How Hydroelectricity Works

by it. The storm passed largely to our east. But even as Helene transformed from hurricane to tropical storm, it caused lots of problems, particularly in eastern Tennessee and western North Carolina. At one point there were reports that said the Walters Dam, also known as the Waterville Dam, had failed. While dam is on the Pigeon River at one end of Waterville Lake, and it is a hydro electric dam.

So today I thought I would talk about how hydro electric dams work while sending lots of love to the folks in western North Carolina and up in Tennessee who continue to endure dangerous and difficult circumstances. If any of y'all are out that way, please please try and be as safe and careful as possible. Fortunately, the reports of

the dam failing. It turned out to be false, but it also meant that people were urged to evacuate, which was probably a good thing considering the massive flooding conditions that have persisted in those areas. So let's talk about hydro electric dams. And there are quite a few things we need to talk about before we even get to hydro electric dams. One of those our use of water power in order to do work that's been going on

for more than a millennium. The Greeks invented a water wheel for doing stuff like milling grain, and early reference can actually be found in the works of Philo of Byzantium, who lived between two eighty BCE and two twenty BCE. It is probably wondering why the heck they were counting backwards with their years, that's a joke. Similar engineering was going on in China, so it wasn't just the Greeks who had thought this up. Chinese engineers had come up

with similar approaches. So this was kind of spun not spontaneously, that's giving the wrong word, but emerging in different parts of the world around the same time period. And folks had figured out that the flow of water was a really good source of work power if you could harness that water properly, and water wheels were the way to go.

This early work would evolve over time, with mills and such becoming much more complex over the following centuries, but that it's an important thing to start with, this idea of harnessing the power of moving water. You typically would have a wheel outfitted with blades. The water would make contact with those blades, pushing the wheel to rotate, and you would use that rotational energy to operate something like the grindstone for a mill, so you could grind grain

down into flour, that kind of thing. That wasn't the only application, but it was a common one. So that sets the stage for part of our equation. Now let's skip way ahead to the early to mid seventeen hundreds, so more than a millennia has passed at this point from the original water wheels. In the mid seventeen hundreds, a French engineer named Bernard Forrest de Belldor wrote an exhaustive treatment on hydraulics, and it was titled Architecture hydra Leik.

It was published in four volumes starting in seventeen thirty seven, with the fourth one, publishing in seventeen fifty three. His work would help inform countless other engineers who are working on things like waterways and water works that sort of stuff. Because Old Bernie he was primarily a military and civic engineer. Much of his work focused on military operations, which obviously require a lot of versatility and resilience. I mean, if you're going to make stuff for the military, it has

to be able to withstand a lot of punishment. And his work actually helped set the foundation for the Industrial Revolution. It guided a lot of mechanical engineers in the eighteenth and nineteenth centuries. Now we'll do another short hop to the end of the eighteenth century. That's when Michael Faraday was born. He was born in England on September twenty second, seventeen ninety one. This was about thirty years after Old Bernie had shuffled off the mortal coil. Faraday grew up

to be a very very clever, smarty pants. Initially he was a chemist and a darned good one, but he also did pioneering work in the fields of magnetism and electricity, sometimes literally as and he literally did work in magnetic and electrical fields because I'm clever, and it was Faraday who proved there was a relationship between magnetism and electricity. If you were to move a permanent magnet near an electrical conductor, then you would induce voltage. You would induce

an electric current to flow through that conductive material. The magnetism was what was doing it, but it only happened as a conductor moved through a magnetic field. If you just put a permanent magnet, even a really strong permanent magnet, next to a conductor, then once that initial fluctuation settled, you would not have an electrical charge. It just wouldn't be flowing. However, if you did keep the magnet moving around the or you move to conductor around a magnet, voila,

you would start to detect an electrical charge. Thus, Faraday learned that a fluctuating magnetic field can induce electricity to flow through a conductive material. This allowed for the creation of both electric motors, which use an electric charge and magnetism to convert that into physical work, and the dynamo, which does the inverse. You do physical work and you

