts mechanical energy into
electrical energy using electromagnetism. A turbine is a device that
converts the ow o air, steam, or water into mechanical energy to
power a generator.
Power plants use huge turbine generators to make the electricity we
use in our homes and businesses. Power plants use many uels to
spin a turbine. They can burn coal, oil, or natural gas to make steam
to spin a turbine. They can split atoms o uranium to heat water intosteam. They can also use the power o rushing water rom a dam or
the energy in the wind to spin the turbine.
The turbine is attached to a shat in the generator. Inside the
generator are magnets and coils o copper wire. The generator can
be designed in two ways. The turbine can spin coils o wire inside
magnets, or can spin magnets inside coils o wire. In either design,
the electrons are pushed rom one copper atom to another inside
the wire by the moving magnetic eld.
In the diagram on the right, coils o copper wire are attached to
the turbine shat. The shat spins the coils o wire inside two huge
magnets. The magnet on one side has its North pole to the ront. The
magnet on the other side has its South pole to the ront.The magnetic elds around these magnets push and pull the
electrons in the copper wire as the wire spins. The electrons in the
coil ow into transmission lines. These moving electrons are the
electricity that ows to our houses. Electricity moves through the
wire very ast. In just one second, electricity can travel around the
world seven times.
Other Ways to Produce ElectricityElectricity can also be produced in other ways. A solar cell turns
radiant energy into electricity. A battery turns chemical energy into
electricity.
A battery produces electricity using two diferent metals in a
chemical solution. A chemical reaction between the metals and the
chemicals rees more electrons in one metal than in the other. One
end o the battery is attached to one o the metals; the other end is
attached to the other metal. The end that rees electrons develops a
positive charge and the other end develops a negative charge. I a
wire is attached rom one end o the battery to the other, electrons
ow through the wire to balance the electrical charge.
A load is a device that does work or perorms a job. I a loadsuch
as a light bulbis placed along the wire, the electricity can do work
as it ows through the wire. In the picture to the right, electrons ow
rom the end o the battery, through the wire to the light bulb. The
electricity ows through the wire in the light bulb and back to the
battery.
CircuitsElectricity travels in closed loops, or circuits. It must have a complete
path beore the electrons can move. I a circuit is open, the electrons
cannot ow. When we ip on a light switch, we close a circuit. The
electricity ows rom the electric wire through the light and back
into the wire. When we ip the switch of, we open the circuit. No
electricity ows to the light.
GeneratorStator
Rotor Turbine Generator Shaft
Wicket
Gate
Tubine
Blades
Water
Flow
TURBINE GENERATOR
ELECTRICAL CIRCUITS
A closed circuit is a complete path allowing electricity
to ow from the energy source to the load.
ENERGY SOURCE
WIRES
LOAD
CLOSED SWITCH
An open circuit has a break in the path. There is no ow of
electricity because the electrons cannot complete the circuit.
ENERGY SOURCE
WIRES
LOAD
OPEN SWITCH
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When we turn a light switch on, electricity ows through a tiny
tungsten wire in an incandescent bulb. The wire gets very hot and
glows. When the bulb burns out, the tiny wire has broken. The path
through the bulb is gone.
When we turn on the TV, electricity ows through wires inside the
set, producing pictures and sound. Sometimes electricity runs
motors in items such as washers or mixers. Electricity does a lot o
work or us. We use it many times each day.
Measuring ElectricityElectricity makes our lives easier, but it can seem like a mysterious
orce. Measuring electricity is conusing because we cannot see it.
We are amiliar with terms such as watt, volt, and amp, but we do
not have a clear understanding o these terms. We buy a 60-watt
light bulb, a tool that needs 120 volts, or a vacuum cleaner that
uses 8.8 amps, and we do not think about what those units mean.
Using the ow o water as an analogy can make electricity easier
to understand. The ow o electrons in a circuit is similar to water
owing through a hose. I you could look into a hose at a given
point, you would see a certain amount o water passing that
point each second. The amount o water depends on how much
pressure is being appliedhow hard the water is being pushed. It
also depends on the diameter o the hose. The harder the pressure
and the larger the diameter o the hose, the more water passes
each second. The ow o electrons through a wire depends on
the electrical pressure pushing the electrons and on the cross-
sectional area o the wire.
VoltageThe pressure that pushes electrons in a circuit is called voltage.
Using the water analogy, i a tank o water were suspended one
meter above the ground with a one-centimeter pipe coming out
o the bottom, the water pressure would be similar to the orce oa shower. I the same water tank were suspended 10 meters above
the ground, the orce o the water would be much greater, possibly
enough to hurt you.
Voltage (V) is a measure o the pressure applied to electrons to
make them move. It is a measure o the strength o the current
in a circuit and is measured in volts (V). Just as the 10-meter tank
applies greater pressure than the 1-meter tank, a 10-volt power
supply (such as a battery) would apply greater pressure than a
1-volt power supply.
AA batteries are 1.5-volt; they apply a small amount o voltage
or pressure or lighting small ashlight bulbs. A car usually has a
12-volt battery; it applies more voltage to push current throughcircuits to operate the radio or deroster. The standard voltage o
wall outlets is 120 voltsa dangerous amount o voltage.
Electrical CurrentThe ow o electrons can be compared to the ow o water. The
water current is the number o molecules owing past a xed
point. Electrical current is the number o electrons owing past a
xed point. Electrical current (I) is dened as electrons owingbetween two points having a diference in voltage.
Current is measured in amperes or amps (A). One ampere is
6.25 X 1018 electrons per second passing through a circuit. With
water, as the diameter o the pipe increases, so does the amount
o water that can ow through it. With electricity, conducting wires
take the place o the pipe. As the cross-sectional area o the wire
increases, so does the amount o electrical current (number o
electrons) that can ow through it.
Water Tank
1 m
Water Tank
10 m
VOLTAGE
Water Tank
1 cm diameterpipe
Water Tank
10 cm diameterpipe
CURRENT
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ResistanceResistance (R) is a property that slows the ow o electrons (the
current). Using the water analogy, resistance is something that
slows water owa smaller pipe or ns on the inside o the pipe.
In electrical terms, the resistance o a conducting wire depends on
which metal the wire is made o and its diameter. Copper, aluminum,
and silvermetals used in conducting wiresall have diferent
resistances.
Resistance is measured in units called ohms (). There are devicescalled resistors, with set resistances, that can be placed in circuits to
reduce or control the current ow.
Ohms LawGeorge Ohm, a German physicist, discovered that in many materials,
especially metals, the current that ows through a material is
proportional to the voltage. In the substances he tested, he ound
that i he doubled the voltage, the current also doubled. I he reduced
the voltage by hal, the current dropped by hal. The resistance o the
material remained the same.
This relationship is called Ohms Law, and can be written in threesimple ormulas. I you know any two o the measurements, you can
calculate the third using the ormulas to the right:
Electrical PowerPower (P) is a measure o the rate o doing work or the rate at which
energy is converted. Electrical power is the rate at which electricity is
produced or consumed. Using the water analogy, electrical power is
the combination o the water pressure (voltage) and the rate o ow
(current) that results in the ability to do work.
