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Producing electricity

Energy resources used to generate electricity are divided into two categories:

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Nonrenewable resources

Nonrenewable resources cannot be replenished. Using them wisely will help them last longer, but when they are gone, they will no longer exist.

Fossil fuels

The majority of electricity used in the United States is generated at power plants that burn fossil fuels to heat water and make steam. The steam is highly pressurized and directed at turbine blades to make them spin.

The three forms of fossil fuels are coal, oil and natural gas. They are known as fossil fuels because they were formed from the remains of animals or plants that lived long ago.

 

• Coal is a hard, black, rock-like substance made up of carbon, hydrogen, oxygen, nitrogen and sulfur. The precursor to coal, called peat, is used as an energy source in many countries. Coal is found in many parts of the United States and throughout the rest of the world. Coal is extracted from the ground at large mines.
  
  
  
  
• Oil is a liquid fossil fuel, sometimes also called petroleum. It is found underground within porous rocks. Oil rigs must drill down to deposits deep below the Earth's surface to obtain oil. More than half of all the oil used in the United States comes from other countries.
  
  
  
  
• Natural gas is made up primarily of a gas called methane. Methane gas is highly flammable and burns cleanly. Natural gas is typically found underground along with oil. Natural gas supplies are abundant from sources in the United States and Canada.

 

Nuclear power

Nuclear power plants use heat from splitting atoms to convert water into steam that turns turbines. These plants rely on uranium, a type of metal that must be mined from the ground and specially processed. Fuel rods containing uranium are placed next to each other in a machine called a nuclear reactor. The reactor causes uranium atoms to split, releasing a tremendous amount of heat.

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Renewable resources

Renewable energy resources can be replenished in a short period of time, so they will never be all used up. Energy companies throughout the country are using renewable resources more and more to generate electricity.

 

 

Biomass

Biomass is organic matter, such as agricultural waste, and wood chips and bark left over when lumber is produced. Biomass can be burned to heat water to make steam, which turns a turbine to make electricity. It also can be converted into a gas, which can be burned to do the same thing.

Biomass includes energy crops such as wood, straw and other crops grown primarily for use as fuel. Energy crops are renewable, but some take a long time to grow, such as trees. Farmers can grow trees on some of their land instead of wheat or other kinds of food. The wood is harvested regularly, cut into small chips and burned to provide heat or run small electric power plants.

Another type of biomass energy is methane gas, a by–product of landfill decay. As garbage rots in the ground, it gives off gases that can be collected and burned to produce heat or electricity.

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Geothermal energy

The word geothermal comes from the Greek words geo, for earth, and therme, for heat. So geothermal means "earth heat." Geothermal energy is steam (or hot water that has been converted to steam) from deep inside the Earth.

Our planet's interior is very hot—at its core, 4,000 miles deep, temperatures may reach more than 9,000°F. This heat is continuously conducted from the Earth's core to the surrounding layer of rock, the mantle.

There are some places around the Earth where magma (hot molten earth from the mantle) pushes up through cracks into the crust near the Earth's surface. Magma can heat nearby rock and water as hot as 700°F. Some of this hot water reaches the Earth's surface as hot springs or geysers, and some stays trapped deep underground in cracks and porous rocks. This hot water can be used directly or converted into steam to turn turbines that generate electricity.

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Hydrogen

Hydrogen is a colorless, odorless gas. Hydrogen can be converted into electricity through a chemical reaction in a device called a fuel cell. Converting hydrogen into electricity produces no pollution—only water and heat.

If the hydrogen comes from a renewable resource such as landfill gas, fuel cells are considered renewable. However, if the hydrogen comes from a nonrenewable resource such as fossil fuels, fuel cells are considered nonrenewable.

Today, some cars run on hydrogen. In the future, hydrogen may be used more widely to fuel vehicles and airplanes, and to provide electricity to buildings.

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Hydropower

Hydroelectric plants use the power of falling water to turn the turbines that help generate electricity. Water that is stored behind a dam is released and directed through special tubes to flow against the blades of turbines and make them turn. Most hydropower facilities are found in hilly or mountainous areas. The most famous hydroelectric facility in the United States is the Hoover Dam.

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Ocean energy

Ocean energy is a form of hydropower. Oceans cover more than 70 percent of the Earth's surface, making them the world's largest solar collectors. The ocean stores thermal (heat) energy that can be used to generate electricity using special turbine generators.

The energy of the ocean's waves and tides also can be used to generate electricity with dams that force ocean water through turbines. This is called tidal energy, or wave power. The world's first wave power station is on the Scottish island of Islay. It generates enough electricity for about 400 homes.

Scientists and engineers around the world are working on systems to use the ocean's energy on a large scale.

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Solar energy

Solar energy is generated without a turbine or electromagnet. Special panels of solar cells, or modules, can capture sunlight and convert it directly into electricity. These panels are known as photovoltaic, or PV. (Photo is Greek for light, and voltaic pertains to electricity.) The electricity they produce can be used right away, fed into the power grid for others to use, or stored in a battery so it also is available on cloudy days.

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Wind power

Wind power is renewable energy that uses the force of the wind to spin turbines. These spinning turbines generate electricity.

Most wind power is produced at wind farms, which are large groups of turbines in consistently windy locations. At peak usage, a very large wind farm can generate enough electricity for all the homes in a small city. Small wind turbines can be used for individual homes, businesses and boats.