We designed a new kind of hydro turbine that prioritizes biodiversity alongside efficient power production.

Meet the RHT

The Restoration Hydro Turbine (RHT) features distinctively thick blades optimized for low head (2-20 m/7-66 ft) that eliminate the need for fine fish screens, reducing O&M and CAPEX costs while increasing plant efficiency.

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

The RHT combines best-in-class performance and reliability with a revolutionary fish-safe design.

The Restoration Hydro Turbine (RHT) is a compact hydroelectric turbine that couples high performance with safe through-turbine fish passage.

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Demonstrated >99% fish passage survival with proprietary blade design

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Demonstrated efficiency >90-93%

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Compact & Cost-Saving

Pre engineered water-to-wire solution reduces excavation & concrete usage, reduces and/or eliminates fish exclusion

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Modern, fish-safe runner retrofits for low-head Francis and Kaplan turbines

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Fish-Safe Design

The RHT’s 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 the RHT blade was validated in a study published in the Journal of Ecohydaulics: Improving survival: injury and mortality of fish struck by blades with slanted, blunt leading edges.

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.
Fish-Safe 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.
An assembled turbine housing.
Operating Envelope
A plot showing the operating envelope for the RHT.
A plot showing the performance of the RHT.
*The maximum operating efficiency of the RHT is 90-93%.
A closeup of an RHT runner.

Fish-Safe Runner Retrofits

The RHT is offered as a runner retrofit 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.

Product Range

The fish-safe RHT is available in radial and axial inflow  configurations with runner diameters measuring from 0.5 m (1.6 ft) to greater than 2.5 m (8.2 ft), and generating capacities from 30 kW to over 3 MW. Direct-drive generation, shortened draft tubes, and submersible housings simplify plant design and minimize installation costs.

The RHT can be adapted to site conditions in a variety of different configurations, including a bulb, pit, S-turbine, open flume S-turbine, and Z-turbine, which can be either pipe-fed or open flume. Scrollcase turbine and radial inflow open flume configurations are also possible. RHTs can be integrated into matrix designs for larger scale deployments of up to 30 MW.

Illustration showing some of the variety of turbine configuration options that are possible for the RHT.

Hydraulic Performance

Natel rigorously tests the RHT’s 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 of net heads up to 10 meters and flow rates up to 1 cms.

Performance tests are conducted to the American Society of Mechanical Engineers PTC-18 standard. The results of our testing work to-date, including third-party tests conducted on a D55 RHT (0.55-diameter runner) have clearly demonstrated >90.5% peak hydraulic efficiency.

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Hydraulic Testing layout

An overview of Natel's fish testing lab.An