What is Energy.doc

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What is Energy?Energy is the Ability To Do Work

It comes in different forms -- heat (thermal), light (radiant), mechanical, electrical,

chemical, and nuclear energy. Energy is in everything. We use energy to do everythingwe do, from making a jump shot to baking our favorite cookies to sending astronauts into

space -- energy is there, making sure we have the power to do it all. There are two types

of energy -- stored (potential) energy and working (kinetic) energy. For example, the

food you eat contains chemical energy, and your body stores this energy until you releaseit when you work or play. Learn more about these different forms of energy.

All forms of energy are stored in different ways, in the energy sources that we use every

day. These sources are divided into two groups -- renewable(an energy source that can

be replenished in a short period of time) and nonrenewable (an energy source that we areusing up and cannot recreate in a short period of time). Renewable and nonrenewable

energy sources can be used to produce secondary energy sources including electricity andhydrogen.

Renewable energy sources include solarenergy, which comes from the sun and can be

turned into electricity and heat. Wind, geothermalenergy from inside the earth,biomass

from plants, and hydropowerand ocean energy from water are also renewable energy

sources.
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However, we get most of our energy from nonrenewable energy sources, which include

the fossil fuels -- oil, natural gas, and coal. They're called fossil fuels because they were

formed over millions and millions of years by the action of heat from the Earth's core andpressure from rock and soil on the remains (or "fossils") of dead plants and animals.

Another nonrenewable energy source is the element uranium, whose atoms we split

(through a process called nuclear fission) to create heat and ultimately electricity.

We use all these energy sources to generate the electricity we need for our homes,businesses, schools, and factories. Electricity "energizes" our computers, lights,

refrigerators, washing machines, and air conditioners, to name only a few uses.

We use energy to run our cars and trucks. Both the gasolineused in our cars, and thediesel fuel used in our trucks are made from oil. Thepropanethat fuels our outdoor grills

and makes hot air balloons soar is made from oil and natural gas.

Scientific Forms of Energy

Materials developed by the National Energy Education Development Project (NEED)

What is Energy?

Forms of Energy

Law of Conservation of EnergyEnergy Efficiency

Sources of Energy

What is energy?

Energy makes change; it does things for us. It moves cars along the road and boats over

the water. It bakes a cake in the oven and keeps ice frozen in the freezer. It plays ourfavorite songs on the radio and lights our homes. Energy makes our bodies grow and

allows our minds to think. Scientists define energy as the ability to do work. People have

learned how to change energy from one form to another so that we can do work moreeasily and live more comfortably.

Forms of Energy

Energy is found in different forms, such as light, heat, sound and motion. There are many

forms of energy, but they can all be put into two categories: kinetic and potential.
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Conservation of energy

To scientists, conservation of energy is not saving energy. The law of conservation ofenergy says that energy is neither created nor destroyed. When we use energy, it doesnt

disappear. We change it from one form of energy into another.

A car engine burns gasoline, converting the chemical energy in gasoline into mechanical

energy. Solar cells change radiant energy into electrical energy. Energy changes form,but the total amount of energy in the universe stays the same. Scientists at the Department

of Energy think they have discovered a mysterious new form of energy called "dark

energy" that is actually causing the universe to grow!

Energy Efficiency

Energy efficiency is the amount of useful energy you get from a system. A perfect,

energy-efficient machine would change all the energy put in it into useful workan

impossible dream. Converting one form of energy into another form always involves aloss of usable energy.


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In fact, most energy transformations are not very efficient. The human body is a good

example.

Your body is like a machine, and the fuel for your machine is food. Food gives you theenergy to move, breathe, and think. But your body isnt very efficient at converting food

into useful work. Your body is less than five percent efficient most of the time. The restof the energy is lost as heat. You can really feel that heat when you exercise!

Sources of energy

We use many different energy sources to do work for us. Energy sources are classified

into two groupsrenewable and nonrenewable. Renewable and nonreneable energy can

be converted into secondary energy sources like electricity and hydrogen.

In the United States, most of our energy comes from nonrenewable energy sources. Coal,petroleum, natural gas, propane, and uranium are nonrenewable energy sources. They are

used to make electricity, to heat our homes, to move our cars, and to manufacture all

kinds of products.


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These energy sources are called nonrenewable because their supplies are limited.

Petroleum, for example, was formed millions of years ago from the remains of ancient

sea plants and animals. We cant make more petroleum in a short time.

Renewable energy sources include biomass, geothermal energy, hydropower, solar

energy, and wind energy. They are called renewable energy sources because they arereplenished in a short time. Day after day, the sun shines, the wind blows, and the rivers

flow. We use renewable energy sources mainly to make electricity.

Electricity and hydrogen are different from the other energy sources because they are

secondary sources of energy. Secondary sources of energyenergy carriers are used

to store, move, and deliver energy in easily usable form. We have to use another energysource to make electricity or hydrogen. In the United States, coal is the number one

energy source for generating electricity. Today the cheapest way to get hydrogen is by

separating it from natural gas, a nonrenewable energy source. Hydrogen can also be

separated from water and from renewables but hydrogen made from these sources is

currently too expensive to compete with other fuels. Scientists are working on ways tomake hydrogen from water and renewables more affordable.

Petroleum(Oil) -- A Fossil Fuel

How Oil Was FormedWhere We Get Oil

Crude Oil is Made into Different Fuels - like gasoline, diesel, andpropane

Oil and the Environment
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HOW OIL WAS FORMED

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 werecovered 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 fromthe earth."

WHERE 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

Russia

United States

Iran

China


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processing the crude oil is similar to what happens to popcorn, it gets bigger after it ispopped.

note: The gain from processing is about 5%.

