Energy Sources

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Chapter 25

• Energy Sources

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25-1 Fossil Fuels

• Petroleum or crude oil, is a liquid source of
  energy made from the remains of plants and
  animals. It along with natural gas, and coal are
  called fossil fuels. When plants and animals
  died, they were covered with layers of sand, mud
  and volcanic ash. Heat, pressure and bacteria
  acted on these buried organisms turning them into
  fossil fuels.

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25-1 Fractional Distillation

• Plants and animals contain large amounts of
  hydrogen and carbon, therefore, petroleum is made
  mostly of these elements. The compounds are
  called hydrocarbons.
• There are different hydrocarbon compounds and
  they must be separated in order to use the
  chemical energy stored in petroleum. The method
  used to separate hydrocarbon compounds is called
  fractional distillation. Crude oil is pumped
  into the chamber and then it is heated. Each
  hydrocarbon compound boils at a different
  temperature thus allowing them to be separated.

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25-1 The good and bad of Fossil Fuels

• You use petroleum every day for electricity and
  transportation but not all the effects of
  petroleum usage are helpful to you or the
  environment. Burning petroleum in cars and at
  electric power plants gives off smoke as well as
  carbon monoxide and other chemicals. These
  particles and compounds affect the quality of the
  air you breathe.

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25-1 Other Fossil Fuels

• Natural gas, like petroleum, is a fossil fuel.
• It is often found lying above liquid petroleum
  below Earth's surface and is extracted with
  petroleum.
• Natural gas is mostly methane CH4 but it also
  contains smaller amounts of hydrocarbons such as
  propane C3H8 and butane C4H10. Carbon dioxide
  and water are given off as chemical byproducts of
  the combustion of these products.

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25-1 Coal

• Coal is a solid fossil fuel made from the remains
  of plants.
• About 1/4th of the world's supply of coal is in
  the U.S.
• It is sometimes mined near the surface but is
  more commonly mined several hundred feet
  underground. The quality of coal depends on its
  age and on the type of plant life from which it
  formed.

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25-1 Fuel Conservation

• Fossil fuel reserves are decreasing as our
  population and industrial demands are increasing.
  
• At our current rate of consumption, the U.S. may
  be out of oil in less than 100 years. Coal is
  more plentiful but like petroleum it is a
  nonrenewable resource.
• All fossil fuels are nonrenewable resources- they
  cannot be replaced after they are used.

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25-2 Nuclear Energy

• A nuclear reactor uses the energy from a
  controlled nuclear fission chain reaction to
  generate electricity.
• Once the core of the reactor contains fuel
  (uranium oxide) a chain reaction starts from a
  single uranium atom splitting in two which
  releases 2 neutrons. In 3 milliseconds, 1
  billion neutrons would be produced. The reactor
  would be out of control. Rods containing boron
  or cadmium are inserted in the reactor to capture
  more neutrons and slow down the chain reaction.
  The core is surrounded by water that cools it.
  The heated water is used to produce the energy.
  The entire building is built with steel lined
  concrete to prevent the escape of radiation from
  the reactor.

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25-2 Nuclear generation of Electricity

• Nuclear fission reactors currently supply over
  20 of our nations electricity.
• One advantage of nuclear energy is that it is
  less harmful to the environment than the use of
  fossil fuels.
• There are disadvantages to nuclear reactors.
• - the water must be cooled before being returned
  to streams/rivers or it will damage the
  ecosystem.
• - there is a risk of the escape of harmful
  radiation. Nuclear reactors have elaborate
  systems of safeguards to ensure this doesnt
  happen. Strict safety precautions and highly
  trained workers prevent most accidents but there
  is always a potential

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25-2 Nuclear Waste Disposal

• Because the fission products have long
  half-lives, they must be stored in containers
  that will last the duration of the period of
  radioactive decay, which can be as long as tens
  of thousands of years.
• After about 3 years there is not enough
  fissionable U-235 left in the fuel pellets to
  sustain the chain reaction. These used fuel
  pellets are called spent fuel. This spent fuel
  and left over uranium are termed nuclear waste.
• After spent fuel is removed from a reactor, it is
  stored in a deep, heavily insulated pool of
  water. Waste must be disposed of in extremely
  durable containers.

