Developing control strategies for a floating oscillating water column wave energy converter

Abstract

The Hawaii Marine Energy Center (HMEC) at the University of Hawaii is advancing in the design of innovative tools for wave energy converter (WEC) research and development, while providing leadership and guidance to expand WEC adoption as a viable renewable energy source, particularly in remote communities throughout Hawaii and the United States Affiliated Pacific Islands.  Key research focuses include designing WEC foundations with fluid-structure interaction considerations, improving wave resource prediction, and studying the far-field impact of WECs while optimizing WEC performance through enhancing hydraulic Power Take-Off systems and emphasizing the integration of control strategies for improved energy capture and efficiency in Oscillating Water Column (OWC) devices.

The initial focus of this work will be on the Halona, a floating OWC concept intended to generate power for ocean observing systems. The project is examining, numerically and experimentally, a control strategy for the WEC. Numerical modeling is underway now that will result in the selection of a strategy that will then be validated through lab and ocean testing. This OWC, nominally rated at 100W, employs an impulse turbine coupled with generator flywheel

technology to extract electric power from ocean waves. The HMEC team is collaborating with Sandia National Laboratory on this work.

Our paper gives an overview of control strategies for OWCs, which include device hydrodynamics and turbine dynamics (Rosati et al 2022). Device response characteristics, known from past basin experiments, sea states at a future deployment location, power generation capability, and robustness of control strategy and hardware are considered when down-selecting control strategies to improve performance. The paper includes a model of device hydrodynamics, utilizing the piston model for the OWC water column as well as a model for turbine control.

By demonstrating the potential of optimized control systems, this work advances the role of OWCs in delivering sustainable and reliable energy solutions for remote and island communities while ensuring robust operation under diverse maritime conditions. 

References:

Rosati, M., Henriques, J.C.C., & Ringwood, J.V. et al (2022). Oscillating-water-column wave energy converters: A critical review of numerical modelling and control. Energy Conversion and Management: X 16 100322.