Natel's Hydro Turbine Technology Could Help Reverse Decline of Atlantic Coast River Herring, New Study Suggests

March 6, 2023

ALAMEDA, Calif. – March 3, 2023 – A new study published in the North American Journal of Fisheries Management shows a 98.2% immediate and 100% delayed survival rate for juvenile alewife passing through the Restoration Hydro Turbine. These results support Natel's hypothesis that a modern style of hydro turbine can hugely improve fish survival outcomes without compromising hydraulic efficiency, and without the use of screens or bypasses. By using fish-safe turbines, hydropower can both combat climate change and reverse biodiversity loss.

Natel Energy and Kleinschmidt researchers stand above Freedom Falls, next to fish holding tanks during alewife passage testing.

Alewife are an anadromous species of river herring, similar to shad, that are native to the east coast of North America. Alewife are born in freshwater habitats and then migrate downstream as juveniles to spend their adult lives in the ocean. Like many other types of fish on the Atlantic coast, a single alewife might encounter multiple hydropower sites as it attempts to migrate from the river to the ocean.

Current best practice for managing downstream passage of fish through hydropower sites is fish exclusion—preventing fish from entering the turbines, usually with screens, and directing them around the turbines, often toward a dedicated bypass. Exclusion methods, however, are frequently inadequate. Many fish, particularly juvenile fish, are able to pass through even fine screens, and they still enter turbines. 

Approximately 1 in 5 fish die when passing through a conventional hydropower turbine. Standard compact turbines have many thin, fast-moving blades that can easily injure or kill fish, and the environmental benefit that those turbines provide in renewable energy is often offset by the blow they deal to aquatic biodiversity. 

Natel’s alewife study was designed to quantify the survival rate of juvenile fish through a novel hydro turbine specifically designed for safe fish passage. The study was conducted in 2021 with Kleinschmidt Associates at the Freedom Falls Hydropower Project, a small, 35-kW plant located at a refurbished historical mill dam on Sandy Stream (home of the Lost Kitchen restaurant).

Natel Energy engineers release juvenile alewives (herring) into the mouth of the penstock through a turbine injector temporarily installed at the Freedom Falls Hydro Plant. The fish will pass from here through the Restoration Hydro Turbine.

484 alewives (Alosa pseudoharengus) measuring 87-132 mm (3-5 in) in length were used for the test. The fish were passed through a .55 m (1.8 ft) Natel Restoration Hydro Turbine (RHT). “The results of this study underscore the opportunity this new turbine technology presents to all those involved in hydropower, including regulators, operators and non-governmental organizations,” said Natel co-founder and Chief Technology Officer Abe Schneider. “We’re confident that we can continue to invest in the immense renewable benefits of hydropower in a way that does not compromise the preservation and well-being of aquatic life through the use of fish-safe turbine technology.”

Natel CTO Abe Schneider holds the live box that was used to recapture the fish after passing through the Restoration Hydro Turbine. This photo shows some of the fish that were not part of the study but safely passed through the turbine because they were naturally occurring in the stream, including an American eel.

The RHT’s design is distinct from a conventional hydro turbine in three major ways, each of which is designed to reduce the likelihood that a fish will be struck by a turbine blade and/or to reduce the likelihood that fish impacted by the blade will be harmed. First, the RHT’s runner blades have very thick leading edges, and there are fewer blades than in a conventional propeller turbine. The RHT’s runner blades are also swept forward from the hub to the tips, in order to direct the fish to pass through the turbine closer to the hub, where blade speeds are lower.

The results of the juvenile alewife study are reinforced by the equally positive results of additional scientific studies Natel has conducted with third-party scientific partners, including the Pacific Northwest National Laboratory and Alden Laboratory. The parallel studies affirm an average of greater than 99% safe passage of other fish species, sizes, and life stages, including American eel and rainbow trout, through the fish-safe Restoration Hydro Turbine.

About Natel Energy 

Natel Energy, Inc. is expediting the energy transition with modern, sustainable hydropower that supports healthy rivers, and with accurate, timely decision-making tools that improve water resource management. Natel’s core innovations include fish-safe, compact, high-performance hydropower turbines and AI-powered water intelligence software that combines satellite and environmental data to deliver highly accurate forecasts. By applying these technologies to upgrade existing hydropower sites and develop new, low-impact projects around the world, Natel is working to save our planet with solutions that address climate change and biodiversity loss. Natel is a privately held company located in Alameda, California in the United States. Visit for more information.

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