Riding the Ocean's Data
Modeling Advancements Could Help Developers Build More Robust, Seaworthy Devices
Wave energy technologies can provide reliable, local power for autonomous underwater vehicles, and at-sea applications across U.S. coastal regions, especially where traditional energy supply is limited or costly. Although some wave energy devices have demonstrated promising performance, most are still in early development. Numerical modeling tools reduce cost and risk in developing wave energy technologies by allowing systems to be tested and optimized before deployment.
At the National Laboratory of the Rockies (NLR), researchers are advancing wave energy modeling through integrated simulation effortss that combine hydrodynamics, device dynamics, and environmental conditions to support technology development and deployment. In practice, this means breaking a complex system into parts—how waves interact with a device, how the device moves in response, and how those interactions affect performance—and modeling each piece with specialized software tools.
WEC-Sim and Capytaine provide complementary capabilities within this workflow: WEC-Sim models the dynamic behavior of wave energy converters (WECs) while Capytaine calculates hydrodynamic forces on floating structures. Together, they give developers a comprehensive understanding of device performance under realistic ocean conditions. Recent advancements make both tools faster, more accurate, and more flexible—helping developers reduce risk, optimize designs, and accelerate device deployment.
Wave energy converters are first modeled in Capytaine to capture hydrodynamic behavior, then brought into WEC-Sim to simulate real-world performance. Animation by Toan Tran, National Laboratory of the Rockies
"The upgrades of the WEC-Sim and Capytaine tools are exciting because they significantly increase physical fidelity, robustness, and flexibility of the numerical tools, enabling more accurate, scalable, and cost-effective WEC simulations that directly improve performance prediction and reliability assessment," said NLR's Thanh Toan Tran, a mechanical engineer and water power researcher.
WEC-Sim, developed in 2014 by NLR and Sandia National Laboratories, provides device performance in real ocean conditions. Capytaine followed in 2018 as an open-source tool for modeling wave-driven forces on floating systems.
Sharper Tools, Sharper Simulations
With WEC-Sim 7.0, the team introduced quadratic transfer functions to better capture second-order forces on large structures and mooring lines. Updates also enhance power take-off flexibility, mooring representation, and force accuracy. Bug fixes, updated libraries, and enhanced documentation make simulations faster and easier to manage.
The variable-hydro feature, a frequent request from users, allows hydrodynamic coefficients to be swapped during a simulation. This bypasses traditional solver limitations—like small-motion assumptions or fixed water depth—allowing developers to simulate a broader range of WEC designs more realistically.
Capytaine updates improve accuracy in shallow and deep water, enable smoother modeling, allow dataset exporting, and address known issues. Together, these upgrades streamline workflows, enhance flexibility, and provide advanced capabilities for evaluating device performance and survivability in real-world conditions.
"These updates deepen the precision and complexity of the tools, improving prediction of marine device loads and performance in chaotic ocean environments, which helps developers see the promise of their technology without costly real-world experimentation," Tran said.
Components Modeled, Confidence Built
WEC-Sim allows modeling down to individual components. Power take-off systems, for example, can be represented with simple linear spring-damper models for early-stage design, or detailed mechanical, hydraulic, and electrical models for deployable devices. Built in MATLAB, WEC-Sim leverages advanced toolboxes to provide high-resolution simulations when needed. This granularity gives developers a clearer view of how each component contributes to overall performance, helping them make confident system-level design decisions.
"If you draw a picture of someone's face, the depictions of eyes, nose, and ears are as important as the whole," said Mohamed Shabara, principal systems development engineer at Solar Turbines and former NLR researcher who worked on WEC-Sim. "The same goes for modeling marine and wave energy systems—we need to model individual pieces accurately and show how they behave together as a system."
Durability and survivability are central to device success. These tools simulate environmental stresses over time, letting developers evaluate structural integrity, fatigue, and operational resilience under extreme ocean conditions. WEC-Sim and Capytaine integrate easily with other software, enabling rapid testing of new ideas without rewriting code and accelerating the pathway from concept to validated device.
The MOST (MATLAB Offshore Simulation Tool) extension, developed at Politecnico di Torino, shows how WEC-Sim's component-level modeling can be applied to more complex floating systems, demonstrating the tool's flexibility beyond standard wave energy devices.
Open Source, Open Water
Open-source software reduces barriers for developers and allows continuous improvement without expensive proprietary licenses. WEC-Sim and Capytaine are actively supported, and Capytaine is still the only maintained open-source solver for floating structures and wave energy converters.
With these updates, WEC-Sim and Capytaine continue to provide marine energy developers with precise, flexible, and practical tools to reduce risk, improve survivability, and accelerate deployment.
Learn more about NLR's marine energy research. Access the WEC-Sim and Capytaine GitHub repositories for the latest releases and updates.
Last Updated April 28, 2026