Carbon-Pros Analyst BlogEnergy Smart: Generation
Most electricity in the United States is generated with steam turbines. The steam comes from superheated water or gasses. Fossil fuels, such as coal, natural gas, and oil, or nuclear-fueled reactors heat water in large boilers to make steam. The steam turns a generator to produce electricity. Gas turbines, fueled by oil or gas, use hot gases to rotate turbines. For small-scale use, diesel engines are used to spin generators and produce electricity.
Instead of superheated water, hydroelectric generators use the pressure from gravity pulling water through a pipe to turn blades in a turbine. The turbine spins a generator to produce electricity. Stored water is released from reservoirs created by dams in a "falling water" hydro system. Alternatively, the force of a river current can be used to turn a turbine in "run-of-the-river" systems.
Coal, gas, and nuclear are the "big three" fuels in US electricity generation. Together they are used to generate about 90% of our electricity. Hydro is a respectable fourth. Renewables, especially wind, are the fastest growing sources of electricity, but they are dwarfed by the big three.