A large pipe carries more water (current) than a small pipe. Water at a
height o 10 meters has much greater orce (voltage) than at a height
o one meter. The power o water owing through a 1-centimeterpipe rom a height o one meter is much less than water through a
10-centimeter pipe rom 10 meters.
Electrical power is dened as the amount o electric current owing
due to an applied voltage. It is the amount o electricity required to
start or operate a load or one second. Electrical power is measured
in watts (W).
Water Tank
No
Resistance
Water Tank
Resistance
RESISTANCE
Water Tank Water Tank
POWER
OHMS LAW
Voltage = current x resistanceV=IxR or V=Ax
Current = voltage / resistanceI=V/R or A=V/
Resistance = voltage / currentR=V/I or =V/A
Power = voltage x currentP=VxI or W=VxA
ELECTRICAL POWER FORMULA
FORMULAS FOR MEASURING ELECTRICY
The ormula pie works or any
three variable equation. Put
your nger on the variable
you want to solve or and
the operation you need is
revealed.
E = I x R
I = E/R
R = E/I
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Electrical EnergyElectrical energy introduces time to electrical power. In the water
analogy, it would be the amount o water alling through the pipe
over a period o time, such as an hour. When we talk about using
power over time, we are talking about using energy. Using our
water example, we could look at how much work could be done by
the water in the time that it takes or the tank to empty.
The electrical energy that an appliance consumes can only be
determined i you know how long (time) it consumes electricalpower at a specic rate (power). To nd the amount o energy
consumed, you multiply the rate o energy consumption (measured
in watts) by the amount o time (measured in hours) that it is being
consumed. Electrical energy is measured in watt-hours (Wh).
Energy (E) = Power (P) x Time (t)or
E = P x tor
E = W x h = Wh
Another way to think about power and energy is with an analogy
to traveling. I a person travels in a car at a rate o 40 miles per hour
(mph), to nd the total distance traveled, you would multiply therate o travel by the amount o time you traveled at that rate.
I a car travels or 1 hour at 40 miles per hour, it would travel 40
miles.
Distance = 40 mph x 1 h = 40 miles
I a car travels or 3 hours at 40 miles per hour, it would travel 120
miles.
Distance = 40 mph x 3 hours = 120 miles
The distance traveled represents the work done by the car.
Electrical PowerWhen we look at power, we are talking about the rate that electrical
energy is being produced or consumed. Energy can be compared to
the distance traveled or the work done by the car. A person would
not say he took a 40-mile per hour trip because that is the rate.
He would say he took a 40-mile trip or a 120-mile trip. We would
describe the trip in terms o distance traveled, not rate traveled. The
distance is the work done.
The same applies with electrical power. You would not say you
used 100 watts o light energy to read your book, because watts
represents the rate you used energy, not the total energy used. The
amount o energy used would be calculated by multiplying the rateby the amount o time you read. I you read or ve (5) hours with
a 100-W bulb, or example, you would use the ormula as ollows:
Energy = Power x Time or E = P x t
Energy = 100 W x 5 h = 500 Wh
One watt-hour is a very small amount o electrical energy. Usually,
we measure electrical power in larger units called kilowatt-hours
(kWh) or 1,000 watt-hours (kilo = thousand). A kilowatt-hour is the
unit that utilities use when billing most customers.
The average cost o a kilowatt-hour o electricity or residentia
customers is about $0.11. To calculate the cost o reading with
a 100-W bulb or 5 hours, you would change the watt-hours into
kilowatt-hours, then multiply the kilowatt-hours used by the cost
per kilowatt-hour, as shown below:
500 Wh divided by 1,000 = 0.5 kWh
0.5 kWh x $0.11/kWh = $0.055
It would cost about ve and a hal cents to read or ve hours using
a 100-W bulb.
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Water is ound in three orms: liquid, solid, and gas. The liquid orm
is water. The solid orm is ice. The gas orm is invisible and is called
water vapor. Water can change between these orms in six ways:
Freezing changes liquid water into ice.
Melting changes ice into liquid water.
Evaporation changes liquid water into water vapor.
Condensation changes water vapor into liquid water. For example,morning dew on the grass comes rom water vapor.
Sublimationchanges ice or snow into water vapor without passing
through the liquid state. The ice or snow seems to disappear
without melting rst.
Deposition changes water vapor into ice without the vapor
becoming a liquid rst. Water vapor alls to the ground as snow.
The Water CycleIn our Earth system, water is continually changing rom a liquid
state to a vapor state and back again.
Energy rom the sun evaporates liquid water rom oceans, lakes andrivers, changing it into water vapor.
As warm air over the Earth rises, it carries the water vapor into the
atmosphere where the temperatures are colder.
The water vapor cools and condenses into a liquid state in the
atmosphere where it orms clouds.
Inside a cloud, water droplets join together to orm bigger and
bigger drops. As the drops become heavy, they start to all. Clouds
release their liquid water as rain or snow. The oceans and rivers
are replenished and the cycle starts again. This continuous cycle is
called the water cycle or hydrologic cycle.
Characteristics of Water
Water is vital to lie on Earth. All living things need water to survive. Water covers 75 percent o
the earths surace. Our bodies are two-thirds water. Water is made o two elements, hydrogenand oxygen. Both are gases. Two atoms o hydrogen combine with one atom o oxygen to
create a molecule o water. The chemical ormula or water is H2O.
WatercoversmostoftheEarthssurface.
Image courtesy o NASA
SolarEnergy
Condensation(gas to liquid)
Precipitation(liquid or solid)
Evaporation(water vapor)
Evaporation(water vapor)
Oceans(liquid)
THE WATER CYCLE
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Water as an Energy SourceHydropowerHumans have used the power o moving water or more than 2,000
years. The rst reerences to water mills are ound in Greek, Roman,
and Chinese texts. They describe vertical water wheels in rivers and
streams. These traditional water wheels turned as the river owed,
turning millstones that ground corn.
By the 4th century AD, water mills were ound in Asia and northern
Europe. In the early 11th century, William the Conqueror noted
thousands o water mills in England. Most used stream and riverpower, but some worked with the tides.
Early water wheels were designed to allow water to ow beneath
the wheel. Later, millers diverted streams to ow over the tops o
the wheels. More recently, wheels were placed on their sidesa
more ecient method.
In the late 1700s, an American named Oliver Evans designed a mill
that combined gears, shats, and conveyors. Ater grain was ground,
it could be transported around the mill. This invention led to water
wheels being the main power source or sawmills, textile mills, and
orges through the 19th century.
In 1826, a French engineer, Jean-Victor Poncolet, designed an
enclosed water wheel so that water owed through the wheelinstead o around it. This idea became the basis o the modern
American water turbine.
In the mid 1800s, James Francis, Chie Engineer o the Locks and
Canal Company in Lowell, MA, designed a water turbine with
curved blades. Known as the Francis turbine, modern variations o
this water turbine are still in use today in hydropower plants.
