Section 1: Fossil Fuels

• Using Energy

  • Furnaces and stoves use thermal energy to heat buildings and cook food. Air conditioners use electrical energy to move thermal energy outdoors. Cars and other vehicles use mechanical energy to carry people and materials from one part of the country to another.

  • To use energy means to transform one form of energy to another form of energy that can perform a useful function.

  • Sometimes energy is transformed into a form that isn’t useful.

  • Power lines carry the electrical energy you use every day.

  • More energy is used in the United States than in any other
    country in the world.

  • Almost 85 percent of the energy used in the United States comes from burning petroleum, natural gas, and coal. Nuclear power plants provide about eight percent of the energy used in the United States.

• Making Fossil Fuels

  • Fossil Fuels: formed from the decaying remains of ancient plants and animals.

  • When fossil fuels are burned, carbon and hydrogen atoms combine with oxygen molecules in the air to form carbon dioxide and water molecules.

• Petroleum: highly flammable liquid formed by decayed ancient organisms, such as microscopic plankton and algae.

  • Petroleum is a mixture of thousands of chemical compounds.

  • The many different compounds that are found in petroleum
    are separated in a process called fractional distillation.

  • Not all of the products obtained from petroleum are burned to produce energy.

• Natural Gas

  • The chemical processes that produce petroleum as ancient organisms decay also produce gaseous compounds called natural gas.

  • Natural gas is burned to provide energy for cooking, heating, and manufacturing.

  • Natural gas contains more energy per kilogram than petroleum or coal does. It also burns more cleanly than other fossil fuels, produces fewer pollutants, and leaves no residue such as ash.

• Coal

  • Coal is a solid fossil fuel that is found in mines underground

    • Coal mines usually are located deep underground.

  • About 90 percent of all the coal that is used in the United States is burned by power plants to generate electricity.

  • Coal mines were once the sites of ancient swamps.

  • Coal also is a complex mixture of hydrocarbons and other chemical compounds.

• Generating Electricity

  • Fossil fuels are burned to generate electricity in a power plant.

• Efficiency of Power Plants

  • When fossil fuels are burned in power plants, not all of the chemical energy stored in the fuels is converted into electrical energy.

  • Only about 35 percent of the chemical energy contained in fossil fuels is converted into electrical energy by power plants. The other 65 percent is converted into thermal energy that is transferred to the environment.

• The Costs of Using Fossil Fuels

  • When petroleum products and coal are burned, smoke is given off that contains small particles called particulates. These particulates cause breathing problems for some people.

  • The carbon dioxide concentration in Earth’s atmosphere has been measured at Mauna Loa in Hawaii. From 1960 to 2000, the carbon dioxide concentration has increased by about 16 percent.

  • One consequence of increasing the atmospheric carbon dioxide concentration could be to cause Earth’s surface temperature to increase.

  • The most abundant fossil fuel is coal, but coal contains even more impurities than oil or natural gas.

  • Mining coal also can be dangerous.

• Nonrenewable Resources: sources that cannot be replaced by natural processes as quickly as they are used.

  • Some predictions show that worldwide oil production will peak by 2005 and then decline rapidly over the following 50 years.

  • Fossil fuels will become more difficult to obtain, causing them to become more costly in the future.

• Conserving Fossil Fuels

  • One way to meet the energy demands would be to reduce the use of fossil fuels and obtain energy from other sources.

Section 2: Nuclear Energy

• Using Nuclear Energy

  • Over the past several decades, electric power plants have been developed that generate electricity without burning fossil fuels.

  • A nuclear power plant generates electricity using the energy released in nuclear fission.

• Nuclear Reactor: uses the energy from controlled nuclear reactions to generate electricity.

  • The core of a nuclear reactor contains the fuel rod bundles. Control rods that absorb neutrons are inserted between the fuel rod bundles. Water or another coolant is pumped through the core to remove the heat produced by the fission reaction.

  • Only certain elements have nuclei that can undergo fission

  • Nuclear fuel pellets are stacked together to form fuel rods. The fuel rods are bundled together, and the bundle is covered with a metal alloy.

  • When a neutron strikes the nucleus of a U-235 atom, the nucleus splits apart into two smaller nuclei. In the process two or three neutrons also are emitted. The smaller nuclei are called fission products.

  • Because every uranium atom that splits apart releases neutrons that cause other uranium atoms to split apart, this process is called a nuclear chain reaction.

  • Nuclear chain reactions take place in a matter of milliseconds. If the process isn’t controlled, the chain reaction will release energy explosively rather than releasing energy at a constant rate.

  • To control the chain reaction, some of the neutrons that are released when U-235 splits apart must be prevented from striking other U-235 nuclei.