One barrel of crude oil, when refined, produces about 20 gallons of finished motor

gasoline, and 7 gallons of diesel, as well as other petroleum products. Most of the

petroleum products are used to produce energy. For instance, many people across the
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United States usepropane to heat their homes and fuel their cars. Other products made

from petroleum include: ink, crayons, bubble gum, dishwashing liquids, deodorant,

eyeglasses, records, tires, ammonia, and heart valves.

OIL AND THE ENVIRONMENT

Products from oil (petroleum products) help us do many things. We use them to fuel our

airplanes, cars, and trucks, to heat our homes, and to make products like medicines and

plastics. Even though petroleum products make life easier - finding, producing, moving,and using them can cause problems for our environment like air and water pollution.

Over the years, new technologies and laws have helped to reduce problems related to

petroleum products. As with any industry, the government monitors how oil is produced,refined, stored, and sent to market to reduce the impact on the environment. Since 1990,

fuels like gasoline and diesel fuel have also been improved so that they produce less

pollution when we use them.

Exploring and drilling for oil may disturb land and ocean habitats. New technologieshave greatly reduced the number and size of areas disturbed by drilling, sometimes called

"footprints." Satellites, global positioning systems, remote sensing devices, and 3-D and

4-D seismic technologies,make it possible to

discover oil reserves while

drilling fewer wells. Plus, theuse of horizontal and

directional drilling make it

possible for a single well to

produce oil from much

bigger areas. Today'sproduction footprints are

only about one-
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fourth the size of those 30 years ago, due to the development of movable drilling rigs and

smaller "slimhole" drilling rigs. When the oil in a well is gone, the well must be plugged

below ground, making it hard to tell that it was ever there. As part of the "rig-to-reefs"program, some old offshore rigs are toppled and left on the sea floor to become artificial

reefs that attract fish and other marine life. Within six months to a year after a rig is

toppled, it becomes covered with barnacles, coral, sponges, clams, and other seacreatures.

If oil is spilled into rivers or oceans it can harm wildlife.When we talk about "oil spills"

people usually think about oil that leaks from ships when they crash. Although this type

of spill can cause the biggest shock to wildlife because so much oil is released at onetime, only 2 percent of all oil in the sea comes from ship or barge spills. The amount of

oil spilled from ships dropped a lot during the 1990's partly because new ships were

required to have a "double-hull" lining to protect against spills. While oil spills fromships are the most well-known problem with oil, more oil actually gets into water from

natural oil seeps coming from the ocean floor. Or, from leaks that happen when we use

petroleum products on land. For example, gasoline that sometimes drips onto the groundwhen people are filling their gas tanks, motor oil that gets thrown away after an oil

change, or fuel that escapes from a leaky storage tank. When it rains, the spilled products

get washed into the gutter and eventually go to rivers and the ocean. Another way that oil

sometimes gets into water is when fuel is leaked from motorboats and jet skis.

A refinery is a factory where crude oil is processed into petroleum products. Because

many different pollutants can escape from refineries into the air, the government

monitors refineries and other factories to make sure that they meet environmental

standards.

When a leak in a storage tank or pipeline occurs, petroleum products can also get into theground, and the ground must be cleaned up. To prevent leaks from underground storage

tanks, all buried tanks are supposed to be replaced by tanks with a double-lining. Thishasn't happened everywhere yet. In some places where gasoline leaked from storage

tanks, one of the gasoline ingredients called methyl tertiary butyl ether (MTBE) made its

way into local water supplies. Since MTBE made water taste bad and many people were

worried about drinking it, a number of states banned the use of MTBE in gasoline, andthe refining industry voluntarily moved away from using it when blending reformulated

gasoline.

Gasoline is used in cars, diesel fuel is used in trucks, and heating oil is used to heat our

homes. When petroleum products are burned as fuel, they give off carbon dioxide, agreenhouse gas that is linked with global warming. The use of petroleum products also

gives off pollutants - carbon monoxide, nitrogen oxides, particulate matter, and unburned

hydrocarbons - that help form air pollution. Since a lot of air pollution comes from carsand trucks, many environmental laws have been aimed at changing the make-up of

gasoline and diesel fuel so that they produce fewer emissions. These "reformulated fuels"

are much cleaner-burning than gasoline and diesel fuel were in 1990. In the next few
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years, the amount of sulfur contained in gasoline and diesel fuel will be reduced

dramatically so that they can be used with new, less-polluting engine technology.

Natural Gas -- A Fossil Fuel

How Natural Gas Was FormedHow We Get Natural Gas

How Natural Gas is Stored and DeliveredHow Natural Gas is Measured

What Natural Gas is Used For

Natural Gas and the Environment

HOW NATURAL GAS WAS FORMED

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 materialand 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 ofone carbon atom and four hydrogen atoms.

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.
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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 earths surface (usually

a vibrating pad under a truck built for this purpose) to collect information about the rocksbeneath. 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 theseareas 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 knownas '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 (smellslike 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 IS 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.
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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 gasremains 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) canbe 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 intogas 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". Verysmall lines, called "SERVICES", connect to the mains and go directly to homes or

buildings where it will be used.

HOW NATURAL GAS IS MEASURED

We measure and sell natural gas in cubic feet (volume) or inBritish Thermal Units

(heat content). Heat from all energy sources can be measured and converted back and

forth between British thermal units (Btu) and metric units. See theEnergy Calculatorfor

help with converting natural gas units.

