Experimental Study of a Lift-Type Wave Energy Converter Rotor in a Freewheeling Mode

Abstract

In pursuit of energy harvesting from ocean waves, our recent progress on studying wave interaction with a lift-type rotor is discussed in this paper. The particular focus is on the characterization of the rotor's unidirectional responsiveness in waves. The rotor consists of six hydrofoil blades in two sets. One blade set has three blades laid out as a vertical-axis wind turbine of the Darrieus type. The other blade set has three blades configured like a Wells turbine. In combination, the formed rotor can be driven by flows in any direction to perform a unidirectional rotation about its vertically mounted shaft. This unidirectional responsiveness of the rotor also holds in waves, making the rotor an effective device for wave energy conversion. For the parametric study of the rotor, hydrofoil blades using different cross-sectional profiles and chord lengths have been employed to configure the rotor. The rotor was then tested in a wave flume under various wave conditions in a freewheeling mode. Experimental results were analyzed and discussed. The yielded research findings will greatly enhance the fundamental understanding of the rotor performance in waves and effectively guide the prototype rotor development for practical applications.

A Review: Design and Optimization Approaches of the Darrieus Water Turbine

“…The numerical results showed that the optimized range of TSR has to be considered in coupling. Coupling with other turbines could also improve the starting ability [118], but the highest power coefficient of the coupled turbine needs further improvement. The goal of coupling was to drive the Darrieus turbine in start-up, and the Darrieus turbine can provide higher efficiency at a higher rotation speed after starting.…”

Rotors for wave energy conversion—Practice and possibilities

“…Other designs for vertical rotor based WECs follow a simplifies philosophy that avoids the reliance on any information or intervention from weather forecasting, sensing, electrical and or mechanical control. For example, a number of FIGURE 13 Vertical-axis unidirectional cyclorotors for wave energy conversion patented by Yang [25] vertical-axis rotor concepts were presented in the articles of Yang et al [10,25,[45][46][47][48]. These rotors have a number of cup blades or curve hydrofoils, as shown in Figure 13.…”

“…The test results of the drag-type rotors were published in [45] and, for lift-type rotors, in [47,48]. Experimental results have demonstrated unidirectional rotation of the rotors, but with noticeable fluctuations in angular velocity.…”

“…For example, a number of vertical‐axis rotor concepts were presented in the articles of Yang et al. [10, 25, 45–48]. These rotors have a number of cup blades or curve hydrofoils, as shown in Figure 13.…”