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How Steam Technology Works

Geyser Basin erupts at twilight in an amazing display of natural steam.
Geyser Basin erupts at twilight in an amazing display of natural steam.
Randy Olson/National Geographic/Getty Images

To witness the incredible power of steam, you don't have to look any further than the eruption of geysers or the explosion of gasses that occurs when lava reaches the ocean. Early man witnessed such sights and has long sought to control the raw power of steam through technology ranging from the basic tea kettle to the modern nuclear power plant.

Regardless of the level of technology involved, steam power comes down to one basic principle: When water is heated to the point of vaporizing, the vaporized water takes up more space than the liquid water did. This is because solids, liquids and gases are each held together by different levels of molecular forces. In solids, the molecules are compact. In liquids, they're further apart. And in gasses, like steam, they're even further apart.

If you heat a can of soup in a fire, the liquid contents will vaporize and eventually expand to the point where the can will explode to release the pressure inside. When this pressure is used to perform a particular task -- like turning a turbine or causing a kettle to whistle -- steam technology is harnessing steam power. The methods of heating, containing, channeling and using steam have changed, but the basic principle remains the same.

Learning to harness the power of steam has been a long process. Greek mathematician Hero theorized the use of steam technology in the second half of the first century. However, it would be well over 1,600 years before the first practical steam engine was created in order to drain water from mines and gardens. The age of steam that followed shaped the course of history by powering the Industrial Revolution, transforming the global shipping industry and revolutionizing modern warfare.

In this article, we'll look at how steam technology developed over the centuries and how our understanding of steam power changed the world.

Early Steam History

The earliest known records of steam technology can be traced back to Alexandria in AD. 75. It was there that the mathematician Hero, also known as "Heros" or "Heron," wrote three books on mechanics and the properties of air and presented plans for a simple steam engine.

Hero's design called for a hollow sphere with bent tubes emerging from either side of it. This mechanism was then filled with water and mounted above a fire. As the heat caused the water inside the sphere to vaporize, steam was forced to vent through the two tubes. This steam-powered propulsion caused the sphere to rotate -- like a wheel turned by bottle rockets.

Hero's method for transforming steam power into motion was the foundation for later steam technology. However, a great number of scientific advancements were necessary before the concepts behind his steam turbine could be put to practical use. Although people like Leonardo da Vinci toyed with the idea of steam power (the inventor suggested in 1495 that steam power could fire a projectile), advancements in engineering and more accurate measurements of temperature and time helped pave the way for the coming age of steam.

In 1606, Giovanni Battista della Porta of Naples recorded his theories about the role

of steam in creating a vacuum. He theorized that if water converted to steam inside a closed container resulted in increased pressure (remember the exploding soup can?), steam condensed to water inside a closed chamber would result in decreased pressure. This new understanding of steam played a vital role in future developments.

In 1679, French scientist and mathematics professor Denis Papin managed to turn della Porta's theory into reality through a surprisingly domestic project: the "Digester or Engine for Softening Bones." The sealed cooking pot was essentially the first pressure cooker. Papin expanded on this device by adding a sliding piston to the top of a closed cylinder full of water. When heated, the expanding steam pushed the piston up. As the steam cooled and became liquid again, the resulting vacuum pulled the piston back down.

In the next section, we'll look at how 17th century inventors began to put emerging steam technology to practical use -- beyond the pressure cooker, that is.

The First Steam Engines

In the late 17th century, England faced a timber crisis as shipbuilding and firewood consumed forests. The ships were necessary for trade and defense, but coal was a suitable substitute for firewood. However, producing more coal meant digging deeper coal mines, which increases the likelihood of water seeping into the mines. There was suddenly an urgent need for new methods of pumping water out of mines.

In 1698, Thomas Savery, a military engineer, obtained a patent for a steam pump and began pitching his "Miner's Friend" to anyone who would listen. The device consisted of a boiling chamber that routed steam into a second container where a pipe with a non-return valve descended into the water that needed to be removed. Cold water was poured over the container of steam and as the water vapor inside cooled to a liquid state, the resulting vacuum drew up water from below. The sucked-up water was unable to flow back past the non-return valve and was then drained through another pipe.