One Btu is the heat required to raise the temperature of one pound of water one degree

Fahrenheit. Ten burning kitchen matches release 10 Btu. One cubic foot of natural gas

has about 1031 Btu. A box 10 feet deep, 10 feet long, and 10 feet wide would hold one

thousand cubic feet of natural gas.
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For example, a candy bar has about 1000 Btu.

Pipeline companies buy natural gas in thousands of cubic feet or Mcf. M = one thousand.

WHAT NATURAL GAS IS USED FOR

Approximately 22 percent of the energy consumption of the U.S. comes from natural gas.

Over one-half of the homes in the U.S. use natural gas as their main heating fuel.

Natural gas is also an essential raw material for many common products, such as: paints ,

fertilizer, plastics, antifreeze, dyes, photographic film, medicines, and explosives. Wealso getpropane, a fuel we use in many of our backyard barbecue grills, when we process

natural gas.

Industry depends on it. Natural gas has thousands of uses. It's used to produce steel,

glass, paper, clothing, brick, electricity and much more!

Homes use it too. More than 62.5 percent of homes use natural gas to fuel stoves,

furnaces, water heaters, clothes dryers and other household appliances. It is also used to

roast coffee, smoke meats, bake bread and much more.

NATURAL GAS AND THE ENVIRONMENT

Natural gas burns more cleanly than other fossil fuels. It has fewer emissions of sulfur,carbon, and nitrogen than coal or oil, and it has almost no ash particles left after burning.

Being a clean fuel is one reason that the use of natural gas, especially for electricity

generation, has grown so much and is expected to grow even more in the future.
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Of course, there are environmental concerns with the use of any fuel. As with other fossil

fuels, burning natural gas produces carbon dioxide, which is the most important

greenhouse gas. Many scientists believe that increasing levels of carbon dioxide andother greenhouse gases in the earths atmosphere are changing the global climate.

As with other fuels, natural gas also affects the environment when it is produced, storedand transported. Because natural gas is made up mostly of methane (another greenhouse

gas), small amounts of methane can sometimes leak into the atmosphere from wells,storage tanks and pipelines. The natural gas industry is working to prevent any methane

from escaping. Exploring and drilling for natural gas will always have some impact on

land and marine habitats. But new technologies have greatly reduced the number and sizeof areas disturbed by drilling, sometimes called "footprints." Satellites, global positioning

systems, remote sensing devices, and 3-D and 4-D seismic technologies, make it possible

to discover natural gas reserves while drilling fewer wells. Plus, the use of horizontal anddirectional drilling make it possible for a single well to produce gas from much bigger

areas.

Natural gas pipelines and storage facilities have a very good safety record. This is very

important because when natural gas leaks it can cause explosions. Since raw natural gashas no odor, natural gas companies add a smelly substance to it so that people will know

if there is a leak. If you have a natural gas stove, you may have smelled this rotten egg

smell of natural gas when the pilot light has gone out.

COAL -- A Fossil Fuel

How Coal Was Formed

How We Get Coal

How Coal is TransportedTypes of Coal

Where We Get Coal

How Coal is UsedCoal and the Environment

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 UnitedStates.

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.
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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 surfacemining and improved mining technology, the amount of coal produced by one miner in

one hour has more than tripled since 1978.


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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-soiland 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 buriedseveral 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. Read about a visit to a real undergroundcoal mine.

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.

TRANSPORTING COAL

After coal is mined and processed,it is ready to be shipped to market.

The cost of shipping coal can cost

more than the cost of mining it.

Most coal is transported by train,but coal can also be transported by

barge, ship, truck, and even

pipeline. About 68 percent of coalin the U.S. is transported, for at

least part of its trip to market, by

train. It is cheaper to transport coalon river barges, but barges cannot

take coal everywhere that it needs

to go. If the coal will be used near

the coal mine, it can be moved bytrucks and conveyors. Coal can

also be crushed, mixed with water, and sent through a "slurry" pipeline. Sometimes, coal-

fired electric power plants are built near coal mines to lower transportation costs.

TYPES OF COAL

Coal is classified into four main types, or ranks (lignite, subbituminous, bituminous,

anthracite), depending on the amounts and types of carbon it contains and on the amount
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of heat energy it can produce. The rank of a deposit of coal depends on the pressure and

heat acting on the plant debris as it sank deeper and deeper over millions of years. For the

most part, the higher ranks of coal contain more heat-producing energy.

Lignite is the lowest rank of coal with the lowest energy content. Lignite coal deposits

tend to be relatively young coal deposits that were not subjected to extreme heat orpressure. Lignite is crumbly and has high moisture content. There are 21 lignite mines in

the United States, producing about seven percent of U.S. coal. Most lignite is mined inTexas and North Dakota. Lignite is mainly burned at power plants to generate electricity.

Subbituminous coal has a higher heating value than lignite. Subbituminous coal

typically contains 35-45 percent carbon, compared to 25-35 percent for lignite. Mostsubbituminous coal in the U.S. is at least 100 million years old. About 42 percent of the

coal produced in the United States is subbituminous. Wyoming is the leading source of

subbituminous coal.

Bituminous coal contains 45-86 percent carbon, and has two to three times the heatingvalue of lignite. Bituminous coal was formed under high heat and pressure. Bituminous

coal in the United States is between 100 to 300 million years old. It is the most abundant

rank of coal found in the United States, accounting for about half of U.S. coal production.

Bituminous coal is used to generate electricity and is an important fuel and raw materialfor the steel and iron industries. West Virginia, Kentucky, and Pennsylvania are the

largest producers of bituminous coal.

Anthracite contains 86-97 percent carbon, and has a heating value slightly lower thanbituminous coal. It is very rare in the United States, accounting for less than one-half of

a percent of the coal mined in the U.S. All of the anthracite mines in the United States

are located in northeastern Pennsylvania.

