Renewable and Nonrenewable Sources of Energy

Renewable energy resources are essentially inexhaustible. They include the following: direct solar sources, biological sources, and geothermal sources. The earth gets its energy principally from the sun, whether directly or indirectly.

Solar energy is used to provide energy to some places. Photovoltaic cells convert sunlight into electricity.

Photovoltaic cells consist of silicon cells sandwiched between glass sheets. The electricity that is generated is stored in batteries. The batteries are designed to store energy for use for as long as three days.

Solar technology is nonpolluting but is expensive due to the high cost of processing silicon into solar cells.

Hydroelectric power uses the potential energy released by falling water. Hydroelectric power is an indirect form of solar energy. The energy of the sun is the driving force in the water cycle, eventually causing rivers to flow as waterfalls. Dams are built to stop flowing rivers and store water. The stored water released near the bottom of a dam turns turbines that produce electricity. The sun’s energy also causes the wind that drive windmills. Windmills are used to pump water, run machines, and generate electricity.

Biological resources include crops, wood, organic wastes, and biofuels.  Geothermal power is generated by using the heat energy from the hot, molten materials inside the earth.

Nonrenewable resources are resources present on earth in limited quantities and will not last very long. Examples of these are fossil fuels and nuclear power.

Fossil fuels are in the form of coal, petroleum, and natural gases. They originate from the remains of prehistoric plants and animals trapped in the earth by geological processes that occurred millions of years ago.

Coal comes from solidified giant ferns, now extinct, buried under rock layers million of years ago. Coal is burned as fuel. Coal, however, is the most polluting of all fossil fuels. It emits noxious gases when burned.

Petroleum is produced naturally from dead prehistoric plants and animals at the bottom of swamps and shallow areas. Partially decayed plants and animals settle to the bottom of bodies of water where they become buried and trapped in mud and sand. This sediment of mud, sand, and dead organisms slowly grows thicker and thicker. Heat and pressure cause the remains to chemically change and eventually form a viscous, sticky liquid called petroleum or crude oil.

Natural gas consists of gaseous hydrocarbons produced from fossil fuels. It is drawn from gas wells, processed, and piped into the homes and factories for use as fuels.

Nuclear power is released from the nucleus of an atom. This energy is called nuclear energy. In producing nuclear energy, a fraction of the mass of atoms is changed into energy by a splitting process called nuclear fission. In nuclear fission, energy is released when the nuclei of heavy atoms are split into fragments.

Another source of energy is the combination of nuclei or light elements to form heavier nuclei. The combining nuclei are called nuclear fusion. The energy comes from the conversion of mass lost after the fusion reaction. Virtually all of the energy in the universe originates from the fusion of hydrogen nuclei in the stars. Nuclear fusion occurs only at very high temperature, around one million degrees Celsius.

So far the fusion process has not yet become practical as an energy source. Scientists are working to learn more about the nuclei of more kinds of atoms so that fusion may someday be used as a major source of energy.

The production of nuclear energy has become a controversial issue because of the danger it poses to life. Nuclear reaction gives off radioactive wastes. Radioactive wastes emit radiations harmful to all living organisms. Society’s fear of nuclear energy becomes a reality in the Three Mile Island and Chernobyl nuclear plant accidents in the United States and the former Soviet Union, respectively.