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Water Power in the News

  • Developing a Fast-Running Turbine Wake Model

    As part of the international collaboration for DTOcean, a project aimed at accelerating the industrial development of ocean-energy power-generation knowledge and providing design tools for deploying the first generation of wave and tidal energy converter arrays, Sandia is developing a fast-running current energy converter (CEC) wake-interaction model. Toward this end, Sandia has begun implementing parametric models that use basic information about CEC devices and inflow conditions to produce a numerical representation of the resulting wake. Currently, two types of models are being investigated.

    Current-energy converter (CEC) wake results using the Larsen parametric model.

    Figure 1. Current-energy converter (CEC) wake results using the Larsen parametric model.

    The first model is based on the analytic solution to the conservation of mass and momentum equations, as derived by Larsen [1] (shown in Figure 1). The model takes into account parameters such as turbulent intensity, coefficient of thrust, and turbine diameter. The model has the ability to calculate multiple turbine wakes simultaneously with little extra effort. However, initial model to data comparisons indicate that the model accuracy may be a concern for CEC application.

    CEC wake as predicted by simplified computational fluid dynamics (CFD) simulation.

    Figure 2. CEC wake as predicted by simplified computational fluid dynamics (CFD) simulation.

    The second modeling method, currently under development, involves creating a numerical database of CEC wake properties. This involves running computational fluid dynamic (CFD) simulations of various CEC devices using a simplified means to represent the turbine within the model (i.e., actuator disk, porous disk, blade element methods). CFD modeling provides the capability to capture features such as near-turbine wake effects and even upstream pressure effects, all of which are ignored when using Larsen’s parametric wake model, resulting in more accurately represented wake fields.

    Once the modeling technique is validated by comparison to physical measurements and the numerical database is populated, the database will then be reduced to empirical relations between CEC properties, inflow conditions, and wake structures and features. The image in Figure 2 shows preliminary results of a CFD simulation using an actuator disk representation of a CEC turbine.

    Wake overlap region as calculated using the velocity deficit sum of squares.

    Figure 3. Wake overlap region as calculated using the velocity deficit sum of squares.

    When varying αmd, Figure 3 shows that the wake recovers more quickly downstream, resulting in a decreased velocity deficit (1 – Uwake/Uupstream) as αmd increases. Note that velocity data were not collected further downstream of the turbine into the Canal expansion because increasing the Canal width significantly decreases flow speed, rendering the velocity deficit calculation inapplicable.

    1. G. C. Larsen, “A Simple Wake Calculation Procedure,” Riso National Laboratory, DK-4000 Roskilde, Denmark, December 1988.
    2. Renkema D.J., “Validation of Wind Turbine Wake Models Using Wind Farm Data and Wind Tunnel
      Measurements,” Master Thesis, Delft University of Technology, 2007.
  • Final FY14 Measurement Campaign in Roza Canal, Yakima, Washington

    Uncertainty exists regarding the effects on local water operations of deploying a current energy converter (CEC) turbine in an irrigation canal for the purposes of producing electricity via the canal’s flowing water. Budi Gunawan and Guild Copeland (in Sandia’s Water Power Technologies Dept.) and Derek Belka (a Water Power Technologies Dept. summer intern student) joined a team from the US Bureau of Reclamation (USBR) and Instream Energy Systems (IES), to directly measure the effects of deploying a CEC turbine in Roza Canal, Yakima, Washington. The team synchronously measured water level, velocity, power, torque, and thrust for two CEC turbine RPM cases.

    Left: Synchronized 2-acoustic Doppler velocimeter measurements at the wake centerline of the turbine; Right: Velocity contours at 3.3 and 10 turbine diameter, downstream of the turbine.

    Left: Synchronized 2-acoustic Doppler velocimeter measurements at the wake centerline of the turbine; Right: Velocity contours at 3.3 and 10 turbine diameter, downstream of the turbine.

    This measurement campaign is the last in a set of field campaigns conducted by the three entities during the summer of 2014. In FY15, Sandia will process the measurements and use the data to develop numerical modeling tools to assess the impact of deploying multiple turbines in the canal.

    IES may deploy another turbine at the same site in FY15 to get a better understanding of turbine–turbine interaction and its effect on turbine performance, water level and velocity distribution, and effects to water operations. If/when this opportunity arises, Sandia will again team up with USBR and IES to take more measurements.

  • Inter-Agency Agreement Signed between DOE’s Wind and Water Power Program and Carderock

    The Department of Energy (DOE) has launched a multiple-year effort to validate the extent to which control strategies can increase the power produced by resonant wave-energy converter (WEC) devices. Many theoretical studies have shown a promise that additional energy can be captured by controlling the power-conversion chains of resonant WEC devices. The numerical models employed in these studies are, however, idealized to varying degrees.

    The 12.2-million-gallon Maneuvering and Sea Keeping (MASK) Basin at the Naval Surface Warfare Center, Carderock.

    The 12.2-million-gallon Maneuvering and Sea Keeping (MASK) Basin at the Naval Surface Warfare Center, Carderock.

    This effort, led by Sandia, comprises both theoretical development as well as experimental validation to systematically address the realities confronting real-world devices. Sandia will leverage its strong capabilities in WEC design, modeling, and testing, combined with world-renowned control-system expertise, over the next few years to develop a device-independent, publically releasable, validated controls platform. The five-year DOE-DoD inter-agency agreement will allow the team to employ the facilities at the Naval Surface Warfare Center, Carderock (Maryland) and will be funded as each phase of the program shows successful results.

    The Maneuvering and Sea Keeping (MASK) Basin has just upgraded the wave-making capabilities by installing two banks of Edinburgh Designs mechanical flaps—a capability that allows operators to produce a wide range of directional, realistic sea states. Further, the 109 × 73 × 6 m basin allows large-scale devices to be tested.

    The first point-absorbing WEC performance-model validation test will occur in the beginning of 2016—focusing on assessing the point-absorbing device’s baseline power performance.

  • Sandia Publishes Five Reports on the Environmental Effects of Wave-Energy Converters
    Example of Hydrodynamic modeling showing wave height and circulation patterns in Monterey Bay, CA.

    Example of Hydrodynamic modeling showing wave height and circulation patterns in Monterey Bay, CA.

    Since 2010, Sandia has been studying changes in wave propagation due to the operation of wave-energy converter (WEC) arrays. This work has primarily focused on applying and enhancing the-open source spectral wave model SWAN (Simulating WAves Nearshore).

