Abstract
Open water testing of marine renewable energy devices represents a significant milestone and hurdle for research teams and companies developing new technologies. For open water testing of tidal turbines, accurate measurements of loading characteristics on the blades or other structural components correlated with power performance metrics can be invaluable to further refine design principles and models, allowing continued improvement and cost reduction of new turbine designs. This work describes the build and operation of a data acquisition system, retrofit to a New Energy vertical-axis turbine, to monitor and record blade loads, power output, and other operation metrics in real time.[RH1] The system described in this work captures blade strain on an active, power-producing turbine and transmits the data wirelessly to an existing MODAQ data collection system, developed by the National Renewable Energy Lab. Blade strain is saved for later conversion to blade loads and correlation with other data streams, including free-stream velocity, rotor rotation speed, rotor azimuthal position, and thrust. Strain gauges are applied along the span of the blade and oriented to measure flapwise bending. Gauges and wires are recessed into the blade and strut to minimize interference with the boundary layer flow. The DAQ-Mast designed to house the data collection instrumentation rotates with the turbine, eliminating the need for major modifications to accommodate slip rings or other components needed to move data and power between the platform and rotating components. In this study we first analyze the performance of the New Energy vertical-axis turbine both with and without the DAQ-Mast system in place. This is accomplished by comparing our data to results from publicly available datasets that characterize the turbine operating without the DAQ-MAST. Secondly, we characterize the cyclic loading on the vertical-axis turbine blade, derived from strain measurements. A description of the publicly available datasets related to this work is included. This study aims provide data of sufficient quality to be used for vertical-axis numerical model validation, to highlight novel, cost effective solutions for making difficult blade measurements, and to illustrate the benefits of more extensive datasets.