Performance characteristics of a cross-flow hydrokinetic turbine in current only and current and wave conditions

Abstract

Testing of a 1:6 scale model of an H-Darrieus cross-flow hydrokinetic turbine (U.S. Department of Energy’s Reference Model 2 River Current Turbine) was conducted in the large towing tank facility at the United States Naval Academy. Tests were conducted in current only conditions at a range of diameter-based Reynolds numbers and at several turbine depths. Reynolds number independence was observed at or above ReD≈1.5×106, with an associated maximum power coefficient, CP of 0.36 at a tip speed ratio, TSR of 3.2. Turbine performance was shown to be fairly insensitive to turbine tip depth. Additionally, tests were conducted with incident waves in addition to current, which were scaled to be large enough to create a shear in velocity across the entire span of the turbine blade. The presence of waves degraded power production slightly when compared to the current only case. When viewed as a function of turbine angular position, the waves were found to amplify or diminish the cyclic signatures in the power measurement depending on the phase difference between the blade angle and wave phase angle. As cross-flow turbines are proposed to be surface mounted, this result suggests that active control strategies may be beneficial in improving power quality.