Experimental performance comparison of Ducted and Freestream hydrokinetic turbines

Abstract

Hydrokinetic energy’s high energy density and predictable nature make it an effective and reliable renewable resource. Ducted hydrokinetic turbines (HKT) offer benefits such as improved flow conditioning and higher power efficiency for the same reference area compared to an equivalent conventional freestream turbine. We designed and constructed an HKT system to characterize the performance of freestream and ducted turbines at various speeds and blade pitch angles in a state-of-the-art tow tank. When comparing the respective optimal blade pitch settings, the ducted turbine’s power efficiency is 19% higher than that of the freestream one. Our ducted turbine measured a peak power coefficient of $C_P=0.47$ despite unfavorable Reynolds number effects. This system’s power and thrust characterization indicates that ducted turbines, with an improved design and more favorable operating conditions, would likely exceed the measured $C_P=0.47$, laying the ground for further design optimization studies.