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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Biconjugate Impedance Matching Control of the HERO WEC: Preprint

Effective control strategies are essential for maximizing the power output of wave energy converters (WECs). In this study, we explore the methodology of port-based modelling which can be used for bi-conjugate impedance matching, a type of reactive control that involves maximizing power transfer by setting the load (PTO) impedance to be the complex conjugate of the source impedance (WEC). Despite its foundational role in electrical engineering, this method has seen limited application in wave energy and has not yet been demonstrated in wave-powered desalination systems. We represent our complex multidisciplinary system as an equivalent circuit to explore frequency-based relations. The HERO WEC, a small-scale, modular point absorber (PA) designed for reverse osmosis desalination is used as a case study to demonstrate port-based modelling for control applications. Improving the performance of wave-powered water desalination systems could play a critical role in addressing freshwater scarcity for coastal communities, especially those in remote or disaster-prone regions.

16 TIDAL AND WAVE POWER↗
DOE OSTI2021

Investigations into Balancing Peak-to-Average Power Ratio and Mean Power Extraction for a Two-Body Point-Absorber Wave Energy Converter

The power harnessed by wave energy converters (WECs) in oceans is highly variable and, therefore, has a high peak-to-average power (PTAP) ratio. To minimize the cost of a WEC power take off (PTO) system, it is desirable to reduce the PTAP ratio while maximizing the mean power extracted by WECs. The important issue of how PTAP ratio reduction measures (such as adding an inertia element) can affect the mean power extracted in a reference model has not been thoroughly addressed in the literature. To investigate this correlation, this study focuses on the integration of the U.S. Department of Energy’s Reference Model 3, a two-body point absorber, with a slider-crank WEC for linear-to-rotational conversion. In the first phase of this study, a full-scale numerical model was developed that predicts how PTO system parameters, along with an advanced control algorithm, can potentially affect the proposed WEC’s PTAP ratio as well as the mean power extracted. In the second phase, an appropriate scaled-down model was developed, and extracted power results were successfully validated against the full-scale model. Finally, numerical and hardware-in-the-loop (HIL) simulations based on the scaled-down model were designed and conducted to optimize or make trade-offs between the operational performance and PTAP ratio. The initial results with numerical and HIL simulations reveal that gear ratio, crank radius, and generator parameters substantially impact the PTAP ratio and mean power extracted.

16 TIDAL AND WAVE POWER↗
DOE OSTI2016

Wave Energy Prize - 1/50th Testing - WECCA Attenuator

This submission of data includes all the 1/50th scale testing data completed on the Wave Energy Prize for the WECCA team, and includes: - 1/50th test data (raw & processed) - 1/50th test data video and pictures - 1/50th Test plans and testing documents - SSTF_Submission (summarized results)

1/50th scale↗
DOE OSTI2021

Dynamic Characterization and Performance Evaluation of a 10-kw Power Take-Off with Mechanical Motion Rectifier for Wave Energy Conversion

The power take-off (PTO) is a key component for wave energy converters (WECs). The dynamic properties of the PTO influence the response of the WEC and should be considered when designing the WEC and not oversimplified. In addition, the efficiency as well as the reliability can play an important role on whether the PTO can be suitable for real-world applications. In this paper, a novel compact PTO rated at 10 kW is designed and prototyped, and a comprehensive nonlinear dynamic model is established for the PTO. Through bench testing, the unknown parameters of the dynamic model are characterized and determined. Further verification shows that the model can predict the dynamic performance of the PTO well. In addition, the test results show that the mechanical motion rectifier PTO can achieve good energy transfer efficiency, especially for low-load and low-speed conditions.

bench test↗
DOE OSTI2023

Power packet networks for wave energy converter arrays

One of the biggest challenges for all renewable energy sources (RES) is that they are variable power generators which will require reactive power or energy storage systems (ESS) to provide reliable power quality (ideally power factor of one) at the power grid generation side. The present invention is directed to a power packet network (PPN) for integrating wave energy converter (WEC) arrays into microgrids. Specifically, an array of WECs can be physically positioned such that the incoming regular waves will produce an output emulating an N-phase AC system such that the PPN output power is constant. ESS requirements are thereby minimized whilst maintaining grid stability with high power quality. This will enable RES integration onto a future smart grid for large-scale adoption and cost reduction while preserving high efficiency, reliability, and resiliency.

