PNNL

Abstract

The potential of hydropower turbines to cause injury or mortality to fish due to the exposure to stressors like blade strike, collision, fluid shear and rapid decompression is a concern. In order to reduce this risk, engineers have begun to develop a conically-arranged, cantilevered electrified bar rack (Center Sender). This device is proposed to be mounted within the intake of a turbine, guiding downstream-passing fish towards the center of the turbine where blade velocities are lower, and blades are thicker, likely reducing the potential for fish to be injured. A simplified version was installed in a flume for testing with rainbow trout (Oncorhynchus mykiss) while examining several parameters such as electrification, bar spacing, bar angle, and water velocity. The most effective settings were observed to be a water velocity of 1.0 m/s with all bars installed at an angle of 40? with electrification on. Other combinations were still effective but had varying results. Interestingly however, a minimal proportion (2.3%) of fish passed at lower velocities with bars electrified and mounted at 20?; suggesting that while it functions well as a guidance device in high velocity conditions, it performs better as a barrier at lower velocities. The study suggests that the Center Sender has promising potential for reducing the effects of hydropower turbines on fish populations by guiding them away from stressors likely to cause injury or mortality. Further research is needed before determining its full potential, but current results encourage its potential use in hydropower operations.