Evaluation of four rugged long-term velocity measurement methods for assessment of hydrokinetic energy production
Four sensors embedded in a tear-shaped buoy are investigated to measure non-instantaneous river velocity to eliminate seasonal elements that can damage velocity instruments when deployed over a long-term period for measurements at energetic sites. Velocity data is required to predict the 95% confidence interval of the power production from hydrokinetic turbines at potential river sites. This novel measurement buoy measures flow velocities inferred from the tilt angle of the buoy using an inertial measurement unit sensor, tension on the wire rope connecting the buoy to the riverbed anchor using a strain gauge sensor, vortex-induced vibration of the mooring line also using an inertial measurement unit sensor, and sound of the water flowing around the buoy using a microphone sensor. The four sensors are embedded in a prototype buoy and tested in a laboratory water tunnel at flow velocities from 0.1 to 1 m/s. The laboratory measurement data is analyzed to find the relationship of each sensor to water velocity based on a phenomenon-based approach. The data from the sensors displayed a nonlinear relationship with flow velocity. Calibration curves were developed for each sensor to measure the flow velocity. The most accurate measurement method is tilt angle method. The average percent error in accuracy for estimation of flow velocities from 0.5 to 1 m/s from tilt angle data is 0.5 %. Each of the sensors embedded in the buoy is critically assessed for its validity to estimate the long-term river velocity at energetic river sites to determine the power production from potential hydrokinetic turbine sites.
hydrokinetic, renewable, flow velocity, measurement