Our most recent milestone makes a significant step toward making hydropower safer for one of Europe’s fish species most endangered by hydropower: the European eel.
Part of “Work Package 4 – Environmental improvements of refurbishments”, this marks the completion of numerical simulations for a redesigned turbine runner specifically optimized to improve eel survival during turbine passage. Since European eels are migratory, their long-established routes often lead them through countless river turbines. Many make it through without harm, but unlucky individuals can be critically injured or killed by the turbine blades. Previous studies have shown that the design of the turbines the eels pass through on their journey plays a big part in their safety, leading to ReHydro taking on the challenge of developing a turbine that greatly reduces the risk eels face on their migration and show that hydropower refurbishment has as many environmental benefits as it has financial ones.
The design work was grounded in a thorough review of eel physiology and literature (read the first steps here) and drew on input from partners across the project: CNR, EDF, EDP, and NINA. Using the European Standard Norm prEN 18110 as a framework, the team built an analytical model for predicting eel survival and embedded it directly into GE Vernova’s simulation pipeline. That allowed them to iterate on turbine runner geometry with both eel safety and hydraulic performance in mind.
The results are encouraging. Compared to a conventional Kaplan turbine design, the optimized turbine shows a notably lower probability of eels being exposed to damaging blade strikes. The key changes were targeted modifications to the leading edge profile and a reduction in blade count, while keeping pressure conditions within safe limits for passing eels. Hydraulic efficiency took a small hit, described in the report as “minimal yet non-negligible”, which ReHydro considers a reasonable trade-off.
The simulations were developed using the Belver hydropower plant in Portugal, operated by EDP, as the reference case.
Work is now turning toward physical validation. Next steps include reduced-scale model testing, a scan of the existing Belver runner for direct comparison, and calibration of the survival models against live fish test data from CNR and EDF field sites. All findings will feed into a final synthesis report under deliverable D4.2.