    The five recently published SAND reports focus on applying SWAN and a modified version known as SNL-SWAN, which includes a WEC module to more accurately model the WECs’ wave energy extraction and their influence on wave propagation to shore. These reports emphasize the sensitivity of model results to wave and WEC model parameters, with specific attention given to assessing the relationship between WEC numbers, types, and configurations deployed and the environmental effects induced by changes in wave propagation and circulation. As such, one report describes coupling SWAN with the SNL-EFDC (Environmental Fluid Dynamics Code) circulation model to investigate changes in nearshore ocean circulation and sediment transport.

    The ongoing work’s overarching goal is to develop, apply, and enable the industry to use WEC-friendly wave-propagation models to assess the environmental effects created by changes in wave climates resulting from deploying ocean wave farms. The SNL-SWAN wave modeling tool and associated methodologies can provide siting guidance for developers, and provide regulators with the information needed to make timely and accurate permitting decisions.

    Example of the use of SNL-SWAN to model WEC arrays in Monterey Bay.

    Example of the use of SNL-SWAN to model WEC arrays in Monterey Bay.

    The five reports are

  • Numerical Simulations of Hydrokinetics in the Roza Canal, Yakima Washington
    Grids used in the refinement study showing the bottom elevation of Roza Canal for models with 19,777, 4,956, and 1,237 cells (left to right).

    Grids used in the refinement study showing the bottom elevation of Roza Canal for models with 19,777, 4,956, and 1,237 cells (left to right).

    Sandia completed two performance-testing studies for hydrokinetic canal effects at Roza Canal in Yakima, Washington. Sandia National Laboratories’ Environmental Fluid Dynamics Code (SNL-EFDC) was used to model the canal and the current-energy-capture device. The first was an evaluation of different grid sizes and refinements to determine an appropriate grid for future modeling efforts. The second study was a set of parameter sweeps to evaluate the impact of important model parameters on the wake characteristics using the optimum grid determined from the first study.

    1. Vertical velocity profiles directly upstream and downstream of the turbine for αmd = 1. As the partial-blockage coefficient (CPB) increases, flow is forced above and below the turbine and the change in water surface elevation, H, increases.

      Vertical velocity profiles directly upstream and downstream of the turbine for αmd = 1. As the partial-blockage coefficient (CPB) increases, flow is forced above and below the turbine and the change in water surface elevation, H, increases.

      For the grid-sensitivity study, three grids were generated, all of which use the same bathymetric data for the Roza Canal. Converged results were achieved with the 19,777-cell grid. Because high resolution is not needed throughout the entire model domain for the second study, the 19,777-cell grid was coarsened in portions of the canal away from the turbine location to improve computational efficiency without sacrificing accuracy.

    2. Based on results from other models calibrated to scale-flume experiments, the model’s two most sensitive parameters appear to be horizontal momentum diffusion and the partial-blockage coefficient, so a parametric study was undertaken to examine their impacts on wake characteristics. As the partial-blockage coefficient increases, the change in water-surface elevation between upstream and downstream of the turbine increases—reflecting the fact that much of the energy a turbine draws from fluid flows comes from potential energy change across the device.
  • Experiment for Improved Modeling of Trailing-Edge Shedding Noise
    Baseline 12.5% thick uncambered NACA 65 series foil (top) and 18% thick cambered MHK foil (bottom).

    Baseline 12.5% thick uncambered NACA 65 series foil (top) and 18% thick cambered MHK foil (bottom).

    To better understand the flow physics associated with shedding from marine hydrokinetic (MHK) foils, Sandia conducted an experimental study in the Penn State University Applied Research Laboratory. Our team tested MHK foil shapes in a free-stream flow to investigate their unsteady lift and trailing-edge shedding characteristics.

    The experimental apparatus was designed so the force gauges (along with the soft beryllium copper attachment screws) were the only attachment points connecting the airfoil to the water tunnel frame to prevent any shorting paths that would bias the force measurements. To understand the details of the flow near the trailing edge of the foil, our team also performed particle shadow velocimetry (PSV) measurements.

    One-sided nondimensional unsteady lift spectrum.

    One-sided nondimensional unsteady lift spectrum.

    The water tunnel was operated over six speeds between 3.0 m/s and 9.6 m/s. The inflow turbulence was very low due to the design of the nozzle design typical of water tunnels.* The unsteady lift was measured for both hyrofoils and was made nondimensional by normalizing the unsteady lift spectrum level and frequency by the chord length, water density, and free-stream velocity. If done properly, the nondimensional spectra at the various speeds should collapse into a single curve. Our results showed the good collapse that occurred for each foil.

    Additionally, we see that MHK (Sandia foil) spectra is a higher level than the NACA 65 series foil. To understand why this is the case, the details of the flow field near the trailing edge will have to be examined. Perhaps the thickness or loading on the Sandia foil has an impact. The PSV results should add some insight here.

     

    *  A small boundary layer builds up on the tunnel wall near the ends of the foil. The boundary layer’s extent on each wall is ~5% of the span. Fillets on the end walls were investigated to evaluate their impact on the unsteady lift. This assessment is ongoing.

  • Measuring Inflow and Wake Flow Turbulence Using a Mobile-Deployed Acoustic Doppler Velocimeter

    Sandia has developed a mobile acoustic Doppler velocimeter (ADV) system that characterizes inflow and wake flow velocity and turbulence around a vertical axis turbine deployed at the Roza Canal, Yakima, Washington. The ADV was mounted on a hydrofoil (see figure, left-hand panel) and deployed using either an aluminum platform mounted on a bridge (center panel) or using a cableway system (right-hand panel).

    The acoustic Doppler velocimeter (ADV) probe, mounted on a hydrofoil (left). The ADV measures inflow velocity immediately upstream of the turbine (center). A cableways system used for deploying the ADV at different points along the canal cross-section (right).

    The acoustic Doppler velocimeter (ADV) probe, mounted on a hydrofoil (left). The ADV measures inflow velocity immediately upstream of the turbine (center). A cableways system used for deploying the ADV at different points along the canal cross-section (right).

    The Sandia team tested the system during a June 2014 site visit. The ADV has a 64 Hz sampling frequency and could be used to study the complex interaction between flow turbulence, turbine-generated power, and turbine wake dynamics. Spectral analyses on the flow turbulence and power generation data are being used to investigate the effect flow turbulence has on power generation. The measurements will also be used for validating numerical tools, such as the Sandia’s Environmental Fluid Dynamics Code (SNL-EFDC) model.

    The Sandia team will make additional site visits to conduct more measurements with different turbine operation scenarios.

