New turbine runner designs could improve American eel survival while maintaining generating performance at the St. Lawrence-FDR Power Project in North America, according to a feasibility study conducted by Natel Energy in collaboration with the New York Power Authority (NYPA).
Funded by the Fish Enhancement, Mitigation and Research Fund (FEMRF), the study used computational fluid dynamics (CFD) modelling to assess preliminary FishSafe Restoration Hydropower Turbine runner designs for the project’s two unit types. The analysis predicted American eel blade strike survival above 98% across all simulated operating conditions, with hydraulic efficiency comparable to the existing turbines.
The proposed runners were designed as in-place replacements, requiring no changes to the dam, powerhouse structure or plant operations. This could offer a retrofit option at a project where fish-friendly turbine technology was evaluated in 2006 and ruled out because of the extensive reconstruction required.
At a gross head of 25m, predicted peak hydraulic efficiencies were 94.6% and 94.3% for the two unit types, within the measurement uncertainty of the existing units’ field-tested efficiency. Projected annual energy production was within 0.5% of existing generation under matched conditions.
The mechanical assessment also concluded that the proposed runners were likely to be manufacturable using conventional methods and compatible with the existing plant infrastructure.
“Fish-friendly turbine replacement had previously been considered infeasible at this project. We are grateful for the FEMRF’s investment in this work and for NYPA’s collaboration in making it possible,” said Abe Schneider, Co-founder and CTO of Natel Energy.
The designs use specialised blade geometries to reduce blade strike mortality risk. Features include leading edges approximately 50cm thick, a progressively slanted leading edge reaching a 35-degree forward slant at the blade tip, and the elimination of converging pinch points between moving and stationary components. Optimised blade thickness distributions are intended to maintain hydraulic efficiency and avoid cavitation.
Natel said previous laboratory studies using similar blade geometries at smaller scale recorded American eel survival rates of 99.2–100%. High survival rates are also expected for other species identified by FEMRF, including lake sturgeon, walleye, northern pike and muskellunge.
St. Lawrence-FDR comprises 16 turbine-generator units operated by NYPA on the US side of the Moses-Saunders Power Dam, which spans the St. Lawrence River at the US–Canada border. Ontario Power Generation operates a further 16 units on the Canadian side, bringing the dam’s combined generating capacity to almost 2000MW.
Under typical conditions, nearly all river flow passes through the turbines, making downstream passage a longstanding concern for migrating adult American eels. Testing at St. Lawrence-FDR in 1997 measured turbine passage mortality at 26.5%.
NYPA’s existing eel conservation measures include an upstream passage ladder installed in 2006 to help juvenile eels access habitat in Lake Ontario. FEMRF, established through the project’s relicensing settlement between NYPA and the US Fish and Wildlife Service, supports fisheries research and mitigation in the Lake Ontario–St. Lawrence River basin.
The feasibility study used original plant construction drawings and data supplied by NYPA. Its hydraulic performance and fish survival findings remain simulation predictions. Physical scale model hydraulic testing, such as to the IEC 60193 standard, is the industry best practice for measurement of hydraulic performance. NYPA has not committed to further studies.
