In this topic you will learn about how alternate sources of energy may be utilized.

Most living things obtain their energy directly or indirectly from the Sun. Scientists have developed materials made mainly of silicon that produce electrons when struck by light. When layered properly, these materials can be made into solar cells. A solar cell is a device that generates an electric current from sunlight.

Fossil fuels were once living plants and animals. Matter from plants and animals living today can produce energy and help conserve fossil fuels. New methods allow us to change both plant and animal materials into high quality fuels. Getting energy from plant and animal materials by changing them into high-quality fuels is called biomass conversion.

Atomic nuclei can produce energy in a nuclear reaction. The splitting of a nucleus with a large mass into two nuclei with smaller masses is a nuclear reaction called nuclear fission. The nucleus is split when struck by a slow moving neutron. Neutrons that are released by one splitting atom can strike additional nuclei and make them split. These nuclei release several more neutrons, starting a reaction that uses its own products to keep going. This continuing reaction is called a chain reaction.

Energy can also be released when nuclei with smaller masses merge to make a nucleus with a larger mass. This process is called nuclear fusion. Nuclear fusion reactions only occur at very high temperatures. In nature, temperatures great enough for nuclear fusion to happen are found in the cores of stars.

The kinetic energy of falling water can be used to turn a wheel. This principle can be used to generate electricity. When electricity is produced by the use of flowing water, it is called hydroelectricity. Hydroelectricity is really a form of solar energy. Presently the U.S. gets about 15 percent of its electricity from hydroelectricity.

At an electric power plant, separate cooling water is used to condense the exhaust steam from the turbines. This water warms up as it cools the steam. If the warmed water were to be released into a river or lake, the increase in temperature would harm the water-dwelling plants and animals. The excess heating of the environment is called thermal pollution.