WHERE WE GET COAL

Coal reserves are beds of coal still in the ground waiting to be mined. The United States

has the world's largest known coal reserves, about 267.6 billion short tons. This is

enough coal to last approximately 236 years at today's level of use.

Coal production is the amount of coal that is mined and sent to market. In 2005, theamount of coal produced at U.S. coal mines reached an all time high of 1,131.5 million

short tons. Coal is mined in 27 states. Wyoming mines the most coal, followed by West

Virginia, Kentucky, Pennsylvania, and Texas.Coal is mainly found in three large regions,the Appalachian Coal Region, the Interior Coal Region, and Western Coal Region

(includes the Powder River Basin).
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Coal Production in Three Regions,2005Millions of Short Tons

1,131.5 million short tons

Appalachian Coal Region:

More than one-third of the coal produced in the U.S. is produced in the

Appalachian Coal Region.

West Virginia is the largest coal-producing state in the region, and the second

largest coal-producing state in the U.S.

Large underground mines and small surface mines.

Coal mined in the Appalachian coal region is primarily used for steam generation

for electricity, metal production, and for export.

Interior Coal Region:

In 2005, Texas was the largest coal producer in the Interior Coal Region,

accounting for about one-third of the regions coal production.

Mid-sized surface mines.

Mid- to large-sized companies.

Western Coal Region:

Over half of the coal produced in the U.S. is produced in the Western Coal

Region.

Wyoming is the largest regional coal producer, as well as the largest coal-

producing state in the nation.


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Large surface mines.

Some of the largest coal mines in the world.

HOW COAL IS USED

About 92 percent of the coal used in the United States, is for generating electricity.Except for a small amount of net exports, the rest of the coal is used, as a basic energy

source in many industries, including, steel, cement and paper. The four major uses of

coal are:

FOR ELECTRIC POWER

Coal is used to generate roughly half of all electricity produced in the United States.

Besides electric utility companies, industries and businesses with their own power plants

use coal to generate electricity. Power plants burn coal to make steam. The steam turns

turbines which generateelectricity.

FOR INDUSTRY

A variety of industries use coal's heat and by-products. Separated ingredients of coal

(such as methanol and ethylene) are used in making plastics, tar, synthetic fibers,

fertilizers, and medicines. The concrete and paper industries also burn large amounts ofcoal.

FOR MAKING STEEL

Coal is baked in hot furnaces to make coke, which is used to smelt iron ore into iron

needed for making steel. It is the very high temperatures created from the use of coke thatgives steel the strength and flexibility for products such as bridges, buildings, and

automobiles.

FOR EXPORT

In 2005, 49.9 million short tons, or about four percent of the coal mined, was exported to

other countries from the United States. Coal is exported to many different countries, butmost trade is with Canada, Brazil, the Netherlands, and Italy. More than half of coal

exports are used for making steel.

Coal exports have been generally shrinking in the past 10 years, while the amount of coalimported from other countries has been growing. In 2005, about 30.5 million short tonsof coal were imported from other countries. Most of these imports (from Colombia,

Venezuela, and Indonesia) were shipped to electric power producers along the U.S.

coastlines. Read about a visit to a coal export facility.

COAL AND THE ENVIRONMENT
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Environmental laws and modern technologies have greatly reduced coal's impact on the

environment. Without proper care, mining can destroy land and pollute water. Today,

restoring the land damaged by surface mining is an important part of the mining process.Because mining activities often come into contact with water resources, coal producers

must also go to great efforts to prevent damage to ground and surface waters.

When coal is burned as fuel, it gives off carbon dioxide, the main greenhouse gas that is

linked with global warming. Burning coal also produces emissions, such as sulfur,nitrogen oxide (NOx), and mercury, that can pollute the air and water. Sulfur mixes with

oxygen to form sulfur dioxide (SO2), a chemical that can affect trees and water when it

combines with moisture to produce acid rain. Emissions of nitrogen oxide help createsmog, and also contribute to acid rain. Mercury that is released into the air eventually

settles in water. The mercury in the water can build up in fish and shellfish, and can be

harmful to animals and people who eat them. The Clean Air Act and the Clean Water Actrequire industries to reduce pollutants released into the air and the water.

The coal industry has found several ways to reduce sulfur, nitrogen oxides, and otherimpurities from coal. They have found more effective ways of cleaning coal before it

leaves the mine, and coal companies look for low-sulfur coal to mine. Power plants use"scrubbers" to clean sulfur from the smoke before it leaves their smokestacks. In addition,

industry and government have cooperated to develop "clean coal technologies" that either

remove sulfur and nitrogen oxides from coal, or convert coal to a gas or liquid fuel. Thescrubbers and NOx removal equipment are also able to reduce mercury emissions from

some types of coal. Scientists are working on new ways to reduce mercury emissions

from coal-burning power plants, since the Environmental Protection Agency (EPA) has

set tighter mercury limits for the future.

NUCLEAR ENERGY (URANIUM) ENERGY FROM ATOMSNuclear Energy is Energy from Atoms

Nuclear Fuel- UraniumNuclear Power Plants Generate Electricity

Types of Reactors

Nuclear Power and the Environment

links pagerecent statistics

NUCLEAR ENERGY IS ENERGY FROM ATOMS

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.
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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.

Innuclear fusion, energy is released when atoms are combined or fused

together to form a larger atom. This is how the sun produces energy.

Innuclear fission, atoms are split apart to form smaller atoms, releasing

energy. Nuclear power plants use nuclear fission to produce electricity.

