TY - JOUR
T1 - A numerical study on the performance of the point absorber Wave Energy Converter integrated with an adjustable draft system
AU - Tan, Jian
AU - Polinder, Henk
AU - Laguna, Antonio Jarquin
AU - Miedema, Sape
PY - 2022
Y1 - 2022
N2 - The Power Take-Off (PTO) rating of Wave Energy Converters (WECs) is generally much higher than the average extracted power. Scientific literature has indicated that downsizing the PTO capacity to a suitable level is beneficial for improving the techno-economic competitiveness. In this paper, a novel design, namely the adjustable draft system, is proposed for point absorbers to implement PTO downsizing. A frequency domain model is established to calculate the performance of the proposed device. From frequency domain analysis, two potential advantages are identified by installing the adjustable draft system. Firstly, the excitation force can be controlled by adjusting the buoy draft, which could be utilized to reduce the required PTO force. This is helpful for downsizing the PTO capacity. Secondly, the relevant natural frequency of the point absorber can be adapted to the operating wave states by varying the buoy draft, which improves the power absorption. A nonlinear approach is adopted specifically for the spherical buoy to include the nonlinear Froude–Krylov force and viscous drag force. The results show that the nonlinear forces have a significant influence on the power absorption when operating close to resonance regions. However, the advantages resulting from the proposed system still can be observed while considering the nonlinear forces. The power absorption can be improved by 27% and 12% in particular cases of regular and irregular wave states respectively.
AB - The Power Take-Off (PTO) rating of Wave Energy Converters (WECs) is generally much higher than the average extracted power. Scientific literature has indicated that downsizing the PTO capacity to a suitable level is beneficial for improving the techno-economic competitiveness. In this paper, a novel design, namely the adjustable draft system, is proposed for point absorbers to implement PTO downsizing. A frequency domain model is established to calculate the performance of the proposed device. From frequency domain analysis, two potential advantages are identified by installing the adjustable draft system. Firstly, the excitation force can be controlled by adjusting the buoy draft, which could be utilized to reduce the required PTO force. This is helpful for downsizing the PTO capacity. Secondly, the relevant natural frequency of the point absorber can be adapted to the operating wave states by varying the buoy draft, which improves the power absorption. A nonlinear approach is adopted specifically for the spherical buoy to include the nonlinear Froude–Krylov force and viscous drag force. The results show that the nonlinear forces have a significant influence on the power absorption when operating close to resonance regions. However, the advantages resulting from the proposed system still can be observed while considering the nonlinear forces. The power absorption can be improved by 27% and 12% in particular cases of regular and irregular wave states respectively.
KW - Adjustable draft system
KW - Nonlinear time domain modeling
KW - Wave Energy Converters
UR - http://www.scopus.com/inward/record.url?scp=85129538618&partnerID=8YFLogxK
U2 - 10.1016/j.oceaneng.2022.111347
DO - 10.1016/j.oceaneng.2022.111347
M3 - Article
AN - SCOPUS:85129538618
SN - 0029-8018
VL - 254
JO - Ocean Engineering
JF - Ocean Engineering
M1 - 111347
ER -