Fossil Fuels make most of our electricity
There is no escaping it.
This according to the US EIA
Steam turbines are used to generate the majority of the world’s electricity and they accounted for about 44% of U.S. electricity generation in 2020. Most steam turbines have a boiler in which a fuel is burned to produce hot water and steam in a heat exchanger, and the steam powers a turbine that drives a generator. Nuclear power reactors use nuclear fuel rods to produce steam. Solar thermal power plants and most geothermal power plants use steam turbines. Most of the largest U.S. electric power plants use steam turbines.
Combustion gas turbines, which are similar to jet engines, burn gaseous or liquid fuels to produce hot gases to turn the blades in the turbine.
Steam and combustion turbines can be operated as stand-alone generators in a single-cycle or combined in a sequential combined-cycle. Combined-cycle systems use combustion gases from one turbine to generate more electricity in another turbine. Most combined-cycle systems have separate generators for each turbine. In single-shaft combined cycle systems, both turbines may drive a single generator. Learn more about different types of combined-cycle power plants. In 2020, combined-cycle power plants supplied about 35% of U.S. net electricity generation.
Combined-heat-and-power (CHP) plants, which may be referred to as cogenerators, use the heat that is not directly converted to electricity in a steam turbine, combustion turbine, or an internal combustion engine generator for industrial process heat or for space and water heating. Most of the largest CHP plants in the United States are at industrial facilities such as pulp and paper mills, but they are also used at many colleges, universities, and government facilities. CHP and combined-cycle power plants are among the most efficient ways to convert a combustible fuel into useful energy.
Hydroelectric turbines use the force of moving water to spin turbine blades to power a generator. Most hydroelectric power plants use water stored in a reservoir or diverted from a river or stream. These conventional hydroelectric power plants accounted for about 7% of U.S. electricity generation in 2020. Pumped-storage hydropower plants use the same types of hydro turbines that conventional hydropower plants use, but they are considered electricity storage systems (see below). Other types of hydroelectric turbines called hydrokinetic turbines are used in tidal power and wave power systems. Learn more about different types of hydroelectric turbines.
Wind turbines use the power in wind to move the blades of a rotor to power a generator. There are two general types of wind turbines: horizontal axis (the most common) and vertical-axis turbines. Wind turbines were the source of about 8% of U.S. electricity generation in 2020.
Ocean thermal energy conversion (OTEC) systems use a temperature difference between ocean water at different depths to power a turbine to produce electricity.
Other types of generators
There are many different types of electricity generators that do not use turbines to generate electricity. The most common in use today are solar photovoltaic (PV) systems and internal combustion engines.
Solar photovoltaic cells convert sunlight directly into electricity. They are used to power devices as small as wrist watches and can be connected together in panels that are connected together in arrays to power individual homes or form large power plants. Photovoltaic (PV) power plants are now one of the fastest growing sources of electricity generation around the world. In the United State, PV power plants were the source of about 2% of total utility-scale electricity generation in 2020.
Internal combustion engines, such as diesel engines, are used all around the world for electricity generation including in many remote villages in Alaska. They are also widely used for mobile power supply at construction sites and for emergency or backup power supply for buildings and power plants. Diesel-engine generators can use a variety of fuels including petroleum diesel, biomass-based liquid fuels and biogas, natural gas, and propane. Small internal combustion engine generators fueled with gasoline, natural gas, or propane are commonly used by construction crews and tradespeople and for emergency power supply for homes.
Other types of electricity generators include fuel cells, Stirling engines (used in solar thermal parabolic-dish generators), and thermoelectric generators .
Energy storage systems for electricity generation include hydro-pumped storage, compressed-air storage, electrochemical batters, and flywheels. These energy storage systems use electricity to charge a storage facility or device, and the amount of electricity that they can supply is less than the amount they use for charging. Therefore, the net electricity generation from storage systems is counted as negative to avoid double counting electricity use for charging the storage system.