Model scale wave energy converter test device; sonic wave probe array shown in foreground.

Model scale wave energy converter test device; sonic wave probe array shown in foreground.

Existing wave energy converter (WEC) designs produce power efficiently over a narrow band of the full wave frequency spectrum. To achieve commercial viability, WECs must be able to absorb and produce power efficiently across a broad range of frequencies. Sandia is developing and validating control strategies to increase power of WEC devices. To make the difficult leap from theoretical studies to deployable WEC hardware, Sandia is performing research on control algorithm development, numerical simulation, and scaled model testing.

The Advanced WEC Dynamics and Controls project is designed to address six top-level objectives:

  1. Use numerical modeling and novel laboratory testing methods to quantitatively compare a variety of control strategies. The Advanced WEC Dynamics and Controls project is exploring the use of system identification methods in model-scale WEC testing. Compared to common testing procedures, our advanced methods, which have been proven in other engineering fields (e.g. aerospace, automotive), provide richer testing results, producing better numerical models and better controls, in less time. This testing methodology will provide developers and researchers a basis for performing their own tests, which will enhance testing efficiency and effectiveness
  2. Produce data, analysis and methodology that assist developers in selecting and designing the best control system for their device. By considering a range of control strategies, this project strives to provide developers with the information they need to make informed decisions about specific strategies for WEC control. Studies comparing different control strategies provide a roadmap to WEC control by examining metrics on control performance as well as implementation requirements (e.g., actuator and sensor requirements, and computational cost).
  3. Use numerical modeling and testing to determine the degree to which developed control strategies are device-agnostic. Sandia’s research focuses on delivering broadly-applicable, quantitative results, methods and best practices that can be applied to a wide range of WEC devices. With a variety of devices being developed by industry, it is critical that the findings and products from this project are not limited to the device(s) considered in this study. Therefore, the research and dissemination strategy of the Advanced WEC Dynamics and Controls project is centered on providing as much device-agnostic value as possible.
  4. Develop strategies to reduce loads, address fatigue, and to handle extreme conditions. For full-scale implementation, a control design must consider not only the increase in power absorption, but also the full system dynamics of the device. Structural dynamics must be considered the control design must be tailored to reduce loads and high-frequency vibration in both operational and extreme conditions. Sandia has developed structural response cancelation methods and will continue to pursue research that improves power absorption while considering the structural requirements imposed by WEC device dynamics.
  5. Full wave-to-wire control: To be of any value to a developer, absorbed (mechanical) power must be converted and delivered to the grid (or some other beneficial application). The steps from generation to power-electronics to transmission are, therefore, integral to systems which must be considered in control design. Control strategy design and assessment in this project will examine the full hydrodynamic-mechanical-electrical system.
  6. Develop novel control strategies and design methodologies: In addition to considering existing WEC control methods, this project leverages Sandia’s control expertise from aerospace, defense, and robotics to develop novel WEC control approaches. Researchers are investigating a number of innovations, including pressure-based state (e.g. excitation) estimation and nonlinear geometric coupling. All developments produced by this project are intended for public use.

Advanced WEC Dynamics and Controls Presentation

 

Model scale WEC device in NSWCCD basin

Model scale wave energy converter test device in Naval Surface Warfare Center, Carderock Division (NSWCCD) Maneuvering and Seakeeping (MASK) basin.

DiagramWECmodel

Diagram of model scale Advanced WEC Dynamics and Controls test device and hardware.