NUCLEAR FUEL - URANIUM

The fuel most widely used by nuclear plants for nuclear fission is uranium.

Uranium is nonrenewable, though it is a common metal found in rocks all overthe world. Nuclear plants use a certain kind of uranium, U-235, as fuel because

its atoms are easily split apart. Though uranium is quite common, about 100

times more common than silver, U-235 is relatively rare. Most U.S. uranium

is mined, in the Western United States. Once uranium is mined the U-235 must

be extracted and processed before it can be used as a fuel.

During nuclear fission, a small particle called a neutron hits the uranium atom

and splits it, releasing a great amount of energy as heat and radiation. More

neutrons are also released. These neutrons go on to bombard other uranium

atoms, and the process repeats itself over and over again. This is called a chainreaction.
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NUCLEAR POWER PLANTS GENERATE

ELECTRICITY

Nuclear power accounts for about 19 percent of the total net electricity

generated in the United States, about as much as the electricity used inCalifornia,Texas and New York, the three states with the most people. In 2006,

there were 66 nuclear power plants (composed of 104 licensed nuclear reactors)

throughout the United States.

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 sizeof 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.

Two types are used in the United States: 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 doesnot 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


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radioactive water flows back to the reactor core, where it is reheated, only to

flow back to the steam generator. Roughly seventy percent of the reactors

operating in the U.S. are PWR.

Nuclear reactors are basically machines that contain and control chain

reactions, while releasing heat at a controlled rate. In electric power plants, thereactors supply the heat to turn water into steam, which drives the turbine-

generators. The electricity travels through high voltage transmission lines and

low voltage distribution lines to homes, schools, hospitals, factories, office

buildings, rail systems and other users.

NUCLEAR POWER AND THE ENVIRONMENT

Compared to electricity generated by burning fossil fuels, nuclear energy is clean.

Nuclear power plants produce no air pollution or carbon dioxide but a small amount of

emissions result from processing the uranium that is used in nuclear reactors.

Like all industrial processes, nuclear power generation has by-product wastes: spent(used) fuels, other radioactive waste, and heat. Spent fuels and other radioactive wastes

are the principal environmental concern for nuclear power. Most nuclear waste is low-

level radioactive waste. It consists of ordinary tools, protective clothing, wiping cloths

and disposable items that have been contaminated with small amounts of radioactive dustor particles. These materials are subject to special regulation that govern their disposal so

they will not come in contact with the outside environment.

On the other hand, the spent fuel assemblies are highly radioactive and must initially bestored 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. An

increasing number of reactor operators now store their older and less spent fuel in dry


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storage facilities using special outdoor concrete or steel containers with air cooling. The

United States Department of Energy's long range plan is for this spent fuel to be stored

deep in the earth in a geologic repository, at Yucca Mountain, Nevada.

Renewable Energy

Renewable energy sources can be replenished in a short period of time. The five

renewable sources used most often are:

o biomass

o

water (hydropower),o geothermal,

o wind,

o solar.

Many important events have occurred during the history of using renewable sources. The

use of renewable energy is not new. Five generations (125 years) ago, wood supplied upto 90 percent of our energy needs. Due to the convenience and low prices of fossil fuels,
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wood use has fallen in the United States. Now, some biomass that would normally be

taken to the dump is converted into electricity (e.g., manufacturing wastes, rice hulls, and

black liquor from paper production).

Overall consumption from renewable sources in the United States totaled 6.8 quads

(quadrillion Btu) in 2006, or about 7 percent of all energy used nationally. Consumptionfrom renewable sources was at its highest point in 1997, at about 7.2 quads.

Historically, low fossil fuel prices, especially for natural gas, have made growth difficultfor renewable fuels. A number of State and Federal Government incentives, including the

Energy Policy Acts of 2002 and 2005, have encouraged the production and use of

renewable fuels. Even with these incentives, the renewables share of the "energy pie" inthe United States is not expected to change much over the next 25 years because we will

also be using more non-renewable fuels. The use of renewable sources is also limited by

the fact that they are not always available (for example, cloudy days reduce solar energy,

calm days mean no wind blows to drive wind turbines, droughts reduce water availability

to produce hydroelectricity). Despite these limitations, renewable energy plays animportant role in the supply of energy. When renewable energy sources are used, the

demand for fossil fuels is reduced. Unlike fossil fuels, most renewable sources do notdirectly emit greenhouse gases.

Each of the energy sources we use is measured, purchased, and sold in a different form.

Many units of measurement are used to measure the energy we use each day. Learn more

about converting energy units in the Units of Measurementsection.

Nonrenewable Energy

Nonrenewable energy sources come out of the ground as liquids, gases and solids. Rightnow, crude oil(petroleum) is the only naturally liquid commercial fossil fuel.Natural gas

and propane are normally gases, and coal is a solid. Coal, petroleum, natural gas, andpropane are all considered fossil fuels because they formed from the buried remains of

plants and animals that lived millions of years ago. Uranium ore, a solid, is mined and

converted to a fuel. Uranium is not a fossil fuel. These energy sources are considerednonrenewable because they can not be replenished (made again) in a short period of

time. Renewable energy sources can be replenished naturally in a short period of time.

Solar Energy -- Energy from the Sun

Energy from the SunPhotovoltaic Energy

Solar Thermal Energy

Solar Thermal Power Plants -parabolic trough, solar dish, and solar power tower

ENERGY FROM THE SUN
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The sun has produced energy for billions of years. Solar energy is the suns rays (solar

radiation) that reach the earth.