• Nuclear Power Plants

  • Nuclear fission reactors produce electricity in much the same way that conventional power plants do.

  • A nuclear power plant uses the heat produced by nuclear fission in its core to produce steam. The steam turns an electric generator.

  • To transfer thermal energy from the reactor core to heat water and produce steam, the core is immersed in a fluid coolant.

• The Risks of Nuclear Power

  • Nuclear power plants do not produce the air pollutants that are released by fossil-fuel burning power plants.

  • The mining of the uranium can cause environmental damage.

  • One of the most serious risks of nuclear power is the escape of harmful radiation from power plants.

  • Nuclear reactors have elaborate systems of safeguards, strict safety precautions, and highly trained workers in order to prevent accidents.

  • An explosion occurred at the Chernobyl reactor in the Ukraine after graphite control rods caught fire. The explosion shattered the reactor’s roof.

• The Disposal of Nuclear Waste

  • Nuclear Waste: any radioactive by-product that results when radioactive materials are used.

  • Low-level nuclear wastes usually contain a small amount of radioactive material.

    • Low-level wastes usually are sealed in containers and buried in trenches 30 m deep at special locations.

  • High-level nuclear waste is generated in nuclear power plants and by nuclear weapons programs.

  • Spent nuclear fuel rods are placed underwater after they are removed from the reactor core. The water absorbs the nuclear radiation and prevents it from escaping into the environment.

• Nuclear Fission

  • Thermonuclear fusion is the joining together of small nuclei at high temperatures.

  • In nuclear fusion, two smaller nuclei join together to form a larger nucleus. Energy is released in the process.

  • An advantage of producing energy using nuclear fusion is

    that the process uses hydrogen as fuel.

  • Another advantage is that the product of the reaction is helium. Helium is not radioactive and is chemically nonreactive.

  • One disadvantage of fusion is that it occurs only at temperatures of millions of degrees Celsius.

Section 3: Renewable Energy Sources

• Energy Options

  • The demand for energy continues to increase, but supplies of fossil fuels are decreasing.

  • Renewable Resource: an energy source that is replaced nearly as quickly as it is used.

• Energy From the Sun

  • The average amount of solar energy that falls on the United States in one day is more than the total amount of energy used in the United States in one year.

  • Solar energy is a renewable resource.

  • Photovoltaic Cell: converts radiant energy from the Sun directly into electrical energy.

  • Solar cells are made of two layers of semiconductor materials sandwiched between two layers of conducting metal.

  • Solar cells convert radiant energy from the Sun to electricity.

  • One layer of semiconductor is rich in electrons, while the other layer is electron poor.

  • Producing large amounts of electrical energy using solar cells is more expensive than producing electrical energy using fossil fuels.

• Energy from Water

  • The potential energy in water stored behind the dam is converted to electrical energy in a hydroelectric power plant.

  • Hydroelectricity: Electricity produced from the energy of moving water

    • Hydroelectric power plants are an efficient way to produce electricity with almost no pollution.

    • Another advantage is that the bodies of water held back by dams can form lakes that can provide water for drinking and crop irrigation.

  • Fish ladders enable fish to migrate upstream past dams.

• Energy from the Tides

  • The gravity of the Moon and Sun causes bulges in Earth’s oceans.

  • Hydroelectric power can be generated by these ocean tides.

  • The efficiency of a tidal power plant is similar to that of a conventional hydroelectric power plant

• Harnessing the Wind

  • Windmills also can use the energy of the wind to generate electricity.

  • Wind energy is converted to electricity as the spinning propeller turns a generator.

  • Only a few places on Earth consistently have enough wind to rely on wind power to meet energy needs.

  • Other disadvantages of wind energy are that windmills can be noisy and change the appearance of a landscape.

• Energy from Inside Earth

  • Heat is generated within Earth by the decay of radioactive elements.

  • Geothermal Energy: The thermal energy that is contained in hot magma

  • Geothermal energy also can be used to generate electricity

  • A geothermal power plant converts geothermal energy to electrical energy.

  • Although geothermal power plants can release some gases containing sulfur compounds, pumping the water created by the condensed steam back into Earth can help reduce this pollution.

• Alternative Fuels

  • The use of fossil fuels would be greatly reduced if cars could run on other fuels or sources of energy.

  • Hydrogen gas is another possible alternative fuel.

  • Hydrogen may one day replace gasoline as a fuel for automobiles. Burning hydrogen produces water vapor, instead of carbon dioxide.

  • Biomass: renewable organic matter, such as wood, sugarcane fibers, rice hulls, and animal manure.