PNNL

Abstract

One of the most immediate, cost-effective, and environmentally sound methods of developing hydropower is through the uprating of existing hydroelectric turbines and generators. In many countries hydroelectric dams have turbines that are near the end of their service life with plans underway to install replacement turbine units that are not only expected to increase generating capacity and reliability but to improve turbine passage survival of fish. In order to validate improvements to the hydraulic environment that may lead to improved turbine passage survival, there is a need to develop a baseline hydraulic characterization of the existing Kaplan turbine units. To develop a hydraulic characterization at Ice Harbor dam in Washington State an autonomous sensor device known as the Sensor Fish was deployed under four different operating conditions and three release elevations. Median nadir pressures varied by operating condition, with values decreasing with operating power. At the Lower 1% operating point the median nadir pressure was 144 kPaA and at the Upper 1% operating point the value was 106 kPaA. The pressure changes during turbine passage varied by operating condition, with values increasing with operating power. At the Lower 1% operating point the median pressure change during turbine passage was 311 kPa and at the Upper 1% operating point the value was 344 kPa. Significant acceleration events (acceleration =95 G) had few differences between treatments, with most differences being within the confidence intervals. There were slightly more significant events in the stay vane/wicket gate region, ranging from 11.8% to 14.3% of releases compared to 6.3% to 13.0% in the runner region. For the rotational velocity the results were similar between the different operating conditions, with slightly more variability in the stay vane/wicket gate region compared with the runner region. When compared to other dams featuring large Kaplan turbines that have been studied using Sensor Fish, the nadir pressures measured at Ice Harbor tended to be the lowest, the pressure changes were typically higher, the percentage of releases with significant acceleration events were similar, and the rotational velocities were typically the lowest. This study provides additional insights into the biological performance of large Kaplan turbine units and will serve as a benchmark for future turbine rehabilitations.