CFD-Based Model Predictive Control for Point Absorber Wave Energy Converter

The Japan Society of Naval Architects and Ocean Engineers Conference Proceedings, Vol. 41 (2025)
Sang-seok Han 1, Min-hong Lee 2
1 Department of Naval Architecture, Ocean and Marine Engineering, University of Strathclyde, the United Kingdom
2 Department of Naval Architecture and Ocean Engineering, Inha University, Republic of Korea

Summary

This study presents a pseudo-Model Predictive Control (pseudo-MPC) strategy for improving energy absorption in point absorber-type Wave Energy Converters (WECs) using high-fidelity Computational Fluid Dynamics (CFD) simulations. Unlike traditional MPC, which requires real-time optimisation, the proposed approach uses a pre-computed damping law based on wave amplitude, enabling real-time responsiveness without intensive computation.

Implemented within STAR-CCM+ using Field Functions and DFBI, the control is designed to dynamically adjust the Power Take-Off (PTO) damping during two-phase flow simulations. A four-stage simulation plan was conducted, including static model validation, wave tank calibration, offline damping optimisation, and planned online control.

Initial results confirm the numerical validity of the CFD setup and quantify energy absorption under fixed damping values across varying wave amplitudes. These outcomes provide a robust foundation for the upcoming implementation of the pseudo-MPC control law, demonstrating that real-time MPC-inspired control can be efficiently realised within CFD environments for future adaptive WEC systems.

Conference paper (2025)
The Japan Society of Naval Architects and Ocean Engineers Conference Proceedings, Vol. 41
DOI: 10.14856/conf.41.0_979
Selected Figures
Front, top, and side views of the computational mesh for the point absorber WEC simulation
Figure 2. Mesh configuration views: (a) front, (b) top, and (c) side.
The computational domain uses a structured mesh with local refinement around the free surface and the point absorber to resolve wave–body interaction. The mesh contains approximately 1.13 million cells for the small-wave case and 2.28 million cells for the large-wave case, while the WEC motion is constrained to the vertical (heave) direction.
Comparison between theoretical and CFD wave elevation for regular-wave validation
Figure 4. Comparison of wave height: theoretical prediction vs. CFD simulation.
The body-free wave-tank simulation was used to verify wave generation before the control study. For the regular-wave condition (H = 0.1 m, T = 1.0 s), the CFD wave elevation closely follows the theoretical target in amplitude, period, and phase, supporting the validity of the numerical wave environment.
Absorbed power histories for small and large regular-wave conditions
Figure 7. Real-time absorbed energy under two regular wave conditions: (a) small wave and (b) big wave.
The offline phase compares energy absorption under fixed damping values selected for two representative regular-wave conditions. Over 50 seconds, the study reports approximately 95 J of absorbed energy for the small-wave case and 4,980 J for the large-wave case. These results form the basis for fitting the wave-amplitude-dependent damping law; the fully dynamic online pseudo-MPC implementation is identified in the paper as planned work.