Generating electricity rom hydropower began in the United
States on July 24, 1880, when the Grand Rapids Electric Light and
Power Company used owing water to power a water turbine to
generate electricity. It created enough power to light 16 lamps in
the Wolverine Chair Factory. One year later, hydropower was used
to light all the street lamps in the city o Niagara Falls, NY.
Dams Yesterday and TodayThe oldest known man-made dams were small structures built
over 5,000 years ago to divert river water to irrigate crops in
Mesopotamia. In 2900 BC, Egyptians in the city o Memphis built a
dam across the Nile River. The dam stopped periodic ooding and
created a reservoir or irrigation and drinking water.
The Romans also built many dams in the rst millennium, but
most o their technical knowledge and engineering skills were lost
during the all o the Roman Empire. Dams did not become major
civil projects until the end o the 19 th century when the need or
large dams coincided with the ability to build them.
Today, there are more than 500,000 dams worldwide. Most dams
are small structures less than three meters high. There are about
40,000 large dams that measure higher than 15 meters.
There are about 80,000 dams in the United States, but less than
three percent (2,400) include power plants used to generate
electricity. The rest were built or recreation, shing, ood control,
crop irrigation, to support the public water supply, or to make
inland waterways accessible to ships and barges. Power plants with
turbines and generators could be added to some o these dams to
produce electricity.
Amid-nineteenthcenturywaterwheel.
WorkersinstallaFrancisturbineatGrandCouleeDam,1947.
AFrancisturbinefeaturescurvedblades.
Image courtesy o U.S. Bureau o Reclamation
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Types of DamsA dam is either an overow or non-overow dam. An overow
dam allows water to spill over its rim. A non-overow dam uses
spillwayschannels going through or around the damto control
the amount o water behind the dam. This also allows a dam
operator to channel water to a hydropower plant when it is needed.
Dams are also categorized by the materials used in their construction
and by their shape. Most dams are made o Earth and clay, gravel,
rock, stone masonry, wood, metal, or concrete.A gravity dam uses only the orce o gravity to resist water
pressure. It holds back the water by the sheer orce o its mass
pressing downward. A gravity dam is built wider at its base to ofset
the greater water pressure at the bottom o the reservoir. Most
gravity dams are made o concrete. The Hoover Dam is an example
o a concrete arch gravity dam (See page 16 for the story of how the
Hoover Dam was built).
An embankment dam is a gravity dam made o rocks and dirt, with
a dense, water-resistant center that prevents water rom seeping
through the dam. The slopes o the dam are atter on both sides,
like the natural slope o a pile o rocks.
Like a gravity dam, an embankment dam holds back water by theorce o gravity acting on its mass. An embankment dam requires
much more material to build than a gravity dam, since rock and
Earth are less dense than concrete.
An arch dam can only be built in a narrow river canyon with solid
rock walls. It is built rom one wall o a river canyon to the other and
curves upstream toward the body o a reservoir. The curved shape
diverts some o the immense orce o the water toward the canyon
walls.
An arch dam is built o stone masonry or concrete and requires less
material than a gravity dam. It is usually less expensive to build.
The Glen Canyon Dam, spanning the Colorado River in Arizona, is
the tallest arch dam in the U.S. It is 216 meters (710 eet) high. It was
opened in 1966 to provide water storage or the arid U.S. Southwest
and to generate electricity or the regions growing population.
A buttress dam consists o a relatively narrow wall that is supported
by buttresses (triangle-shaped supports) on the downstream side.
Most buttress dams are made o concrete reinorced with steel.
Thick buttresses help the dam withstand the pressure o water
behind it. While buttress dams use less material than gravity dams,
they are not necessarily cheaper to build. The complex work o
orming the buttresses may ofset the savings on construction
materials. A buttress dam is desirable in a location that cannot
support the massive size o a gravity dams oundation.
GRAVITY DAM
EMBANKMENT DAM
ARCH DAM
BUTTRESS DAM
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A Hydropower PlantThere are three main parts o a typical hydropower plant: the
reservoir, the dam, and the power plant (turbines and generators).
The reservoir stores the water (potential energy). The dam contains
the water with openings in the dam controlling the waters ow. The
power plant (turbine and generator) converts the kinetic energy in
the moving water into electricity.
A reservoir holds water behind the dam to create a greater distance
between the water in the reservoir and the river below. The distancethe water drops rom the reservoir to the turbine is the head; the
higher the drop, the greater the head. The amount o moving water
is called the ow; more ow equals more orce. The mass o the
water in the reservoir exerts pressure to move the water; the greater
the mass, the greater the pressure.
The generation o electricity begins with water owing rom
the reservoir into openings on the upstream side o the dam to
penstocks, which are very large pipes. The water ows down the
penstocks to turbines at the bottom, spinning the turbines to
power the generators. The generators produce electricity, which is
sent to transmission lines where it begins its journey to consumers.
The water that entered the penstocks returns to the river below the
dam and continues its downstream journey.
Electricity from HydropowerAlmost 20 percent o the worlds electricity is produced by
hydropower. In the Northern Hemisphere, Canada produces 59
percent o its electricity rom hydropower, while Mexico produces
13 percent. In the United States, 7-10 percent o electricity comes
rom hydropower, depending on the supply o water. That is enough
power to supply 28 million households.
HYDROPOWER DAM
RIVER
SWITCHYARD
view from above
MAGNETS
COPPER COILS
ROTATINGSHAFT
1. Water in a reservoir behind a hydropower dam ows through a large intakescreen, which lters out large debris, but allows sh to pass through.
2. The water travels through a large pipe, called a penstock.
3. The force of the water spins a turbine at a low speed, allowing sh to passthrough unharmed.
4. Inside the generator, the shaft spins coils of copper wire inside a ring ofmagnets. This creates an electric eld, producing electricity.
5. Electricity is sent to a switchyard, where a transformer increases the voltage,
allowing it to travel through the electric grid.
6.Water ows out of the penstock into the downstream river.
GENERATOR
GENERATOR
TURBINE
RESERVOIR
IntakeDAM
PENSTOCK
DETA
IL
1
2
3
4
5
6
GENERATORS AT A HYDROPOWER PLANT
ThegeneratorsattheSafeHarborhydropowerplantinsouthernPennsylvania.
0.6
%5.9
%
48.5
%
19.6
%
21.3
%
1.4
%
1.3
%
0.4
%
Coal
NaturalGas
Uranium
Hydropower
Biomass
Wind
Geothermal
Other
RENEWABLENON-RENEWABLE
50%
40%
30%
20%
10%
0%
1.1
%
Petroleum
Data: EIA
U.S. ELECTRICITY PRODUCTION, 2008
Norway
Brazil
Canada
Switzerland
Vietnam
India
Mexico
China
Egypt
United States Data: EIA, 2008
98%
87%
69%
61%
41%
19%
19%
17%
13%
7%
The percentage ofelectricity that is consumedfrom hydropower inselected countries.
