Sea trials of Sigma wave energy converter-Power and efficiency

Sigma Energy has performed its foremost prototype tests of a scaled wave energy converter (WEC) in a real sea environment. The prototype was a point absorber with a circular buoy, a mechanical power take-off (PTO) system and a counterweight, moored to the seabed as a tension leg platform with three equal tendons. In these extensive experiments, numerous device characteristics were measured and analysed. The paper presents these sea trials, focusing on the power and efficiency of the device. The power has been calculated from the data recorded at 6 locations along the PTO system. In that way, a decay of capture width ratio (CWR) from the one absorbed from the waves to the one delivered to the electrical network was found and analysed. Also, losses of the main elements of the PTO system were defined, calculated and ranked. Optimal sea and loading conditions were indicated, giving the maximal values of the efficiencies. These optimal conditions are physically explained, and the challenges in their prediction are discussed. In addition to the results of numerous 20-min tests, the paper presents the long-term average values of the efficiencies, covering all the tests performed, and accounting for the probabilities of different sea conditions.

Automated summary

Sigma Energy has conducted initial prototype tests of a scaled wave energy converter (WEC) in an actual sea environment. The prototype, which consisted of a circular buoy, a mechanical power take-off (PTO) system, and a counterweight, was moored as a tension leg platform to the seabed with three equal tendons. The experiments measured and analyzed various characteristics of the device. This paper presents the sea trials, with a focus on the device's power and efficiency. The study calculated the power based on data recorded at six locations along the PTO system, revealing a decay of capture width ratio (CWR) and the losses of the main elements of the PTO system. The optimal sea and loading conditions were determined, explaining the highest efficiencies achieved and discussing the challenges in predicting them. The paper also presents the long-term average values of the efficiencies, encompassing all the tests performed and accounting for different sea conditions.