Our approach to hydropower turbine design prioritizes biodiversity without compromising performance metrics.

Natel FishSafe™ RHT Designs

Restoration Hydro Turbine (RHT) designs feature uniquely thick and forward-slanted blades, which enable safe through-turbine passage of fish. Safe fish passage eliminates the need for fine fish exclusion screens, reducing O&M and CAPEX costs and increasing plant efficiency. RHT runners can be designed for turbines at sites with up to 40 meters (130 feet) of head and without limit on turbine diameter.

Technician Alex Conn sights the runner as he assembles an RHT.

RHTs combine best-in-class performance —high efficiency and resistance to cavitation —with a revolutionary FishSafe™ design.


Demonstrated safe fish passage with proprietary blade design

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Demonstrated efficiency >90-93%

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Modern, FishSafe™ runner retrofits for low and medium head sites

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Natel's FishSafe™ Design

RHTs feature thick, slanted blades transport fish away from the leading edge into wide inter-blade regions and downstream to the outlet. The progressive slant of the blades from hub to tip also minimizes the likelihood of severe strike and eliminates the risk of entrapment between moving and stationary parts.

The design basis for RHT blades has been validated and published in peer-reviewed studies:
Journal of Ecohydraulics: "Improving Survival: Injury and Mortality of Fish Struck by Blades with Slanted, Blunt Leading Edges."
Transactions of the American Fisheries Society: "Safe Passage of American Eel Through A Novel Hydropower Turbine."
North American Journal of Fisheries Management: "Juvenile Alewife Passage through a Compact Hydropower Turbine Designed for Fish Safety."

Learn more about our fish passage testing, why fish-safe is different from fish-friendly, and why fish-safe turbines matter.

Curved Blade
deflects fish around
Graphic showing how the shape of the RHT deflects fish around the blade.
FishSafe™ Runner
Illustration showing where detail image is located on a larger runner.
Tip Slant
reduces severity of strike
Illustration showing how the RHT tip slant reduces the severity of any fish strikes.

Natel FishSafe™ Runner Retrofits

RHT runners can be designed as a replacement for existing conventional runners in low and medium head turbines, allowing existing hydropower installations to significantly improve efficiency, energy output and fish safety without major changes to power plant infrastructure.

RHT runners meet draft criteria developed for the Section 247 program.

Hydraulic Performance

Natel rigorously tests RHT performance at our in-house closed-loop hydraulic test facility. We use world-class instrumentation to measure flow, pressure, torque, and speed in scale-model turbine tests. Performance tests are conducted to the American Society of Mechanical Engineers PTC-18 standard.
A plot showing the performance of the RHT.
*The maximum operating efficiency of the RHT is 90-93%.

Abrasion Resistance

The same principles that guide the fish safety of RHT designs also reduce blade erosion. Tests following the IEC Standard 62364 showed that the unique blade shape that characterizes RHT designs demonstrated high resistance to abrasion. The testing found that the thickness of RHT blades produced a stagnation effect on sediment slurry while the blade sweep also decreased the contact velocity of sediment impacting the runner. The outcome of these effects resulted in six times less material loss on an RHT-style blade sample as compared to a conventional propeller blade.

Broad Product Range

FishSafe™  RHT runners can be designed for any turbine configuration with runner diameters between about .5 and 6 m (1.5-20 ft) that operate at head up to 40 m (130 ft). Typical turbine configurations include vertical or horizontal axis, axial or radial inflow, and straight or elbow draft tubes. RHT runners can be coupled to any common power takeoff including direct drive synchronous or permanent magnet generators with fixed or variable speed operation.

Illustration showing some of the variety of turbine configuration options that are possible for the RHT.
Controls wiring.
Turbine install
Kelsey and Ian