A steam engine is a thermal engine that performs mechanical work using steam as its working fluid. Steam engines are external combustion engines, where the working fluid is separated from the products of combustion. Non-combustion heat sources such as solar, nuclear or geothermal energy may be used. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In the cycle, the water is heated and transformed into steam inside a boiler that operates at high pressure. When it expands through pistons or turbines, mechanical work is performed. The steam under reduced pressure is then discharged into the atmosphere, or condensed and pumped back into the boiler.
In general use, the term "steam engine" may refer to integrated steam plants (including boilers, etc.) such as railroad steam locomotives and portable engines, or may refer only to piston or turbine machinery, as in The beam motor and stationary steam engine. Specialized devices, such as steam hammers and pylons of steam piles, depend on the vapor pressure supplied by a separate boiler.
The use of boiling water to produce mechanical movement dates back more than 2000 years, but the first devices were not very practical. The Spanish inventor Jeronimo de Ayanz and Beaumont obtained a patent for a rudimentary steam water pump in 1606. In 1698 Thomas Savery patented a steam pump that used steam in direct contact with the water being pumped. Savery's steam pump used condensing steam to create a vacuum and draw water into a chamber, and then applied pressurized steam to pump more water.
Thomas Newcomen's atmospheric engine was the first commercial real steam engine with a piston, and was used in 1712 for pumping in a mine. They became popular for mining and 104 were in use in 1733, eventually more than two thousand of them were installed.
In 1781 the Scottish engineer James Watt patented a steam engine that produced a continuous rotating movement. Watt's ten horsepower engines allowed a wide range of manufacturing machinery to be powered. The engines could be located where water and charcoal or wood fuel could be obtained. By 1883, engines that could provide 10,000 horsepower had become feasible. The stationary steam engine was a key component of the Industrial Revolution, allowing factories to locate where hydraulic power was unavailable. The atmospheric engines of Newcomen and Watt were large compared to the amount of energy they produced, but the high pressure steam engines were light enough to be applied to vehicles such as traction engines and railway locomotives.
Alternative piston piston engines continued to be the dominant source of energy until the early 20th century, when advances in the design of electric motors and internal combustion engines gradually resulted in the replacement of reciprocating piston motors in use Commercial, Turbines in power generation. Considering that the vast majority of global electricity generation is produced by turbine-type steam engines, the "steam age" continues with energy levels well beyond those of the 19th and 20th centuries.