use magnetism and you generate electricity through the process. Essentially the way This works is you start with a permanent magnet and you use this permanent magnet to essentially surround a loop of wire in the magnetic field. The loop of wire you would mount on an axle that you could rotate, and the ends of the wire themselves they would connect to what are called slip rings, one each, So one end of the loop is on one slippering, the other end of the loop is on another slipper,

both of which are around this axle that rotates. So then imagine that you have connecting to the slooper rings brushes that in turn connect to electrical wires. So the brushes can conduct electricity as well. They just rest against the slip ring. So those electrical wires then connect to a circuit. Let's say that our circuit connects to a

light bulb. It's a really simple electrical circuit. So one end connects to the slipperings that in turn are connected to either end of a loop inside this permanent magnet, and the other ends connect to the electrodes on a light bulb. So rotating this loop of wire inside the permanent magnet means that the loop is going through the magnet's magnetic field. And that is the same as having

a fluctuating magnetic field. So it induces an electrical charge to flow in the loop, and electricity flows through the slipp rings, through the brushes to the wires, and you have yourself a simple electrical generator. So in this case, the generator is connected to the light bulb and it lights up as current is supplied to it. Now, this

particular arrangement would be an AC generator alternating current. Now to understand why, let's think of those two wires that we have connected to either ends of the loop through these brushes and slipperings. Right, So one wire connected to the light bulb to the slippering is wire A. The other one we'll call wire B. So wire A effectively is connected to one end of this loop, and wire

B is connected to the other end of the loop. Now, imagine we've got this loop of wire nestled between the north and south poles of a magnet, and we've frozen time. At the moment, it is in rotation, but we've frozen time, so everything's frozen, and right now the loop is horizontal in reference to the magnets on either side, so it's at a ninety degree angle to the magnetic fields. That's when the magnetic field is strongest, at least it's most strongly affecting the loop. The A side of our loop

is closest to the north pole of the magnet. The B side of our loop is closest to the south pole, and we rotate so that side A is moving upward with reference to the magnet. Side B is moving downward because it's rotating right now. When the loop is vertical with reference to the permanent magnet, then we're at the weakest point with reference to the magnetic field. But the rotation continues. Now side A is moving downward in reference to the magnet and the south pole, and side B

is moving upward toward the north pole. The flow of electricity then reverses direction. So every half rotation this happens right so as as side A is moving up, electricity flows in one direction. As side A starts to move down. Once it's completed that half rotation, electricity moves in the opposite direction. It is an alternating current, and this happens over an over again, So that is a type of

alternating current. We're going to take a quick break. When we come back, I will talk about what you would do if you wanted to create a generator that created direct current. But first let's take this quick break. Okay, So we talked about an alternating current generator, a dynamo if you will, how do you create direct current where the direction of current remains consistent it doesn't change. Well, A lot of smaller electrical generators use this to create

direct current. It's great for powering lots of devices that require direct current. It's not so great for transmitting power across great distances. You really need alternating current for that if you want to do it without a lot of electricity loss along the way, But we'll talk about that in a second. So you do this with a device

called a commutator. That's the important component in a direct current generator, and essentially it's a special kind of segmented collar that goes around this rotating axle, and the segments are insulated from each other, so you can think of there being a gap in this collar that separates one side from the other. The commutator essentially reverses the reversal.

