Experimental and Numerical Investigation into the Energy Conversion Process in Single and Multi Chamber Oscillating Water Column Wave Energy Converters

Doyle, Simeon and Aggidis, George and Ilic, Suzana (2021) Experimental and Numerical Investigation into the Energy Conversion Process in Single and Multi Chamber Oscillating Water Column Wave Energy Converters. PhD thesis, Lancaster University.

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Abstract

Ocean waves are an immense energy resource at our doorstep that we are yet to truly harness. Harvesting of such a complex form of energy in the harshest environments gives wave energy conversion very unique challenges requiring continual innovation toward creating a more competitive contributor to the renewable energy mix. Innovations should not only benefit the wave energy sector but other technological applications by providing attractive novel synergetic deployment opportunities. This thesis presents an innovative solution to the issue of high wave energy costs. Research is based on a particular category of Wave Energy Converters (WECs) - the Multi-Oscillating Water Columns (M-OWCs) with focus on a unique technology, the Waves2Watts (W2W) device. The first phase involves concept verification through experimental modelling and the subsequent phase focuses on additional aspects of M-OWC technology, more specifically as an integrated breakwater. This project is novel in its methodology through the pragmatic approach of modelling each aspect of the W2W evolution with predecessors serving as benchmarks. This includes modelling several different WEC models with three different Power Take-Off systems enabling fair cross comparison for each evolutionary step toward the final M-OWC breakwater concept, which displays 36.1% efficiency in irregular waves. Both pneumatic and wave tank numerical modelling supports conclusions and provides additional insight into behaviour. The M-OWC concept generates greater power than the singular OWC benchmark by a factor equal to the number of OWCs. Furthermore, the additional width of the M-OWC, even at suboptimal chamber spacings shows better capture efficiency. These results reveal the potential of the final W2W Modular M-OWC breakwater WEC through the scalability of its power. The benefits of such a concept is anticipated to significantly reduce wave energy costs through increased capacity and novel integration fulfilling two roles – wave energy absorption and coastal protection.