Proceedings of OMAE2007 26 th International Conference on Offshore Mechanics and Arctic Engineering Special Symposium on Offshore Renewable Energy 10-15 June 2007 - San Diego, California OMAE2007-29254 INFLUENCE OF AN IMPROVED SEA-STATE DESCRIPTION ON A WAVE ENERGY CONVERTER PRODUCTION. Marie-Aurélie Kerbiriou, Marc Prevosto, Christophe Maisondieu IFREMER, ERT/Hydrodynamics - Metocean Department, BP 70 - 29280 PLOUZANE Aurélien Babarit, Alain Clément Ecole Centrale de Nantes, LFM, BP 92101 - 44321 NANTES ABSTRACT Sea-states are usually described by a single set of 5 parameters, no matter the actual number of wave systems they contain. We present an original numerical method to extract from directional spectra the significant systems constituting of a complex sea-state. An accurate description of the energy distribution is then given by multiple sets of parameters. We use these results to assess the wave climatology in the Bay of Biscay and to estimate the power harnessable in this area by a particular Wave Energy Converter, the SEAREV. Results show that the fine description of sea-states yields a better assessment of the instantaneous device response. The discrepancy between the classical and multi-sets descriptions show that the new one is preferable for the assessment of harnessable power and for device design. Keywords: Sea-States, Wave Energy, Wave Energy Converter, Spectral Data, Systems Extrac- tion. 1 INTRODUCTION Marine technologies require an accurate description of complex sea states accounting for the contributions of different wave systems. Such a fine description can benefit to coastal engineering, ship building, design of floating structures such as FPSO or drilling platforms. For instance the effect of the superimposed wave sys- tems differing in direction, peak frequency, frequency bandwidth and significant wave height can be assessed separately. Once the individual systems properties are known, linear and non linear interactions between sys- tems can also be taken into account when computing efforts on structures. Regarding wave energy harnessing, the estimate of lo- cal energy potential considerably varies with the natural characteristics of the conversion device: depending on the concept of the Wave Energy Converter, (oscillant, overtopping, point absorber, resonant or not), produc- tion capacities may dramatically drop with temporal or spatial changes in waves directionality, frequency distri- bution or height. Moreover, wave energy harnessing feasibility is strongly restricted by environmental, social and logis- tical constraints, which reduce the possible locations for WEC units. As a consequence, providing a complete, detailed and statistically weighted description of local sea states is a powerful design tool to adjust WEC proper characteristics to possible implementation places. In spite of its focus on wave energy harnessing, this 1 Copyright © 2007 by ASME Proceedings of the 26th International Conference on Offshore Mechanics and Arctic Engineering OMAE2007 June 10-15, 2007, San Diego, California, USA OMAE2007-29254