Most of the electricity in the United States is produced using steam turbines
A turbine converts the kinetic energy of a moving fluid (liquid or gas) to mechanical energy. In a steam turbine, steam is forced against a series of blades mounted on a shaft. The steam rotates the shaft connected to the generator. The generator, in turn, converts its mechanical energy to electrical energy based on the relationship between magnetism and electricity.
In steam turbines powered by fossil fuels (coal, petroleum, and natural gas), the fuel is burned in a furnace to heat water in a boiler to produce steam.
Most of U.S. electricity is generated using fossil fuels
In 2015, coal was used for about 33% of the 4 trillion kilowatthours of electricity generated in the United States.
In addition to being burned to heat water for steam, natural gas can also be burned to produce hot combustion gases that pass directly through a natural gas turbine, spinning the turbine's blades to generate electricity. Natural gas turbines are commonly used when electricity use is in high demand. In 2015, nearly 33% of U.S. electricity was fueled by natural gas.
Petroleum can be burned to produce hot combustion gases to turn a turbine or to make steam that turns a turbine. Residual fuel oil and petroleum coke, products from refining crude oil, are the main petroleum fuels used in steam turbines. Distillate (or diesel) fuel oil is used in diesel-engine generators. Petroleum was used to generate less than 1% of all electricity in the United States in 2015.
Nuclear power provides about one-fifth of U.S. electricity
Nuclear power plants produce electricity with nuclear fission to create steam that spins a turbine to generate electricity. Most U.S. nuclear power plants are located in states east of the Mississippi River. Nuclear power was used to generate nearly 20% of all U.S. electricity in 2015.
Renewable energy sources provide 13% of U.S. electricity
Hydropower, the source of about 6% of U.S. electricity generation in 2015, is a process in which flowing water is used to spin a turbine connected to a generator. Most hydropower is produced at large facilities built by the federal government, like the Grand Coulee Dam. The West has many of the largest hydroelectric dams, but there are many hydropower facilities operating all around the country.
Wind power is produced by converting wind energy into electricity. Electricity generation from wind has increased significantly in the United States since 1970. Wind power provided almost 5% of U.S. electricity generation in 2015.
Biomass is material derived from plants or animals and includes lumber and paper mill wastes, food scraps, grass, leaves, paper, and wood in municipal solid waste (garbage). Biomass is also derived from forestry and agricultural residues such as wood chips, corn cobs, and wheat straw. These materials can be burned directly in steam-electric power plants, or they can be converted to a gas that can be burned in steam generators, gas turbines, or internal combustion engine-generators. Biomass accounted for about 2% of the electricity generated in the United States in 2015.
Geothermal power comes from heat energy buried beneath the surface of the earth. In some areas of the United States, enough heat rises close enough to the surface of the earth to heat underground water into steam, which can be tapped for use at steam-turbine plants. Geothermal power generated less than 1% of the electricity in the United States in 2015.
Solar power is derived from energy from the sun. Photovoltaic (PV) and solar-thermal electric are the two main types of technologies used to convert solar energy to electricity. PV conversion produces electricity directly from sunlight in a photovoltaic (solar) cell. Solar-thermal electric generators concentrate solar energy to heat a fluid and produce steam to drive turbines. In 2015, nearly 1% of U.S. electricity generation came from solar power.