Pentair Fairbanks Nijhuis’ bi-directional was specifically developed and optimized to generate energy from ultra-low head tidal streams in a dam type construction. The turbine blades can rotate 180 degrees and are able to rotate when the tide is reversing. Due to variable speed control the turbine maintains maximum efficiency during the complete tidal cycle. So efficiency is equal in both flow directions. The turbine can also be operated as pump. Research by the EU Interreg project Pro-Tide has shown that this turbine has the best available technology when it comes to generating energy from tides and scores almost 100% on fish-friendliness.
The bi-drectional turbine offers a solution to a global ecological problem of fish mortality caused by migration through turbines. Test results show that the turbine is nearly 100% fish-friendly. Part of the fish-friendly alterations to the turbine is the unique shape of the propeller vane. This creates a favorable flow in the water that allows the fish to migrate safely through the turbine. In addition, the space between the propeller vanes is much wider, which substantially reduces the risk of impact. The applied fish-friendly principles are based on the previously developed and patented fish-friendly pump and turbine.