  • Investigating the Value of Simulated Wind Data for Wave Resource Characterization at US Test Sites
    Comparison of National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) observations and those from National Data Buoy Center (NDBC) Buoy Station 46050 near the North Energy Test Site (NETS) offshore of Newport, Oregon.

    Comparison of National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) observations and those from National Data Buoy Center (NDBC) Buoy Station 46050 near the North Energy Test Site (NETS) offshore of Newport, Oregon.

    Sandia is cataloging wind, surface current, and wave data at US test sites to provide detailed and consistent wave-resource data that wave-energy developers can use to evaluate and compare different test sites. As part of this effort, Sandia compared National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) simulations for wind speed and direction with historic observations of these parameters from buoys at the North Energy Test Site (NETS) offshore of Newport, Oregon.

    Monthly averaged values of wind speed and direction were found to agree well with values obtained from a decade and a half of meteorological observations from the National Data Buoy Center (NDBC) Buoy Station 46050. This comparison suggests that CFSR simulated data may be used in place of buoy data for improved assessment of wind conditions at US test sites; CFSR data generally has better spatial coverage than buoy data as well as longer periods of record, allowing assessment of wind characteristics closer to the test site with more accurate wind statistics.

    See an earlier news post about this work.

  • Sandia Funded to Model Power Pods for Utility-Scale Wave-Energy Converter

    Planning an open-water test facility for utility-scale wave-energy converters (WECs) within the US requires a multifaceted approach. Concerns regarding

    • the siting and permitting, the environmental interactions,
    • the device performance, and
    • the cost of the facility must all be simultaneously addressed.

    The DOE has started to investigate a utility-scale WEC testing facility with the recent awards to Oregon State University (OSU) and California State University–San Luis Obispo to evaluate launching a facility off of either the Oregon or California coast.

    Artist’s conception of a submerged power pod. (Illustration courtesy of Ocean Power Technologies, http://oceanpowertechnologies.com/pod.html.)

    Artist’s conception of a submerged power pod. (Illustration courtesy of Ocean Power Technologies, http://oceanpowertechnologies.com/pod.html.)

    These test sites are intended to be WEC-type agnostic, meaning that they should be suitable for deployment of a variety of device embodiments. Additionally, these sites are intended to have multiple berths open to developers, thus allowing multiple devices to be tested simultaneously. The method for transmitting power from multiple devices back to shore normally involves a central power pod that conditions the power before transmitting it to shore.

    As part of this effort, Sandia will work with OSU to look at the requirements for a facility-provided power pod. This work will evaluate the power characteristics of multiple device embodiments. The set of power characteristics will be used to model the power pod’s internal power electronics, thus assisting the project team in determining the applicability of a single set of pod electronics. Additional modeling to determine a floating pod’s dynamics will be used to assist the project team in evaluating power pod placement within the water column.

    Modeling of power characteristics through the power pod electronics allows deeper insight not only for the utility-scale test facilities, but is also an important step for understanding the requirements for large array deployments. These modeling efforts are anticipatory of the upcoming needs of the marine hydrokinetic industry and are expected to help frame the same conversation industry will conduct as it deploys its arrays.

  • Wave Energy Resource Characterization at US Test Sites

    Sandia is creating on an open-source catalog for wave-energy converter (WEC) developers with a detailed and consistent wave resource characterization at three US test sites

    • the Wave Energy Test Site (WETS) in Kaneohe Bay, HI;
    • the North Energy Test Site (NETS) offshore of Newport, OR; and
    • a potential site offshore of Humboldt Bay, CA.

    Hindcast simulation data will be used at each site to calculate resource characteristics, as suggested by the draft International Electrotechnical Commission (IEC) Technical Specification (TS) on Wave Energy Characterization. Researchers at the Hawaii National Renewable Energy Center (HINREC) and the Northwest National Marine Renewable Energy Center (NNMREC) have completed wave hindcast simulations at WETS and NETS, respectively. Sandia is working on a 10-year hindcast simulation for the Humboldt Bay area and investigating spatial variability of the wave resource.

    Wave-energy resources have been analyzed and presented in various ways throughout the literature. For example, efforts have included analyses of measured buoy data and/or hindcast simulation data; some consider full directional spectra, while some only consider bulk parameters; extreme event analyses are often neglected or considered in separate studies. This ambiguity and difficulty in comparing assessments are some of the reasons that the IEC began the process of creating a TS. [1]  Sandia will generally follow the TS’s guidelines for this Humboldt Bay effort by analyzing directional wave spectra produced from a simulated hindcast.

    Average monthly values of the six parameters specified by the IEC TS on Wave Energy Characterization near Humboldt Bay, California. Data is taken from NDBC46212 from 2004–2012 as an example. The error bars signify one standard deviation.

    Average monthly values of the six parameters specified by the IEC TS on Wave Energy Characterization near Humboldt Bay, California. Data is taken from NDBC46212 from 2004–2012 as an example. The error bars signify one standard deviation.

    The six parameters suggested by Lenee-Bluhm et al. [2] and specified in the TS for characterizing a sea state are

    1. omnidirectional wave power,
    2. significant wave height,
    3. energy period,
    4. spectral width,
    5. direction of maximum directionally resolved wave power, and
    6. directionality coefficient.

    Definitions can be found in [Reference 2]. Joint probability distributions and estimates of weather windows and extreme events will also be provided. An example of the parameters specified above are shown in the figure, which is analyzed from buoy data (NDBC46212) in 40 m depth. Further information can be found in the Marine Energy Technology Symposium 2014 paper that was presented on this work. [3]

    [1] Folley, M., Cornett, A., Holmes, B., Lenee-Bluhm, P., Liria, P., “Standardising resource assessment for wave energy converters,” Proceedings of the 4th Annual International Conference on Ocean Energy, Dublin, Ireland, 2012.

    [2] Lenee-Bluhm, P., Paasch, R., Özkan-Haller, H.T., 2011, “Characterizing the wave energy resource of the US Pacific Northwest,” Renewable Energy, 36(8), 2106–2119 (August 2011).

    [3] Dallman, A., Neary, V., “Initial Characterization of the Wave Resource at Several High Energy U.S. Test Sites,” Proceedings of the 2nd Marine Energy Technology Symposium, Seattle, WA, April 15–18, 2014.

     

  • Sandia Completes Hydrostructural Analysis of Ocean Renewable Power Company’s TidGen® Turbine
    Ocean Renewable Power Company’s TidGen® turbine. The bolt locations analyzed in CACTUS are labeled in blue.

    Ocean Renewable Power Company’s TidGen® turbine. The bolt locations analyzed in CACTUS are labeled in blue.