Unfortunately for Savery, the steam pump didn't achieve the success in the mining industry he had hoped for. Most of his sales were made to private estates that wanted to drain excess water and repurpose it for home and garden needs. Because the steam chamber's heating and cooling had to be managed manually, the engine was somewhat impractical. The engine could also only draw up water from a limited depth -- a deep mine required a series of engines installed at various levels.

However, in 1712 the blacksmith Thomas Newcomen and assistant John Calley, a glassblower and plumber, created a more effective steam-powered pump system. The Newcomen Engine combined Savery's separation of the boiler and steam cylinder with Papin's steam-driven piston.

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While Savery sought to replace conventional horse-driven pumps with his engine, Newcomen sought to use a steam-driven pump to do the work of horses. Newcomen's engine was similar to Savery's. It included a steam-filled chamber that was cooled by a quick injection of cold water to create a vacuum-inducing change in atmospheric pressure. This time, however, the force of the vacuum pulled a piston down and pulled a chain that activated a pump on the other end of a suspended beam. When the water in the piston cylinder turned to steam again, it pushed the piston up and a weight on the other side of the beam reset the pump.

The Newcomen engine proved to be a major success and was used in hundreds of mines across Britain and abroad. While the engine operated at a slow pace, the cost of its operation was cheaper than maintaining a stable of horses. Engineers soon began to tinker with the Newcomen Engine -- improving the cylinders, valves and fuel efficiency of the steam pump. The creation of stronger iron made the engine more durable. Smelters soon found they no longer had to operate next to rivers, as the Newcomen Engine could be used instead of water wheels to power furnace bellows.

In the next section, we'll look at the advancements made by James Watt, whose discoveries are largely credited as bringing about the age of steam.

Watt and the Steam Engine

James Watt revolutionized steam technology with his early steam engine.
James Watt revolutionized steam technology with his early steam engine.
Hulton Archive/Getty Images

While the Newcomen Engine and Savery's "Miner's Friend" certainly employed steam technology, today's steam engine is generally credited to the work of one man: James Watt.

Trained as an instrument maker in London, Watt eventually found employment near Glasgow University in Scotland. When one of the University's Newcomen Engines needed repairs, Watt found himself elbow-deep in the inner workings of steam technology. Watt soon recognized a basic design flaw: Time, steam and fuel were wasted by having both heating and cooling take place inside the piston cylinder.

Watt solved the problem by creating the separate condenser. He added a chamber separate from the cylinder (which he also insulated), where steam would be cooled to create the necessary vacuum. This separation allowed the piston cylinder to remain the same temperature as the entering steam with no energy wasted heating it and the water inside. Additionally, the separate condenser could be kept at a much lower temperature and required less cooling.

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After partnering with Matthew Boulton, Watt was able to produce a faster, more fuel-efficient engine using the separate condenser. The pair's attempt to find new uses for their successful engine led to two more crucial inventions -- the double-acting engine and the fly-ball governor.

The fly-ball governor created an automated method of opening and shutting steam valves to a piston. Sun and planet gear were fixed to a wheel-driven shaft. As steam power caused the rod to spin, the two balls spun outward from the shaft. When they reached their highest point, they caused the steam valve to shut. As their spinning slowed, they spun back toward the rod and caused the valve to open again. This transformed the motion in the steam engine from back and forth -- reciprocating motion -- into the circular motion required to operate a wheel.

The double-acting engine helped make the steam engine more efficient by harnessing the power of formerly idle steam to push down pistons.

In the next section, we'll look at the Cornish Engine: the next step in steam engine technology.

The Cornish Engine

Steam powered the Industrial Revolution. Power looms were used in textile manufacturing in 1844.
Steam powered the Industrial Revolution. Power looms were used in textile manufacturing in 1844.
Hulton Archive/Getty Images

James Watt's innovations set the stage for the Industrial Revolution -- beginning with the textile industry in the late 18th century. Wool had long been processed by hand and was later done so with the aid of water mills. But a number of new inventions soon saw factories powered by steam.

The Boulton and Watt engine was incredibly successful but other inventors were still intent on improving the technology. However, Boulton and Watt commanded a monopoly over the steam engine business as their engine was protected by strict patents.