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25-2 Fusion Power

• Imagine the amount of energy the sun must give
  off to hear Earth 93 million miles away. The
  process that created the sun is thermonuclear
  fusion.
• Thermonuclear fusion is the joining together of
  small nuclei at high temperatures.
• If we could make this happen in a laboratory, we
  would likely have the answer to Earths energy
  problems.
• The temperature needed to carry out a nuclear
  fusion reaction is over one million degrees
  Celsius.
• Hydrogen is the most abundant element in our
  universe and the products of nuclear fusion are
  not radioactive. Someday nuclear fusion may
  provide a permanent and economical way to
  generate electricity.

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25-3 Breeder Reactors

• A breeder reactor is a nuclear reactor that
  produces, or breeds, new fuel as it operates.
  In a breeder reactor, some of the neutrons
  produced by the fission of U-235 are absorbed by
  the U-238 nuclei while other neutrons cause
  fission of U-235.
• The U-239 nuclei decays in several days to form
  Pu-239 which is fissionable. After operating
  several years, a breeder reactor can produce
  twice as much fissionable fuel than it started
  with.
• It posses the same risks as other nuclear
  reactors.

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25-4 Alternative Energy sources

• Using fossil fuels and nuclear fission for our
  energy needs has many disadvantages. Both
  methods are used to boil water to produce steam.
  Other materials can be burned to give off energy
  as well.
• Biomass is renewable organic matter such as wood,
  sugar cane fibers, rice hulls and animal manure.
  Biomass can be burned to convert the stored
  chemical energy to thermal energy.
• Biomass burning is probably the oldest use of
  natural resources for human needs.

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25-4 Solar Energy

• The sun is Earths only source of NEW energy.
• Methods of collecting and using solar energy are
  usually divided into two categories, passive and
  active solar energy.
• Passive solar heating is the direct use of the
  suns energy in maintaining comfortable indoor
  temperatures.
• In active solar heating, solar panels collect and
  store solar energy. A device used to convert
  solar energy into electricity is the photovoltaic
  cell, also called the solar cell.
• This method of producing electricity is more
  expensive on a large scale than the use of
  nonrenewable fuels. Solar energy is a pollution
  free resource that is becoming more economical as
  technology develops

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25-4 Hydroelectricity
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25-4 Hydroelectricity

• Near the base of hydroelectric dams, water is
  allowed to rush out through tunnels.
• The rushing water spins a turbine, rotating the
  shaft of an electric generator to produce
  electricity.
• Hydroelectric power plants are a very efficient
  way to produce electricity with almost no
  pollution.
• After the initial cost of building a dam and
  power plant, the electricity is relatively cheap.
  However, artificial dams can disturb the balance
  of natural ecosystems.

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25-4 Tidal Energy
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25-4 Tidal Energy

• A kind of hydroelectric power can be generated by
  ocean tides. The moving water can be trapped at
  high tide by building a dam at the opening of a
  river or bay. The flowing water at low tides
  spins a turbine, which operates an electric
  generator. Energy generated by tidal motion is
  called tidal energy.
• There are only a few places on Earth where the
  difference between high and low tide is large
  enough to be an efficient energy source.

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25-4 Wind energy
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25-4 Wind energy

• A windmill is a turbine that is turned by the
  wind instead of steam or water. The windmill
  spins and rotates and electric generator to
  produce electricity.
• Only a few places on Earth consistently have
  enough wind to rely on wind power to meet their
  energy needs.
• Wind generators do not use up any resources, they
  do not pollute the atmosphere or water but they
  do change the appearance of a landscape.

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25-4 Geothermal Energy
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25-4 Geothermal Energy

• Beneath the surface of Earth lies hot gases and
  molten rock which give off heat. This heat or
  thermal energy from inside Earth is called
  geothermal energy.
• In some places, Earths crust has cracks or thin
  spots in it. These areas allow some of the
  geothermal energy to rise up near the surface of
  Earth. EX volcanoes, geysers shoot steam and
  hot water i.e. Old Faithful
• Wells can be drilled to pump out hot water that
  ranges in temperature from 150-350 degrees. The
  steam can be used to rotate turbines and turn
  electric generators. There are only certain
  places on Earth where geothermal energy is
  accessible as an economical energy resource.