    Sandia performed an independent hydrostructural analysis of the Ocean Renewable Power Company (ORPC) TidGen® turbine, with a focus on the bolted-joint connections. Sandia’s CACTUS hydrodynamics software was used to predict dynamic loads on the turbine, and these loads served as input to structural dynamics analysis, performed using Abaqus finite-element analysis (FEA) software.

    The analysis examined bolt loads with considerations for ultimate and fatigue loading. The bolt hardware was explicitly modeled using beam elements in the FEA model, and bolt loads were processed directly from simulation results. The figure shows the turbine geometry and the location of the analyzed bolts. The fatigue failure analysis predicted that life cycles are well within the design service life of the ORPC TidGen® turbine. Nevertheless, analysis did predict low margins of safety on bolts and loss of preload during extreme operating conditions.

    Further analyses are recommended to investigate the benefits of increasing the size of the shaft-end bolts and increasing the preload on the foil-frame bolts.

  • Understanding Seasonal Effects of WEC Operation using the SNL-SWAN Wave Model Application
    Significant wave height differences between model simulation results for extreme conditions with and without the WEC array, here consisting of 50 F-2HB device types. The initial wave heights ranged from 3 to 4.9 m and initial wave periods ranged between 11.5 and 18.1 sec over the four seasons. The initial wave direction was 300°.

    Significant wave height differences between model simulation results for extreme conditions with and without the WEC array, here consisting of 50 F-2HB device types. The initial wave heights ranged from 3 to 4.9 m and initial wave periods ranged between 11.5 and 18.1 sec over the four seasons. The initial wave direction was 300°.

    Sandia researchers are investigating the seasonal effects of a wave-energy converter (WEC) array on nearshore wave propagation using SNL-SWAN. WECs were simulated as obstacles with frequency-dependent transmission coefficients that were determined based on the incoming wave height and period. The research team created frequency distributions of seasonal wave parameters (significant wave height, peak wave period, and wave direction) from hourly time series of National Oceanic and Atmospheric Administration National Data Buoy Center (NOAA NDBC) wave data collected between 1987 and 2013 in Monterey Bay, California. Median and extreme seasonal wave conditions were determined from frequency distributions and used as inputs to SNL-SWAN. The model was run with and without an array of 50 WECS consisting of floating two-body heaving converters (F-2HB) or floating oscillating water column (F-OWC) device types centered on the 40 m depth contour.

    Initial model results indicate that wave-height reductions were largest directly in the lee of the array and ranged from less than 1% to nearly 10%, depending on initial wave conditions (see the figure). The F-2HB device type resulted in slightly larger decreases in wave height compared to the F-OWC buoy due to the closer spacing of individual WECs in the array; F-OWC effects were more dispersed.

    Wave-height reductions were largest when initial peak wave periods were between 8 and 12 seconds, which is the wave-period range where power extraction is maximized for both WEC types regardless of initial wave height. These optimal initial wave periods were generally observed during winter for southerly wave directions and during summer and spring for west-northwesterly initial wave directions. Wave periods were largely > 13.5 seconds during extreme wave conditions; therefore decreases in wave height were more pronounced for median wave conditions.

    The results from wave seasonality studies such as this will be used to guide the selection of conditions with which to run full-ocean circulation models that consider waves, currents, and winds. The ocean circulation model, coupled with sediment transport simulations, will indicate potential coastal geomorphological variability due to the presence of WEC arrays.

  • Sandia, NREL Release Wave Energy Converter Modeling and Simulation Code: WEC-Sim
    An image of the Reference Model 3 (RM3) heaving two-body point absorber model as set up (left) and run (right) in WEC-Sim.

    An image of the Reference Model 3 (RM3) heaving two-body point absorber model as set up (left) and run (right) in WEC-Sim.

    Sandia and the National Renewable Energy Laboratory (NREL) are partnered in a three-year project to develop and verify WEC-Sim, an open-source numerical modeling tool to analyze and optimize wave-energy converters (WECs). On June 30th, the team publicly released Version 1.0 of WEC-Sim for free access to any interested users and code developers. WEC-Sim has the ability to model devices comprised of rigid bodies, power-take-off systems, and mooring systems. Simulations are performed in the time-domain by solving the governing WEC equations of motion in six degrees of freedom, as described in the WEC-Sim User Manual. The User Manual also presents two tutorials that describe how to set up and run WEC-Sim simulations. Additionally, a WEC-Sim tutorial video was developed to demonstrate how to set up and run the code.

    Over the course of the past few months, the team has validated WEC-Sim with Reference Model 3 (RM3) experimental data collected as part of DOE’s reference model project. (WEC-Sim code had previously been verified through code-to-code comparisons of WEC archetypes using the commercial codes AQWA, WaveDyn, and OrcaFlex.) The RM3 design, a two-body heaving point absorber, is shown at right. The response amplitude operator (RAO) for relative heave motion between the float and the spar was used for model validation. The data plot (below) shows the experimental data and the WEC-Sim simulation results. The results agree well, especially for the lower range of wave periods.

    Comparison between experimental and WEC-Sim simulation results for RM3 relative heave motion.

    Comparison between experimental and WEC-Sim simulation results for RM3 relative heave motion.

    The SNL-NREL team has also made WEC-Sim user friendly with a programming format that allows users to construct the physical system based on a library of rigid bodies and joint connections, rather than requiring that the user formulate the governing WEC equations of motion. The user now has a library of WEC-Sim blocks corresponding to different body types and joints, which they use to construct their WEC as it looks physically.

    The team also successfully worked with MathWorks to overcome limitations the WEC-Sim team found when modeling WECs in the Matlab/Simulink/SimMechanics framework.

    The WEC-Sim project is funded by the DOE’s Water Power Program. In FY15, the WEC-Sim team plans to perform dedicated wave-tank experiments for more rigorous WEC-Sim code validation.

  • Investigations on Marine Hydrokinetic Turbine Foil Structural Health Monitoring Presented at GMREC METS
    Fiber-optic Bragg grating (FBG) sensors on a sectioned turbine foil.

    Fiber-optic Bragg grating (FBG) sensors on a sectioned turbine foil.

    Structural health-monitoring (SHM) systems can provide key information to improve marine hydrokinetic (MHK) device management: reduce operations & maintenance costs, mitigate failures, and improve capacity factor. While present systems include instrumentation to measure power output, few adequately monitor mechanical loads and structural response, which are equally important for determining device performance and integrity. Fiber-optic Bragg grating (FBG) sensors could prove to be a reliable and unobtrusive marine power measurement tool; however, externally adhered FBGs have not been extensively studied on submerged, dynamic structures.

