The term “prime mover” conjures the notion of someone or something that has a lot of influence. Tesla is a prime mover in the car industry. Taylor Swift is a prime mover in popular music.
In the world of energy, prime mover refers to any device that receives force and motion from a natural source (flowing water, fuel combustion) and imparts motion, especially to machinery.
When applied to the generation of electricity, prime mover refers to (i) the engine, turbine, water wheel, or similar machine that drives an electric generator; or (ii) a device that converts energy to electricity directly (e.g., photovoltaic solar and fuel cells).1
A hydraulic (water) turbine converts the energy of flowing water into mechanical energy. A hydroelectric generator converts that mechanical energy into electricity. The first facility to demonstrate that electricity could be generated and transmitted to customers at scale was the 37 MW Adams hydropower plant at Niagara Falls in 1985. Hydropower received a massive boost from President Roosevelt’s New Deal programs that built the largest dams in the world, such as Hoover Dam in Nevada (1936) and Grand Coulee Dam in Washington (1942). The water turbine generated the lion’s share of electricity through World War II.
Charles Parson’s steam turbine (1884) would revolutionize electricity generation. Because it extracts thermal energy from pressurized steam, the steam turbine can be driven by a wide range of energy sources: oil, gas, coal, solar thermal, municipal solid waste, and enriched uranium. Its power output would eventually surpass the water turbine, and it erased a crucial geographic limitation of hydropower: it could be located anywhere, not just where rivers flow. In 2020, the steam turbine generated more than three-quarters of the world’s electricity and about 44% in the United States.
The first gas turbine in the United States used to generate electric power went online in Oklahoma City in 1949. The gas turbine has several notable advantages compared to the steam turbine. It has a lower installation cost, it requires less space, it does not require large amounts of water for cooling, and a combined cycle facility using a gas turbine has a high conversion efficiency. The gas turbine began to rapidly replace the steam turbine powered by coal in the early 2000s.
The solar cell and the wind turbine have dramatically changed the electric power industry over the past two decades. Dramatic technological improvements in the efficiency of solar cells and the design of wind turbines have translated to equally dramatic declines in the cost of electricity from those sources. In the United States, wind and solar power are far cheaper than coal and nuclear power, and they are competitive with natural gas in most regions. The urgent need to reduce greenhouse gas emissions and other impacts of the fossil fuel energy system has augmented their economic competitiveness.
1 U.S. Energy Information Administration, https://www.eia.gov/tools/glossary/index.php?id=Prime%20mover
