MARINET experiment KNSWING testing an I-Beam OWC attenuator

Abstract

The research and results presented in this paper concerns experiments on wave energy conversion carried out in the one meter deep wave tank at the Hydraulic and Maritime Research Center (HMRC) at University College Cork, Ireland in 2013. The purpose is to investigate how much power an attenuator – a ship shaped wave energy converter facing the waves with its bow – can absorb along its sides in a range of regular and irregular wave conditions.The experiments were carried out in model scale 1:50 resembling the wave conditions and water depth of the Danish part of the North Sea and a 150m long wave energy converter with 20 Oscillating Water Column (OWC) chambers on each side. The damping applied to each chamber by the Power Take Off (PTO) is modeled by forcing the air through a hole with an area of about 1.3% of the chamber water surface area.The results in irregular wave conditions shows that the converter can absorb more than 2.5MW of wave power that in wave conditions with significant wave heights of 5m. A capture width ratio between 20% and 25% was measured in the most frequent wave conditions with average periods between 5 and 7s with significant wave height of 2 m. In short crested waves the energy absorption was slightly better due to the directional spreading of energy.The tests in monochromatic waves indicate capture width ratios up to 35% in waves with a steepness of 2.5%. The capture width ratio decreases somewhat in steeper waves.The experiments with the attenuator wave energy converter demonstrated its seaworthiness and ability to absorb wave energy. The results form a valuable base for the development of a numerical model of the system that will be used for further optimization and development.