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What is solar power

What is solar power?
The primary source of all energy on planet Earth is from the sun. Solar power is power
generated directly from sunlight. Solar power can be used for heat energyor converted into
electric energy.
Renewable Energy
When we use solar power, we don't use any of the Earth's resources like coal or oil. This
makes solar power a renewable energy source. Solar power is also clean power that doesn't
generate a lot of pollution.
Solar Power for Heat
Solar power can be used for heating up homes and other buildings. Sometimes solar power
for heating can be passive. This is when there are no mechanical components used to move
the heat around. Passive heating helps to keep houses warm in the winter, to heat up
swimming pools, and even makes our car warm when we park it outside (which is nice in the
winter, but not so much on a hot summer day).
Active heating is when there are mechanical components to help move the heat around. The
sun could be used to heat up water or air that is then pumped around a building to provide
even heat in all the rooms.
Solar Power for Electricity
When most of us think of solar power, we think of the solar cells that turn rays of sunshine
into electricity. Solar cells are also called photovoltaic cells. The word "photovoltaic" comes
from the word "photons", which are particles that make up sunlight, as well as the word
"volts", which is a measurement of electricity.
Today solar cells are commonly used in small handheld devices like calculators and wrist
watches. They are becoming more popular for buildings and homes as they become more
efficient. One nice thing about solar cells is that they can be placed on the roof of a building
or home, not taking up any extra space.
Solar cells on a house used for making electricity
How do solar cells work?
Solar cells convert the energy of photons from the sun into electricity. When the photon hits
the top of the cell, electrons will be attracted to the surface of the cell. This causes a voltage
to form between the top and the bottom layers of the cell. When an electric circuit is formed
across the top and the bottom of the cell, current will flow, powering electrical equipment.
It takes a lot of solar cells to power a building or a home. In this case, a number of solar cells
are connected into a large array of cells that can produce more total energy.
History of Solar Power
The photovoltaic cell was invented in 1954 by researchers at Bell Labs. Since then, solar cells
have been used on small items such as calculators. They have also been an important power
source for spaceships and satellites.
Starting in the 1990s the government has funded research and offered tax incentives to people
using clean and renewable power such as solar energy. Scientists have made advances in the
efficiency of the solar cell. Today solar cells are around 5 to 15% efficient, meaning a lot of
the energy of the sunlight is wasted. They hope to achieve 30% or better in the future. This
will make solar energy a much more economical and viable energy alternative.
Are there any drawbacks to solar power?
Solar power has two major drawbacks. One drawback is that the amount of sunshine in a
specific place changes due to the time of day, the weather, and the time of the year. The other
drawback is that with current technology it takes a lot of expensive photovoltaic cells to
produce a decent amount of electricity.
Fun Facts about Solar Power
The world's largest solar thermal plants are located in the state of California.
 Many large photovoltaic plants are being built around the world. Some of the largest
are located in China, Canada, and the United States (Nevada).
 If only 4% of the world's deserts were covered in photovoltaic cells, they could
supply all of the world's electricity.
 Many people think that as solar panels become more efficient and less expensive they
will become a standard feature of new homes and buildings.
 In 1990 a solar powered aircraft flew across the United States using no fuel.
 Albert Einstein won a Nobel Prize in 1921 for his research into photovoltaic power.
What is wind power?
Wind power is energy, such as electricity, that is generated directly from the wind. It is
considered a renewable energy source because there is always wind on the Earth and we
aren't "using up" the wind when we make energy from it. Wind power also does not cause
Wind Turbines and Wind Farms
In order to make electricity from wind, energy companies use large windmills called wind
turbines. They are called this because they use turbine generators to generate the electricity.
In order to create a lot of energy capable of powering thousands of homes, energy companies
build large wind farms with lots of wind turbines. They usually build these in consistently
windy places. Some companies build wind farms out in the ocean. These are called offshore
wind farms.
How tall are wind turbines?
Wind turbines are really big structures. The tower itself is typically between 200 and 300 feet
tall. When you add in the height of the blades, some turbines tower 400 feet high! The blades
are quite big, too. There are typically three wind blades on a wind turbine. Each blade is
usually between 115 and 148 feet long.
How does a wind turbine work?
A wind turbine works the opposite of a fan. Instead of using electricity to turn the blades to
make wind, it uses the wind to turn the blades to make electricity.
