Parsons� radial flow steam turbine-generator, 1891.

UNITED KINGDOM - FEBRUARY 16: Until the invention of the steam turbine by Charles Parsons (1854-1931) in 1884, steam engines could not turn fast enough to produce electricity efficiently on a large scale. Used at the Cambridge Electric Light Station, this radial flow turbine-generator was the first to prove that turbines could be run as economically as the best steam engines. It used the energy of high-pressure steam at 200 degrees centigrade to run the turbine. Turning at 4,800 revolutions per minute, it had a power output of 100 kilowatts a second and operated for 30 years. Steam turbines still drive most generators today. (Photo by SSPL/Getty Images)