So the wires connect to the commutator via brushes, and because of the break in the collar, it's almost like the wires are switching which side of the loop they're connected to. Remember before I was saying wire A and wire B to say like wire A is always connected to one side of our rotating loop and wire B is connected to the other side. But with a commutator, technically the wires are switching which side of the loop

they're connected to with every half rotation. So because the wires are effectively swapping electrodes, the actual flow of electricity remains in the same direction the whole time. I know this is really tricky. It's tricky for me to explain. It's tricky to understand without the use of visual aids. I highly recommend that if you want to learn more about this, just go to YouTube and search how commutators

work or how direct current generators work. That'll clear stuff up because you'll be able to see an illustration and understand what I'm talking about here. But it is a very clever workaround, Like you're still technically generating alternating current if you were just looking at the loop itself, but because of this commutator, you end up with direct current as your output. The important thing for our discussion is that using a coil of conductive wire. Material moving through

a magnetic field induces electricity to flow. So if you have access to a source of physical power so that you can rotate this loop of wire, then you can generate electricity without expending a lot of effort yourself. Now you can have this connected to something like a crank or whatever that you physically turn and generate electricity that way. I actually have an emergency radio that works in this principle. You can crank the radio and it will generate enough

electricity to power the radio. So if you are in an emergency where there's no you know, access to power, you can listen to radio signals and find out what's going on. A lot of bicycle lamps work in this way too. The lamps connect to the actual pedals, the pedal system of the bike, and so as you pedal the bike, you're also powering the dynamo that provides electricity to the lamp so that you can light your way

if you're riding around in the dark. So if you were to offload this physical work to something else, then you can generate electricity without having to you know, exhaust people in the process. This is how stuff like wind power works. How hydro power works. Actually, it's how nuclear power works. Nuclear power doesn't do it through water, it does it through steam. I guess technically you could say water because it's water vapor, but yeah, it generates high

pressure steam to turn turbines. But you know, hydro power just uses flowing water to turn turbines. Wind power obviously uses wind to turn turbines, but all of these ultimately end up powering electrical generators. So with a hydro electric dam, you've got your dam. Your dam blocks the passage of water, and you've got essentially a lake that forms on one side, and you do allow water to go through the dam, otherwise it wouldn't generate electricity for you. But on the

other side you have your your continuing river. Right, So inside the dam itself, you've got channels or pipes where you allow water to pass through from an area of higher elevation to lower elevation. And what you're doing is you're allowing gravity and water to do a whole lot of work on your behalf. Now, the difference between the area of high elevation and the area of low elevation is called the dam's head. The amount of head determines sort of the pressure. How much pressure is going through

this system. So if there's a very small difference in elevation, then the pressure is going to be much lower. If there's a greater difference, if the water is coming from very high and moving to very low elevation, then that water's going to be moving at much greater pressure. And at the base of this channel or pipe that's in the dam, you have a turbine, and a turbine's essentially a type of fan with blades that are designed to turn when the whole mess of water is flowing through

the turbine. There are different designs of turbines. We're going to talk about those in a moment. So the type of turbine you use is typically determined by the kind of dam you're building, and the things like how much elevation change are you working with, how much pressure is going through what sort of flow rate are you looking at, like is it going to be a high flow rate or low flow rate? All of these things will determine which turbine would be best suited for that particular application.

Because not all turbines work perfectly under all conditions. Some are ideal for very specific applications, and you want to use the one that's best suited for the way you're working, because that's going to be the most efficient means for you to generate electricity. Now, you can then take the alternating current created by one simple generator, and with the use of transformers, you can boost the voltage that is output for the purposes of transmitting electricity across long distances.

Higher voltages transmit through wires with less power loss over length of transmission. So typically for transmission, you want to boost the voltage up really high if you're going to

be transmitting that electricity across longer distances. We're talking about alternating current here again, Like if it's direct current, you typically want to keep your load that is, the thing that's using the electricity fairly close to the area of creating the electricity in the first place, the power plant in other words, But with alternating current, you want to up the voltage so that you can push this electricity out to where it needs to be, and then you

would have a secondary transformer on the other end that would step down the voltage for the purposes of distributing the electricity to power homes and businesses and that kind of thing. So you've got transformers on either end, on one end to really boost the voltage, on the other end to bring the voltage back down. And transformers are actually pretty simple. You could argue that they are not more than meets the eye. You have essentially two coils