When the wind turns the blades, the blades turn a shaft inside the turbine. This shaft is big,
but turns slowly. The shaft, however, is connected to a number of gears which causes a
smaller shaft to turn much faster. This smaller shaft drives the electrical generator which
generates the electricity that can be used by homes and businesses.
The parts inside a wind turbine help to generate electricity
What if there isn't any wind?
If there isn't any wind, then no energy will be generated by the wind turbine. However,
engineers do a lot of measurements and calculations to figure out the best areas to place the
wind turbines. The wind won't be blowing all the time, but the important thing is how much
the wind blows on average.
History of Windmills
Windmills have been used since the Middle Ages in order to harness the energy of the wind.
They were initially used to pump water or to grind flour. They are still used in many places of
the world today to pump water. It was in the late 1800s and early 1900s that windmills were
first used to generate electricity.
Are there any drawbacks to wind power?
One major issue some people have with wind power is how the wind turbines mess up the
view or landscape. Other drawbacks include the large blades killing birds and noise pollution
from the turbine. Most people agree that the positives of a fully renewable and clean energy
resource far outweigh the negatives.
Fun Facts about Wind Power
For a wind turbine to make money it must be placed in a spot with an average annual
wind speed of 15 miles per hour.
 In 2011, the top wind power producing state in the United States was Texas. Texas
was followed by Iowa, California, Minnesota, and Illinois.
 Around 3% of the electricity in the United States in 2011 was provided by wind
power. This was enough to power around 10 million homes.
 Tax breaks and new technologies have helped the output from wind power to grow
significantly in the last 10 years.
 The largest wind farm in the United States is the Horse Hollow Wind Energy Center
in Texas. It has 421 wind turbines.
What is hydropower?
Hydropower is power that is generated from moving water such as rivers.
Renewable Energy
Hydropower is a renewable energy source. This means that using a dam or a river to
generate electricity doesn't use up any limited resources like coal or gasoline.
How do we get power from water?
Falling or flowing water from a big river has a lot of energy. We can harness this by forcing
the water through a pipe called a penstock. As the water flows through the pipe it turns the
blades of a turbine which spins an electric generator. As long as the water is flowing, the
generator will be able to provide electricity.
Electricity can be generated by water moving through a dam
There are three main ways that engineers design hydroelectric power plants:
Storage System - The storage system uses a dam. The dam slows the flow of a river
and stores up water in a lake. A portion of the water is released into the river at the
bottom of the dam. The fall of the water, and the water pressure from the lake, forces
the water through the dam and spins turbine generators. Dams are expensive to build,
but they also help control flooding, can create a large recreational lake, and can
provide fresh water for surrounding towns.
Run-of-the-river System - In a run-of-the-river system the turbines are spun by the
natural flow of the river. These systems have the advantage of not creating a huge
lake and flooding the area above the dam. As a result, they have less overall impact
on the environment. However, in order to provide continuous electricity, the river
they use must stay full throughout the year, as the flow is not regulated by a dam.
Pumped Storage System - This system is like the storage system except it uses pumps
to pump used water back up into the reservoir. The way this works is that during the
night, when electricity use is much less, it uses the extra electricity to pump the water
back up to the top of the dam and refill the reservoir. This improves the overall
efficiency of the hydropower plant.
Go here to read about the ocean power technologies tidal and wave power.
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History of Hydropower
Using rivers to power mechanical devices is not a new concept. As far back as ancient times,
thousands of years ago, people used hydropower to perform tasks such as grinding grain into
flour. In the late 1800s scientists first figured out how to use hydropower to generate
electricity. The first hydroelectric power plant was built in Wisconsin in 1882. Since then,
many more power plants have been built in the United States including the Hoover Dam in
1936 and the Grand Coulee Dam in 1942.
Are there any drawbacks to hydropower?
Like any power source there are some drawbacks to hydropower. One drawback is the loss of
land and the damage to the local ecosystem caused when a lake is created by a dam. This can
also cause people to have to relocate and leave their homes. Another disadvantage is methane
emissions generated by the reservoirs. Dams and turbines can also hurt fish and disrupt their
migration to spawning grounds.
Fun Facts about Hydropower
There are over 2,000 hydroelectric power plants in the United States.
 Many countries, such as Norway and Brazil, get a significant portion of their
electricity (as much as 85%) from hydropower.
 The largest dam and hydroelectric power plant in the world is the Three Gorges Dam
in China. It provides 22,500 Megawatts of electricity!
 Most of the dams in the United States were not built to supply power. They were built
for flood control and to provide local irrigation.
