The Engines of Progress
Charting our thermal efficiency journey
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We have witnessed how knowledge can “evaporate” our need for matter and compress the cost of goods. All of this requires energy. While the invention of agriculture was an energy revolution of our stomachs, humanity would likely have remained agrarian if it were not for another energy revolution: the Industrial Revolution, which fed the fires of our machines. Here, we chart the progress of engine technology and thermal efficiency and how these heat machines changed our world.
As I discussed previously, technology is counter-entropic. It is the search for improbable combinations of atoms that work together in new, useful ways.
notes that this requires a “crystallized” form of energy or power source. Until the Industrial Revolution, energy was largely limited to that which could be done by animal or human power. The key breakthrough to unlocking a future of growth was the capability to harness heat energy to do work.In the late 1600s, the idea that water could be heated into steam and used to make things move was not new. Thousands of years earlier, inventors had built devices that did just that, but these simple machines were little more than amusement pieces and curiosities. They were inventions, novel ideas that had unrealized potential. It took the hard work and ingenuity of engineers and entrepreneurs to find ways of transforming them into true innovations. And like most such innovations in the story of human progress, no single individual can lay claim to having invented them.
External Combustion
External combustion technology was the first to be commercialized. In external combustion, heat energy is directed into a medium (usually water) where it boils to do work. I begin this analysis with the Newcomen steam engine because it was the first heat engine to become widely used. Invented circa 1705, this simple steam engine was massive, inefficient, and difficult to operate. The design employed a coal-fed boiler that heated water into steam. Above it, a cylinder collected that steam below a piston. The pressure of the steam pushed up upon the piston, and at the apex, cool water was injected into the cylinder, creating a partial vacuum. This vacuum allowed the pressure of the air to push the piston back down to where the process could be repeated.
First installed commercially in 1712, the Newcomen engines were used primarily to pump water out of coal mines. They serve as a great example of how necessity breeds innovation but also the other way around. The machines enabled coal miners to explore deeper deposits for Britain’s rapidly growing coal demand and the machines themselves helped fuel that demand with their voracious appetite for the fossil fuel. This was due to their poor thermal efficiency of roughly 0.5 percent. Thus, the Newcomen engines were only economically viable near coal mines.
It didn’t take long for engineers to address the Newcomen design limitations. In the 1760s, James Watt realized that most of the engine’s heat energy was wasted reheating the cylinder after it had been cooled. He fixed this by designing a separate cylindrical condenser where cool water was injected, allowing the main cylinder to remain hot. He also devised new seals, better machining techniques, and other innovations that increased thermal efficiency to between 2 and 3 percent. The first Watt engine went into operation in 1776.
Watt went on to further improve his design, developing a “double-acting” engine by 1783 that admitted steam to both sides of the piston, alternating back and forth. This double action could be used to convert a simple “up and down” motion into a more useful circular motion with a broader range of use cases, including powering early factories. With the Watt engine, waterwheels were no longer needed. Nascent factories could now operate their machines anywhere, not just near sources of running water.
These early steam engines were “atmospheric,” most of the “work” was done by the weight of the atmosphere pushing down on a partial vacuum created when condensing steam. Watt and others remained resistant to using what was then called “strong steam” or high-pressure engines for safety reasons. But in theory, a “strong steam” engine could be more compact, lighter, and more efficient than an atmospheric engine ever could.
By 1811, continued technological advancement made high-pressure engines possible. The Cornish engine used high-pressure steam to push down on the piston (as opposed to atmospheric pressure), helped along by a vacuum underneath. The design was aided by the advancement of boiler technology. New flued boilers were cylindrical and laid horizontally, and thus could take significantly more pressure than prior “haystack” designs.
By 1830, single-flued boilers gave way to multitubular designs that greatly increased the surface area in contact with water, heating the water into steam far more efficiently. Additional improvements in design and materials more than tripled thermal efficiency to about 10 percent and made the steam engine compact enough for mobile applications. These improvements made steam-powered ships and the first practical locomotives possible, including the famous “Rocket” (pictured below).
The last major iteration of the steam engine, the steam turbine, emerged in the closing decades of the 19th Century. Designed and promoted by Charles Algernon Parsons, the steam turbine eschewed pistons, and instead used hot high-pressure steam to rotate a turbine. This design breached over 20 percent thermal efficiency. The steam turbine was almost immediately put to use on ships enabling faster sea travel, but also became the method of choice for generating electricity. Turbines began providing affordable electricity just as the first electric light bulbs hit the market.
Internal Combustion
Steam engines remained an important power source into the 20th Century and through the so-called “Second Industrial Revolution,” but their limitations had been reached. The second industrial revolution was not defined by coal and external combustion, it was instead driven by petroleum and internal combustion. Liquid petroleum could be refined into specialty fuels like kerosene, diesel, and gasoline and be easily transported via pipelines. Petroleum products were better for the environment as well. Compared to coal, they emit fewer pollutants and about 30 percent less carbon dioxide for a given unit of energy.
