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Short answer: Natel Energy’s FishSafe™ Restoration Hydro Turbines (RHTs) have produced unusually high observed survival in controlled and field tests, including 98.6% to 100% immediate survival for hatchery-reared rainbow trout in Oregon. That is meaningful evidence that a turbine can be redesigned to reduce turbine-passage injuries. It is not proof that every fish species, operating condition, or hydropower facility is harmless.
The work concerns downstream passage of freshwater fish through turbine machinery—not protection of marine ecosystems generally. A dam can still block upstream migration, alter habitat and temperature, trap sediment, and change river flows even when fish survive the runner.
What problem is Natel trying to solve?
Conventional hydropower can injure or kill fish through blade strikes, sudden pressure changes, turbulence, shear forces, and entrainment at intakes. Operators often keep fish away from turbines with racks, fine screens, bypass channels, spill, or other diversion systems. Those measures can require substantial civil works, reduce usable flow, and create maintenance and operating constraints.
Natel’s approach is different: redesign the turbine so downstream-migrating fish can pass through the runner with less risk. The company calls the resulting product family FishSafe™ Restoration Hydro Turbines. The technology is aimed mainly at river and irrigation-canal facilities, particularly low-head, small, modular, or modernization projects.
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How the Restoration Hydro Turbine is designed
An RHT is a turbine design framework, not simply a conventional runner with a protective coating. Natel reports several geometry changes intended to reduce both the chance and severity of a blade strike:
- Thicker blades change the relationship between fish body size and blade thickness.
- Rounded or blunt leading edges are intended to make contact less damaging than impact with a thin, sharp edge.
- Forward-slanted blades alter the blade path from hub to tip and are intended to reduce direct, lethal strikes.
- Compact, low-head-oriented configurations can suit smaller facilities and some existing civil works.
- Propeller-, Kaplan-, and Francis-style arrangements can be developed for different hydraulic settings, according to Natel and the U.S. Department of Energy (DOE).
The concept may reduce or eliminate the need for certain fine-screen and bypass configurations at suitable sites. It does not mean that every intake, tailrace, spillway, or other plant component becomes safe automatically. Design performance depends on head, flow, rotational speed, fish size, debris, sediment, and the route fish take through the facility.
Sources: Natel Energy and the DOE design summary.
What testing has actually shown
The strongest public evidence is a 2025 peer-reviewed paper by Pacific Northwest National Laboratory (PNNL) and Natel researchers covering field trials at the Monroe Drop Facility in Jefferson County, Oregon. The site is associated with an irrigation-canal drop structure.
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| Test | Reported conditions | Result and qualification |
|---|---|---|
| 2020 rainbow-trout trial | Three-blade, propeller-type RHT, 1.9 m (about 6.2 ft) diameter; approximately 5–5.3 m of head; hatchery-reared trout 200–530 mm long | 100% immediate survival in the tested group, with examination and a 48-hour holding period |
| 2022 rainbow-trout trial | Same field turbine and site; large hatchery-reared rainbow trout | 98.6% immediate survival in the tested group, with no immediate mortality or major injury attributed to passage |
| Combined trout work | 166 treatment fish and 141 control fish across the two years | Controls were released without turbine passage for comparison; findings apply to the tested fish and conditions |
| American-eel testing | 55 cm RHT unit, approximately 10 m of head and roughly 667–670 rpm | DOE reported survival of 47 tested eels under those conditions |
The peer-reviewed study is published in Environmental and Sustainability Indicators, volume 27, article 100801 (2025), DOI 10.1016/j.indic.2025.100801. Read the paper at ScienceDirect and the bibliographic record at DOAJ. Natel also publishes summaries of the 2020 trout study and 2022 large-trout study.
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Those percentages describe observed survival in specified passage trials. They do not mean that every fish species will perform identically or that the turbine is safe under every flow, head, speed, or loading condition.
- The trout were hatchery-reared, and hatchery fish may differ from wild fish in stress response, handling tolerance, and behavior.
- The principal field evidence covers rainbow trout at one Oregon facility and one 1.9-meter turbine.
- Immediate examination and a 48-hour holding period may not detect every delayed or sublethal effect.
- Juveniles, larvae, eggs, fish with different body shapes, and other species may respond differently to pressure and blade contact.