HYDROPOWER AROUND THE WORLD
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Hoover Dam is located in Black Canyon on the Colorado River, about
30 miles southeast o Las Vegas, NV. It was authorized by Congress
in 1928 to provide electricity, ood control, and irrigation or the
arid Southwest. It was built in the early 1930s at the height o the
Great Depression, providing much needed jobs or thousands o
workers.
Hoover Dam is a concrete arch gravity type dam, in which the power
o the water is held back by the orce o gravity, as well as the arch
shape. It is 726.4 eet tall rom the oundation rock to the roadway
on the crest o the dam. There are towers and ornaments that rise 40
eet above the crest and weigh more than 6,600,000 tons.
Beore construction o the dam itsel could begin, the Colorado River
had to be diverted around the construction site. Four concrete-
lined tunnels (each 50 eet in diameter and 4,000 eet long) were
drilled through the canyon walls, two on each side o the canyon.
Then temporary earthen coferdams were built above and below
the site to channel the river water through the tunnels and protect
the construction site.
When the diversion tunnels were no longer needed, the upstream
entrances were closed by huge steel gates and concrete plugs were
placed in the middle o the tunnels. Downstream sections o the
tunnels are used as spillways or the dam. The temporary coferdams
were torn down once the dam was completed.
There are 4,360,000 cubic yards o concrete in the dam, power plant,
and other structures necessary to the operation o the dam. This
much concrete would build a tower that is 100 eet square and 2
miles high, or pave a standard highway that is 16 eet wide rom San
Francisco to New York Citya distance o more than 2,500 miles.
Setting the concrete produced an enormous amount o heat. The
heat was removed by placing more than 582 miles o 1-inch stee
pipe in the concrete and circulating ice water through it rom a
rerigeration plant that could produce 1,000 tons o ice in 24 hours
It took ve years to build the dam, power plant, and othe
structures. During construction, a total o 21,000 men worked onthe daman average o 3,500 men daily. A total o 114 men died
during construction o the dam, but none is buried in the concrete
although stories to that afect have been told or years.
Beore construction o the dam could begin, the ollowing projects
were necessary:
the construction o Boulder City to house the workers;
the construction o seven miles o highway rom Boulder City
to the dam site;
the construction o 22.7 miles o railroad rom Las Vegas to
Boulder City and an additional 10 miles rom Boulder City to the
dam site; and the construction o a 222-mile-long power transmission line
rom Caliornia to the dam site to supply energy or construction
Once the dam was completed and the Colorado River was contained
a reservoir ormed behind the dam called Lake Mead, which is an
attraction to boaters, swimmers, and shermen. The Lake Mead
National Recreation Area is home to thousands o desert plants and
animals that adapted to survive in an extreme place where rain is
scarce and temperatures soar.
Summarized from the U.S. Bureau of Reclamation, U.S. Department of the Interior
website: www.usbr.gov/lc/hooverdam/faqs/damfaqs.html.
Building Hoover Dam: Transforming the Desert Southwest
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Types of HydropowerHydropower acilities can be categorized into two main types:
conventional and pumped storage. Conventional projects
account or over 80 percent o hydropower generation in the U.S.
Conventional hydropower plants use the available water rom
rivers, streams, canal systems, or reservoirs to produce electrical
energy.
Some conventional projects include reservoirs and some do not.
Projects with dams and reservoirs, known as impoundmentfacilities, store water and use it to generate electricity when there
is the demand.
Projects without reservoirs are known as diversion acilities or run-
o-river projects. Diversion projects do not require dams; instead,
a portion o a river is diverted or channeled through a canal or
penstock. Electricity rom the Canadian side o Niagara Falls is
generated through a diversion acility.
Run-of-river projects have turbines installed in ast-owing
sections o the rivers, but they do not signicantly slow down the
rivers ow. The ow o water at run-o-river and diversion projects
continues at about the same rate as the natural river ows.
Pumped Storage PlantsAnother type o hydropower plant is known as a pumped storage
plant. A pumped storage plant circulates water between two
reservoirsone higher than the other. When the demand or
electricity is low, the plant uses electricity to pump water to the
upper reservoir and stores the water there until it is needed.
When there is a high demand or electricity, the water is released
rom the upper reservoir to ow through turbines and back into the
lower reservoir to quickly generate electricity.
A pumped storage plant is in many ways like a huge battery that
stores the potential energy o the water in the upper reservoir untilthere is a demand or electricity, which it can generate very quickly
by releasing the water.
RUN-OF-RIVER PROJECT
Image courtesy o U.S. Army Corps o Engineers
PUMPED STORAGE PLANT
Image courtesy o U.S. Army Corps o Engineers
NIAGARA FALLSNiagara FallsNatural WonderNiagara Falls produces one quarter o Ontarios electricity, but the
hydropower does not come directly rom the alls. Rushing water
is diverted rom the Niagara River, upstream rom the alls, to a
powerhouse. There the water drops 120 eet through penstocks.
The rushing water provides energy to turbines at the bottom,
spinning shats that are three eet in diameter and attached to the
generators, which rotate 250 times a minute to produce electricity.
Ater the water ows past the turbines, it runs through a tunnel and
empties back into the river.
ChiefJosephDamontheColumbiaRiverinWashington.
SenecaPumpedStorageGeneratingStationaboveKinzuaDamontheAlleghenyRiverinWarrenCountynearWarren,PA.
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Maneuvering Around a DamThe impact o dams on the migration o sh, especially spawning
salmon and steelhead in the Northwest, is an important issue
today. Some dams have sh ladders built in to allow sh to migrate
upstream to spawn. Fish ladders are a series o small pools arranged
like stair steps. The sh jump rom pool to pool, each pool higher
than the one beore, eventually bypassing the dam.
When the sh swim downstream to return to the ocean, they need
to bypass the dam again. Headed downstream, sh are divertedaround dams through spillways.
Navigation DamsDams to produce electricity are not the only dams built across
rivers. Navigation dams are built to make sure there is enough water
or boats and barges as they travel up and down rivers.
When a dam is built across a river that is used by boats and barges,
a canal is dug adjacent to the dam or the boats to use. The boats
bypass the dam through locks in the canal. Each lock has large
upstream and downstream doors that can be opened and closed.
A boat traveling upstream is moving rom a lower water level to ahigher water level. When the boat enters a lock, the doors are closed
and water is let in so that the water level in the lock rises. The boat
rises with the water until it is level with the upstream water level.
The upstream door opens, and the boat moves on to the next lock.
A boat may need to go through several locks beore it reaches the
river on the other side o the dam.
Hydroelectric Power Plant SafetyThe purpose o a dam is to contain a large amount o water that
could cause major destruction downstream i the dam ails, so
saety is an important issue. Some dams have ailed in the past,
but large dam ailure is not considered a signicant threat today.The major dams in use today were designed by engineers to last
or generations, and to withstand Earthquakes, oods, and other
potential hazards.
