Steam turbine

By 1884, the reciprocating steam engine had ruled for a century—and reached its limits. James Watt's descendants had refined the design to remarkable efficiency, but the fundamental architecture constrained further progress. Pistons, connecting rods, and crankshafts imposed mechanical limits on speed and power. The largest reciprocating engines topped out at a few thousand horsepower and operated at slow speeds fundamentally mismatched to the high rotational speeds that electrical generators required. Charles Parsons saw the path beyond reciprocation.

Parsons was an Anglo-Irish engineer working at Clarke Chapman in Newcastle upon Tyne, a shipbuilding and engineering firm. His insight was that steam could drive rotation directly, without the intermediary of linear piston motion. In a turbine, expanding steam flows continuously through multiple stages of blades mounted on a central shaft. Each stage extracts energy from the steam as it expands and cools, spinning the shaft at thousands of revolutions per minute. The steam never reverses direction; energy transfer is continuous rather than reciprocating.

The challenge was engineering, not concept. Hero of Alexandria had described a rotating steam device in the first century CE. But Hero's aeolipile was a toy—it couldn't scale. Parsons's genius was designing a multi-stage turbine where steam expanded progressively through successive blade rings, each stage extracting energy while the steam dropped in pressure and temperature. This staged approach avoided the metallurgical nightmare of trying to handle high-pressure, high-temperature steam in a single expansion.

Parsons's first turbine, built in 1884, generated 7.5 kilowatts while spinning at 18,000 revolutions per minute. This was revolutionary: reciprocating engines achieved perhaps 100 RPM. The high speed was perfect for electrical generation, where generator efficiency increases with rotational speed. Within years, Parsons turbines were powering central generating stations, making electricity cheap enough for widespread use.

The competing design came from Gustaf de Laval in Sweden. De Laval's impulse turbine accelerated steam through a converging-diverging nozzle to supersonic velocities, then directed it against a single wheel of blades. This simpler design worked but created enormous centrifugal stresses—the blades wanted to fly apart. De Laval's turbines were limited in power by material strength. Parsons's reaction design, which extracted energy more gradually across multiple stages, proved more scalable.

The cascade from Parsons's invention restructured the energy economy. Central-station power generation became practical because turbines could be built in sizes impossible for reciprocating engines—25,000 kilowatts by 1912, vastly larger than any piston engine. Ships adopted steam turbines for propulsion; Parsons famously demonstrated his turbine-powered Turbinia at Queen Victoria's 1897 Diamond Jubilee naval review, streaking past the assembled fleet at 34 knots while the Navy's fastest ships could only manage 27.

Today, steam turbines generate approximately 80% of the world's electricity. Nuclear power plants, coal plants, and combined-cycle gas plants all use steam turbines in their final energy conversion stage. The turbine Parsons built in his workshop—designed to spin a generator that produced enough electricity for a few light bulbs—has scaled to units producing over a gigawatt. The principle remains identical: expanding steam spinning through staged blade rings, continuous rotation instead of reciprocating thrust.

The steam turbine demonstrates how enabling technologies create new possibilities. Without high-speed rotation, electrical generators couldn't achieve economic efficiency. Without economical generators, central-station power was impractical. Without central-station power, electric lighting and motors remained curiosities. Parsons's turbine didn't just improve on the reciprocating engine—it enabled the entire electrical civilization that followed.