Solar energy can be converted into other forms of energy, such as heat and electricity. Inthe 1830s, the British astronomer John Herschel used a solar thermal collector box (a

device that absorbs sunlight to collect heat) to cook food during an expedition to Africa.Today, people use the sun's energy for lots of things.

Solar energy can be converted to thermal (or heat) energy and used to:

Heat water for use in homes, buildings, or swimming pools.

Heat spaces inside greenhouses, homes, and other buildings.

Solar energy can be converted to electricity in two ways:

Photovoltaic (PV devices) or solar cells change sunlight directly into

electricity. PV systems are often used in remote locations that are not connectedto the electric grid. They are also used to power watches, calculators, and lighted

road signs.

Solar Power Plants - indirectly generate electricity when the heat from solar

thermal collectors is used to heat a fluid which produces steam that is used topower generator. Out of the 15 known solar electric generating units operating in

the United States at the end of 2006, 10 of these are in California, and 5 in

Arizona. No statistics are being collected on solar plants that produce less than 1

megawatt of electricity, so there may be smaller solar plants in a number of otherstates.

The major disadvantages of solar energy are:

The amount of sunlight that arrives at the earth's surface is not constant. It

depends on location, time of day, time of year, and weather conditions.

Because the sun doesn't deliver that much energy to any one place at any one

time, a large surface area is required to collect the energy at a useful rate.

PHOTOVOLTAIC ENERGY

Photovoltaic energy is the conversion of sunlight into electricity. A photovoltaic cell,

commonly called a solar cell or PV, is the technology used to convert solar energy

directly into electrical power. A photovoltaic cell is a nonmechanical device usuallymade from silicon alloys.


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Sunlight is composed of photons, or particles of solar energy. These photons contain

various amounts of energy corresponding to the different wavelengths of the solarspectrum. When photons strike a photovoltaic cell, they may be reflected, pass right

through, or be absorbed. Only the absorbed photons provide energy to generateelectricity. When enough sunlight (energy) is absorbed by the material (a

semiconductor), electrons are dislodged from the material's atoms. Special treatment of

the material surface during manufacturing makes the front surface of the cell morereceptive to free electrons, so the electrons naturally migrate to the surface.

When the electrons leave their position, holes are formed. When many electrons, each

carrying a negative charge, travel toward the front surface of the cell, the resulting

imbalance of charge between the cell's front and back surfaces creates a voltage potential

like the negative and positive terminals of a battery. When the two surfaces areconnected through an external load, electricity flows.

The photovoltaic cell is the basic building block of a photovoltaic system. Individualcells can vary in size from about 1 centimeter (1/2 inch) to about 10 centimeter (4 inches)

across. However, one cell only produces 1 or 2 watts, which isn't enough power for most

applications. To increase power output, cells are electrically connected into a packagedweather-tight module. Modules can be further connected to form an array. The term

array refers to the entire generating plant, whether it is made up of one or several


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thousand modules. The number of modules connected together in an array depends on

the amount of power output needed.

The performance of a photovoltaic array is dependent upon sunlight. Climate conditions(e.g., clouds, fog) have a significant effect on the amount of solar energy received by a

photovoltaic array and, in turn, its performance. Most current technology photovoltaicmodules are about 10 percent efficient in converting sunlight. Further research is being

conducted to raise this efficiency to 20 percent.

The photovoltaic cell was discovered in 1954 by Bell Telephone researchers examining

the sensitivity of a properly prepared silicon wafer to sunlight. Beginning in the late

1950s, photovoltaic cells were used to power U.S. space satellites (learn more about thehistory of photovaltaic cells). The success of PV in space generated commercial

applications for this technology. The simplest photovoltaic systems power many of the

small calculators and wrist watches used everyday. More complicated systems provide

electricity to pump water, power communications equipment, and even provide electricity

to our homes.

Some advantages of photovoltaic systems are:

1. Conversion from sunlight to electricity is direct, so that bulky mechanical

generator systems are unnecessary.2. PV arrays can be installed quickly and in any size required or allowed.

3. The environmental impact is minimal, requiring no water for system cooling and

generating no by-products.

Photovoltaic cells, like batteries, generate direct current (DC) which is generally used forsmall loads (electronic equipment). When DC from photovoltaic cells is used forcommercial applications or sold to electric utilities using the electric grid, it must be

converted to alternating current (AC) using inverters, solid state devices that convert DC

power to AC.

Historically, PV has been used at remote sites to provide electricity. In the future PV

arrays may be located at sites that are also connected to the electric grid enhancing the

reliability of the distribution system.

SOLAR THERMAL HEAT

Solar thermal(heat) energy is often used for heating swimming pools, heating water used

in homes, and space heating of buildings. Solar space heating systems can be classified as

passive oractive.

Passive space heating is what happens to your car on a hot summer day. In buildings, theair is circulated past a solar heat surface(s) and through the building by convection (i.e.

less dense warm air tends to rise while more dense cooler air moves downward) . No
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mechanical equipment is needed for

passive solar heating.

Active heating systems require a collector to absorb and collect solar radiation. Fans or

pumps are used to circulate the heated air or heat absorbing fluid. Active systems ofteninclude some type of energy storage system.

Solar collectors can be eithernonconcentrating orconcentrating.

1) Nonconcentrating collectors have a collector area (i.e. the area that intercepts the

solar radiation) that is the same as the absorber area (i.e., the area absorbing the

radiation). Flat-plate collectors are the most common and are used when temperaturesbelow about 200o degrees F are sufficient, such as for space heating.

2) Concentrating collectors where the area intercepting the solar radiation is greater,

sometimes hundreds of times greater, than the absorber area.