Wilson, David G.↗
DOE OSTI2021

Mountain waves can impact wind power generation

Abstract. Mountains can modify the weather downstream of the terrain. In particular, when stably stratified air ascends a mountain barrier, buoyancy perturbations develop. These perturbations can trigger mountain waves downstream of the mountains that can reach deep into the atmospheric boundary layer where wind turbines operate. Several such cases of mountain waves occurred during the Second Wind Forecast Improvement Project (WFIP2) in the Columbia River basin in the lee of the Cascade Range bounding the states of Washington and Oregon in the Pacific Northwest of the United States. Signals from the mountain waves appear in boundary layer sodar and lidar observations as well as in nacelle wind speeds and power observations from wind plants. Weather Research and Forecasting (WRF) model simulations also produce mountain waves and are compared to satellite, lidar, and sodar observations. Simulated mountain wave wavelengths and wave propagation speeds (group velocities) are analyzed using the fast Fourier transform. We found that not all mountain waves exhibit the same speed and conclude that the speed of propagation, magnitudes of wind speeds, or wavelengths are important parameters for forecasters to recognize the risk for mountain waves and associated large drops or surges in power. When analyzing wind farm power output and nacelle wind speeds, we found that even small oscillations in wind speed caused by mountain waves can induce oscillations between full-rated power of a wind farm and half of the power output, depending on the position of the mountain wave's crests and troughs. For the wind plant analyzed in this paper, mountain-wave-induced fluctuations translate to approximately 11 % of the total wind farm output being influenced by mountain waves. Oscillations in measured wind speeds agree well with WRF simulations in timing and magnitude. We conclude that mountain waves can impact wind turbine and wind farm power output and, therefore, should be considered in complex terrain when designing, building, and forecasting for wind farms.

17 WIND ENERGY↗
DOE OSTI2026

Performance Evaluation of an Offshore Wave Measurement Buoy in Monochromatic Waves

The accurate measurement of waves underpins marine energy resource characterization, device design, and project development. Datawell wave buoys are widely deployed and have long served as a trusted standard for wave measurements. We quantify the measurement performance, including wave elevation and energy flux estimation, of a Datawell DWR-MkIII buoy using prescribed monochromatic heave motions on a large-amplitude six-degree-of-freedom motion platform at the National Laboratory of the Rockies, assuming the buoy behaves as an ideal wave follower. Commanded motions were validated with an optical motion tracking system while buoy elevation and raw acceleration were recorded. Wave elevations were propagated to wave energy flux estimation using four methods, including one frequency-domain method and three time-domain methods. The Bayesian optimization was applied for design of experiments, and records from three test sites were also applied and evaluated in the present study. Results show two error regions within the nominal period range of 1.6 s to 30 s. For wave periods between 5 s and 25 s, the buoy provides accurate wave height measurements. For short periods less than 5 s, the 1.28 Hz sampling frequency induces sub-Nyquist artifacts that bias elevation and can drive maximum energy flux estimation errors above 100%. For long periods exceeding 25 s, the buoy reported elevation is underpredicted with error depending on period but relatively independent of wave height, with maximum wave height and wave energy flux errors reaching 64% and 87%, respectively. Furthermore, analysis of three field-derived cases shows that frequency-domain estimates at 1.28 Hz agree within 2% of the corresponding 100 Hz estimates, while larger method-dependent differences are observed for the Hilbert method.

16 TIDAL AND WAVE POWER↗
DOE OSTI2017

LCOE Analysis of Surge-Mode WEC

Spreadsheet which provides estimates of reductions in Levelized Cost of Energy for a surge-mode wave energy converter (WEC). This is made available via adoption of the advanced control strategies developed during this research effort.

16 TIDAL AND WAVE POWER↗
DOE OSTI2016

Centipod WEC, Advanced Controls, WaveDyn Models

Archive containing the WaveDyn models used for analysis of the Centipod WEC with and without Advanced Controls, i.e. the WaveDyn files contain a baseline model which can be run alone, and a model predictive control (MPC) model which must be run when connected to the MPC controller. The controller dynamic link library (DLL) is also contained within this archive. The code archive for the MPC controller is linked in this submission.