- Survival through the runner does not establish successful migration, population recovery, or safety elsewhere in the plant.
The 2025 paper identifies the need for additional species, wild-fish, and environmental-condition testing. The accurate formulation is: the tested RHT achieved 98.6% to 100% immediate survival for the studied hatchery-reared rainbow trout under the reported operating conditions.
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Why the tests matter for small hydropower
Many earlier turbine-passage studies focused on smaller fish moving through larger machines. Natel’s trials examined relatively large, adult-sized rainbow trout passing through a compact 1.9-meter turbine. That is relevant to low-head irrigation drops and other small facilities where large exclusion screens or bypass channels may be difficult to install.
DOE says Natel received nearly $9 million across seven Water Power Technologies Office programs over eight years for RHT development. DOE also summarizes earlier work reporting 100% observed survival for 60 rainbow trout and 47 American eels under their respective test conditions. Those results are encouraging, but the species, sample sizes, turbine units, operating conditions, and observation windows differ between studies. See the DOE trout-and-eel report and the DOE PNNL test summary.
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Fish-safe turbine passage is only one part of river connectivity. An RHT does not automatically:
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- Provide upstream passage through a dam or diversion.
- Restore spawning or rearing habitat.
- Restore natural seasonal flows or water temperatures.
- Recreate sediment transport.
- Prevent predation below a dam.
- Protect fish at screens, spillways, intakes, or other turbines.
- Address poor water quality or cumulative impacts from multiple dams.
For that reason, “protecting marine life” is too broad a description of the demonstrated work. The evidence is primarily about reducing turbine-related injury to downstream-migrating freshwater fish.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Could an existing plant be retrofitted?
Natel says its designs can be developed for existing civil works and several turbine configurations. That is not the same as a universal drop-in replacement. A feasibility study would need to examine:
- Available head, seasonal flow, pressure, and required rotational speed.
- Runner diameter, intake geometry, powerhouse dimensions, and draft-tube constraints.
- Generator, drivetrain, controls, grid, and dispatch compatibility.
- Debris, sediment, icing, drought, and flood conditions.
- Species, life stages, body lengths, migration timing, and regulatory passage standards.
- Construction access, outage duration, commissioning tests, and post-installation monitoring.
- The total installed cost compared with screens, bypasses, spill, operational changes, or retirement.
Natel reports peak hydraulic efficiency of up to approximately 94% on its technology page and says some modernization scenarios could produce up to 10% more output by reducing flow losses. These are company-reported, site- and operating-point-dependent figures. Peak hydraulic efficiency is not the same as annual energy production, which also depends on available flow, generator efficiency, outages, and environmental operating limits. See Natel’s technology page.
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Commercial status and questions for a buyer
RHTs are B2B infrastructure, not a consumer product with a published price list. A prospective owner would generally need site engineering, turbine integration, regulatory review, and a project-specific fish-passage plan. Public pages do not establish a universal equipment price, installation cost, or independently verified portfolio-wide performance dataset.
Before selecting a supplier, an owner or regulator should request:
- Hydraulic-efficiency curves and expected annual energy production for the specific site.
- Fish-survival data matching local species, sizes, life stages, and operating conditions.
- Independent test protocols, raw observations where available, and plans for delayed-injury monitoring.
- Civil-works modifications, generator compatibility, warranty, service, spare-parts, and outage terms.
- The regulatory pathway and a monitoring plan after commissioning.
DOE documents dated March 19, 2026 describe proposed laboratory and field work on American-eel passage through an RHT. That shows continuing validation and development; it should not be read as proof that every proposed test has been completed or that broad commercial deployment has been independently established. The proposal is described at DOE’s NEPA page.
The bottom line on Natel’s fish-safe turbines
Natel has credible peer-reviewed and DOE-supported evidence that its redesigned turbine can let particular freshwater fish pass through with very high observed survival. The Oregon trout trials are the strongest public field evidence, but they involve hatchery-reared fish, a limited number of species and sites, and defined operating and observation conditions. RHTs may be a valuable modernization option where turbine passage is the central problem. They are not a blanket guarantee for wild fish, every hydropower plant, upstream migration, or the broader ecological effects of dams.
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