 A large portion of the hydropower generated in the United States occurs in the
western states. The number one producer of hydropower is Washington state which
produced 29% of the nations hydropower in 2011.
What is biomass energy?
Biomass sounds like a complicated word, but it really isn't. Biomass is just any material made
by plants and animals that we can covert into energy.
Biomass has energy stored in it from the sun. Plants get energy from the sun through a
process called photosynthesis. Animals get their energy indirectly from the sun by eating
Renewable Energy
Biomass energy is considered a renewable energy source because we can always grow more
plants and trees. It is not an infinite resource, however, as there is only so much land and
water to grow plants.
Main Types of Biomass Energy
Biomass Energy comes in many shapes and forms. The majority of biomass energy in the
United States comes from wood. Other popular forms of biomass include crops such as corn,
manure, and even garbage.
How do we get power from biomass?
Burning - One way to release the energy from biomass is to burn it. The heat from
burning biomass can be used to heat homes or to create steam which can then
generate electricity. One example of this is burning a fire in your home. You burn the
wood, which is the biomass, and it releases energy which heats your home.
Methane gas - When biomass rots it produces methane gas. Methane gas can be used
to make natural gas which is a common source of energy. This means that when
garbage rots in landfills, that stinky gas can be used for energy!
Biofuels - Some crops, like corn and sugar cane, can be converted into a biofuel
called ethanol. Ethanol can be used instead of gasoline in many cars. Another type of
biofuel is biodiesel. Biodiesel can be made from vegetable oils and animal fats.
Biodiesel can be used as heating oil and also to power cars and busses.
Methane gas from landfills can be used to generate electricity
History of biomass Energy
Biomass has been used as a source of heat energy since man first discovered fire. Many
people around the world still burn wood as their primary source of heat during the winter.
The use of biofuels such as ethanol has been around for some time as well. It was used as
lamp fuel in the United States in the 1800s. The first Model-T Fords used ethanol for fuel
until 1908. Recently, biomass and biofuels have become popular as an alternative to fossil
fuels such as gasoline.
Are there any drawbacks to biomass energy?
Some of the negatives to using biomass energy include:
Air pollution from burning
 Releasing green house gasses such as carbon dioxide into the atmosphere
 Burning trash and waste can release harmful chemicals and gasses into the
 The land cleared for growing corn and sugar cane can reduce habitats and
destroy ecosystems
 The land used for growing biomass could be used to grow other crops for food
 Growing biomass can use fertilizers and other chemicals that can cause water
Despite all the negatives associated with biomass energy, many people believe that it is a
better and cleaner alternative to burning fossil fuels such as oil and coal.
Fun Facts about biomass Energy
The methane gas from cow manure can be used to create energy.
Most of the gasoline sold in the United States contains some ethanol.
 Garbage is burned for energy as well. This not only makes use of trash for energy, but
reduces the amount of trash that goes into landfills. This process is called Waste-toEnergy.
 Farmers create energy from animal manure using tanks called digesters. The digesters
produce biogas, which can be used to generate electricity.
 The main ingredient needed for ethanol is sugars. These sugars are found in plants
such as corn, rice, sugar cane, barley, switch grass, and even grass clippings.
 Biodiesel is the fastest growing alternative fuel in the United States.
What is geothermal energy?
The inside, or core, of the Earth is very hot. This heat sometimes breaks through to the
surface of the Earth through volcanoes or geysers. When we use heat from the Earth to
generate energy it's called geothermal energy. The name geothermal is a combination of the
word "geo", which means earth, and "thermal", which means heat.
Sustainable Energy
The Earth is constantly being warmed by its core. When we use geothermal energy we don't
use up resources like we do when we burn gas or coal. Although we do use up a tiny bit of
the Earth's heat, it is a very little amount in comparison to the overall heat of the Earth. This
makes geothermal energy a type of sustainable energy.
Geothermal power plants are very clean and have little negative impact on the environment.
Geothermal heat pumps can keep homes warm
How do we get power from the Earth?
There are three main ways that we harness and use geothermal energy:
Geothermal heat pumps - About 10 feet below the surface of the Earth, the ground is a
consistent temperature between 50 and 60° F throughout the year. Geothermal heat
pumps take advantage of this constant temperature to heat or cool water. By moving
water through the Earth it can be heated in the winter or cooled in the summer. This
water can then be used by a heat exchanger to heat or cool the air in a home. This can
be a very efficient and inexpensive way to heat or cool buildings.
