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.
Free E-Mail News Updates
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
SOURCES AND RELATED WEB SITES