SOLAR THERMAL POWER PLANTS

Solar thermal power plants use the sun's rays to heat a fluid, from which heat transfer

systems may be used to produce steam. The steam, in turn, is converted into mechanical

energy in a turbine and into electricity from a conventional generator coupled to the

turbine. Solar thermal power generation works essentially the same as generation fromfossil fuels except that instead of using steam produced from the combustion of fossil

fuels, the steam is produced by the heat collected from sunlight. Solar thermal

technologies use concentrator systems due to the high temperatures needed to heat thefluid. The three main types of solar-thermal power systems are:

Parabolic trough the most common type of plant. Solar dish

Solar power tower

SOLAR ENERGY AND THE ENVIRONMENT
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Solar energy is free, and its supplies are unlimited. Using solar energy produces no air or

water pollution but does have some indirect impacts on the environment. For example,

manufacturing the photovoltaic cells used to convert sunlight into electricity, consumessilicon and produces some waste products. In addition, large solar thermal farms can also

harm desert ecosystems if not properly managed.

Wind Energy -- Energy from Moving Air

Energy from the Wind

The History of Wind

How Wind Machines WorkTypes of Wind Machines

Wind Power Plants

Wind Production

Wind and the Environment

links page

ENERGY FROM WIND

Wind is simple air in motion. It is caused by the uneven heating of the earths surface by

the sun. Since the earths surface is made of very different types of land and water, itabsorbs the suns heat at different rates.

During the day, the air above the land heats up more quickly than the air over water. The

warm air over the land expands and rises, and the heavier, cooler air rushes in to take its

place, creating winds. At night, the winds are reversed because the air cools more rapidlyover land than over water.
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In the same way, the large atmospheric winds that circle the earth are created because the

land near the earth's equator is heated more by the sun than the land near the North and

South Poles.

Today, wind energy is mainly used to generate electricity. Wind is called a renewable

energy source because the wind will blow as long as the sun shines.

The History of Wind

Since ancient times, people have harnessed the winds energy. Over 5,000 years ago, theancient Egyptians used wind to sail ships on the Nile River. Later, people built windmills

to grind wheat and other grains. The earliest known windmills were in Persia (Iran).

These early windmills looked like large paddle wheels. Centuries later, the people ofHolland improved the basic design of the windmill. They gave it propeller-type blades,

still made with sails. Holland is famous for its windmills.

American colonists used windmills to grind wheat and corn, to pump water, and to cutwood at sawmills. As late as the 1920s, Americans used small windmills to generateelectricity in rural areas without electric service. When power lines began to transport

electricity to rural areas in the 1930s, local windmills were used less and less, though

they can still be seen on some Western ranches.

The oil shortages of the 1970s changed the energy picture for the country and the world.It created an interest in alternative energy sources, paving the way for the re-entry of the

windmill to generate electricity. In the early 1980s wind energy really took off in

California, partly because of state policies that encouraged renewable energy sources.Support for wind development has since spread to other states, but California still

produces more than twice as much wind energy as any other state.

The first offshore wind park in the United States is planned for an area off the coast of

Cape Cod, Massachusetts (read an article about the Cape Cod Wind Project).

HOW WIND MACHINES WORK

Like old fashioned windmills, todays wind machines use blades to collect the winds

kinetic energy. Windmills work because they slow down the speed of the wind. The wind

flows over the airfoil shaped blades causing lift, like the effect on airplane wings, causing

them to turn. The blades are connected to a drive shaft that turns an electric generator toproduce electricity.

With the new wind machines, there is still the problem of what to do when the wind isnt

blowing. At those times, other types of power plants must be used to make electricity.

TYPES OF WIND MACHINES
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There are two types of wind machines (turbines) used today based on the direction of the

rotating shaft (axis): horizontalaxis wind machines and vertical-axis wind machines.

The size of wind machines varies widely. Small turbines used to power a single home orbusiness may have a capacity of less than 100 kilowatts. Some large commercial sized

turbines may have a capacity of 5 million watts, or 5 megawatts. Larger turbines are often

grouped together into wind farms that provide power to the electrical grid.

Horizontal-axis

Most wind machines being used today are the horizontal-axis type. Horizontal-axis wind

machines have blades like airplane propellers. A typical horizontal wind machine stands

as tall as a 20-story building and has three blades that span 200 feet across. The largestwind machines in the world have blades longer than a football field! Wind machines

stand tall and wide to capture more wind.

Vertical-axis

Verticalaxis wind machines have blades that go from top to bottom and the mostcommon type (Darrieus wind turbine) looks like a giant two-bladed egg beaters. The type

of vertical wind machine typically stands 100 feet tall and 50 feet wide. Vertical-axis

wind machines make up only a very small percent of the wind machines used today.

The Wind Amplified Rotor Platform (WARP) is a different kind of wind system that is

designed to be more efficient and use less land than wind machines in use today. The
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WARP does not use large blades; instead, it looks like a stack of wheel rims. Each

module has a pair of small, high capacity turbines mounted to both of its concave wind

amplifier module channel surfaces. The concave surfaces channel wind toward theturbines, amplifying wind speeds by 50 percent or more. Eneco, the company that

designed WARP, plans to market the technology to power offshore oil platforms and

wireless telecommunications systems.

WIND POWER PLANTS

Wind power plants, orwind farms as they are sometimes called, are clusters of wind

machines used to produce electricity. A wind farm usually has dozens of wind machines

scattered over a large area. The world's largest wind farm, the Horse Hollow WindEnergy Center in Texas, has 421 wind turbines that generate enough electricity to power

230,000 homes per year.

Unlike power plants, many wind plants are not owned by public utility companies.