Direct use - Another way to take advantage of the Earth's heat is to directly use hot
water from hot springs. This water can be used with heat exchangers to heat up homes
and buildings. It also can be used to heat pools.
Generating electricity - Finally, geothermal energy can be used by power plants to
create electricity. Power plants take advantage of extremely hot water that is between
one and two miles deep in the Earth. Some power plants pipe the steam directly up to
the generator. They are called dry steam power plants. Other power plants, called
flash steam plants, use high pressure from deep in the Earth to create steam to drive
the generator.
Generating electricity using a geothermal power plant
History of Geothermal Energy
The use of geothermal energy is nothing new. People used hot springs as far back as Ancient
China. The Ancient Romans took the concept a step further and used hot springs as a way to
heat flooring and public baths.
The first use of geothermal energy for electricity was in 1904 when the geothermal electric
generator was invented. A few years later, in 1911, the first geothermal electric plant was
built. In the 1940s, the heat pump began to be used for heating buildings, but it didn't become
popular until the 1970s oil crisis.
Are there any drawbacks to geothermal energy?
Probably the main disadvantage to geothermal energy is the cost. It can be very expensive to
build a geothermal plant. Building a plant can also be risky for a power company as the steam
can potentially run out at a given site. The main environmental disadvantage is the possibility
of releasing toxic gasses when the well is drilled into the ground.
Fun Facts about Geothermal Energy
The majority of geothermal electric plants in the United States are found in the
western portion of the country. California is the number one producer, followed by
Nevada, Utah, Hawaii, and Idaho.
 The United States is the largest producer of geothermal electricity.
 In 2011, the Philippines generated around 16% of their total electricity using
geothermal electric plants. Iceland produced 26% of their total electricity using
geothermal energy.
 It is possible for geothermal electric plants to cause earthquakes.
 The best place to find geothermal resources is along plate boundaries. This is also
where you find the most volcanoes and get the most earthquakes.
Wave and Tidal Energy
Turning the energy of the ocean's waves and tides into power that we can use is a new and
unproven technology. However, the potential is there for a significant renewable and
environmentally clean energy source.
What is wave energy?
Wave energy is energy harnessed from the waves of the ocean. Waves are formed by wind
moving across the surface of the ocean. A large amount of energy is stored in waves.
A wave power device
What is tidal energy?
Tidal energy is energy produced by the tides of the ocean. Tides are produced by the pull
of gravityfrom the Moon as well as the spin of the Earth. There is a lot of energy in the
movement of that much water.
Renewable Energy
Wave and tidal power is considered renewable energy because we don't "use up" anything
when we convert their energy to something usable like electricity.
How do we get power from waves?
There are three main ways that scientists think we can capture the power of waves:
Surface devices - These devices gain power from the waves moving them up and
down on the surface of the ocean.
Underwater devices - These devices range from balloon type objects attached to the
ocean floor to long tubes that stretch over a long distance. When the waves cause
them to oscillate, they move a turbine and create electricity.
Reservoir - These devices take advantage of the waves moving water into a reservoir
on the coastline. As water moves back out into the ocean it is forced down a tube and
turns the blades of turbine. The turbine then converts the energy into electricity.
How do we get power from the tides?
There are also three main ways that tidal energy is
Tidal Barrages - A tidal barrage works like a
dam. When the tide goes high, the reservoir
fills up. When the tide drops, the dam lets the
water out. In both directions the moving water
can spin the blades of turbines to create
Tidal Fences - These are smaller structures
than a barrage. A number of vertical turbines
form a fence between two land masses. When
the tide moves in or out, the turbines spin and
generate electricity.
Tidal Turbines - These are individual turbines
placed anywhere there is a strong tidal flow.
History of Wave and Tidal Energy
Concepts for wave energy have existed since the 1800s, however modern wave technology
began in the 1940s with the experiments of scientist Yoshio Masuda. Funding into wave
energy technology has recently increased due to the need for renewable energy sources. The
first wave power plant in the world opened in 2008 at the Agucadoura Wave Farm in
Tidal power to turn water wheels and grind grains was used as far back as Roman times and
the Middle Ages. The idea of using tidal power for electricity is fairly recent, but the costs
have been too high to make it a major energy source. Recent technological advances have
shown that it could become a competitive and viable source.
Are there any drawbacks to wave and tidal energy?
The main disadvantage to these technologies today is cost. The cost of installing and
maintaining a large wave or tidal power plant is too expensive versus other alternatives such
as wind farms. Another drawback is the limited number of locations where current
technologies can be economically installed.
