WATER WHEELS AND GENERATORS
IT’S A COOL MORNING IN EARLY NOVEMBER. The sun is peeking out from some clouds, promising good weather for the season. Fall is well along on Cape Cod: Halloween has come and gone, and in the upland forests most of the leaves have fallen from the oak and locust trees. The beaches are practically empty, and out at sea great flocks of birds can be seen migrating south for the winter.
I’m zipping along the Massachusetts Turnpike with Julie and her friends Amaya and Natasha—the water power team. Today is our field trip—we’re driving to the town of Northfield, in western Massachusetts, to investigate the hydropower projects located there, along the Connecticut River. Julie and her team discovered Northfield while gathering information for their class project on water power. I called ahead and arranged for a tour. We’ve packed a picnic lunch, hoping to eat outside somewhere along the river.
The drive from Boston will take a couple of hours, so I’m hoping the girls will tell me more about their project along the way. Meanwhile, I fill them in on the solar energy team’s class presentation, the week before. Tom, Paul, and José invited me to attend, and I thought it went really well. “The guys only had a half hour, which wasn’t enough time to share everything they’d learned,” I say. “But they also turned in a written report that included stuff they didn’t have a chance to present to Mrs. Flannery’s class.”
“Was Tom nervous?” Julie wants to know. “He was acting a little obsessed about it at home.”
“A little, at first, but once they got going he relaxed,” I tell her. “Paul said he wished they’d left more time for questions at the end. José was cool with how it went—he was just glad to be done.”
“Well, we’re putting together a really great project, too.” Julie is ready to move on. Legs tucked under her on the front seat, she looks back at her friends for support. In my rearview mirror, I can see Amaya and Natasha nodding vigorously in agreement.
“Are you all studying everything, or have each of you taken a piece of the research?”
“Oh, we each have a different part of the project,” Julie answers matter-of-factly. “We’re starting with the water cycle, ’cause that’s where water comes from in the first place. I’m doing that part, since I learned all about it last summer.”
I catch Natasha’s eye in the mirror. Tall for a sixth grader, she keeps her dark hair short and dresses in purples and blues. “What part are you doing, Natasha?” I ask.
The Water Cycle
Rivers carry fresh water from the land back into the oceans.
“Well, I like history, so I’m researching how they used water power in the old days,” she explains. “It’s mostly about water wheels and how they work.”
“That’s great,” I say. “You know, there are still some old water wheels on Cape Cod—one is pretty near where I live.” I shift my gaze in the mirror. “Amaya, how about you?”
The Stony Brook Watermill on Cape Cod
Driven by a water wheel, this mill was used in the old days to grind grain into flour.
Amaya leans forward so I can hear her soft voice. “I’m going to do the part about damming up rivers to make hydroelectric power,” she answers. Cornrows braided tightly to her scalp, she projects an air of calm confidence. Julie says she’s one of the smartest girls in their class. “I’ll explain to the class how a water turbine works to make electricity. That’s why I’m really glad we’re making this trip to see a dam.”
“Me too,” Natasha chimes in. “I’ve been reading on the Web about this pumped storage plant they have in Northfield. I hope we can learn more from the people who run it.”
“What is pumped storage?” I ask.
“That’s when they pump water from the river up to a lake—really a reservoir—at the top of the mountain,” she replies. “They do that at night, when most of us are sleeping. Then they release it during the day, and it runs down a tunnel in the mountain through a turbine, making electricity when we all need it. It’s a really smart idea.”
Rivers are part of the water cycle.
“I see. So, they store water up in the reservoir, then use it to run the turbine when we need lots of electricity.”
“Anyway,” says Julie. “I think it’s really cool. And another thing is, I’ve been studying about how you can use the tides to make electricity!”
“Really? You mean the ocean tides, like we see all the time on Cape Cod?”
Pumped-Water Energy Storage
This map shows the reservoir on top of Northfield Mountain, with water ready to run down through a turbine to the Connecticut River.
Pumped-Water Energy Storage
Water from the reservoir runs through the turbine to generate electricity, and then is pumped up again to be reused.