of wire or cable inside a transformer. Now you also have an iron core inside the transformer. The easiest way I would use to envision the iron core is think about like almost like a picture frame, but it's made out of iron. And so you've got a left side and a right side of this right on the left side you have looped a coil of conductive wire, and on the right side you have a different loop of conductive wire. Let's say the left side is our primary

coil or our primary winding. This length is ultimately connected to a source of electricity, so our generator. In other words, so the incoming electricity goes to the primary winding of our transformer. The other side, the other coil, it connects to an outgoing path. This is our secondary winding. And what happens with the voltage depends upon the difference between the number of turns or coils per side of primary versus secondary. So let's say we want to step up

the voltage. We've got electricity coming from our generator. We want to step up the voltage so that we can push electricity across miles and miles and miles of cable. So to step it up, we have the electricity pass through the primary winding wrapped around this iron core, and the secondary winding. We have double the number of turns that the primary winding has. So let's say the primary winding has you know, twenty loops around the iron core.

The secondary winding has forty loops wrapped around the iron core. And as alternating current electricity flows through the primary winding, it generates a magnetic field. This magnetic field is also guided by that shared iron core, and the magnetic field is also fluctuating because we're talking about alternating current, right, The current itself is changing directions many times a second, which means the magnetic field essentially is doing little flippy

flops many times a second. And our secondary set of turns or coils, remember it has twice as many as the primary. It's within range of this fluctuating magnetic field that's guided by the iron core, and that means we have another case of induction. It is inducing electric charge in the secondary windings, and because there are more turns

in this winding, it's stepping up the voltage. We get more voltage coming out than we did going in because of this relationship between the number of turns or coils in the two windings. So we zap electricity across miles and miles of cable. Because voltage is kind of like pressure, so the higher the voltage, the stronger the push is. Now the other end of those miles of cable, we have another transformer, only this one has a secondary coil or secondary winding that has fewer turns or loops than

our primary winding does. So, once again, the fluctuating magnetic field generated by the primary coil induces an electric charge in the secondary coil. But because there are fewer loops in this secondary coil, we have a step down in voltage. Now that's the bare basics of electrical transformers. There is more to it than that. That gets more complicated. So I guess you could argue that, yes, there is more than meets the eye, but it's good enough for our

purposes of this episode. All Right, Now we're going to take another quick break. When we come back, I'm going to talk about the evolution of turbines and which turbine is best used for a power generation scenario, and then we'll conclude with a little more talk about hydroelectric power and where that really got started. But first let's take another quick break. Okay, we're going back to turbines. So there is a long history of engineering for these things

as well. A nineteenth century French engineer named ben wa fournee a Ron, whose name I have totally butchered, developed a turbine that was based on a water wheel design created by his former instructor Claude Burden. As the Encyclopedia Britannica puts it, in eighteen twenty seven, ben Wah built quote a small six horsepower unit in which water was directed outward from a central source onto blades or veins

set at angles in a rotor end. Quote. He called it a turbine, and we would continue you tweaking his design to create more efficient powerful water wheels. Now, initially these were not used as hydroelectric power generators. They were instead used to do physical work for industrial purposes such as milling grain. However, much later at the end of the nineteenth century, his designs would be used in some hydroelectric dams, namely the American side of Niagara Falls in

eighteen ninety five. In eighteen forty nine, however, an American engineer named James Francis created a turbine designed that would later be known as the Francis turbine. These turbines work well if they're either in horizontal or vertical alignment, so they're pretty versatile. They're also good for medium to large scale hydroelectric operations, and it's what I would call a semi reaction turbine. So there are different types of turbines.

Some are called impulse turbines. Impulse turbines work from water forcing the turbine to turn. It's the force of impact of water against turbine that causes rotation. Those are impulse turbines. Reaction turbines depend on something else like water pressure, where the design of the fan blades in the turbine means that you have an area of low pressure on one side of the blades and high pressure on the other, and that difference in pressure causes the turbine to rotate.