Instead they are owned and operated by business people who sell the electricity producedon the wind farm to electric utilities. These private companies are known as Independent

Power Producers.

Operating a wind power plant is not as simple as just building a windmill in a windy

place. Wind plant owners must carefully plan where to locate their machines. Oneimportant thing to consider is how fast and how much the wind blows.

As a rule, wind speed increases with altitude and over open areas with no windbreaks.

Good sites for wind plants are the tops of smooth, rounded hills, open plains orshorelines, and mountain gaps that produce wind funneling.

Wind speed varies throughout the country. It also varies from season to season. In

Tehachapi, California, the wind blows more from April through October than it does in

the winter. This is because of the extreme heating of the Mojave Desert during thesummer months. The hot air over the desert rises, and the cooler, denser air above the

Pacific Ocean rushes through the Tehachapi mountain pass to take its place. In a state like

Montana, on the other hand, the wind blows more during the winter. Fortunately, these

seasonal variations are a good match for the electricity demands of the regions. InCalifornia, people use more electricity during the summer for air conditioners. In

Montana, people use more electricity during the winter months for heating.

WIND PRODUCTION

In 2005, wind machines in the United States generated a total of 17.8 billion kWh peryear of electricity, enough to serve more than 1.6 million households. This is enough

electricity to power a city the size of Chicago, but it is only a small fraction of the

nation's total electricity production, about 0.4 percent. The amount of electricitygenerated from wind has been growing fast in recent years, tripling since 1998.
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New technologies have decreased the cost of producing electricity from wind, and growth

in wind power has been encouraged by tax breaks for renewable energy and green pricing

programs. Many utilities around the country offer green pricing options that allowcustomers the choice to pay more for electricity that comes from renewable sources.

Wind machines generate electricity in 25 different states in 2005. The states with themost wind production are California, Texas, Iowa, Minnesota, and Oklahoma.

The United States ranks third in the world in wind power capacity, behind Germany andSpain and before India. Denmark ranks number five in the world in wind power capacity

but generates 20 percent of its electricity from wind. Most of the wind power plants in the

world are located in Europe and in the United States where government programs havehelped support wind power development.

WIND AND THE ENVIRONMENT

In the 1970s, oil shortages pushed the development of alternative energy sources. In the1990s, the push came from a renewed concern for the environment in response toscientific studies indicating potential changes to the global climate if the use of fossil

fuels continues to increase. Wind energy is an economical power resource in many areas

of the country. Wind is a clean fuel; wind farms produce no air or water pollution

because no fuel is burned. Growing concern about emissions from fossil fuel generation,increased government support, and higher costs for fossil fuels (especially natural gas and

coal) have helped wind power capacity in the United States grow substantially over the

last 10 years.

The most serious environmental drawbacks to wind machines may be their negative

effect on wild bird populations and the visual impact on the landscape. To some, theglistening blades of windmills on the horizon are an eyesore; to others, theyre a beautiful

alternative to conventional power plants.

Geothermal Energy -- Energy from the Earth's Core

What is Geothermal Energy?

Energy Inside the EarthWhere Is Geothermal Energy Found?

Uses of Geothermal Energy

Direct Use of Geothermal EnergyGeothermal Power Plants

Geothermal Heat Pumps

Geothermal Energy and the Environment
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WHAT IS GEOTHERMAL ENERGY?

The word geothermal comes from the Greek words geo (earth) and therme (heat). So,geothermal energy is heat from within the earth. We can use the steam and hot water

produced inside the earth to heat buildings or generate electricity. Geothermal energy is a

renewable energy source because the water is replenished by rainfall and the heat iscontinuously produced inside the earth.

ENERGY INSIDE THE EARTH

Geothermal energy is generated in the earth's core, about 4,000 miles below the surface.Temperatures hotter than the sun's surface are continuously produced inside the earth by

the slow decay of radioactive particles, a process that happens in all rocks. The earth has

a number of different layers:

The core itself has two layers: a solid iron core and an outer core made of very hot

melted rock, called magma.

The mantle which surrounds the core and is about 1,800 miles thick. It is made up of

magma and rock.

The crust is the outermost layer of the earth, the land that forms the continents andocean floors. It can be three to five miles thick under the oceans and 15 to 35 miles thick

on the continents.


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The earth's crust is broken into pieces called plates. Magma comes close to the earth's

surface near the edges of these plates. This is where volcanoes occur. The lava that erupts

from volcanoes is partly magma. Deep underground, the rocks and water absorb the heatfrom this magma. The temperature of the rocks and water get hotter and hotter as you go

deeper underground.

People around the world use geothermal energy to heat their homes and to produce

electricity by digging deep wells and pumping the heated underground water or steam tothe surface. Or, we can make use of the stable temperatures near the surface of the earth

to heat and cool buildings. (See Uses of Geothermal Energybelow.)

WHERE IS GEOTHERMAL ENERGY FOUND ?

Most geothermal reservoirs are deep underground with no visible clues showing above

ground.

Geothermal energy can sometimes find its way to the surface in the form of:

volcanoes and fumaroles (holes where volcanic gases are

released) hot springs and

geysers.

The most active geothermal resources are usually found along major plate boundaries

where earthquakes and volcanoes are concentrated. Most of the geothermal activity in theworld occurs in an area called the Ring of Fire. This area rims the Pacific Ocean.

When magma comes close to the surface it heats ground water found trapped in porous

rock or water running along fractured rock surfaces and faults. Such hydrothermal
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resources have two common ingredients: water (hydro) and heat (thermal). Naturally

occurring large areas of hydrothermal resources are called geothermal reservoirs.

Geologists use different

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