Attempts to create a more harmonious relationship between hydro power plants and the fish which pass through their turbines are not new. But the latest effort by the US Department of Energy’s laboratory must surely be described as one of the most innovative to date.

In their efforts to provide currently unavailable information about the journey fish encounter when passing through turbines, research scientists at the Pacific Northwest National Laboratory (PNNL) in Washington state, US, have created a sensor fish.

‘During FY 1998 we began the development of a sensor package that can serve as a surrogate fish,’ senior research scientists at PNNL, Bob Johnson and Duane Neitzel, explained. The new strain of fish is not designed to mimic a real fish or to behave like a live specimen — its sole purpose is to provide information which will ultimately improve fish survival at dams.

‘The objective of the sensor development is to measure forces experienced by biological organisms during the passage through hydro power facilities,’ Johnson and Neitzel added. ‘This information will provide the DOE’s Advanced Hydropower Turbine Project with the biological criteria required to design environmentally friendly turbines, while maintaining current generation efficiencies.’

PNNL researchers are currently in their second year of working on the sensor fish, which originated as the result of collab-oration between Johnson and Neitzel. The idea was unveiled at a PNNL management meeting in 1997 and discussions were held with DOE staff and the US Army Corps of Engineers during 1998.

PNNL researchers wanted to work with the Advanced Hydro Turbine Project and they also needed the Corps of Engineers’ permission to test the fish at its Columbia river dams. McNary and Bonneville dams were selected as being appropriate test sites because the Corps is already conducting fisheries tests related to special turbine designs, such as the minimum gap turbine at Bonneville. What is more, the fish release and recovery systems needed to deploy the sensor fish are already in place at the two dams.

Funding for development of the sensor fish has come from PNNL’s internal sources, while testing at McNary and Bonneville dams has been funded by DOE money from the Advanced Hydro Turbine Project.

Testing times

In May this year the sensor fish faced its first tests at McNary dam. The objective was to test the recovery process developed for releasing and recovering the fish into the turbines. All went satisfactorily. Researchers were able to collect the fish after it passed through the turbines.

The electronics in the fish were also assessed to determine if it could survive turbine passage and still collect data. The first test went well. ‘We recorded pressure and acceleration data successfully from two passes through a McNary turbine,’ Neitzel said. During one test the complex wiring was damaged slightly but Johnson and Neitzel were able to use this information to improve the design. Once the damage had been repaired the test was repeated a few days later and the fish came though intact without any further harm. A couple of design alternatives related to buoyancy were also assessed and data recording turbine exposure time was evaluated.

All information from the McNary dam assessment will be used to build more sensor fish which will be tested at Bonneville dam this winter. The objective here will be to characterise the physical forces that a fish might encounter during turbine passage. Sensor fish will be exposed to the turbine environment for less than one minute and all tests are expected to be completed within two to three weeks.

But what happens to the sensor fish after Bonneville? ‘We have two objectives,’ Johnson says. ‘We expect to market the use of the sensor fish, with DOE and the Corps of Engineers, in order to evaluate the newly developed and improved turbine designs.’ Neitzel explained that the design information will also be used to build the sensor fish for new applications. Unfortunately, at this stage, he cannot comment on what such applications might be.

Successful development

Johnson and Neitzel are keen to demonstrate just how crucial the sensor fish data will be for the successful development of fish friendly turbines. They say the most important result from this work will be the ability of fisheries biologists to understand the environmental conditions that fish can tolerate during turbine passage. Without this knowledge, the researchers do not believe turbine engineers will be able to design fish friendly turbines.

PNNL sees the sensor fish as an excellent opportunity — it will complete the sketchy information which exists about environmental conditions in turbines and other hard to measure environments.