Shift Key Summer School: How Does a Power Plant Work?

Just two types of machines have produced the overwhelming majority of electricity generated since 1890. This week, we look at the history of those devices, how they work — and how they have contributed to global warming.

This is our second episode of Shift Key Summer School, a series of “lecture conversations” about the basics of energy, electricity, and the power grid for listeners of all backgrounds. This week, we dive into the invention and engineering of the world’s most common types of fossil- and nuclear-fueled power plants. What’s a Rankine cycle power station, and how does it use steam to produce electricity? How did the invention of the jet engine enable the rise of natural gas-generated electricity? And why can natural gas power plants achieve much higher efficiency gains than coal plants?

Shift Key is hosted by Jesse Jenkins, a professor of energy systems engineering at Princeton University, and Robinson Meyer, Heatmap’s executive editor.

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Here is an excerpt from our conversation:

Robinson Meyer: It’s interesting thinking about the deployment of steam and these Rankine cycle generators in the late 19th century for us as people who care about the power grid. These are interesting techniques as they’re deploying electricity for the first time. But the use of coal to convert water into steam and the use of steam power actually comes way earlier than any of this, right? Like, it’s steam. That is actually the 19th century — the core 19th century and late 19th century, especially — energy medium. And actually, the history of the 19th century energy is switching from wood and hydropower to coal-powered steam.

And already by the time that the Pearl Street station is built in New York, the United States is crisscrossed with steam engines. Our economy already runs on steam. It’s actually the application of steam and coal — which at that point are kind of old and fundamental technologies to economic function — to power generation. They didn’t have to make any huge discoveries around steam and coal. They were already using steam and coal in factories, they just weren’t intermediating it through the electricity grid.

Jesse Jenkins: That’s right. And in all these cases, you’re just trying to convert that steam, the expansion of that steam, into motion, whether that’s the pistons of a steam engine or the pistons of a reciprocating generator attached to a dynamo in Pearl Street, or, in a lot of factories, just a bunch of belts, right? That would then move equipment throughout the facility. It’s just a lot easier to move energy around, and more precise to do that as electricity. And so over time, the devices in industrial facilities all converted over to using electricity directly, and then you could generate your energy somewhere far away.

And this is the other, second advantage of steam turbines. What made Westinghouse so successful is that they have large economies of scale, so it’s a lot cheaper to generate power from a big steam turbine than the equivalent amount of power from a lot of little steam engines. And that wasn’t … I mean, that’s true for reciprocating engines, but they kind of top out, given their complexity.

The Pearl Strait station generators were in the 100-kilowatt scale. I think there were six of them, originally, so 600 kilowatts, and they only powered a few hundred lights, which is remarkable. These lights, the original lights, were incredibly inefficient, so it took something like 1,000 watts or more per light bulb. Whereas again, now we’re down to like, 10 to 15 watts in an efficient LED bulb. But anyway, they were in that kind of hundreds of watts scale, and that kind of maxed out the scale of the reciprocating engines. Steam turbines you could increase and increase and increase into the megawatt scale, and by doing that utilities or generators were able to lower the cost of energy while expanding customer bases.

Mentioned:

Powering the Dream: The History and Promise of Green Technology, by Alexis Madrigal

This episode of Shift Key is sponsored by …

The Yale Center for Business and the Environment’s online clean energy programs equip you with tangible skills and powerful networks—and you can continue working while learning. In just five hours a week, propel your career and make a difference.

Music for Shift Key is by Adam Kromelow.