Dams are required by law to be monitored continuously and
inspected routinely or potential saety problems. State and ederal
agencies, as well as dam owners, are involved in the process. Security
procedures against terrorist attacks have also been put into place.
Federal RegulationThe Federal Energy Regulatory Commission (FERC) is the
ederal agency that oversees all non-ederal hydropower plants on
navigable waterways and ederal lands. FERC is in charge o licensing
new plants and relicensing older plants when their licenses expire.
FERC is charged with ensuring that all hydropower plants minimize
damage to the environment. Many concerns about relicensing
involve natural resource issues. Hydropower projects generally
alter natural river ows, which may afect sh populations and
recreational activities, both positively and negatively. New
construction or expansion may also afect wildlie habitat, wetlands,
and cultural resources. People who live downstream o the projects
also want to be assured that the dams are sae.
FISH LADDER
Image courtesy o Bonneville Power Administration
NAVIGATION DAM
Image courtesy o U.S. Army Corps o Engineers
TheshladderatBonnevilleDamontheColumbiaRiverinthePacicNorthwest.
AnaerialviewoftheSooLocksandtheInternationalBridgeatSaultSteMarie,MI.
SAFETY INSPECTIONS
Image courtesy o Tennessee Valley Authority
AnengineeronTVAsRopeAccessTeaminspectsoneofthefourspillwaygatesatFontanaDam.
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Advantages and DisadvantagesUsing hydropower as an energy source has many advantages over other energy sources, but hydropower has signicant disadvantages too
because o its impact on the environment.
Advantages of HydropowerHydropower is a clean energy source. It is ueled only by moving
water, so it does not produce emissions. Hydropower does not
increase the level o greenhouse gases in the atmosphere.
Hydropower is a renewable energy source. The total amount o
water in a hydropower system does not change; the moving water
is used to generate electricity and returned to the source rom
which it came.
Hydropower is usually available when it is needed. Engineers can
control the ow o water through the turbines to produce electricity
on demand as well as the amount o electricity generated.
Hydropower is an established, proven, and domestic source o
energy produced in the United States.
Hydropower is an economical way to produce electricity.
Maintenance costs o hydropower acilities are low. Once a plant is
up and running, the water ow that powers it is ree. The electricity
generated by hydropower acilities is the cheapest electricity in
the country.
Hydropower is an ecient way to produce electricity. The average
hydropower plant is about 95 percent ecient at converting the
energy in the moving water into electricity.
Dams create reservoirs that ofer a wide variety o nonenergy
benets to communities, such as recreational shing, swimming,and boating. The reservoirs can also increase the property value o
the adjacent land.
Hydropower acilities can help manage the water supply, providing
ood control and a reliable supply o drinking water during
drought. Many dams were built or ood control. The power plants
were an additional benet.
Hydropower dams are very sae and durablebuilt to last or
hundreds o years.
Hydropower is a exible energy source in meeting electricity
generating needs quickly. Hydropower plants can begin generating
electricity within minutes o increased demand. Most hydropowe
plants can also provide reliable and dependable baseload power.
Only three percent o existing dams in the U.S. contain generators
Without building any new dams, existing dams have the potentia
to generate 23,000 MW o power, enough electricity or over 6
million households.
Disadvantages of HydropowerHydropower plants are dependent on water supply. When there
is a drought, or example, hydropower plants cannot produce asmuch electricity.
Hydropower dams on rivers permanently change the natura
ecology o large areas o land, upstream and downstream. When
a dam is built, the resultant reservoir oods large areas o land
upstream rom the dam. The natural ecology o the river and
adjacent land downstream is changed by a reduction in soi
deposition.
Hydropower dams can impact water quality and ow. Reservoirs
can have low dissolved oxygen levels in the water, a problem
that can be harmul to sh and downstream riverbank habitats
Maintaining water ow downstream o a dam is also critical or the
survival o habitats.Some sh populations, such as salmon, migrate upstream to reach
spawning grounds. Dams can block sh rom completing this
natural migration process. Fish ladders may be built to help sh
swim upstream.
Development o new hydropower resources can be very expensive
because dams have been built at many o the more economica
locations. New sites must compete with other potential uses o the
land.
Thedown-riversideoftheSafeHarborhydropowerplantinsouthernPennsylvania.
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The Tennessee Valley Authority (TVA) is a public utility established by
Congress in 1933 as one o Franklin Roosevelts solutions to the Great
Depression. The Tennessee Valley was in bad shape in 1933. Much o the
land had been armed too hard or too long, depleting the soil. The best
timber had been cut. TVA developed ertilizers, taught armers how to
improve crop yields, and helped replant orests, control orest res, and
improve habitat or wildlie and sh.
The most dramatic change in Valley lie came with the advent o
electricity generated by TVA dams that also controlled oods andimproved navigation. Electricity brought modern amenities to
communities and drew industries into the region, providing desperately
needed jobs.
During World War II, the country needed more electricity and TVA
engaged in one o the largest hydropower construction programs ever
undertaken in the United States. At the programs peak in 1942, twelve
hydropower projects and a steam plant were under construction at the
same time, employing 28,000 workers. By the end o the war, TVA had
completed a 650-mile navigation channel the length o the Tennessee
River and had become the nations largest electricity supplier.
Today, TVAs system consists o a mix o energy sources, including:
29 hydroelectric dams and 1 pumped storage plant;
11 coal-red and 8 combustion-turbine power plants;
3 nuclear power plants;
16 solar power sites;
1 wind-power site; and
1 methane gas site.
TVA operates a system o 49 dams and reservoirs on the 652-mile-long
Tennessee River and its tributaries, as well as managing 293,000 acres
o public land. TVA manages the complete river system as an integrated
unit to provide a wide range o benets, including:
year-round navigation;
ood control;
electricity generation;
recreational opportunities;
improved water quality; anda reliable water supply to cool power plants and meet municipal and
industrial needs.
The Tennessee Valley Authority: A Vision Born from Hydropower
PresidentFranklinD.RooseveltsignstheTVAActin1933.
Right:ThededicationoftheDouglasDaminDandridge,TN,1943.
TheFontanaDaminNorthCarolinaasitnearscompletionin1944.
Images courtesy o Tennessee Valley Authority
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A Case Study in Removing a Small Dam
When the Costs Outweigh the BenetsIn May 1999, Portland General Electric (PGE) announced plans to
decommission (tear down) its 95-year-old hydropower project on
the Sandy River in Oregon. The project will eliminate expensive
maintenance costs to the power plant and avoid the cost o bringing
sh protection up to todays standards. The project consists o
dismantling the ollowing:the 47-oot-high Marmot Dam;
a concrete-lined canal that takes water rom Marmot Dam to
the Little Sandy River;
the 16-oot-high Little Sandy Dam;
a 15,000-oot-long wooden ume (articial water channel); and
a 22-megawatt powerhouse.
Marmot Dam was removed in 2007, restoring the Sandy to a ree-
owing river or the rst time in nearly a century. Within hours
the Sandy River looked like a natural river. Torrents o water carried
sediment downstream, helping create natural bends, bars, and
logjams. The Little Sandy Dam was removed in 2008.