In addition, internal combustion engines could harness that energy more efficiently than external combustion because they removed the intermediary medium (water) and directly combusted the fuel instead. They also could be made more compact and power-dense. Like the steam engine and many other innovations, the history of internal combustion is convoluted with no clear “inventor.” It was instead a series of good ideas whose time had come in the latter half of the 19th Century.
Two basic engine designs would come to dominate. Both directed a fuel/air mixture into a series of pistons where it was ignited to create a small explosion. The pressure of this mini-explosion was then used to draft a shaft connected to a flywheel. In diesel engines, pressure alone ignited the fuel/air mixture. In gasoline engines, on the other hand, a carefully timed ignition spark was required. The first successful four-stroke engine, known as the “Otto cycle,” began production in 1876.
These early engines were less thermally efficient than steam but were more compact, lightweight, and better suited to mobile applications. For this reason, gasoline won in a three-way race with steam and electricity to power the automobile that would go on to replace horses. More efficient diesel engines became the engine of choice for trucks, ships, and trains. The single greatest achievement of internal combustion, however, was unlocking powered flight.
While unpowered gliders had been experimented with for some time, powered flight was thought, by many, to be impossible due to the limitations of engine technology. This was among the primary challenges that the Wright Brothers faced. They needed a powerful, compact, and lightweight engine, something that steam couldn’t provide. In fact, at the time, internal combustion engines couldn’t either. The Wrights were forced to innovate and fashion a custom engine out of an aluminum block. In another example of how innovation can be self-reinforcing, it is notable that the Wright’s aluminum engine would have been impossible just a generation earlier.
Aluminum deposits on Earth are rarely pure, thus extraction of the metal was historically expensive; aluminum was worth more than gold. By the turn of the 20th Century, however, aluminum prices had fallen due to the development of the Bayer refining process in 1889. This energy-intensive process was made possible by…you guessed it…the proliferation of relatively efficient steam-powered electricity generation plants.
By the 1930s, internal combustion engines controlled the skies and surpassed the efficiency of steam turbines. By the 1950s, diesel engines were achieving thermal efficiency ratings of nearly 50 percent, or roughly double that of the most capable steam turbines a few decades earlier. And like external combustion engines that began with pistons, internal combustion eventually found its way to rotating turbines.
The jet engine was simultaneously and independently invented in Germany and Britain in the 1930s. They utilized a turbine-driven compressor to compress incoming air where it could then be mixed with kerosene fuel and ignited in a combustion chamber. The high-pressure explosion of gasses rocketed out the rear of the engine, providing a forward propulsive force. As it exited, some of this explosive energy was captured by a turbine that, in turn, drove the front compressor. Lacking any pistons, jet engines created little vibration, reducing wear and tear and enabling them to reach higher speeds. The jet turbine ultimately made air travel faster, safer, and more affordable.
Atoms to Bits
Engine innovation did not stop there, but the vast leaps in thermal efficiency were over. In part, because we approached the physical limits of using heat energy to do work. At the same time, the third industrial revolution, the information technology revolution, focused more on bits instead of atoms. The IT revolution augmented our minds, not our bodies. It doesn’t take much energy to run a computer. Nonetheless, computers have been instrumental in designing new gas turbine blades and other engine parts, making them lighter, cheaper, and able to withstand higher pressure and heat.
In this era, a new fossil fuel is emerging front and center: natural gas. Natural gas is more environmentally friendly than petroleum, emitting fewer pollutants and about 30 percent less carbon emissions per unit of energy. Engineers have also developed the Combined Cycle Gas Turbine (CCGT) to harvest this energy with greater efficiency. With CCGT, natural gas is ignited and used to drive a turbine, much like a jet engine. Instead of dumping the hot exhaust, however, it is used to heat water and transform it into steam. The steam is then used to drive a separate turbine. CCGT devices have broken 60 percent thermal efficiency, providing low-cost, low-environmental impact energy for this new world of bits.
Charting all of this above, we can see that the “social supercomputer” has led a path of ever-increasing energy efficiency. Our ability to extract the energy stored in fossil fuels has improved dramatically, from 0.5 to 64 percent thermal efficiency. At the same time, our preferred fuel has become significantly less carbon-intensive and less polluting. We can expect that, so long as the “social supercomputer” continues humming along, this trend will continue. This is crucial because, without energy abundance, there can be no progress at all.
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The future of fuel-to-energy efficiency is bright! Thermoelectrics could help capture more energy from waste heat and things like solid oxide fuel cells or companies like Lightcell energy might squeeze more energy out of fuels.
https://en.wikipedia.org/wiki/Thermoelectric_generator
https://en.wikipedia.org/wiki/Solid_oxide_fuel_cell
https://www.lightcellenergy.com/