The Francis turbine is kind of a combo between the two. So it's turned partly through the force of water hitting the blades and partly through this pressure differential. So it's a semi reaction turbine, is how. Some people call it a reaction turbine. Some say, well, it's not a true reaction turbine. So that's kind of where I get wishy washing called semi reaction turbine. But yeah, that area of low pressure on one side and high pressure on the

other is part of the reason this turbine turns. Also, incoming water is direc acted inward toward the center of the turbine, so the water enters radially. So water is entering from around the turbine, around the circumference of the turbine, if you will, but it flows out axially, meaning the water is ejected in parallel to the axis of the turbine's rotation. And these turbines make up more than half of the kinds used in hydroelectric dams today. They're kind

of like the Goldilocks of turbines. They're good for dams that are in the middle spot, the sweet spot. Lester Allen Pelton created his own turbine in the eighteen seventies, so this is after Francis has created the Francis turbine. This one we call the Pelton wheel and it kind of makes me think of like a ferris wheel or a vertical water wheel. It works best for hydroelectric facilities that have a high head, so a high difference in elevation between where the water is retained and where the

water is allowed to go. So you want high head but low flow rate. And so you want a large difference in that elevation but a low flow rate. That's where the Pelton wheel has a sweet spot. It is a pure impulse turbine, so again this is the type that turns because the force of water pushes against it and that causes rotation. That's another type that's used in some hydroelectric facilities. Then in the early nineteen hundreds there was an Austrian engineer named Victor Kaplan who developed the

Kaplan turbine. This is another This one's our reaction turbine. So again this one's good for actually high flow rate but low head, so low difference in elevation between the retaining water and the flowing water, right, and but high rate of flow, so that's good for those operations. The Pelton wheel is good for low flow, high head, high changes in elevation, and the Francis turbine is the sweet

spot between the two. Now again, originally these turbines were used to do a lot of other stuff rather than just generate electricity. They were used to conduct like physical work. The first hydroelectric application I can find was in eighteen seventy eight. So again, some of these turbines had been invented and put into use for decades by the time we get to eighteen seventy eight, so they were not

being used to generate electricity. They were being used to mill grain or operate heavy hammers, that kind of stuff. In eighteen seventy eight you had a case where someone actually used water and a water wheel to generate electricity to power a lamp. It was kind of like a proof of concept. This was in Rothbury, Northumberland, an a massive Victorian house. They call it a house. I think of it as like a mansion. I look at pictures of this place and it's just it's so huge. It

even as a name. It's Cragside is the name, because the English they love to name their houses. So yeah, this one was called Cragside still is called Cragside, and this one was owned by a hoity toity, Not no big surprise, because again it's an enormous house. So in eighteen seventy eight there was this feller named William Armstrong.

Not just a feller, he was Baron. Baron Armstrong. He figured he would make use of hydraulic power to provide the kinetic energy necessary to operate an electrical generator, and this generator in turn would provide an electrical current to a lamp inside Cragside itself, And so Cragside had a lamp that depended upon hydropower. Armstrong apparently later used hydro power to provide electricity for some other stuff, including an electrical rotisseriy. So he was a man after my own heart,

or at least stomach. In eighteen eighty two, in Wisconsin, here in the good old us of A, the Fox River became the site of the Vulcan Street Plant. This was a small hydro electric facility that used a water wheel to harness the power of the Fox River and create electricity for a couple of paper mills as well as a nearby home. Who's home, Well that would be HJ. Rogers. So who was HJ. Rogers? Well, if you guess that it was the dude who ran the paper mills, you

would be right. So the water wheel worked and after some tweaking, it worked well. Originally it didn't work at all. It didn't manage to light the lamps, but they did fix that problem. However, even when it was working well, it didn't provide steady, reliable electricity because the flow of the river wasn't constant or consistent. So the voltage varied with the amount of flow going through the river, and

it wasn't always safe to use that electricity. Sometimes, if the river was pushing pretty hard, you could end up with short circuits, which can be pretty risky. But the floodgates, so to speak, were open at that point, and soon hydro power plants began to take shape along various rivers. Lots of lake began to take shape too, because engineers were building dams for the purposes of harnessing this hydro

