Effects of wave spectrum representation on power production estimations from point absorbers

Abstract

This study presents a first long term (30 years) assessment to quantify the effects of both, the wave spectrum representation, and occurrences of multi-modal sea states, on power production estimations from a point-absorber Wave Energy Converter (WEC). Analysis in 3 different offshore locations (Portugal, Ireland and The Netherlands) is included to ensure robustness of results. In general, traditional methods based on the use of the JONSWAP spectrum, with an adequate gamma shape value, can lead to mean overestimation in yearly power production $>12\text{\%}$ when compared to reference hindcast spectral data. This can be partially reduced when capping is applied to power production, but still can be close to $10\text{\%}$. An alternative method is proposed to modulate the JONSWAP spectrum at each time step which helps to reduce differences, but leads to slight yearly underestimations (−2.5 to −5% in average). Although in all analyzed sites the occurrences of multi-modal spectra is $>30\text{\%}$, contribution to errors due to misrepresentation of these sea states are estimated to be of about $2.5\text{\%}$. These findings provide valuable insights on the uncertainties introduced in power production estimations, related to wave conditions characterization, that can have important economic impact when planning for large scale deployments.