FishSafe™️ designs by Natel, manufacturing by trusted industry partners.

Natel FishSafe™ RHT Designs

Restoration Hydro Turbine (RHT) designs feature uniquely thick and forward-slanted blades, which enable safe through-turbine passage of fish and other aquatic organisms. 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.

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

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Demonstrated 98-100% safe fish passage with proprietary blade design.

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High Performance

Demonstrated hydraulic efficiency 90-93%.

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Retrofit Ready

Modern, FishSafe™ runner replacements for sites up to 40 m (130 ft) in head.

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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.

Turbine selection chart comparing RHT designs to Francis and Kaplan designs
Illustration showing some of the variety of turbine configuration options that are possible for the RHT.

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

The design basis for RHT blades has been validated and published in peer-reviewed studies.

Wide, Curved Blade
deflects fish around
Graphic showing how the shape of the RHT deflects fish around the blade.
FishSafe™ RHT 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.

Funding for Natel FishSafe™ Runner Retrofits

The RHT is offered as a runner replacement for low-head Francis and Kaplan turbines, allowing existing hydropower installations to significantly improve efficiency, energy output and fish safety without major changes to power plant infrastructure.

The RHT meets draft criteria developed for the Section 247 program, which provides government incentives to modernize hydropower plants.

In particular, RHTs meet requirements totaling up to 11 points in subcategory 3(a)1: Fish Passage, by improving existing fish passage and protection, creating new fish passage and protection, benefitting species of conservation concern and/or culturally significant species, and providing watershed-scale benefits.

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.

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.

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Turbine install
Kelsey and Ian