Patent royalties cost mining companies a great deal of money. Inventor Richard Trevithick noticed the plight of the mines in his native Cornwall and set out to create an engine that avoided Boulton and Watt's patented technologies. Trevithick believed he could create an engine that did away with Watt's separate condenser by using high-pressure steam.

While the use of high-pressure steam had been theorized, it had not been executed successfully. Eighteenth century boilers were incapable of withstanding high pressure for long periods of time. But at the beginning of the 19th century -- ironically, just as Watt's patents were expiring -- Trevithick discovered that modern boilers could now withstand higher pressures. At the same time, American inventor Oliver Evans experienced similar achievements.

Trevithick's new Cornish Engine was cheaper, lighter and smaller than the Boulton and Watt engine. Arthur Woolf further improved the use of high-pressure steam in 1804. The London brewery engineer realized the idea of compounding -- a method where excess steam from one piston is used to fire a second piston and then a third. This method results in less heat loss.

In the next section we'll look at the rise of the steam locomotive.

The Steam Locomotive

Cornish inventor and engineer Richard Trevithick's steam locomotive successfully hauled 25 tons of cargo and 36 passengers at Pen-y-Darren, Wales in 1804.
Cornish inventor and engineer Richard Trevithick's steam locomotive successfully hauled 25 tons of cargo and 36 passengers at Pen-y-Darren, Wales in 1804.
Hulton Archive/Getty Images

Inventors were working on designs for steam-powered cars even as the first steam pumps were fine-tuned in the late 1600s. While some believe Ferdinand Verbiest created a working steam car in 1672, more evidence suggests French inventor Nicolas-Joseph Cugnot made the first steam-powered vehicle in 1769. But while the research and development of steam-powered cars continued for some time, the idea was most successful in the form of the rail-mounted steam locomotive.

The man behind the Cornish Engine, Richard Trevithick, was also a key individual in the development of the steam locomotive. It's important to note that train tracks already existed in the 1770s in various industrial areas of England. Iron-enforced wooden rails called tramways had been built for horses to pull carts of coal. In 1804, Trevithick unveiled a steam-powered engine capable of hauling 10 tons of iron for 10 miles. In 1808, Trevithick's Portable Steam Engine was displayed on a circular track in central London.

Another British engineer, George Stephenson, picked up two decades later where Trevithick left off. Stephenson's work in developing increasingly efficient steam engines for transporting coal led to the decision to create a rail link between Durham coalfields and a shipping port in Stockton. Stephenson suggested that the plan also permit the engines to carry passengers. In 1825, Stephenson conducted Locomotion No. 1 on its first journey -- carrying cargo and an estimated 600 passengers.

While the development of steam cars remained a mere scientific curiosity for the next 100 years, the steam-powered locomotive took off. The engine operated on a system of wheels rotated by a steam-driven piston. Engineers worked continuously to improve the system by increasing steam pressure, applying compounding and adding additional wheels.

The Steam Locomotive transformed the way people thought about distance.
The Steam Locomotive transformed the way people thought about distance.
Frans Lemmens/Iconica/Getty Images

The railway proved a vital part of the­ Industrial Revolution, changing the way in which cargo was transported across land and tying together distant populations. Steam powered the railways until diesel engines and electric power came to the forefront in the 20th century.

In the next section, we'll look at how steam technology changed the seas.

The Steamship

Steam-powered boats like the one in "Moonlight on the Mississippi" soon replaced vessels driven by sails or manpower.
Steam-powered boats like the one in "Moonlight on the Mississippi" soon replaced vessels driven by sails or manpower.
American School/­The Bridgeman Art Library/Getty Images

Just as steam revolutionized land transportation with the invention of the locomotive, it also became the dominant power source on water -- replacing manual oars and sails. The early development of the steamship closely parallels that of the steam locomotive and the steam engine itself. In the late 1600s, Denis Papin, innovator of the steam piston and pressure cooker, theorized the use of steam-driven impellers to power a boat.

However, it was 1763 before Jonathan Hull was granted the first steamship patent for a tug boat for port use that used Savory's Engine to power a water wheel. Unfortunately for Hull, both Savory's Engine and the Newcomen engine were unable to produce sufficient horsepower. It was only after James Watt's contributions to steam technology that early steamboats became feasible.