PGE is giving about 1,500 acres o land to the Western Rivers
Conservancy. This land will orm the oundation o a natural
resource and recreation area in the Sandy River Basin. Covering
more than 9,000 acres, the area will be owned and managed by the
U.S. Bureau o Land Management.
BEFORE DEMOLITION
DURING DEMOLITION
Images courtesy o U.S. Geological Survey
A Case Study in Improving Ecology at a DamObservers in the Grand Canyon o the Colorado River have noticed
a decline in the number o sandbars used as campsites. This decline
is attributed to Glen Canyon Dam, which controls the ow o the
Colorado through the canyon. Most o the sediment and sand now
gets trapped behind the dam.
The rapids that make the
Grand Canyon so popular with
white-water raters are created
by debris anspiles o rock
ragmentsthat tumble down
rom tributaries during intense
rainall. The debris ans used to
be cleaned out yearly by oods
o water that owed through the
canyon during spring snowmelt
in pre-dam years.
The dam dramatically reduced
the ow o water through the
canyon. This drop in water ow limits the ability o the river to move
rock debris. In the absence o oods, there will be a continuingbuildup o boulders and smaller rocks on many rapids, which could
become more dangerous to navigate. Elimination o yearly ooding
also allowed silt to build up in backwater channels, leading to the
extinction o our native sh.
The U.S. Bureau o Reclamation, which operates Glen Canyon Dam,
released an unusually high ow o water during the spring o 1996
to see i it could rebuild beaches and restore other habitats that
have deteriorated since the dams completion in 1963. Two other
high ows were released in November 2004 and March 2008.
I scientists nd that periodic ooding is successul at rebuilding
the sandbars, maintaining the rapids, and reducing sediment in
upstream tributaries, it will become a part o long-term plans orthe operation o the dam.
HIGH FLOW
Image courtesy o U.S. Geological Survey
Rapidsarecausedbylargebouldersthatgetstuckontheriverbed.
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New Hydropower InitiativesThe mission o the U.S. Department o Energy (DOE) Hydropower
Program is to:
conduct research to improve the benets o hydropower; and
develop new technologies to increase hydropower capacity.
One DOE initiative promotes upgrades at existing hydropower
plants to increase their eciency and capacity. Upgrades will
include replacing old turbines and generator parts with more
ecient equipment, ne-tuning the perormance o existing
equipment, and automating operations.
Upgrades that involve only eciency increases have little
environmental impact and provide benets such as ewer sh
deaths and improved water quality. Upgrades that increase
capacity by adding turbines or raising the height o the reservoir
have greater potential to impact the environment.
The DOE plan also includes retrotting (adding power plants to)
existing dams to generate electricity. Since only three percent o
the dams in the U.S. have power plants, there are opportunities
to add them to many existing dams, including storage and ood
control dams, and navigation dams. Most environmental impacts
have already occurred as a result o construction and operation o
the dams.
The increased electricity provided by the DOE initiative could
replace 18 large (500 MW) coal-red power plants, reducing carbon
dioxide emissions.
New Turbine SystemsThe Department o Energy also supports research into new
technologies. Hydropower plants can cause injuries or death to sh
and impact water quality. New hydropower turbine technologies
could minimize these efects. Benets o new turbine technologies
include:
reduced sh mortality;
improved water quality; and
reduction in carbon dioxide (CO2) emissions.
FISH-FRIENDLY TURBINE
FISH BYPASS
Images courtesy o Grant County Public Utility District
Image courtesy o Alden Lab
AttheWanapumDamontheColumbiaRiver,ash-friendlyturbinerunnerthatisdesignedtohelpsalmonsmoltspassthroughtheturbinewithoutinjuriyisbeingtested.
Right:Across-sectionofash-friendlyturbine.
Alden LabFounded in 1894, Alden Lab is the oldest hydraulic laboratory in
the United States and one o the oldest in the world. Alden has
developed a new hydraulic turbine runner to reduce sh injury
and death as part o the DOE program. Results o pilot-scale tests
indicate that sh survival through the turbine would be 94-100
percent. Studies are being planned or a hydropower site.
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Energy from the TidesNear shore, the ocean rises and alls with the tides. Tides contain
an enormous amount o energy. Some power stations harness the
energy in the changing tides to generate electricity.
Tides are caused by the gravitational orces between the Earth and
moon. The moon pulls on the ocean water that is closest to it. This
creates a bulge in the surace o the water, called a tidal bulge.
Because the Earth is rotating, the water on the opposite side o the
Earth also orms a tidal bulge. These bulges produce high tides.Between the tidal bulges is lower water that produces low tides.
Tidal BarrageA tidal power station, or tidal barrage, is built across an estuary,
the area where a river runs into the ocean. The water here rises and
alls with the tides.
A tidal barrage is like an underwater ence with gates and turbines
held in a caisson, a supporting structure. As the tide rises, the water
ows through the barrage, spinning the turbines, then collects in
the estuary. When the tide drops, the water in the estuary ows
back to the ocean. The water again turns the turbines, which are
built to generate electricity when the water is owing into and outo the estuary.
Tidal Stream PowerAnother source o tidal power relies on strong, steady ocean
currents. This technology is known as tidal stream power.
Underwater turbines can be installed in the ocean in places with
strong tidal currents or steady ocean currents.
Marine Current Turbines Ltd, based in Bristol, England, has developed
the worlds largest tidal stream system, known as SeaGen. A SeaGen
device is operating in Strangord Lough (a shallow bay situated on
the east coast o Northern Ireland). The turbine regularly delivers
1.2 MW to the Northern Ireland grid.
The SeaGen consists o two large rotors, each driving a generator.
The twin rotors are mounted on wing-like extensions on either side
o a steel tower that is set into a hole drilled in the sea oor.
New York Citys East River ProjectThe city and state o New York have partnered with Verdant Power
to harness the energy in the ebb and ow o the tides in Manhattans
East River. The Roosevelt Island Tidal Energy (RITE) Project is planning
to install a kinetic hydropower system o 100-300 tidal turbines
anchored on the bottom o the river. The project could generate
up to 10 MW o electricity. Monitoring o the six initial turbines was
completed in 2008. Evaluatedor perormance and or
environmental impact, the rst
stage was deemed a success.
Verdant Power is now moving
orward with the next stage o
development.
TIDAL BULGE
EARTH
MOON
Gravitational Attraction
Ro
ta
tio
noftheEarth
NEART
IDAL
BU
LGEFA
RTIDA
LBULGE
TIDAL BARRAGE
TIDAL FLOW
DIRECTIONDAM
TURBINE
Tidal water is captured at high tide behind a
dam. When the tide turns, the water is released
to the sea, passing through a set of turbines.
TIDAL STREAM POWER
Image courtesy o SeaGen
AnartistsrenderingoftheSeaGentidalstreamsystem.
FreeFlowSystemturbinebeinginstalledinEastRiver,NY.