Both wave and tidal energy can also have some effect on the environment. Large tidal
barrages can make it difficult for migrating fish. Also, spinning turbines can injure animals
and fish.
Fun Facts about Wave and Tidal Energy
Tidal turbines are more expensive to build and maintain than wind turbines, but
produce more energy. They also produce energy more consistently as the tide is
continuous while the wind doesn't always blow.
 Wave and tidal energy converters are located near the coastline. It is easier to install,
maintain, capture the energy, and retrieve the energy when they are located close to
the coast.
 The United States has no tidal power plants.
 There are two existing large tidal barrages in the world today. One is in France and
the other in Canada.
Oil (Petroleum)
Oil was formed from the remains of animals and plants that lived millions of
years ago in a marine (water) environment before the dinosaurs. Over the
years, the remains were covered by layers of mud. Heat and pressure from
these layers helped the remains turn into what we today call crude oil. The
word "petroleum" means "rock oil" or "oil from the earth."
Where does Oil come from?
Crude oil is a smelly, yellow-to-black liquid and is usually found in underground areas called
reservoirs. Scientists and engineers explore a chosen area by studying rock samples from the
earth. Measurements are taken, and, if the site seems promising, drilling begins. Above the hole, a
structure called a 'derrick' is built to house the tools and pipes going into the well. When finished, the
drilled well will bring a steady flow of oil to the surface.
Oil was formed from the remains of animals and plants that lived millions of years ago in a marine
(water) environment before the dinosaurs. Over the years, the remains were covered by layers of
mud. Heat and pressure from these layers helped the remains turn into what we today call crude
oil. The word "petroleum" means "rock oil" or "oil from the earth."
How we get Oil?
Crude oil is a smelly, yellow-to-black liquid and is usually found in underground areas called reservoirs.
Scientists and engineers explore a chosen area by studying rock samples from the earth. Measurements
are taken, and, if the site seems promising, drilling begins. Above the hole, a structure called a 'derrick'
is built to house the tools and pipes going into the well. When finished, the drilled well will bring a
steady flow of oil to the surface.
The world's top five crude oil-producing countries are:
• Saudi Arabia
United States
How coal was formed?
Coal is a combustible black or brownish-black sedimentary rock composed mostly of carbon and
hydrocarbons. It is the most abundant fossil fuel produced in the United States.
Coal is a nonrenewable energy source because it takes millions of years to create. The energy in coal
comes from the energy stored by plants that lived hundreds of millions of years ago, when the earth
was partly covered with swampy forests. For millions of years, a layer of dead plants at the bottom of
the swamps was covered by layers of water and dirt, trapping the energy of the dead plants. The heat
and pressure from the top layers helped the plant remains turn into what we today call coal.
How we get coal
Mining the Coal
Coal miners use giant machines to remove coal from the ground. They use two methods: surface or
underground mining. Many U.S. coal beds are very near the ground's surface, and about two-thirds of
coal production comes from surface mines. Modern mining methods allow us to easily reach most of our
coal reserves. Due to growth in surface mining and improved mining technology, the amount of coal
produced by one miner in one hour has more than tripled since 1978.
Surface mining is used to produce most of the coal in the U.S. because it is less expensive than
underground mining. Surface mining can be used when the coal is buried less than 200 feet
underground. In surface mining, giant machines remove the top-soil and layers of rock to expose large
beds of coal. Once the mining is finished, the dirt and rock are returned to the pit, the topsoil is
replaced, and the area is replanted. The land can then be used for croplands, wildlife habitats,
recreation, or offices or stores. Underground mining , sometimes called deep mining, is used when the
coal is buried several hundred feet below the surface. Some underground mines are 1,000 feet deep. To
remove coal in these underground mines, miners ride elevators down deep mine shafts where they run
machines that dig out the coal.
Surface mining:
Underground mining:
Processing the Coal
After coal comes out of the ground, it typically goes on a conveyor belt to a preparation plant that is
located at the mining site. The plant cleans and processes coal to remove dirt, rock, ash, sulfur, and
other unwanted materials, increasing the heating value of the coal.
Natural Gas
Where does Natural Gas come from?
Millions of years ago, the remains of plants and animals decayed and
built up in thick layers. This decayed matter from plants and animals is
called organic material -- it was once alive. Over time, the mud and soil
changed to rock, covered the organic material and trapped it beneath
the rock. Pressure and heat changed some of this organic material into
coal, some into oil (petroleum), and some into natural gas -- tiny
bubbles of odorless gas. The main ingredient in natural gas is methane,
a gas (or compound) composed of one carbon atom and four hydrogen
In some places, gas escapes from small gaps in the rocks into the air; then, if there is enough activation
energy from lightning or a fire, it burns. When people first saw the flames, they experimented with
them and learned they could use them for heat and light.
