Experimental investigation of multiple oscillating water column wave energy converters integrated in a floating breakwater: energy extraction performance
Howe, DP and Nader, J-R and MacFarlane, G, Experimental investigation of multiple oscillating water column wave energy converters integrated in a floating breakwater: energy extraction performance, Applied Ocean Research, 97 Article 102086. ISSN 0141-1187 (2020) [Refereed Article]
Currently, ocean wave energy technology is in its infancy relative to the mature renewable energy technologies such as wind and solar. Due to its early stage of development, ocean wave energy has high associated Levelised Cost of Electricity (LCOE), a measure of lifetime costs relative to lifetime energy production. Several solutions have been derived in an attempt to reduce this high LCOE, of which breakwater integration of wave energy converters presents a viable option. Current full-scale commercial and demonstration devices indicate that OWC device integrated breakwaters are typically limited to nearshore and onshore operational regions. However, industries such as aquaculture and offshore wind are exploring the viability of placing these structures in deeper waters, where these traditional concepts would not be applicable, providing opportunity for the development of floating offshore multi-purpose structures. This article describes a proof-of-concept for a floating breakwater integrated with Oscillating Water Column (OWC) Wave Energy Converters (WEC). For an integrated device of this type there are multiple key aspects that are inter-related and each must be understood: energy extraction performance, wave attenuation and quantifying platform motions. In order to adequately report on each aspect in a logical manner the study is presented in two parts. This paper covers the energy extraction aspects, while the second part deals with wave attenuation and motion characteristics . The wave energy extraction characteristics of the installed devices are explored across parameters including device configurations, breakwater width, power take-off damping, wave height and motion constraints, all of which was achieved through model scale hydrodynamic experimentation. The major findings indicate that OWC device spacing is a key parameter in the design of multi-device structures, as device-device interaction can have constructive or destructive interferences on the energy extraction. Additionally, the results of the OWC device performance, under the influence of the aforementioned parameters, provides new insights to the development of floating offshore multi-purpose structures and their feasibility.
oscillating water column, wave energy, floating breakwater, hydrodynamic experimentation, performance