Image courtesy o Verdant Power
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WavesOcean waves are caused mainly by wind. The size o waves depends
on the speed o the wind, wind duration, and the distance o water
over which the wind blows. Usually, the longer the distance the
wind travels over water or the harder it blows, the higher the waves.
Winds o 30 miles per hour can cause 15-oot waves. Very strong
winds can cause waves 40-50 eet high.
As the wind blows over the water, there is riction between the wind
and the surace o the water. The wind pulls the surace water inthe direction it is going. The water is much denser than the air and
cannot move as ast, so it rises, and then it is pulled back down by
the orce o gravity. The alling waters momentum moves it below
the surace, and water pressure rom below pushes it up again.
This tug o war between gravity and water pressure creates wave
motion.
Ocean waves are, thereore, the up and down motion o surace
water. The highest point o a wave is the crest; the lowest point is
the trough.
The height o a wave is the distance rom the trough to the crest.
The length o a wave is the distance between two crests. Waves
usually ollow one another, orming a train. The time it takes twocrests in a train to pass a stationery point is known as the period o
a wave. Wave periods tell us how ast the waves are moving.
Harnessing Wave EnergyThe energy in waves can be harnessed to generate electricity.
Studies show that waves of the coasts o Oregon and Washington
have good potential or generating electricity.
There are two main types o wave energy generation devices,
xed and oating. Fixed devices are built into clifs along a coast.
One xed device is the oscillating water column. The column, or
chamber, is partially submersed in the water. As the waves ow in
and out o the chamber, the air inside the chamber is compressed
and decompressed. The orced air spins a turbine. The generatorattached to the turbine produces electricity.
Another xed device is a tapered channel (TAPCHAN) system. I t
consists o a channel connected to a reservoir in a clif. The channel
gets narrower as it nears the reservoir, causing the waves to increase
in height.
When the waves are high enough, they spill over the top o the
channel into the reservoir. The stored water ows out o the
reservoir through a turbine, generating electricity.
The TAPCHAN system is not useable in all coastal areas. Ideal
locations have consistent waves, good wave energy, and a tidal
range o less than one meter.
WAVE MEASUREMENTS
CREST LENGTH
TROUGH
HEIGHT
TAPCHAN SYSTEM
RESERVOIR
TURBINEHOUSING
OCEAN
CLIFF FACE
TAPERED
CHANNEL
OSCILLATING WATER COLUMN
CHAMBER
Wave
VENT T URBI NE WAVE
Air pushed
through by
incoming wave
VENT TURBINE
CHAMBER
WAVE
CLIFF FACE
Wave
VENT T URBI NE WAVE
CHAMBER
Air pulled backas wave
retreats
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ATTENUATOR
FLOATING TUBES
JOINTS
Virtual Hydropower
ProspectorDeveloped by the Idaho
National Laboratory, this online
geographic inormation system
(GIS) tool is designed to assist
you in locating and assessing
natural stream water energy
resources in the United States.
Users can view data regarding
hydropower projects across theUnited States including:
Water Energy Resource Sites
Potential Projects
Hydrography
Power Systems
Transportation
Areas and Places
Land Use
SEAGEN ATTENUATORS
Image courtesy o SeaGen
AnartistsrenderingoftheSeaGentidalstreamsystem.
TheVirtualHydropowerProspector:http://hydropower.id.doe.gov/prospector/index.shtml
Floating DevicesSeveral oating wave devices are also under development. They
generate electricity as they are moved by the motion o waves.
One such device, called an attenuator, is a series o our tubes
that are linked together with hinged joints. Passing waves cause
each tube to rise and all like a giant sea snake. The motion tugs
at the joints linking the tubes. The joints act as a pumping system,
pushing high pressure oil through a series o motors that drive the
generators to produce electricity. The wave energy devices will beconnected to the seaoor by transmission lines.
Future of HydropowerThe uture o hydropower includes both challenges and
opportunities, and it will continue to be a major part o the U.S.
and global energy mix or many years. As the nation and the world
develop strategies to deal with global climate change, hydropower
will play a signicant role by producing clean, economical electricity
without carbon dioxide emissions.
Advances in turbine design and other mitigation strategies will
continue to reduce the impact o conventional hydropower acilities
on sh populations, water quality, and the environment. New
technologies will also allow acilities to become more ecient and
generate more electricity. The addition o power plants to existing
dams will increase the overall capacity o the hydropower industry.
The development and implementation o technologies that harness
the power o moving water, whether it is rom ree-owing streams,
the tides, ocean currents, or waves, will also contribute to the uture
o hydropower in the United States and the world.
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B.C. Hydropower used by the Greeks to turn water wheels or grinding grains more than 2,000 years ago.
Mid-1770s French hydraulic and military engineer Bernard Forest de Blidor wrote Architecture Hydraulique, a our-
volume work describing vertical- and horizontal-axis machines.
1775 U.S. Army Corps o Engineers ounded, with establishment o Chie Engineer or the Continental Army.
1879 The rst hydroelectric plant was built in the U.S. at Niagara Falls.
1880 Michigans Grand Rapids Electric Light and Power Company, generating electricity by dynamo belted to a
water turbine at the Wolverine Chair Factory, lit up 16 brush-arc lamps.
1881 Niagara Falls city street lamps powered by hydropower.
1882 Worlds rst hydroelectric power plant began operation on the Fox River in Appleton, WI.
1886 About 45 water-powered electric plants in the U.S. and Canada.1887 San Bernardino, CA opens rst hydroelectric plant in the west.
1889 Two hundred power plants in the U.S. use waterpower or some or all generation.
1901 First Federal Water Power Act. No one could build or operate a hydroelectric plant on a stream large
enough or boat trac without special permission rom Congress.
1902 U.S. Bureau o Reclamation established.
1907 Hydropower provided 15 percent o U.S. electrical generation.
1920 Hydropower provided 25 percent o U.S. electrical generation. Federal Power Act establishes Federal
Power Commission authority to issue licenses or hydro development on public lands.
1933 Tennessee Valley Authority was established, taking charge o hydroelectric potential o the Mississippi
River in the Tennessee Valley.
1935 Federal Power Commission authority extended to all hydroelectric projects built by utilities engaged in
interstate commerce.
1936 Hoover Dam began operating on the Colorado River. Using multiple Francis turbines, the Hoover Dam
plant produces up to 130,000 kilowatts o power.
1937 Bonneville Dam, the rst Federal dam, begins operation on the Columbia River. Bonneville Power
Administration established.
1949 Hydropower provided almost 33 percent o the nations electrical generation. Conventional capacity
tripled in United States since 1920.1977 Federal Power Commission disbanded by Congress. A new agency was created, the Federal Energy
Regulatory Commission (FERC).
1980 Conventional hydropower plant capacity nearly tripled in United States since 1940.
Today Between 710 percent o U.S. electricity comes rom hydropower, depending on water supply. In total,
the U.S. has about 80,000 MW o conventional capacity and 18,000 MW o pumped storage capacity.
