Natel’s Restoration Hydro Turbine (RHT) is designed to enable safe downstream passage across fish species. Natel is conducting original turbine passage science to understand passage effects for key fish species through the RHT across operating conditions and to inform fish-safe turbine and plant designs.
In 2019, Natel performed controlled laboratory strike tests at Alden Laboratory to understand the effect of the uniquely thick, curved leading edge of the RHT on fish survival. The scientific findings are published in the Journal of Ecohydraulics and guide Natel's fish-safe turbine design process.
The results of this study indicate that the RHT’s thick, slanted blade design can enable >99% safe passage of salmonids that pass through standard trash racks at the intake.
Fish passage testing in the field
Natel has conducted turbine passage tests of rainbow trout, a representative salmonid species, at the Monroe Hydro Project with Pacific Northwest National Lab (PNNL), as well as passage tests of juvenile alewife (representative of Alosines, i.e. shad and river herring) with Kleinschmidt Associates at the Freedom Falls hydro plant in Maine.
The results of the trout study, completed in fall 2020, confirmed 100% safe fish passage for salmonids up to 400 mm (15 inches) passing downstream through the 1.9 meter diameter D190 RHT. Results from the juvenile alewife study, completed in fall 2021, confirmed 99-100% survival of Alosines in this delicate life stage. Additional data from the Alosine study is in review for peer-reviewed publication.
Monroe Fish Passage Testing Video
Test of Juvenile Alewife Passage through the RHT
In-house fish passage testing
Our in-house closed-loop hydraulic test facility enables Natel to lead the hydropower industry in through-turbine fish passage science with the high-speed video-equipped test stand, which allows direct observation of fish as they move through the turbine.
Natel has performed preliminary studies on passing rainbow trout, white sturgeon, bluegill and American eel through our 55 cm diameter RHT test unit. In the fall of 2021, Natel conducted formal testing with PNNL on 174 American eels passing through the RHT test unit operating at 667 rpm under 10 m of hydraulic head. Following the test the eels were monitored for 48 hours with 100% survival. Additional data from the American eel study will be released pending peer-reviewed publication.