electric power. So, for example, here in my home state of Georgia, there are no natural lakes in the state. Every single lake in Georgia was man made, created by damming up rivers for the purposes of generating hydro power. I grew up not far from Lake Lanier, which is a fairly famous one, largely because a lot of communities

were destroyed through the creation of that lake. Like there are urban legends to this day of ghost towns beneath the waters of Lake Lanier, where the only inhabitants are the spirits of the dead and enormous catfish, Like there's always stories about almost supernaturally large catfish in Lake Lanier. Anyway, Lake Laneer exists because the beaver dam and we needed to create a way to generate electricity. But that's the

case with every lake in the state of Georgia. Now, globally, hydropower makes up about half of all electricity that's generated from renewable sources. That's different than saying it's half of all electricity. It's not. It's just if we take renewable sources as its own pie, the slice that belongs to hydropower is about half of that pie. Here in the United States a little less than that, it's more like

forty percent. If we look at overall electricity production, then it shrinks down to seven percent for the United states, because now we're looking at not just renewable sources, we're looking at things like you know, natural gas and that kind of stuff. Interestingly, one way that we use hydropower today is to supplement other types of renewable energy by creating a kind of water battery. So here's how it works.

You have a pair of reservoirs. You have one reservoir that's at a higher elevation than the other, and you keep water in the upper reservoir until you need it. So that's your power storage, that's your battery bank. When the grid needs more electricity than what you can provide through other sources, like let's say it's wind power. Let's say you've got a wind farm, but there's just very little wind blowing, and meanwhile the electrical grid requires more

electricity than the wind farm can provide. Well, then you can open up the gates in that upper reservoir so that water flows through a channel or a pipe at the base of which you have a turbine. This ends up turning the turbine generating electricity. Use that electricity to supplement what the wind farm is supplying and meet the needs of the power grid. But let's say you're in a row of windy days and the wind farm is

generating more electricity than what the grid actually needs. Well, then you would use the excess electricity to pump the water in the lower reservoir back into the upper reservoir. Right, you have to expend energy to get the water back into the upper one. You're recharging the battery in other words, so the water goes back up to the upper reservoir

where it sits until it's needed the next time. So when you are switching to renewable sources of energy, because so many of them are dependent upon factors that are not always present, Like you know, solar power requires sunlight, when power requires wind, and there's a real worry that what happens if you go without wind for a while

or it's a really overcast time of year. That's when you would make use of things like this, where you have power stored in the form of water sitting in a reservoir that can then be released into a lower reservoir, turning a turbine in the process generating electricity very clever as long as you know conditions allow for the return of a normal set where you're back to depending on wind or solar or accommodation of the two, or even

something else. And meanwhile, you can pump the water back up into the upper reservoir for the next time you need it. So there you go. That's a quick rundown on hydro electricity how that works. If you ever get a chance to tour a hydro electric facility, I recommend doing it. They're very fascinating. Hoover Dam is one of the ones that has one of the most famous tours here in the United States. It's one I have yet

to go on. My partner has gone on it, and she tells me that it was fascinating, and she's not a techie engineering kind of person, so the fact that she found it really fascinating tells me that that's a darn good tour and I need to take it. It's sad that, out of all the times I've headed out toward Las Vegas, I've never actually taken the time to do a side trip over to the Hoover Dam. So I'm gonna have

to do that in the not too distant future. Anyway, Again, if you happen to have been in the path of Helene while that storm was just raging, across the Southeast. I hope you and all those you love are safe and healthy. Please be careful out there. Show love to those who have been affected by this kind of thing. It has been absolutely devastating for so many communities. And pay attention, like just to the communities around your area.

I think showing compassion and critical thinking is always important, but it's particularly important in trying times where people are at a real disadvantage. I hope all of you are doing well, and I will talk to you again really soon. Tech Stuff is an iHeartRadio production. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.