Abstract
In this study, the wave-energy-converter of Oscillating-Water-Column type with Projecting-Wall (PW-OWC) is treated, on which an impulse-turbine is installed as a secondary energy converter from air-flow to electricity. When the primary conversion from wave motion to air-flow is improved by PW, as well as the secondary one from air-flow to electricity is refined by applying an impulse-turbine, then the optimum design is newly required of the total system consisting of the primary and the secondary conversion systems. The air-flow after the primary conversion is introduced in the air chamber to the entrance of turbine, where air-flow (Q) with pressure difference (ΔP), difference between the pressure at entrance and that at exit, makes the secondary conversion with rotating the turbine to generate electricity. Accordingly, Q and ΔP are the common parameters connecting the primary conversion system and the secondary one. A numerical model on hydraulics can provide Q and ΔP for an assigning incident wave. The characteristics of the impulse turbine is obtained under the constant flow condition and found independent from its size for the certain range of Q and ΔP. For the coupled analysis of the total system, a graphical method is tried. On the same Q vs P chart, both the hydraulic characteristic curve and the turbine curve can be drawn. The intersection point gives the possible combination of Q and ΔP, which satisfies the primary and the secondary systems at the same time. After the verification by the prototype field experiment, this method can be found useful as a practical design tool for PW-OWC.