    Professors Erick Johnson and David Miller of Montana State University led the team in helping to characterize FBG sensors on a sectioned turbine foil. Dry results demonstrated very high correlation and response from the FBG sensors, up to coupon failure. The environmentally soaked samples and sensors were subject to many failure modes and verified the developer’s recommendation to not externally adhere the FBG strain sensors without additional mechanical and environmental protections.

    Sandia’s Instrumentation and Materials & Manufacturing Reliability Program presented their initial work to explore SHM for MHK turbine foils at the 2014 Global Marine Renewable Energy Con­ference. This research was also accepted for publication in the Proceedings of the 2nd Marine Energy Technology Symposium. The research resulted from a cooperative research and development agreement between Ocean Renewable Power Company, Sandia, and the National Renewable Energy Laboratory. Micron Optics, Inc., (MOI) also helped guide sensor selection.

  • Upgrades to SNL-EFDC: A Tool to Balance Marine Hydrokinetic Energy Generation Efficiency with Environmental Response

    SNL-EFDC is an open-source tool developed to support the marine renewable-energy industry by enabling simultaneous evaluation of array power production and environmental effects, facilitating optimal device placement. SNL-EFDC is an augmented version of US EPA’s Environmental Fluid Dynamics Code (EFDC) that has been well validated against real world river, lake, tidal, and other coastal environments. Sandia has included a new module within SNL-EFDC that simulates energy conversion by marine hydrokinetic (MHK) current energy converter (CEC) devices and evaluates commensurate changes in the turbulent kinetic energy and turbulent kinetic energy dissipation rate.

    SNL-EFDC has recently been upgraded to be compliant with visual EFDC (VEFDC), Tetra Tech’s graphical user interface (GUI), VEFDC was designed to develop and edit orthogonal grids needed by EFDC, edit all the input files required by the program, and visualize the output. VEFDC includes a Windows/geographical information system-based interface for creating necessary EFDC input files and displaying output results; it also includes a number of utility programs. Altogether, VEFDC was designed to replace the GEFDC (GridEFDC) and VOGG (Visual Orthogonal Grid Generator) tools as well as EFDC Version 1.1. Tetra Tech has preliminarily agreed to make VEFDC freely available to the MHK community if Sandia develops SNL-EFDC to work seamlessly with this GUI.

    Top view of depth-averaged velocities of flow past a three-actuator-disk-array as simulated by SNL-EFDC. The model was compared with the data collected in the Chilworth flume at University of Southampton, UK.

    Top view of depth-averaged velocities of flow past a three-actuator-disk-array as simulated by SNL-EFDC. The model was compared with the data collected in the Chilworth flume at University of Southampton, UK.

    VEFDC expects a very specific format when reading the main EFDC input file, EFDC.INP. Moreover, VEFDC will read a set of binary output files generated during the course of an SNL-EFDC run. If VEFDC is to be used as the GUI for MHK simulations, then SNL-EFDC must be able to both read the file format of EFDC.INP written by VEFDC as well as to write binary output files readable by VEFDC. Both of these formats (input and output files) differ from those used by EFDC Explorer (EE), the formerly free GUI that was used by SNL-EFDC to develop MHK models and visualize the model results.

    SNL-EFDC has been upgraded to determine whether it is reading the VEFDC or EE version of input files. This allows SNL-EFDC to be used for all legacy models built when EE was the GUI of choice while also being able to read VEFDC input files after transition to the new GUI. Tetra Tech is in the process of gathering the necessary files to specify VEFDC binary output. As soon as these are received, they will be incorporated directly into SNL-EFDC so that MHK simulations can be visualized with VEFDC. Existing output formats compatible with EE will be maintained so that legacy models can still be run and visualized with EE, while also ensuring that VEFDC is the GUI of choice when moving forward.

    Finally, efforts to finalize the SNL-EFDC model verification journal article continue. It is important to verify that the recent code changes do not affect the model results; models used in the development of this manuscript are being baselined with the new SNL-EFDC executable. Chris Chartrand (in Sandia’s Water Power Technologies Dept.) has recently joined the SNL-EFDC development team. He is currently analyzing the source code in order to gain a full understanding of the model and the methods implemented, and will become a significant contributor to the upcoming code development.

  • Biofouling Studies on Sandia’s Marine Hydrokinetic Coatings Initiated at PNNL’s Sequim Bay

    Sandia’s Materials & Manufacturing Reliability Program has begun testing their novel marine hydrokinetic (MHK) coatings at the Sequim Bay facility, which is a part of Pacific Northwest National Laboratory (PNNL). Tests will reveal anti-biofouling efficacy of coatings developed for MHK technology and of commercial coatings.

    (Left) High-velocity current tank. (Middle) Inside view of the high-velocity current tank. The tank is 36' long, 5' wide, and ~30" deep. (Right) Controlled-coatings test tank.

    (Left) High-velocity current tank. (Middle) Inside view of the high-velocity current tank. The tank is 36′ long, 5′ wide, and ~30″ deep. (Right) Controlled-coatings test tank.

    Over 150 coupons (1×1, 3×3, and 8×8 inches) will be examined in testing tanks using water from Sequim Bay—to measure attachment of bacteria, algae, barnacles, and other species native to the bay’s environment. PNNL’s George Bonehyo is leading the testing.

  • SNL-SWAN Beta Code Development: Frequency-Dependent Wave-Energy Converter Module

    Sandia is developing accurate methods to simulate altered wave propagation due to the operation of wave farms by enhancing the open-source spectral wave model, SWAN. The new model, SNL-SWAN, remains open source and will help the wave-energy converter (WEC) industry assess the potential environmental effects created by changes in wave climates associated with the deployment of various sizes and configurations of wave farms in the ocean.

    Energy spectra at gauge in the lee of the WEC-array for OR 2 (top) and OR 3 (bottom) and directional spreading on (left-hand side) and off (right-hand side).

    Energy spectra at gauge in the lee of the WEC-array for OR 2 (top) and OR 3 (bottom) and directional spreading on (left-hand side) and off (right-hand side).

    Recently, Sandia modified the SNL-SWAN Alpha code to include a frequency-dependent WEC module. This latest version has been named SNL-SWAN Beta. The SWAN test cases were run to verify the baseline code’s functionality, and the frequency-dependent functionality of SNL-SWAN Beta’s WEC module was verified. This was accomplished by comparing the shape of the incident energy spectrum (before the WEC) to the lee energy spectra (after the WEC), and noting varying energy absorption in different frequency bins.