Julie thinks about that for a minute. “I don’t think they’re making electricity with the tide down on the Cape,” she says finally. “Most of those projects are up north, where the tides are really high and strong.”
We drive on for a while. Julie has brought some peanuts as a snack and shares them with the other girls and me. Natasha has taken an iPad out of her backpack, and she and Amaya are chatting as they gaze at the screen.
I’m thinking about what the girls have told me so far about their project: starting with the water cycle, then looking at water power in the old days. There will be a section on making hydropower by damming rivers, of course, and something about how a turbine works. Julie’s idea of learning how the tides can be used to make electricity is very creative—I need to remember to ask her more about it later.
But first things first. “Natasha,” I say, “tell me more about water wheels. How do they work?”
She looks up from her screen. “Amaya and I were just looking at pictures of water wheels I found on the Web,” she explains.
“A water wheel is like a wheel on a bike, but with paddles attached to it instead of a rubber tire. If you put the water wheel in a stream, the fast-moving water hits the paddles and makes the wheel go around. Here’s a good picture if you want to see it.” She turns the screen toward me.
An Undershot Water Wheel
Rushing water in the stream spins the wheel, which powers a generator.
“I’m driving now so I can’t look, but please show me when we stop somewhere,” I answer. “So, the power of the water in the stream is making the water wheel turn?”
“Yes,” answers Natasha, the other two nodding. “That’s called an undershot water wheel because thewater hits the bottom of the wheel and travels under it.”
“That’s right,” Amaya adds. “And Natasha also found some water wheels where the water runs through a pipe and hits the top of the wheel instead of the bottom. The water rushing out of the pipe makes the wheel spin forward. That one’s called an overshot water wheel, because the water flows over the top. There’s a cool picture where you can actually see the wheel turning!”
“Good work! It will be fun to look at what you’ve found.” In my mind, I’m seeing the water wheel turning. I know that the center or hub of the wheel is fastened to a kind of bar, so that when the wheel turns, the bar turns with it.
“How do you use the power of the spinning water wheel to do something else, like make electricity?” I ask.
Julie speaks up. “We know that you can connect the water wheel to something called a generator. When the water wheel turns, that turns stuff inside the generator. But we don’t know what really happens inside there to make the electricity.”
These girls are on the right track, for sure. “Do you know what electricity actually is?” I ask.
Julie responds for her team. “Tom told me he learned about it in class, and then you explained some more to him and the others,” she begins. “You have atoms and these super-tiny particles they’re made of. Especially the electrons—those are the important parts for making electricity.”
“Right so far,” I affirm. “Electricity is actually a stream, like the stream of water that turns your water wheel,” I continue. “But instead of water, the stream of electricity is made of moving electrons.
Electricity is actually a stream, like the stream of water that turns a water wheel.
“To create that stream of electricity, we need to push or pull some electrons loose from the atom they belong to. Then they need a wire they can flow along. All we need is a way to knock them loose from inside their atoms!”
Amaya looks very focused, like she’s imagining electrons flying around the edge of an atom. Then she asks, “So how do we do that? Knock the electrons loose?” All the girls look at me expectantly.
“Well … there’s different ways to do it,” I venture. “Tom and the other guys found out that one way is by using the sun’s energy and some different kinds of atoms. Atoms that attract electrons or easily lose them.
“But with your water wheel and generator, the secret is magnets!” I glance back at the girls in the rear seat. “Do you know what a magnet is?”
“Sure, we do,” says Amaya. “Last year we got to play with them in science class. What’s so special about a magnet?”
Natasha is quick to answer. “It attracts stuff to it, especially metal things made of iron,” she explains. “We have magnets on our refrigerator to hold notes and things.”
“Right,” I say, “and here’s the really neat part. When you move a magnet past a certain kind of metal wire, electricity is created, or generated, in that wire. That’s the trick. The magnet loosens some of the electrons from the atoms in the metal. And once they’re free, those electrons flow along the wire as electricity.”
When you move a magnet past a metal wire, electricity is created.
Julie is thinking about the generator. “So, inside the generator is a magnet and a bunch of wires?”