History of Hydropower Timeline
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Careers in the Hydropower Industry
Energy Industry Analysts assess the signicance o developments
and trends in the energy industry and use this inormation or current
and uture regulatory policies. Energy industry analysts require
a degree in nance, management, or other business, industrial,
mechanical or other engineering eld.
Accountants establish accounting policy, providing guidance to
energy companies or reporting issues.
Auditors review nancial inormation about energy companies
to ensure they are in compliance with government regulations.
Accountants and Auditors require a bachelors degree in accounting.
Administratorsprovide general oce clerical support to proessional,
program, or technical staf members utilizing typing skills and a
knowledge o oce automation hardware and sotware systems.
Administrative support staf may be responsible or timekeeping,
government procedures and other personnel matters.
Communications Professionals must possess excellent writing and
speaking skills, a customer service attitude and the ability to respond
quickly in a dynamic environment. Communications proessionals
require a bachelors degree in communications or English.
Economists closely ollow and analyze trends in the various energy
industries to make sure a healthy competitive market is in place. They
consult with experts in energy economics, market design, anti-trust
and other issues, and use economic theory on real-world problems
and situations. Economists require a bachelors degree in economics.
Hydrologists research the distribution, circulation, and physical
properties o underground and surace waters, and study the
orm and intensity o precipitation, its rate o inltration into thesoil, movement through the earth, and its return to the ocean and
atmosphere.
Hydrologists apply scientic knowledge and mathematical principles
to solve water-related problems in societyproblems o quantity,
quality, and availability. They may be concerned with nding water
supplies or cities and irrigated arms, or controlling river ooding
and soil erosion. They may also work in environmental protection
preventing or cleaning up pollution and locating sites or sae
disposal o hazardous wastes. The work o hydrologists is as varied
as the uses o water and may range rom planning multimillion dollar
interstate water projects to advising homeowners about backyard
drainage problems.
A bachelors degree is adequate or entry-level positions. Students
who plan to become hydrologists should take courses in the physical
sciences, geophysics, chemistry, engineering science, soil science,
mathematics, computer science, aquatic biology, atmospheric
science, geology, oceanography, hydrogeology, and the management
or conservation o water resources. In addition, some background
in economics, public nance, environmental law, and government
policy is needed to communicate with experts in these elds.
Information Technology Specialists do systems programming, of-
the-shel sotware management, database administration, network
and telecommunications operations/administration, security
implementation, disaster recovery, electronic ling, and customer
service support. Inormation Technology specialists require a
bachelors degree in Inormation Technology.
Power Plant Operators control machinery that makes electric power
They control and monitor boilers, turbines, and generators and adjus
controls to distribute power demands among the generators. They
also monitor the instruments that regulate the ow o electricity
rom the plant. When power needs change, they start or stop the
generators and connect or disconnect them rom the circuits. Many
operators use computers to keep records o switching operations
to track the loads on generators and lines, and to prepare reports o
unusual incidents, malunctions, or repairs that occur during thei
shit.
Power Distributors and Dispatchers operate equipment tha
controls the ow o electricity rom a power plant through
transmission lines to substations that supply customers needs. Theyoperate converters, transormers, and circuit breakers. Dispatchers
monitor the equipment and record readings at a pilot boarda map
o the transmission grid system. It shows the status o circuits and
connections with substations and industrial plants.
Dispatchers also anticipate power needs, such as those caused by
changes in the weather. They call control room operators to start or
stop boilers and generators. They also handle emergencies such as
line ailures and route electricity around the afected areas. In addition
dispatchers operate and monitor the equipment in substations. They
step up or step down voltage and operate switchboard levers, which
control the ow o power in and out o the substations.
Civil Engineers make site visits, prepare engineering studies, and
design or evaluate various types o hydroelectric dams, powerhouses
and other project structures. They develop graphs, charts, tables
and statistical curves relating to these studies or inclusion in
environmental impact statements and assessments and dam saety
reports. Civil engineers require a bachelors degree in engineering.
Environmental Engineers o proposed hydroelectric projects review
environmental reports and exhibits. A main component o the job
is to study aspects o environmental impact issues, determine the
scope o the problem, and propose recommendations to protect
the environment. They perorm studies to determine the potentia
impact o changes on the environment. Environmental engineers
require a bachelors degree in engineering.
Electrical Engineers design and develop electrical systems andequipment, evaluate electrical systems, and ensure stability and
reliability. Electrical engineers require a bachelors degree in
engineering.
Hydropower Engineers work with teams o environmental scientists
and engineers to review, analyze, and resolve engineering and
environmental issues associated with proposals to construct and
operate hydroelectric projects, including major dams, reservoirs, and
power plants. Hydropower engineers require a bachelors degree in
engineering.
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Hydropower Resources and Career InformationBureau of Land ReclamationExplores the Hoover Dam. Learn how the dam was built, view
construction era photographs, and learn how the dam operates as
one o the largest hydroelectric power plants in the country. The
site includes educational resources or teachers.
www.usbr.gov/lc/hooverdam/index
Career Voyages
There are two interesting resources or all careers. Watch InDemand Occupation Videos at www.careervoyages.gov/
careervideos-main.cm. This website eatures short videos or
occupations ound in the Bureau o Labor Statistics Occupational
Outlook Handbook. This is an excellent place to see careers in
action. Click on InDemand Magazine to view or download
several magazines with an introduction to the diferent career
paths in construction, energy, advanced manuacturing, and
health care, and the young proessionals who have chosen those
careers.
www.careervoyages.gov
Federal Energy Regulatory CommissionVisit the Students Corner section to learn more about hydropower.
This website includes games and photos o dams and hydropower
plants.
www.ferc.gov/students/index
Foundation for Water and Energy EducationWatch a video o hydroelectric power production, take a virtual
tour o a hydroelectric plant and a generator, and learn how a
hydroelectric project can afect a river.
www.fwee.org
Hydro Research FoundationLearn about hydropower as a renewable energy resource and take
a Hydro Venture, an excellent resource that explores all aspects o
hydropower using real lie photos.
www.hydrofoundation.org
Idaho National LaboratoryHas extensive inormation about hydropower and new
technologies.http://hydropower.id.doe.gov/
National Hydropower AssociationsCovers basic inormation (see Fact Sheets under Hydro Facts)
about hydropower in all o its orms, both conventional and
new technologies as well as hydropower issues as they relate to
legislative and regulatory issues. The website also includes many
links to other hydropower resources and is a great place to start
or everything that is hydro.
www.hydro.org
PBS: Building BigThere is a section on dams. Ater learning about the diferent
types o dams, take the dam challenge. As a consulting damengineer, you decide whether to repair, take down, or leave alone
several diferent dams.
www.pbs.org/wgbh/buildingbig/dam/index.html
U.S. Department of EnergyEnergy Information AdministrationUp-to-date data and inormation on all energy sources, including
hydropower.
www.eia.doe.gov
Dams Contribute to Other Employment
When Hoover Dam (near Boulder City, Nevada) was built on theColorado River, it created