振盪衝擊式波能轉換器在捕獲係數上之機械阻抗效應

Mechanical Impedance Effects on the Capture Factor of OWSC

波浪能，屬於海洋再生能源的主要部份，吸引了許多研究者及發展者的關注，也造就了許多類型的波能轉換器之發明與發展。本文以理論與實驗的手段探討其中一種稱為“振盪衝擊式”波能轉換器（oscillating wave surge converter, OWSC）。OWSC可視作由一片接受波浪衝擊的擺動板連接能量輸出系統（power take-off, PTO）而成。我們針對板體的擺動首先發展水動力學方程式，其中出現與波浪場、板體的恢復力矩以及PTO相關之機械阻抗項。當PTO阻尼與前進波的阻抗相同，且PTO的慣性和剛性、板體的恢復力矩與駐波的阻抗互相抵消時，方程式顯示板體的能量捕獲條數達到最大值。為了驗證理論，我們以一個可調PTO阻尼及板體質量與質心的OWSC模型進行造波水槽實驗。並使用高速相機來記錄板體的擺動以及應變規來測量PTO的受力，最後得到與理論預測相當接近的實驗結果。 As the major portion of oceanic renewable energy, wave energy has drawn significant attentions, resulting in many inventions and developments of wave energy converter (WEC). This paper theoretically and experimentally examines one kind of WEC, the Oscillating Wave Surge Converter(OWSC), which can be regarded as a wave-surged flapper connected with a power take-off (PTO). We first develop hydrodynamic equations for the oscillation of the flapper in terms of mechanical impedances associated with the wave field, the restoring moment of the flapper body, and the PTO. The equations show that the capture factor is maximized when the impedances associated with the PTO's damping and the progressive wave field are matched, and the impedances associated with the PTO's inertia and stiffness, the restoring moment of the flapper body and the standing wave field cancel altogether. To verify the theory, experiments are conducted in a wave flume for a model OWSC which has a tunable PTO and a movable mass inside the flapper body with its flapping motions recorded using a high-speed camera and the forces experienced by the PTO measured using strain gauges. Experimental results obtained are considerably close to the theory's predictions.