Signature Projects are intended to bring focus to a selection of the U.S. Departments of Energy's Water Power Technology Office (WPTO) projects. By designating a Signature Project, the project reports, data sets, and associated papers can be easily discoverable. By bringing together all aspects of a project, whether a completed legacy project or an ongoing investigation, the MRE community can be informed of what investigations have been undertaken, which have succeeded, what tools are available, and where gaps in information persist.

LUPA

Project Information

Status:	Ongoing
Start Date:	2020/04/01
Source:	LUPA Website
Organization:	Pacific Marine Energy Center (PMEC), Oregon State University (OSU)
Contact:	Bryson Robertson

Project Purpose: The Laboratory Upgrade Point Absorber (LUPA) Project was designed to create an open-source, modular numerical and physical WEC system to create a common benchmark for WEC hydrodynamics, controls, mooring systems, and student learning.

Project Description: The Lab Upgrade Point Absorber (LUPA) project, sponsored by the U.S. Department of Energy (DOE), has developed open-source modular point absorber for WEC hydrodynamics, controls, mooring systems, and student learning. A visual of the experimental and numerical LUPA WEC are shown in Figure 1. The LUPA development team collaborated with the DOE National Marine Energy Centers (NMECs), Sandia National Laboratory (SNL), National Renewable Energy Laboratory (NREL), and private industry in the development of the LUPA WEC physical specimen and experimental device.

Figure 1: (Left) Computer rendering of the LUPA in SOLIDWORKS. (Right) LUPA deployed in the Large Wave Flume at Oregon State University.

Methods: The LUPA WEC system includes both physical and numerical version of the technology. The physical LUPA WEC system is modular and can be modified to change float and heave plate geometries, mooring systems, PTO systems and controls, and operating modes. LUPA can operate in three configurations with varying number of bodies and degrees of freedom: 1) one-body heave-only, 2) two-body heave-only, and 3) two-body six-DOF. The physical LUPA WEC specifications are given in Table I.

The experimental LUPA WEC has an actively controllable linear-to-rotary belt-driven PTO system, and can be actively controlled via a bespoke MATLAB Simulink control interface. The PTO and Simulink interface are designed to allow for the emulation of the wide range of PTO systems currently in commercial development. The following experimental measurements (sensors) are included: PTO torque (motor drive), PTO rotational speed (motor encoder), relative motion between spar and float (draw wire), float translational accelerations, rotations, and angular velocities via an inertial measurement unit (IMU), and PTO belt tension (load cells).

In addition to the physical system, each experimental LUPA WEC test campaign is supported by the development and release of a companion WEC-Sim numerical model which can be found here: https://github.com/PMEC-OSU/LUPA_WEC-Sim. There is also a tutorial of LUPA on WecOptTool which can be found here: https://sandialabs.github.io/WecOptTool/_examples/tutorial_3_LUPA.html.

Findings: The project’s findings can be summarized as following:

Design and engineering (Bosma et al. 2021): The physical design, initial numerical results, and lessons learned are explored here in an effort to promote transparency in WEC design and engineering. Details of the power take-off system, onboard sensors, scaled wave conditions, equations of motion, floating body stability, and motion constraint deflection analysis are also explored for LUPA.
Number of bodies and degree of freedom constraints (Beringer et al. 2023): It is often necessary to simplify the number of hydrodynamically active WEC bodies and degrees of freedom due to time, cost, and complexity. The effects of these simplifications on body motions, power capture, and PTO damping control can be significant as demonstrated through LUPA’s ability to change the number of bodies and degrees of freedom, while holding all other variables constant in both experiments and numerical models.
Control co-design in WecOptTool (Ströfer et al. 2023): Through a case study, it is shown how control co-design methods can be used to optimize, and obtain sensitivities of, LUPA’s PTO parameters to extract the most power. Combining control co-design tools and approaches with LUPA’s modularity—which allows swapping different PTO components—makes for a powerful research and design tool.
Wave resource upsampling (Mankle et al. 2022, Mankle et al. 2023, Mankle et al. 2023): Mankle et al. investigated the impact averaging intervals of high temporal resolution time series have on the variability of power and hydrodynamic forces on WECs and platforms. Simulations with a field-scaled LUPA showed an increase in power variability for very-short averaging intervals and demonstrated the importance accurate statistical representation of waves has on WEC modeling.
Passive and reactive PTO control (Bosma et al. 2023): Using LUPA’s advanced control interface in MATLAB Simulink, two PTO control strategies were explored experimentally, namely velocity proportional (passive) and velocity and position proportional (reactive) feedback. Results show a greater potential for energy capture with reactive control than passive control, showing a capture width increase of three times for some wave periods.

View LUPA photos in the Tethys Engineering Photo Library.

PRIMRE/Signature Projects/LUPA

LUPA