More than 52% of renewable energy comes from hydropower. However, hydropower plants can harm ecosystems, especially killing fish with their turbines. Fortunately, optimized hydraulic turbines and fish passage facilities recently entered the market, making the new generation of hydropower plants more fish friendly.

Hydropower plants convert the power of water into mechanical and electrical power. The hydraulic turbine allows for this conversion. However, fish generally cannot pass through the turbines unharmed. The primary exceptions include some low head (<8m) turbines, like water wheels and Archimedes screws. However, these do not work for large hydropower plants. Therefore, two strategies have been developed for higher head hydropower: fish passage facilities and fish friendly turbines.

Improved fish passages:

Fish passages are hydraulic structures that allow the upstream and downstream migration of fish when a dam impedes their migration. For example, fish ladders consist of a channel with typical bed slope between 5% and 10%, with pools separated by transversal baffles. Fish ladders mostly enable upstream migration. Fish passages also exist for downstream fish migration, coupled with screens behind the turbine that prevent fish entrance and divert fish to the fish passage. While effective, fish passages add cost to hydropower dam construction. Improved turbines offer a potentially better alternative.

Fish friendly turbines:

The Alden turbine specifically works with higher head sites. The Alden turbine has spiral blades wrapped around the shaft (as seen in image below). The shaft rotates around a vertical axis. Maximum efficiency can reach 90%, with fish survival rate of more than 90%.

Alternatively, the Minimum Gap Runner turbine (MGR) has a modification of the Kaplan turbine. The gaps between the adjustable runner blade and the hub, and between the blade tip and the discharge ring, are minimized at all blade positions. Such modifications decrease fish injury and mortality caused by grinding and by local high shear stresses and turbulence. Additionally, the modifications improve turbine efficiency.

Improved turbines support a future for hydropower:

With continued need for zero and low carbon energy, and with many countries pursuing additional hydropower projects, innovations such as these can help to reduce the negative consequences of hydropower and support its role as a significant renewable energy source.

Featured image courtesy of Voith GmbH & Co. KGaA.

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