“That’s exactly right!” I answer excitedly. “The bar sticking out of your water wheel sticks right into the generator. Inside the generator, at the end of the bar, is a round magnet. As the water wheel turns, the magnet spins, and its surface moves past many coils of copper wire. This loosens electrons in the wire. They flow out of the generator and into the wires that go into our homes, to power our lights and refrigerator and other things.”
Julie wants to make sure she understands. “The water wheel is turned by the water,” she repeats. “The wheel is attached to a generator. When the water wheel turns, it makes the magnet inside the generator spin. The spinning magnet knocks electrons loose from coils of wire. The electrons make a stream of electricity that travels along wire to our homes. Is that right?”
As the water wheel turns, that makes the magnet spin.
I take one hand off the steering wheel and give her a knuckle bump. “Perfect!”
By now we’ve turned off the Mass ’Pike and are heading north along the Connecticut River on Route 91. The girls are glued to the car windows, catching glimpses of the great river flowing by on our right. After a few minutes, Amaya leans forward and asks Julie, “Is this the river that has the dam on it?”
“I think so,” Julie answers.
“This is the one,” I confirm. “It’s called the Connecticut River because the state of Connecticut is where it pours into the Atlantic Ocean. But the river actually begins farther north, in Vermont and New Hampshire, and right here it’s flowing through our state of Massachusetts.
“Pretty soon we’ll come to Turners Falls, where the dam we’re visiting is located. The manager is going to show us the generator that produces the electricity, and how they channel water to it from behind the dam.”
“Gramps, could we have lunch first?” Julie reminds me. “I’m pretty hungry!”
Map of the Connecticut River
All the dams on the Connecticut River are shown here. The Turners Falls dam is number 6 on the map.
When we get to Turners Falls, I follow the river past the dam, looking for a good picnic spot. Upstream of the dam, the river is really more like a big lake, backed up behind the huge concrete obstruction. We park in a small residential neighborhood and spread our blanket on the grass overlooking the water. (After our trip, I found the spot on Google Earth and took a picture of it.)
Here is our picnic spot. The dam is under the bridge. At the left end of the bridge, water is falling into the spillway.
As the girls pull bag lunches out of their backpacks. I see sandwiches, soft drinks, chips, and what look like homemade cookies. “My mom made enough cookies for all of us!” Amaya announces proudly.
For several minutes, the only sound is munching. On the placid surface of the reservoir, a pair of ducks paddle along the shore, tilting tails in the air now and then as they pluck their vegetarian lunch from the shallows.
We’re sampling Amaya’s cookies when Natasha straightens and points downriver to the dam. “Is that where we are going to meet the guy who will show us the generator and everything?” she asks.
“That’s right,” I respond, licking cookie crumbs off my upper lip. “But before we head down there, could I see those pictures of water wheels on your iPad?”
Different Kinds of Water Wheels
In this undershot wheel, water hits the bottom of the wheel.
Different Kinds of Water Wheels
The overshot type, where the water hits the top of the wheel.
Different Kinds of Water Wheels
Another common kind of wheel, where falling water hits near the center of the wheel’s edge, is called a breastshot wheel.
“Sure!” Hopping up, Natasha strides over to the car and returns with her tablet. She taps the Photos icon and then a folder titled Water Wheels.
“See,” she says, flipping through the photos. “This is the overshot type, where the water hits the wheel at the top, and this one is undershot, with the water at the bottom.”
“I see that. I wonder why there are different kinds?”
“And here’s a video I found, showing the overshot wheel in motion.”
Video of Water Wheel
“Cool!” The video from Japan shows a water wheel with a big gear attached to it, which turns as the water pushes the overshot wheel. “I can see that the gear is connected to a small generator, which is producing enough electricity to power a light bulb,” I point out.
Amaya leans over to peek at the screen. Then she looks out over the water and downstream toward the dam. “That’s what is happening down in that dam,” she says quietly. “Only much, much bigger. I can’t wait to see inside it!”
The Turners Falls dam close up.
“Let’s go, then!” We quickly gather up our lunch things, find a trash bin, then pile back into the car, headed for the dam.