16 TIDAL AND WAVE POWER↗
DOE OSTI2024

TEAMER: Performance mapping of Re Vision's Persistance PTO

Contains datasets from experimental measurements that were used to validate Re Vision's Persistence PTO's efficiency and performance. These measurements were obtained using a dynamometer test bench setup. The data includes open-circuit voltage and loss measurements to validate machine characteristics, efficiency mapping tests to determine the generator's performance mapping, and efficiency mapping tests to determine the converter's efficiency over the feasible operating range. This data was collected between June 2023 and September 2023. The data was collected at the National Renewable Energy Laboratory's Flatirons Campus, Colorado, United States. The data was collected using NREL's 5-kW dynamometer test bench, equipped with a torque sensor and various voltage and current sensors fed to a dedicated data acquisition system. Units for the data are included in the data file headers for each data series. A text editor or spreadsheet software such as Excel is required to view the *.csv data. The data are also provided in *.mat files. To view data plots, a Matlab script with *.mat files are provided.

16 TIDAL AND WAVE POWER↗
DOE OSTI2019

Advanced WEC Dynamics and Controls MASK3 Test

Sandia National Laboratories and the Department of Energy (DOE) have completed on a multi-year program to examine the effects of control theory on increasing power produced by resonant wave energy conversion (WEC) devices. The tank tests have been conducted at the Naval Surface Warfare Center Carderock Division (NSWCCD) Maneuvering and Sea Keeping Basin (MASK) in West Bethesda, MD. This report outlines the "MASK 3 " wave tank test within the Advanced WEC Dynamics and Controls (AWDC) project. This test represents the final test in the AWDC project. The focus of the MASK 3 test was to consider coordinated 3 -degree-of-freedom ( 3 DOF) control of a WEC in a realistic ocean environment. A key aspect of this test was the inclusion of a "self-tunine mechanism which uses an optimization algorithm to update controller gains based on a changing sea state. The successful implementation of the self-tuning mechanism is the last crucial step required for such a controller to be implemented in real ocean environments.

16 TIDAL AND WAVE POWER↗
DOE OSTI2019

WEC-Sim Array Development and Experimental Comparison Study: Preprint

Wave energy is still considered to be an emerging industry, and one significant contribution that researchers are making is to find solutions that reduce costs. The National Renewable Energy Laboratory and Sandia National Laboratories have contributed to this by creating WEC-Sim, an opensource modeling toolbox, to assist with early design decisions related to the design of wave energy converters (WECs). Previously, studies involving WEC-Sim have focused on single WEC modeling. In this paper, we will conduct a validation study to investigate the accuracy and ability of WEC-Sim to model arrays of WECs. The results from the WEC-Sim array simulations are compared to those from an existing experimental study. In addition, the array model is used to investigate the interaction between the WECs in the array and the influence of array spacing on the WECs' hydrodynamic performance.

16 TIDAL AND WAVE POWER↗
DOE OSTI2018

U.S. Navy Wave Energy Test Site: Update for International Marine Renewable Energy Conference.

Hawaii Natural Energy Institute (HNEI) at the University of Hawaii (UH), provides key research support to the Navy’s Wave Energy Test Site (WETS), off Marine Corps Base Hawaii. This is the nation’s first grid-connected site, supporting the nascent commercial wave energy sector by providing and supporting Wave Energy Conversion (WEC) device test infrastructure. Through DOE and Navy support, HNEI provides environmental monitoring, independent WEC device performance analysis, numerical modeling, wave forecasting and hindcasting, and critical marine logistical support for WEC device developers.

16 TIDAL AND WAVE POWER↗
DOE OSTI2018

Ocean Testing at WETS – Ramping Up

Hawaii Natural Energy Institute (HNEI) at the University of Hawaii (UH), provides key research support to the Navy’s Wave Energy Test Site (WETS), off Marine Corps Base Hawaii. This is the nation’s first grid-connected site, supporting the nascent commercial wave energy sector by providing and supporting Wave Energy Conversion (WEC) device test infrastructure. Through DOE and Navy support, HNEI provides environmental monitoring, independent WEC device performance analysis, numerical modeling, wave forecasting and hindcasting, and critical marine logistical support for WEC device developers. Present and future planned WEC deployments were discussed.

16 TIDAL AND WAVE POWER↗