Beaver Dams Inspire Fish-Friendly Hydropower Design

John Roach
National Geographic News
July 15, 2005
Hydropower—electricity produced by flowing water—is an
efficient form of renewable energy, but it often comes at a high cost to
the environment and society. Now a technology inspired by beaver dams
and airplanes may help eliminate these drawbacks.

Engineers with NatEl America, a Grapevine, Texas-based renewable energy company, have developed a new way to generate electricity using the dimensions of a beaver dam and the physics of fixed-wing aircraft.

"We need to figure out how to live with the acceleration [of water] due to gravity in a fashion which is comparable to how beavers have done that," said NatEl America's president, Daniel Schneider.

Beaver dams usually stand no more than ten feet (three meters) tall and integrate a series of steps into the slope. This is a height and design surmountable by migrating fish, Schneider said. The dams are also a natural part of the environment in many parts of the world.

In contrast, conventional hydropower technologies often rely on the construction of tall dams that flood the area behind them. This displaces animals and people, and it degrades the surrounding ecosystem, said Abe Schneider, Daniel's son and the company's vice president of engineering.

The height and spinning turbines of conventional hydropower dams also impede the passage of migrating fish, he added.

"With our approach, you can achieve the same energy capacity [as a conventional dam] but in a way that utilizes the energy in falling water in smaller increments, using much smaller dams," Abe said.

Linear HydroEngine

With a goal to have no more impact on a stream than a series of beaver dams, the Schneider's proprietary hydropower technology harnesses the energy of flowing water using the same engineering principles that allow fixed-wing aircraft to fly.

"Aviation deals with fluid flow just as hydropower deals with fluid flow, or fluid energy," Abe explained. "In aviation there are two major kinds of aircraft: helicopters and fixed-wing airplanes."

To travel from New York to London, people fly airplanes, not helicopters. However, the hydropower industry only uses the engineering concept analogous to a helicopter's rotors, Abe said.

NatEl's technology uses the engineering concept of fixed-wing aircraft to generate electricity. They call it the Linear HydroEngine, because its main moving parts travel in a predominantly linear fashion.

The engine uses winglike hydrofoils mounted on a pair of belts to convert the energy of water at low dams into a rotational output at twoaxles. The axles, in turn, drive a generator.

The foils move slowly and are spaced sufficiently apart to allow fish passage. The pressure-drops through the engine are minimal, which means the fish avoid decompression sickness, or the bends, as they pass through the machine.

Daniel added that the system integrates a series of steps that are within the physiological limits of migrating fish. For the same reason that humans need a staircase to travel between floors of a building, fish need a staircase to successfully navigate dams.

A prototype has successfully run for 10,000 hours, but the technology is not ready for mass production. "We're not yet at that point where we're Wal-Mart and have it on the shelf," Daniel said.

Robert Davinroy, director of the U.S. Army Corps of Engineers' Applied River Engineering Center in St. Louis, Missouri, was introduced to the technology early this year. He said it is efficient and environmentally friendly.

"All the environmental-type players are excited about it," he said. "They are mainly concerned the turbines chew up fish. The HydroEngine does not; the fish can pass through the system."

Target: Existing Dams

NatEL America hopes to introduce the Linear HydroEngine technology to the thousands of existing low-head dams built for functions like irrigation, ship navigation, and flood control. A low-head dam is a dam of low height, usually fewer than 15 feet (4.5 meters).

Adding to these dams the capacity to generate electricity from the water already flowing through them captures the potential hydropower energy with minimal impact on the environment, Abe said.

NatEl is coordinating with Davinroy's Applied River Engineering Center and other federal, state, and nongovernmental groups to install the Linear HydroEngine at a low-head dam on the Mississippi River.

According to Davinroy, there are 26 low-head dams on the Mississippi where the technology is applicable. Dozens more are on tributaries of the Mississippi.

"They have to go through some hoops to get it approved by the FERC [U.S. Federal Energy Regulatory Commission], but once approved and installed, it has great potential," he said.

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