Hydroelectric dams place public utilities at odds with conservationists who argue that dams unduly stress migrating fish during spawning season. That's where a robo-fish comes in.
For years, it was widely assumed that most fish met their demise while traversing the plant's spinning turbine blades, however recent research has illustrated that this is but one of many dangers fish face including enormous pressure differentials within the turbine chamber itself, the rapid acceleration (or deceleration) of water flow, and pounding turbulence. And since dumping real fish into a hydro turbine to see what happens doesn't actually tell us where the danger areas are, researchers at the US Pacific Northwest National Lab have developed this robotic stand-in.
As lead researcher on the project, Daniel Deng, explained in a study published by the American Institute of Physics:
To design or operate hydroelectric facilities for maximum power generation and minimum ecological impact, it is critical to understand the nature of the hydraulic conditions or physical stresses to which fish are exposed when they pass through complex hydraulic environments and to identify the locations within turbines and operations where conditions are severe enough to injure or kill fish. While field studies using live fish are necessary for the evaluation of turbine biological performance, they are limited in that they cannot determine the specific hydraulic conditions or physical stresses experienced by the fish, the locations where deleterious conditions occur, or the specific causes of the biological response.
As such, the Sensor Fish has been designed to accurately recreate, measure, and record the physical forces that a fish would experience while traversing the depths of a hydro turbine. Researchers at the Pacific Northwest National Lab developed the first iteration in 2004 and recently updated the device to accommodate both existing turbine designs and the emerging classes of small-scale or pumped storage hydro plants. The second generation Sensor Fish is roughly the same size, shape, and buoyancy as a juvenile salmon measuring 8.8cm in length, 2.5cm in diameter, and weighing in at 42 grams.
Plus, it's packed to the gills with sensory equipment. Everything from pressure changes and acceleration to rotational velocity and water temperature are collected at a rate of 2,048 measurements per second over its approximately five minute trip through the facility. The device can withstand up to 174 psi of pressure, 200 G's of acceleration, and 104°C temperature swings without failing — that's twice as accurate as the first generation.
What's more, the second generation Sensor Fish only costs about £750 to build; unlike its £3,000 predecessor. Granted they're still built by hand at this point but PNNL hopes to pair with a manufacturer to produce these devices on a commercial scale. These Sensor Fish have already been put to use over the last year evaluating a pair of dams in Washington state and are scheduled to run through three more facilities—one in Alaska, another in Australia, and one in the Mekong River—over the next 12 months. It's certainly a departure from the days when we stocked lakes and waterways by simply throwing the little swimmers out the back of passing planes. [AIP via PNNL]