How we get Natural Gas?
The search for natural gas begins with geologists (people who study the structure of the earth) locating
the types of rock that are usually found near gas and oil deposits.
Today their tools include seismic surveys that are used to find the right places to drill wells. Seismic
surveys use echoes from a vibration source at the earth's surface (usually a vibrating pad under a truck
built for this purpose) to collect information about the rocks beneath. Sometimes it is necessary to use
small amounts of dynamite to provide the vibration that is needed.
Scientists and engineers explore a chosen area by studying rock samples from the earth and taking
measurements. If the site seems promising, drilling begins. Some of these areas are on land but many
are offshore, deep in the ocean. Once the gas is found, it flows up through the well to the surface of the
ground and into large pipelines. Some of the gases that are produced along with methane, such as
butane and propane (also known as 'by-products'), are separated and cleaned at a gas processing
plant. The by-products, once removed, are used in a number of ways. For example, propane can be
used for cooking on gas grills.
Because natural gas is colorless, odorless and tasteless, mercaptan (a chemical that has a sulfur like
odor) is added before distribution, to give it a distinct unpleasant odor (smells like rotten eggs). This
serves as a safety device by allowing it to be detected in the atmosphere, in cases where leaks occur.
Most of the natural gas consumed in the United States is produced in the United States. Some is
imported from Canada and shipped to the United States in pipelines. Increasingly natural gas is also
being shipped to the United States as liquefied natural gas(LNG).
We can also use machines called "digesters" that turn today's organic material (plants, animal wastes,
etc.) into natural gas. This replaces waiting for thousands of years for the gas to form naturally.
How natural gas stored and delivered
The gas companies collect it in huge storage tanks, or underground, in old gas wells. The gas remains
there until it is added back into the pipeline when people begin to use more gas, such as in the winter to
heat homes.
Natural gas is moved by pipelines from the producing fields to consumers. Since natural gas demand is
greater in the winter, gas is stored along the way in large underground storage systems, such as old oil
and gas wells or caverns formed in old salt beds. The gas remains there until it is added back into the
pipeline when people begin to use more gas, such as in the winter to heat homes.
When chilled to very cold temperatures, approximately -260 degrees Fahrenheit, natural gas changes
into a liquid and can be stored in this form. Liquefied natural gas (LNG) can be loaded onto tankers
(large ships with several domed tanks) and moved across the ocean to deliver gas to other
countries. Once in this form, it takes up only 1/600th of the space that it would in its gaseous state.
When this LNG is received in the United States, it can be shipped by truck to be held in large chilled
tanks close to users or turned back into gas to add to pipelines.
When the gas gets to the communities where it will be used(usually through large pipelines), the gas is
measured as it flows into smaller pipelines called "MAINS". Very small lines, called "SERVICES",
connect to the mains and go directly to homes or buildings where it will be used.
Uranium (nuclear)
Nuclear energy is energy in the nucleus (core) of an atom. Atoms are tiny
particles that make up every object in the universe. There is enormous
energy in the bonds that hold atoms together.
Nuclear energy can be used to make electricity. But first the energy must
be released. It can be released from atoms in two ways: nuclear fusion
and nuclear fission.
In nuclear fusion, energy is released when atoms are combined or fused together to form a larger atom.
This is how the sun produces energy.
In nuclear fission, atoms are split apart to form smaller atoms, releasing energy. Nuclear power plants
use nuclear fission to produce electricity.
Nuclear Fuel
Atoms are made up of three major particles: protons, neutrons and electrons. The most common
fissionable atom is an isotope (the specific member of the atom's family) of uranium known as uranium235 (U-235 or U 235 ), which is the fuel used in most types of nuclear reactors today. Although
uranium is quite common, about 100 times more common than silver, U-235 is relatively rare.
Nuclear power plants generate electricity
Most power plants burn fuel to produce electricity, but not nuclear power plants. Instead, nuclear plants
use the heat given off during fission as fuel. Fission takes place inside the reactor of a nuclear power
plant. At the center of the reactor is the core, which contains the uranium fuel.
