Humans have been harnessing energy from rivers for thousands of years. Think water wheels from Ancient Greece and modern hydropower plants, like the Hoover Dam. Brown University engineers have a new take on a hydropower device that could harness enough energy to power communities in remote locations or along fast-flowing rivers.
At a marina along the Taunton River, researchers are getting ready to test an instrument designed to generate electricity from moving water. The device has slender rectangular paddles that mimic the movement of flying or swimming animals, “such as bats and insects and whales,” said graduate student Michael Miller.
Miller said the paddles, or “wings,” produce electricity as they flap up and down. The motion creates a vortex. “So it’s the same motion as a whale’s tail, but instead of thrusting through the water, we’re taking energy out of the water,” said Miller.
The team built this prototype to produce one kilowatt of energy – enough to power a small house. They call it the Water Wing. Engineers have attached it to a boat to simulate how the wings would move in a flowing river.
Brown University engineering professor Shreyas Mandre can feel the energy the wings are making. He’s holding a rope that’s attached to the wings. When the boat gets going, “…the wings will start to move and we'll feel it, because it will pull [on the rope]. You should feel it, too (chuckles).”
As the boat speeds up the rope pulls hard. It feels like a kite tugging at the string. The device can adjust the angle and span of the paddles, like a bird adjusting its wings, to capture the movement of water.
Mandre said water currents are promising sources of energy. Tides are predictable. Rivers never stop flowing. You don’t have to wait for the wind to blow or the sun to come out.
In the United States, tides and river currents have the potential to power 67 million homes. But keep in mind. It’s an energy source that still remains largely untapped because it’s been hard to design a device that works efficiently underwater. Mandre thinks the Water Wing is the answer. It’s working exactly as he expected.
“Our wings – they don't have a special shape,” said Mandre. “They can just be a blade of steel, a blade of metal, a rectangular blade of metal. So we can make them as long as we want and intercept a large area of the flow, even if the flow is moving slowly, we can generate more power with relatively simple machinery.”
Relatively simple machinery also keeps costs down, said Mandre. Many of the existing tidal energy devices are expensive to make because they’re big and bulky, often with rotating parts.
The Water Wing’s simple, but efficient design appeals to Tom Derecktor, who’s partnered up with Brown University on this project. His small business BluSource Energy engineers and manufactures renewable energy projects. Derecktor built the Water Wing and finds the paddles easy to work with.
“If they were damaged, you could snap them off, you could replace them with a new one,” said Derecktor. “You can work on the generator – all those things. It swings up and swings down. So ease of maintenance is a great strong suit and a great selling point of all of this.”
Many states, including Rhode Island, are trying to mix up their energy portfolio. But Derecktor thinks this type of tidal energy device is more promising for communities in remote locations or along riverbanks, where the flow of water is fastest in shallow areas.
“You know you're not going to compete with natural gas the way it's selling in this country,” he said. “But at locations where your fuel costs are challenging or where you have a steady flow, it seems criminal not to harness that.”
The Water Wing is still in a test phase. The team’s goal is to build one that produces 50 kilowatts. They want to take it to the Amazon River, where that amount of energy can power an entire village.
George Hagerman, a renewable energy expert at Virginia Tech University, thinks starting out in a river, instead of the ocean, is wise.
“[It] gives them a chance to look at the viability of their technology,” said Hagerman. “Will it hold up over time? What kind of maintenance schedules? What needs to be replaced periodically? What pieces and components? I think their strategy makes a lot of sense.”
Hagerman agrees the Water Wing’s design sets it apart from other devices that have been developed so far.
The U.S. Department of Energy is funding this project through a program that’s competitive to snag. The team’s challenge in the next couple of years will be to figure out how to attach a bigger version of the Water Wing to the bottom of a river – and make sure it works. If they can accomplish that, then it’s off to the Amazon.
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