Hydroelectric turbines may indeed be a non-polluting source of electricity, but their spinning blades can nonetheless kill larger fish that are passing through. A new type is designed not to do so, while maintaining a compact form factor.
First of all, there are already relatively fish-safe hydroelectric turbines. They're typically pretty big, however, to accommodate their proportionally larger, wider-spaced blades. This means that not only are they often more expensive than other models, but they're also more difficult to incorporate into smaller dams.
That's where the Restoration Hydro Turbine (RHT) is designed to come in. Manufactured by California-based Natel Energy, it has an inner diameter of just 1 to 3 meters (3.3 to 9.8 ft) – depending on the model – while also incorporating blades with a blunt, slanting leading edge.
This design reportedly deflects fish away from the blades, significantly reducing the likelihood of direct contact. That said, the blades are claimed to be just as efficient as their conventional counterparts when it comes to spinning up in the flowing current. Additionally, no flow-impeding fish-proof screens are required.
In a study conducted this September, scientists from Washington state's Pacific Northwest National Laboratory (PNNL) assessed the fish-friendliness of a 1-megawatt RHT, that is part of the just-completed Monroe Hydro Project – it's located on a canal in the city of Madras, Oregon. A total of 60 tagged rainbow trout were released through the 1.9-m (6.2-ft)-diameter turbine, each fish up to 15 inches (381 mm) in length.
A PNNL-designed device known as the Sensor Fish was also sent through, which is a sensor-equipped gadget that measures the stress that would be placed on a fish in the same situation.
When the trout were recaptured downstream from the RHT, it was found that all of them had made it through alive and uninjured. According to Natel Energy, "This is surprisingly good performance given the compactness of the turbine relative to the large size of fish tested."
Source: Natel Energy