The uranium fuel is formed into ceramic pellets. The pellets are about the size of your fingertip, but each
one produces the same amount of energy as 150 gallons of oil. These energy-rich pellets are stacked
end-to-end in 12-foot metal fuel rods. A bundle of fuel rods is called a fuel assembly.
Fission generates heat in a reactor just as coal generates heat in a boiler. The heat is used to boil water
into steam. The steam turns huge turbine blades. As they turn, they drive generators that make
electricity. Afterward, the steam is changed back into water and cooled in a separate structure at the
power plant called a cooling tower. The water can be used again and again.
Types of reactors
Just as there are different approaches to designing and building airplanes and automobiles, engineers
have developed different types of nuclear power plants. Most popular of them are: boiling-water reactors
(BWRs), and pressurized-water reactors (PWRs).
In the BWR, the water heated by the reactor core turns directly into steam in the reactor vessel and is
then used to power the turbine-generator. In a PWR, the water passing through the reactor core is kept
under pressure so that it does not turn to steam at all -- it remains liquid. Steam to drive the turbine is
generated in a separate piece of equipment called a steam generator. A steam generator is a giant
cylinder with thousands of tubes in it through which the hot radioactive water can flow. Outside the
tubes in the steam generator, nonradioactive water (or clean water) boils and eventually turns to steam.
The clean water may come from one of several sources: oceans, lakes or rivers. The radioactive water
flows back to the reactor core, where it is reheated, only to flow back to the steam generator.
Nuclear reactors are basically machines that contain and control chain reactions, while releasing heat at
a controlled rate. In electric power plants, the reactors supply the heat to turn water into steam, which
drives the turbine-generators. The electricity is shipped or distributed through transmission lines to
homes, schools, hospitals, factories, office buildings, rail systems and other customers.
Nuclear Steam Supply System:
The reactor core is composed of four main elements:
THE FUEL. Nuclear fuel consists of pellets of enriched uranium dioxide encased in 12-foot long
pencil-thick metal tubes, called fuel rods. These fuel rods are bundled to form fuel assemblies. A
nuclear plant can operate continuously for up to 2 years. To run this long, a reactor must have as
many as 100 to 300 fuel assemblies.
THE CONTROL RODS. The control rods contain material that regulates the rate of the chain
reaction. If they are pulled out of the core, the reaction speeds up. If they are inserted, the
reaction slows down.
THE COOLANT. A coolant, usually water, is pumped through the reactor to carry away the heat
produced by the fissioning of the fuel. This is comparable to the water in the cooling system of a
car, which carries away the heat built up in the engine. In a reactor, as much as 330,000 gallons
of water flow through the reactor core every minute to carry away the heat.
THE MODERATOR. A moderator, water, slows down the speed at which atoms travel. This
reduction in speed actually increases the opportunity to split, thereby releasing energy.
Although engineering designs are quite complex, these four elements -- the fuel, the control rods,
the coolant and the moderator -- are the basic components of a nuclear reactor.
Nuclear power and the environment
Like all industrial processes, nuclear power generation has by-product wastes: radioactive waste and
heat. Nuclear generated electricity does not emit carbon dioxide into the atmosphere.
Radioactive wastes are the principal environmental concern for nuclear power. Most nuclear waste is
low-level nuclear waste. It is ordinary trash, tools, protective clothing, wiping cloths and disposable
items that have been contaminated with small amounts of radioactive dust or particles. These materials
are subject to special regulation that govern their storage so they will not come in contact with the
outside environment.
On the other hand the irradiated fuel assemblies are highly radioactive and must be stored in specially
designed pools resembling large swimming pools (water cools the fuel and acts as a radiation shield) or
in specially designed dry storage containers. Most nuclear fuel is stored under water. A few reactors
store their older and less radioactive fuel in dry storage facilities outside using special concrete or steel
containers with air cooling.
Hydrogen is the chemical element with atomic number 1.
It is represented by the symbol H. At standard
temperature and pressure, hydrogen is a colorless,
odorless, nonmetallic, tasteless, highly flammable
diatomic gas with the molecular formula H2. With an
atomic weight of 1.00794 u, hydrogen is the lightest
Hydrogen is the simplest element known to man. Each
atom of hydrogen has only one proton. It is also the most
plentiful gas in the universe. Stars are made primarily of
The sun is basically a giant ball of hydrogen and helium gases. In the sun's core, hydrogen atoms
combine to form helium atoms. This process—called fusion gives off radiant energy.