British and French inventors (including steam locomotive pioneer Richard Trevithick) worked on the concept but created only slow, cumbersome vessels. But during the same time period, Robert Fulton successfully tested a prototype steam boat for river use. In 1807, he launched the Clermont, a paddle-wheel boat that soon proved capable of transporting passengers and cargo miles up and down stream. The success spread to Europe, where in 1812, British engineer William Symington débuted the Charlotte Dundas, the first successful steam-powered passenger boat.

When it came to ocean travel, ships outfitted with sails were given auxiliary steam power to use when wind power was insufficient. One such vessel, "Savannah," became the first steam-powered ship to cross the Atlantic in 1819.

Steam power quickly replaced sails. By 1815, more than 40 steam vessels were operating out of Liverpool. By 1826, businessmen linked to the sail industry went so far as to send a petition for government intervention to protect their business. Steam power dominated naval transportation until the rise of diesel-powered engines in the second half of the 20th century.

In the next section, we'll look at the invention of the steam turbine and find out how it became an essential part of electrical generation.

The Steam Turbine

In the 1830s, British physicist Michael Faraday created an early electric generator called the dynamo. Other inventors soon set out to perfect a method by which a steam engine could create the rotary motion necessary to produce electricity. They soon discovered that there was a limit to the number of revolutions per minute a steam-driven piston could provide. But the solution to this problem was to be found, ironically enough, in the very technology Hero proposed in A.D. 75: the steam turbine.

Whereas Hero's steam turbine called for steam to be jetted from the perimeter of the object to be rotated, early 19th century engineers proposed directing steam straight onto blades attached to the perimeter of a wheel. However, steel was not yet strong enough to hold up to the stress of such rapid rotation. In 1884, British engineer Charles Algernon Parsons put new steel technology to use. He created a turbine capable of using compounded steam that turned a dynamo at 18,000 revolutions a minute. In 1890, his steam turbine and accompanying electric generator were installed in the Forth Banks power station. The technology soon spread through Europe.

Parsons also applied his steam turbine technology to naval purposes, introducing his vessel, Turbinia, at Queen Victoria's Diamond Jubilee in 1897. Parsons was subsequently commissioned to fit a Royal Navy destroyer with a turbine engine.

In the next section, we'll look at modern advancements in steam turbine technology.

Modern Steam

Steam is no remnant of the Industrial Revolution. Even nuclear power plants employ steam technology.
Steam is no remnant of the Industrial Revolution. Even nuclear power plants employ steam technology.
Guy Vanderelst/Photographer's Choice RF/Getty Images

The steam turbine continues to be a major factor in electric power generation throughout the world. Even nuclear power plants use the heat from a controlled nuclear chain reaction to produce needed steam. In the United States, more than 88 percent of all electricity is produced by steam turbines [source: Popular Mechanics].

As mentioned earlier, there are basically three stages of matter: Solid, liquid and gas. Each stage is held together by a different level of molecular force. With water, gaseous steam takes up space due to its molecules being furthest apart. However, when enough pressure is applied to steam, an amazing thing happens. The molecules are forced together to the point that the water becomes more like a liquid again, while retaining the properties of a gas. It is at this point that it becomes a supercritical fluid.

Many of today's power plants use supercritical steam, with pressure and temperature at the critical point. This means supercritical steam power plants operate at much higher temperatures and pressures than plants using subcritical steam. Water is actually heated to such a high pressure that boiling does not even occur.

The resulting high-pressure fluid of supercritical steam provides excellent energy efficiency. With the aid of high pressure, supercritical steam turbines can be driven to much higher speeds for the same amount of heat energy as traditional steam power. They also release less CO2 exhaust into the atmosphere. Additionally, new high-pressure boilers built with rocket technology are being developed to further control the levels of CO2 emitted. Some boilers will even cool the steam back into a liquid and channel it into the ground to capture emissions.

The future is bright for steam on other fronts as well. In the search for alternative automobile fuel systems, some scientists continue to pursue the 15th century dream of a car driven on steam power.

To learn more about steam engines, steampun­k and other steamy topics, look over the links on the next page.

Related How Stuff Works Articles

More Great Links


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