A century ago, few homes had electricity and cars were a rare sight. Today, much of the world’s energy is turned into electricity for homes, to power equipment in factories, and to fuel our cars, buses, aircraft and other transports. These are some of the main sources of this energy.
The first oil wells were drilled less than 150 years ago but oil and petroleum which comes from it has become the most important energy source, almost 40 percent of the world’s energy supply comes from oil. Most oil is found in the Middle East and has to be taken by tankers or pipelines to places where it is used around the world.
Coal is the world’s second most important source of energy. It makes up about 27 percent of the total energy sources. Coal is fossil fuel and is made from plants that lived and died in swamps 300 million years ago. The world’s coal reserves will last about another 190 years. This is nearly three times as long as gas (67 years) and almost five times as long as oil (41 years).
The third major supply of power comes from gas that occurs in nature beneath the earth’s shell. It accounts for 23 percent of the world whole energy sources. The gas is primarily methane, with a few ethanes, propane and supplementary gases. It is collected and transported to where it is needed by pipelines, and has replaced the extremely polluting coal gas that used to be made by flaming coal.
The fourth most important power source (7% of the world total energy source) is nuclear power. A nuclear reaction releases massive amounts of heat which in turn heats water or other liquid and drives a turbine to produce electrical energy. The first nuclear power station to generate electricity for community use was Calder Hall, UK, which opened in 1956.
Flowing stream of water has been used as a power supply since the Middle Ages and water mils were once a familiar vision. Modern hydro power uses water flowing through turbines in dams to generate energy.
The suns heat can be stored to make energy. Mirrors and glass were used to accumulate heat in ancient times, but the first houses to use solar heating were not built until 1955. Solar energy is becoming more popular and the technology is getting better all the time. The world’s largest solar energy generating plants are in the Mohave Desert, California, USA. They are designed to use the sun’s rays to heat oil which drives a generator. It creates enough electricity for a small town.
Wind mills were used in Persia (now Iran) in the 7th century and in Europe since the 12th century but they were first used for making electricity in the late 19th century. Today, California USA is the world’s leading region for winds generated electricity. Tehachapi wind resource, California, produces as much wind energy as the rest of the USA combined.
Using waves and marine currents to discharge energy is costly and as so far small amount. The first and largest tidal power station on the Rance river, St Malo, France was completed in 1967. It is able to produce enough energy each year to supply power to 120,000 households.