When scientists talk about global warming they usually reference it to the start of the Industrial Revolution (ca. 1760–1840). That’s when CO2 emissions from burning coal first began to change the composition of Earth’s atmosphere. Previously, the CO2 content was around 275 ppm (parts per million). Today it is 415 ppm and climbing. How this all started is worth understanding.
The slideshow presents block diagrams of the first three heat engines that started the Industrial Revolution. They were all developed in England with the intent of replacing manual labor with coal-powered machines. Their first use was removing water from deep mine shafts, but they evolved way beyond that.
The Savery engine was able to remove water from mines with a two-cycle operation that involved manually opening and closing each of four valves in a specific sequence. When cooling water is poured onto the cylinder the steam condenses creating a partial vacuum. This draws water up into the main pipe. When fresh high-pressure steam enters the cylinder, that water is then pushed upwards where a drainage ditch can divert it away from the mine. Operation was slow and cumbersome, and errors in the sequence or timing of the valves caused occasional explosions. It also suffered from the same 32 foot water draw limit as a siphon. Still, it was better than a “bucket brigade” or other manual methods, and allowed for increased ore production.
The Newcomen engine improved on Savery’s design in two important ways. First, it used a piston and cylinder attached to a rocker arm with mechanical linkages (green lines) that automated the opening and closing of valves. Second, the rocker arm could be attached to any load that needed lifting (water, ore, workers, equipment) and got around the siphon limit.
The James Watt engine included some final modifications that really jump-started the Industrial Revolution. First, it separated the condenser from the piston and cylinder. That improved the efficiency by not having to heat, cool, then reheat the large metal cylinder — the cylinder was always hot and the condenser was always cool, and that reduced the amount of coal needed to run the engine. Second, the rocker was attached to a “crankshaft” that converted the linear motion of the piston into rotational motion. Rotational motion can power everything from saws to lathes to wheels, so Watt engines soon powered the factories and mills all around England.
The Watt engine was such a success that by 1850, the country was burning 62.5 million tons of coal each year. And each ton of burned coal releases 7172 pounds of CO2. [If you’re wondering how 1 ton of coal can produce more than 1 ton of CO2, note that the O2 comes from the air, not the coal.] Other fuels like natural gas and oil replaced coal when and where they became available, but burning those fuels also releases CO2. So over the years since then, we’ve added 140 ppm of this greenhouse gas to our atmosphere. And that’s why we’re now seeing the effects of Earth’s climate warming.
Fossil fuels are gradually being phased out. That’s a good thing since we now have other renewable energy sources, supplemented by nuclear, that do not emit CO2. But it’s still good to know the history of how we got here. You know what they say: “Those who cannot remember the past are condemned to repeat it.” — George Santayana, The Life of Reason, 1905.
Next Week in Sky Lights ⇒ An Ice-Powered Heat Engine