    SNL-SWAN Beta was then used to model the Columbia Power array tests performed in the Oregon State Tsunami Wave Basin. The results of these simulations were then compared to the experimental data from these wave tank tests, and also to simulations using

    • the baseline SWAN code,
    • SNL-SWAN Alpha, and
    • the OSU Module for SWAN.

    Baseline SWAN models the WEC as a constant transmission coefficient; SNL-SWAN Alpha calculates a constant effective power transmission coefficient based on the WEC’s power performance data; and the OSU module is a function external to SWAN that is used to modify the wave spectra at the line of WECs, and then repropagate that spectra to the next line of WECS.

    Theoretically, the OSU Module and SNL-SWAN Beta version should be very similar because they are both frequency dependent. However, because the OSU module is external to SWAN, and requires multiple runs of SWAN, there may be numerical artifacts from the additional boundary conditions.

    This work was published in the GMREC/METS 2014 conference proceedings, and presented in Seattle on April 17, 2014.

  • SNL-SWAN Beta Code Development: Frequency-Dependent Wave-Energy Converter (WEC) Module

    Sandia is developing accurate methods to simulate altered wave propagation due to the operation of wave farms by enhancing the open-source spectral wave model, SWAN. The new model, SNL-SWAN, remains open source and will help the WEC industry assess the potential environmental effects created by changes in wave climates associated with the deployment of various sizes and configurations of wave farms in the ocean.

    Energy spectra at gage in the lee of the WEC-Array for OR2 (top) and OR3 (bottom) and directional spreading on (LHS) and off (RHS).

    Energy spectra at gage in the lee of the WEC-Array for OR2 (top) and OR3 (bottom) and directional spreading on (LHS) and off (RHS).

    Recently, Sandia modified the SNL-SWAN Alpha code to include a frequency-dependent WEC module. This latest version has been named SNL-SWAN Beta. The SWAN test cases were run to verify the baseline code’s functionality, and the frequency-dependent functionality of SNL-SWAN Beta’s WEC module was verified. This was accomplished by comparing the shape of the incident energy spectrum (before the WEC) to the lee energy spectra (after the WEC), and noting varying energy absorption in different frequency bins.

    SNL-SWAN Beta was then used to model the Columbia Power array tests performed in the Oregon State Tsunami Wave Basin. The results of these simulations were then compared to the experimental data from these wave tank tests, and also to simulations using

    • the baseline SWAN code,
    • SNL-SWAN Alpha, and
    • the OSU Module for SWAN.

    Baseline SWAN models the WEC as a constant transmission coefficient; SNL-SWAN Alpha calculates a constant effective power transmission coefficient based on the WEC’s power performance data; and the OSU module is a function external to SWAN that is used to modify the wave spectra at the line of WECs, and then repropagate that spectra to the next line of WECS.

    Theoretically, the OSU Module and SNL-SWAN Beta version should be very similar because they are both frequency dependent. However, because the OSU module is external to SWAN, and requires multiple runs of SWAN, there may be numerical artifacts from the additional boundary conditions.

    This work was published in the GMREC/METS 2014 conference proceedings, and presented in Seattle on April 17, 2014.

  • Biofouling Studies on Sandia’s Marine Hydrokinetic (MHK) Coatings Initiated at PNNL’s Sequim Bay

    Sandia’s Materials & Manufacturing Reliability Program has begun testing their novel MHK coatings at Pacific Northwest National Laboratory’s Sequim Bay facility. Tests will reveal anti-biofouling efficacy of coatings developed for MHK technology and of commercial coatings.

    (Left) High-velocity current tank. (Middle) Inside view of the high-velocity current tank. The tank is 36' long, 5' wide, and ~30" deep. (Right) Controlled-coatings test tank.

    (Left) High-velocity current tank. (Middle) Inside view of the high-velocity current tank. The tank is 36′ long, 5′ wide, and ~30″ deep. (Right) Controlled-coatings test tank.

    Over 150 coupons (1×1, 3×3, & 8×8 inches) will be examined in testing tanks using water from Sequim Bay—to measure attachment of bacteria, algae, barnacles, and other species native to the bay’s environment. PNNL’s George Bonehyo is leading the testing.

  • WEC-Sim Code Development Meeting at the National Renewable Energy Laboratory
    Reference Model 3 (RM3) heaving two-body point absorber full-scale dimensions.

    Reference Model 3 (RM3) heaving two-body point absorber full-scale dimensions.

    Sandia’s Kelley Ruehl and Carlos Michelen (both in Sandia’s Water Power Technologies Dept.) traveled to the Boulder, Colorado, for a WEC-Sim meeting at the National Renewable Energy Laboratory’s (NREL’s) National Wind Technology Center from March 3–5 in their combined effort to prepare for the public release of the WEC-Sim code, scheduled for June 2014.

    One of the major accomplishments was to complete preliminary WEC-Sim code validation by comparison to the Reference Model 3 (RM3) experimental data collected by revision as part of DOE’s reference model project. The RM3 design, a two-body heaving point absorber, is shown at right. The response amplitude operator (RAO) for relative heave motion between the float and the spar was used for model validation.

    The data plot (below) shows the experimental data and the WEC-Sim simulation results. The results agree well, especially for the lower range of wave periods. Previously, the WEC-Sim code has been verified through code-to-code comparisons of two wave energy converter (WEC) archetypes using the commercial codes AQWA, WaveDyn, and OrcaFlex. The latest results demonstrate initial validation of the WEC-Sim code’s functionality.

    Comparison between experimental and WEC-Sim simulation results for RM3 relative heave motion.

    Comparison between experimental and WEC-Sim simulation results for RM3 relative heave motion.

    Further WEC-Sim code validation is planned for FY15. The WEC-Sim team plans to perform dedicated wave-tank experiments for WEC-Sim code validation.

    During the meeting at NREL, the WEC-Sim team also worked on cleaning up the code and creating a plan for the coming months leading to the beta release.

  • Tidal Energy Resource Assessment in the East River Tidal Strait, New York

    Sandia recently worked together with Verdant Power, Inc., and Oak Ridge National Laboratory to conduct two-months of high-resolution velocity and turbulence measurements using acoustic Doppler velocimeters (ADVs) at the Roosevelt Island Tidal Energy (RITE) site. Verdant Power was recently given permission by Federal Energy Regulatory Commission to deploy up to 30 axial-flow turbines at this site. This study’s main goal was to examine the temporal variation of

    • current speeds,
    • current directions,
    • turbulence intensities, and
    • power densities.
    (a) The RITE study site, (b) current speed time series, and (c) the joint probability distribution of the current speeds and the current directions.

