Steampunk is driven by a fascination with the height of the industrial revolution, when steam engines were the major driving force behind technological advances. But when did steam power first come about and how does it work?
Basically, a steam engine is an engine which uses steam to provide the force behind mechanical movement. When water is heated to the boiling point, it expands into steam. This expansion process creates energy which can be targetted into pistons, forcing the pistons to move. The expanded water (steam) is then siphoned off, cooled and returned to the boiler. As the steam is released from the piston, the piston contracts and prepares for another blast of steam.
The modern internal combustion (car) engine works in a similar way except–rather than external heating of the water to steam and funneling the pressure of the steam into a piston, the modern internal combustion engine fills the compressed piston with a flammable liquid. When the liquid (petrol or gasoline) is ignited, the resulting expansion of the liquid to gaseous state, forces the piston to move. The gas is then released as exhaust and the piston returns to a compressed state. There is a lot more to a car engine than this, but that’s the basics. The fuel for a car engine is burnt or expended to make the piston move, whereas the steam from a steam engine is converted back to water and can be used again.
Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be used. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In the cycle, water is heated and transforms into steam within a boiler operating at a high pressure. When expanded through pistons or turbines, mechanical work is done. The reduced-pressure steam is then condensed and pumped back into the boiler.
In general usage, the term steam engine can refer to either the integrated steam plants (including boilers etc.) such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine. Specialized devices such as steam hammers and steam pile drivers are dependent on the steam pressure supplied from a separate boiler.
Using boiling water to produce mechanical motion goes back over 2000 years, but early devices were not practical. The Spanish inventor Jerónimo de Ayanz y Beaumont obtained the first patent for a steam engine 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 further pump the water. Thomas Newcomen’s atmospheric engine was the first commercial true steam engine using a piston, and was used in 1712 for pumping in a mine.
In 1781 James Watt patented a steam engine that produced continuous rotary motion. Watt’s ten-horsepower engines enabled a wide range of manufacturing machinery to be powered. The engines could be sited anywhere that water and coal or wood fuel could be obtained. By 1883, engines that could provide 10,000 hp had become feasible. The stationary steam engine was a key component of the Industrial Revolution, allowing factories to locate where water power was unavailable. The atmospheric engines of Newcomen and Watt were large compared to the amount of power they produced, but high pressure steam engines were light enough to be applied to vehicles such as traction engines and the railway locomotives.
Reciprocating piston type steam engines remained the dominant source of power 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) steam engines in commercial usage, and the ascendancy of steam turbines in power generation. Considering that the great majority of worldwide electric generation is produced by turbine type steam engines, the “steam age” is continuing with energy levels far beyond those of the turn of the 19th century.