A steam turbine is a machine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft, possibly using a renewable energy heat source. Its modern manifestation was invented by Charles Parsons in 1884.[1][2] Fabrication of a modern steam turbine involves advanced metalwork to form high-grade steel alloys into precision parts using technologies that first became available in the 20th century; continued advances in durability and efficiency of steam turbines remains central to the energy economics of the 21st century.
The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible expansion process. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator-about 85% of all electricity generation in the United States in the year 2014 was by use of steam turbines.[3] A steam turbine connected to an electric generator is called a turbo generator.
As of 2021, among the largest steam turbines in the world is the Arabelle steam turbines manufactured by GE based on an original design by Alstom.[4] An Arabelle turbine is 7 m in diameter, weighs 4000 tons and spins at 1500 rpm. In a typical nuclear installation, another 4000 tons of supporting steel structure is required, as well as 1000 tons of pumps, valves, and pipes.[4]
Technical concerns include rotor imbalance, vibration, bearing wear, and uneven expansion (various forms of thermal shock). In large installations, even the sturdiest turbine is capable of shaking itself apart when operated out of trim.
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