Can Fish Teach us to Make Hydropower in Calm Waters?

• fish
• water
• hydropower
• alternative energy
• environment

Hydropower researchers at the University of Michigan are borrowing strategies from fish to maximize the energy that can be harvested from slow-moving water. For example, trout use spinning eddies that form on both sides of a stationary object, like a rock, to help conserve energy as they swim upstream. The vortexes that form alternate from one side of the rock to the other, so fish swimming upstream slalom between these whirlpools. Schools also use vortexes created by the fish ahead to conserve energy when swimming upstream.

The University of Michigan team’s design harnesses these alternating vortexes: Aluminum cylinders joined to built-in electromagnets form a ladder-shaped device. As flowing currents swirl past a cylinder, the vortexes that form above and below push and pull the cylinders to generate electricity. Inventor Michael Bernitsas estimates the bobbing action can yield 51 watts per cubic meter at water speeds of 3 knots, depending on the number and size of the cylinders. The device, known as Vortex-Induced Vibrations for Aquatic Clean Energy, or VIVACE, attracted Navy interest for its potential to generate power at flow speeds slower than the 5-knot minimum of most turbines. To maximize the system’s efficiency, Bernitsas draws insight from the anatomy of fish. Sandpaper-like surface roughness on the cylinders mimics scales to form more energetic whirlpools. Flexible plates designed like a fish’s tail could speed up cylinders in very slow-moving water or decrease the cylinder movement, which would help to protect aquatic life. “We may design a tail that’s adjustable and has sensors, but I’m not anywhere near that yet,” Bernitsas said. “Simply, we are not as smart as fish at this point.”

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