    (a) The RITE study site, (b) current speed time series, and (c) the joint probability distribution of the current speeds and the current directions.

    Due to its relatively straight and uniform channel geometry, the tidal current at the site is highly regular, which is desirable because it allows accurate electricity supply forecasting. The mean ebb and mean flood flow directions are nearly bidirectional.

    The turbulence level and unsteady loads at the site are shown to increase with the mean current speed. The study also found that insufficient temporal resolution measurements can cause low pass filtering, leading to underestimations of the tidal energy resource and the device loads.

  • High-Fidelity Hydrostructural Analysis of Ocean Renewable Power Company’s (ORPC’s) TidGen® Turbine

    Sandia is performing a high-fidelity hydrostructural analysis of the Ocean Renewable Power Company’s (ORPC’s) TidGen® turbine using the computational fluids dynamics (CFD) tool Star CCM+® and the structural-dynamics modeling capability in the Abaqus finite-element analysis (FEA) software.

    Hydrodynamic loadings from the CFD simulation will provide inputs to the Abaqus FEA model through fluid–structure coupling. The mesh for the CFD model is shown in the figure. This project’s goal is to elucidate the turbine components’ structural dynamic response during ORPC’s open-water demonstration in Cobscook Bay, Maine, which took place between September 2012 and July 2013; with a specific focus on the joint connections.

    Mesh for the Star CCM+® model of the TidGen® device.

    Mesh for the Star CCM+® model of the TidGen® device.

    The results of this study will provide critical guidance to improve the structural design of the TidGen® turbine.

  • Sandia–Atmocean Inc.’s New Mexico Small Business Assistance Project
    Figure 1.  Atmocean’s OHS™ with five pumping modules, with one pumping module expanded.

    Figure 1. Atmocean’s OHS™ with five pumping modules, with one pumping module expanded.

    Sandia led a six-month project funded by the New Mexico Small Business Assistance (NMSBA) on “Subsea Modeling of an Innovative Wave Energy Array Using OrcaFlex Software,” in which we supported developing and modeling the mooring system for Atmocean Inc.’s Ocean HydroPower System (OHS™). This project involved three New Mexico small businesses

    • Atmocean Inc. (wave-energy converter [WEC] developer),
    • Reytek Corporation (WEC fabricator), and
    • Mesa Analytics (WEC modeler).
    Figure 2.  WaveHub resource based on NDBC and Met Office UK data.

    Figure 2. WaveHub resource based on NDBC and Met Office UK data.

    Sandia’s role was to model the Atmocean Inc. WEC array in OrcaFlex, in support of their upcoming wave-tank and open-ocean tests at WaveHub. This required Sandia to perform a preliminary resource assessment for the WaveHub site (wave characteristics shown in Figure 2) and approximate the site’s current using the current power law with a maximum speed of two knots

    Sandia also developed an OrcaFlex model of the OHS™ system, requiring accurate modeling of the power take-off system and variable sea anchors, which only apply a resistive force when moving upward. The OrcaFlex model was then run for four regular wave cases both with and without current:

    1. Pacific Northwest summer waves,
    2. WaveHub summer waves,
    3. WaveHub winter waves, and
    4. a survival wave.

    Following Sandia’s OHS™ system model development in OrcaFlex, Kelley Ruehl (Water Power Technologies Dept.) led the November 25th NMSBA technology-transfer and closeout meeting at Reytek’s Albuquerque facility.

    Figure 3.  Atmocean’s OHS™, as modeled in OrcaFlex, with one pumping module expanded.

    Figure 3. Atmocean’s OHS™, as modeled in OrcaFlex, with one pumping module expanded.

    Sandia presented the simulation results, which will be used to characterize the OHS™ loads and to drive mooring-system design improvements, to Phil Kithil of Atmocean Inc. and Phil Fullam of Reytek Corp. Sandia also delivered the numerical model files and led a short training course on how to set up, modify, run, and post-process the OHS™ system’s OrcaFlex model.

    These efforts leveraged Sandia models already developed for the DOE Water Power Program.

  • Evaluating Hydrokinetic Turbine Operation within Roza Canal, Yakima, Washington
    Instream Energy Systems turbine deployment at the Roza Canal site in Yakima, Washington.

    Instream Energy Systems turbine deployment at the Roza Canal site in Yakima, Washington.

    The DOE Water Power Program has recently identified the need to better understand the potential for hydrokinetic (HK) energy development within existing canal systems. HK turbine operation alters water surface elevations and modifies its flow in canals. Primary canal-water uses—for irrigation, in flood management, and/or for conventional hydropower plant—will not tolerate significant altera­tions or hydrodynamic energy losses. Sandia is collaborating with U.S. Bureau of Reclamation and Instream Energy Systems, who has been deploying a vertical-axis turbine at the site, to characterize the effect of HK turbine operation in the Roza Canal using field measurements and numerical modeling (SNL-EFDC and HEC-RAS modeling and simulation packages).

    The adopted approach is to conduct field measurements and then use them to derive important modeling parameters, such as velocity, water level, discharge, and turbine thrust for a single turbine. Then, propagate these parameters to model the impact of arrays of HK turbines in the canal. Three field measurement campaigns are planned for spring and summer 2014, to provide better insight on the HK turbine operation for different flow conditions.

  • WEC-Sim Code Development Updates and Meeting
    Comparison of WEC-Sim implementation for the RM3 two-body point absorber (a) using the new physical-system formulation and (b) using the old equation-of-motion formulation.

    Comparison of WEC-Sim implementation for the RM3 two-body point absorber (a) using the new physical-system formulation and (b) using the old equation-of-motion formulation.

    Sandia and NREL are involved in a three-year project to develop and verify WEC-Sim, an open-source numerical modeling tool to analyze and optimize wave-energy converters (WECs). The code, written in Matlab/Simulink/SimMechanics, was recently restructured significantly after its internal alpha release.

    The new programming format allows users to construct the physical system based on a library of rigid bodies and joint connections, rather than requiring that the user formulate the governing WEC equations of motion. The user now has a library of WEC-Sim blocks corresponding to different body types and joints, which they use to construct their WEC as it looks physically. The figure shows the Reference Model 3 (RM3) as modeled previously (b, equation of motion) and as modeled in the new format (a, physical system).

