See Inside June 2007

A Good Turn

A fish-friendly hydroelectric turbine gets new life

Nearly two years ago Alden Research Laboratory in Holden, Mass., hauled the scale model of a promising hydropower turbine out of its massive test flume and set it in a dim corner of the company's hydraulics laboratory building. As an innovation developed in the 1990s, the device proved quite promising in reducing one of hydropower's drawbacks: the turbines kill creatures that pass through them. The novel design enabled at least 98 percent of fish to survive. But orphaned by federal budget cuts, it has sat gathering dust. Now a new push has begun to retool the turbine for potential commercial use.

Conventional turbines, which resemble the blades of an electric fan, kill as many as 40 percent of the fish that are swept through them. Working from U.S. Department of Energy funds first granted in 1994, Alden Lab teamed up with Concepts NREC in White River Junction, Vt., to develop a fish-friendly turbine. The design features three rotor blades wrapped around a conical hub to create a kind of helix. A rotating case covers the rotor blades, so that only a fraction of their edges are exposed. The turbine has no gaps between the blades, fewer blades and a slower spin rate. All these features lower the chance of a fish being injured by moving parts. Moreover, the flow of water through the turbine is smooth, creating less potentially harmful shearing force.

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