This radiant energy sustains life on earth. It gives us light and makes plants grow. It makes the wind
blow and rain fall. It is stored as chemical energy in fossil fuels. Most of the energy we use today came
from the sun's radiant energy.
Hydrogen gas is lighter than air and, as a result, it rises in the atmosphere. This is why hydrogen as a
gas (H2) is not found by itself on earth. It is found only in compound form with other elements.
Hydrogen combined with oxygen, is water (H2O). Hydrogen combined with carbon, forms different
compounds such as methane (CH4), coal, and petroleum. Hydrogen is also found in all growing things—
biomass. It is also an abundant element in the earth's crust.
Hydrogen has the highest energy content of any common fuel by weight(about three times more than
gasoline), but the lowest energy content by volume (about four times less than gasoline). It is the
lightest element, and it is a gas at normal temperature and pressure.
Hydrogen gas, H2, was first artificially produced and formally described by T. Von Hohenheim (also
known as Paracelsus, 1493–1541) via the mixing of metals with strong acids. He was unaware that the
flammable gas produced by this chemical reaction was a new chemical element. In 1671, Robert Boyle
rediscovered and described the reaction between iron filings and dilute acids, which results in the
production of hydrogen gas. In 1766, Henry Cavendish was the first to recognize hydrogen gas as a
discrete substance, by identifying the gas from a metal-acid reaction as "inflammable air" and further
finding in 1781 that the gas produces water when burned. He is usually given credit for its discovery as
an element. In 1783, Antoine Lavoisier gave the element the name hydrogen (from the Greek hydro
meaning water and genes meaning creator) when he and Laplace reproduced Cavendish's finding that
water is produced when hydrogen is burned
Hydrogen and energy carrier
Energy carriers move energy in a usable form from one place to another. Electricity is the most wellknown energy carrier. We use electricity to move the energy in coal, uranium, and other energy sources
from power plants to homes and businesses. We also use electricity to move the energy in flowing water
from hydropower dams to consumers. It is much easier to use electricity than the energy sources
Like electricity, hydrogen is an energy carrier and must be produced from another substance. Hydrogen
is not widely used today but it has great potential as an energy carrier in the future. Hydrogen can be
produced from a variety of resources (water, fossil fuels, biomass) and is a byproduct of other chemical
processes. Unlike electricity, large quantities of hydrogen can be easily stored to be used in the future.
Hydrogen can also be used in places where it’s hard to use electricity. Hydrogen can store the energy
until it’s needed and can be moved to where it’s needed.
How is hydrogen made
Since hydrogen doesn't exist on earth as a gas, we must separate it from other elements. We can
separate hydrogen atoms from water, biomass, or natural gas molecules. The two most common
methods for producing hydrogen are steam reforming and electrolysis (water splitting). Scientists have
even discovered that some algae and bacteria give off hydrogen.
Steam reforming is currently the least expensive method of producing hydrogen and accounts for about
95 percent of the hydrogen produced in the United States. It is used in industries to separate hydrogen
atoms from carbon atoms in methane(CH4). Because methane is a fossil fuel, the process of steam
reforming results in greenhouse gas emissions that are linked with global warming.
Electrolysis is a process that splits hydrogen from water. It results in no emissions but it is currently a
very expensive process. New technologies are being developed all the time.
Hydrogen can be produced at large central facilities or at small plants for local use. Every region of the
country (and the world) has some resource that can be used to make hydrogen. Its flexibility is one of
its main advantages.
About 9 million metric tonnes of hydrogen are produced in the United States today, enough to power
20-30 million cars or 5-8 million homes. Nearly all of this hydrogen is used by industry in refining,
treating metals, and processing foods. Most of this hydrogen is produced in just three states: California,
Louisiana, and Texas.
The National Aeronautics and Space Administration (NASA) is the primary user of hydrogen as an
energy fuel; it has used hydrogen for years in the space program. Liquid hydrogen fuel lifts the space
shuttle into orbit. Hydrogen batteries—called fuel cells—power the shuttle’s electrical systems. The only
by-product is pure water, which the crew uses as drinking water.
Hydrogen Fuel CellHydrogen fuel cells (batteries) make electricity. They are very efficient, but expensive
to build. Small fuel cells can power electric cars. Large fuel cells can provide electricity in out of the way
places with no power lines.
Because of the high cost to build fuel cells, large hydrogen power plants won't be built for a while.
However, fuel cells are being used in some places as a source of emergency power to hospitals and to
wilderness locations. Portable fuel cells are being sold to provide longer power for laptop computers, cell
phones, and military applications.
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