RICHLAND, Wash. – Salmon need only a few seconds to pass through the turbines that power the dams on the Columbia River, but those few seconds are dangerous and sometimes fatal.
As salmon and other fish bump through the turbulent water, they can experience decompression, or the bends, scientists say. Or worse, they can be battered by turbine blades.
Not until the last decade have researchers been able to measure exactly what happens to fish inside the turbines. A sensor fish, developed at the Pacific Northwest National Laboratory (PNNL) in Richland, Wash., has been providing scientists with that information and the data needed to guide fish-friendly turbine development.
The project’s most recent funding came last week from the U.S. Department of Energy. The $299,906 grant will be used to design the fourth generation of sensor fish, which is smaller than earlier models. The new size will allow the “robo fish” to more easily fit through smaller turbines, says project manager Tom Carlson.
“We’ll be able to look at some of the turbines that were put in place at locations that were not considered before,” Carlson says. Previous models could only fit through the Columbia River’s large dams. The new design will be able to fit through turbine prototypes, which are of particular interest to Carlson. He says this smaller design also will be useful in studying hydropower pump storage.
The “robo fish” passes through turbines just as normal salmon do, but along the journey it collects data. Carlson says the technology is a six-degree-of-freedom sensor, measuring how fish accelerate in all directions – up, down and sideways – along with pitch, roll and yaw motions. This provides evidence of how fish experience passing through a turbine.
“Everybody tries to imagine what it might be like to be a fish. I don’t think any of us do it very well,” Carlson says. “The experience of the fish may be quite different. … They may not have the same sensation of water flow that we might imagine as humans when we’re swimming.”
Carlson says there’s been a great deal of effort on the Columbia River to make sure fish don’t go through turbines. Only a small percentage of fish miss the engineering bypasses or dam spills that help fish avoid swimming through turbines, he says.
Summer-run Chinook are most often among the unlucky few because they swim at great depths, causing them to more easily miss the constructed fish passages. Carlson says on the lower portion of the river 25 percent to 30 percent of smolt Chinook pass through turbines, possibly being injured or killed.
Summer runs are the most deadly, says National Marine Fishery Service biologist Paul Wagner.
The federal goal for fish passage states that 93 percent of fish must survive in the summer and 96 percent in the spring – at each federal dam. Wagner says there’s debate about whether this is actually happening.
Though no other scientists have begun using sensor fish in turbine tests, Carlson says researchers from as far away as Australia and China who are looking for safer fish passages and more efficient turbines have asked about them.
To meet that demand, Carlson plans to find a manufacturer who will build the “robo fish” and sell them to other researchers. Profits would be used for additional project development and lab infrastructure.
“Like most science and engineering, the more people you have looking at a problem, the more opportunity you have to evaluate alternatives, the more rapid progress you make,” Carlson says.
Manufacturing sensor fish would be a small step toward the Department of Energy’s goal of encouraging more hydropower generation, he says.
The DOE awarded nearly $17 million last week to projects in 11 states. The projects will focus on smaller hydropower resources, those producing less than 30 megawatts or enough to power about 7,000 homes.
Already the synthetic salmon have helped researchers suggest structural changes to turbines. One way is to improve how water flows through turbines, which helps fish and generates power more efficiently—a win-win, Carlson says.
The many aging turbines in the Pacific Northwest that need to be replaced, especially at federal dams, may benefit from PNNL’s research.
Making sure the turbine designs are fish friendly is important because new turbines can last 40 to 50 years, Carlson says.
“Over the next several years we’ll have a very unique opportunity to put in place turbines that will be inherently safer for the fish that pass through them. The sensor fish is a very important tool for assessing the different designs that may be considered,” Carlson says.
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