    On January 20–22, Sandia hosted NREL’s Michael Lawson and Yi-Hsiang Yu for a WEC-Sim meeting held in Albuquerque, NM. During the meeting, the team focused on

    • finalizing the code’s transition to its new programming structure,
    • making the code more user friendly, and
    • creating a WEC-Sim library.

    The team also successfully worked with MathWorks to overcome limitations the WEC-Sim team found when modeling WECs in the Matlab/Simulink/SimMechanics framework. The team plans to continue WEC-Sim code development using the Matlab/Simulink/SimMechanics for the code’s external beta release, which is scheduled for summer 2014.

  • Current Energy Converter Array Optimization Framework
    Cobscook Bay regional and local (inset) model domains including schematic of ORPC TidGen™ unit (bottom left).

    Cobscook Bay regional and local (inset) model domains including schematic of ORPC TidGen™ unit (bottom left).

    In FY13, Sandia developed a framework to identify optimal placement locations—leading to marine hydrokinetic (MHK) current energy converter (CEC) device array configurations that will maximize energy production and minimize environmental effects. The CEC array optimization framework was applied to Cobscook Bay, Maine, the first deployment site of the Ocean Renewable Power Company’s (ORPC) TidGen CEC device.

    The framework used a hydrodynamic modeling platform, known as SNL-EFDC, to investigate flow patterns before and after MHK array placements. In addition to maximizing device performance, the optimization framework also considered potential environmental effects to avoid conditions that may alter fish behavior and sediment-transport trends. Although the optimization framework’s usefulness was demonstrated in 2013, several questions remained regarding the hydrodynamic model’s sensitivity to setup and forcing conditions.

    Three 5-CEC arrays investigated during FY13; unoptimized preliminary layout (left panel), an environmentally constrained optimized array (center panel), and a power optimized array without environmental constraints (right panel). The color contour shows percent change in velocity vs. baseline (no CEC devices). The placement footprint is outlined by a white rectangle. Cells with depths less than 23 m are blacked out as they are potentially too shallow for placement.

    Three 5-CEC arrays investigated during FY13; unoptimized preliminary layout (left panel), an environmentally constrained optimized array (center panel), and a power optimized array without environmental constraints (right panel). The color contour shows percent change in velocity vs. baseline (no CEC devices). The placement footprint is outlined by a white rectangle. Cells with depths less than 23 m are blacked out as they are potentially too shallow for placement.

    Currently, Sandia is testing the effects the model’s grid resolution has on device-performance and flow-pattern predictions. Original modeling efforts vertically resolved the water column with five layers. The coarse layering scheme was chosen to reduce computational demands for initial optimization framework development, where over 50 simulations were conducted. Sandia is now testing the hydrodynamic models sensitivity to vertical resolution by comparing model results between simulations with 3, 5, 15, and 25 vertical layers. We recently conducted the simulations and are now analyzing the results.

    We are also investigating the model grid’s horizontal orientation to determine if any bias in grid/flow direction exists. The initial studies used a grid aligned with the net flow direction determined from one acoustic Doppler current profiler dataset. To the best of our knowledge, this dataset represents conditions within the site; however, we must still investigate grid-orientation bias. We are investigating the hydrodynamic model sensitivity by comparing simulations with grids orientated at +10°, +5°, –5°, and –10° with respect to the original orientation.

  • DOE-Sponsored Reference Model Project Results Released

    The Sandia-led Reference Model Project (RMP), sponsored by the U.S. Department of Energy (DOE), is a partnered effort to develop marine hydrokinetic (MHK) reference models (RMs) for wave energy converters and tidal, ocean, and river current energy converters. The RMP team includes a partnership rmpHeaderbetween DOE; four national laboratories—Sandia National Laboratories (SNL), the National Renewable Energy Laboratory (NREL), Pacific Northwest National Laboratory (PNNL), and Oak Ridge National Laboratory (ORNL); two consulting firms—Re Vision Consulting, LLC, and Cardinal Engineering; the University of Washington; and Pennsylvania State University.

    The RMP was initiated to:

    • Develop a well-documented methodology for marine energy conversion (MEC) technology design and economic analysis to harness tidal, river, and ocean energy and advance the technology and knowledge base toward commercial viability;
    • Develop four MEC reference resource sites modeled after actual tidal, river, ocean current energy and wave energy sites that industry and the R&D community can use to develop their MEC technologies and levelized cost of energy (LCOE) estimates to compare to the LCOE baselines in this report; and
    • Demonstrate the methodology’s application by designing four reference MEC device/array archetypes for the modeled MEC reference resource sites identifying cost drivers and estimating baseline LCOE for each MEC device/array archetype.

    The RMP download page contains links to an overarching report that provides project details, supplementary documents, including supporting design and analysis reports, and Excel spreadsheet files that provide detailed cost breakdown structure and LCOE for each RM. We encourage MHK developers with similar MEC technology archetypes to apply our methodology, with the appropriate reference resource sites, to design and estimate LCOEs for their technologies.

  • Advanced Controls of Wave Energy Converters May Increase Power Capture Up to 330%

    Although ocean waves represent an enormous energy resource, most existing WEC designs efficiently produce power only within a narrow wave frequency range. Advanced control of the power-conversion chain can alter this paradigm. Models have shown absorbed-power increases ranging from 100% to 330%. To move from idealized, theoretical paper studies to deployable WEC hard­ware, requires rigorous research.

    The Department of Energy has recognized this work’s importance in two substantial ways. First, three recent federally funded industry awards were related to advanced-controls topics. Second, Sandia was selected to lead an effort to realize these potential gains in controlled experiments.

    Sandia will leverage strong capabilities in WEC design, modeling, and testing combined with our world-renowned control-system expertise to develop a device-independent, publicly releasable, validated power-conversion-chain control platform.

    A heaving two-body point absorber modeled in WEC-Sim.

    A heaving two-body point absorber modeled in WEC-Sim.

  • Sandia Releases Open-Source Hydrokinetic Turbine Design Model, CACTUS
    CACTUS geometry for Sandia turbine.

    CACTUS geometry for Sandia turbine.

    In an effort to support marine hydrokinetic (MHK) developers and companies as they advance their technologies, Sandia recently released an open-source version of CACTUS (Code for Axial and Cross-flow TUrbine Simulation) and an accompanying user’s manual authored by Jon Murray and Matt Barone (both in Sandia’s Aerosciences Dept.).

    Sandia developed CACTUS to design hydrokinetic turbines and to analyze hydrodynamic performance. Based on a vortex wake method, simulations can be completed in minutes, allowing users to efficiently explore many design iterations.

    A comparison of power coefficient between experiment and CACTUS simulation.

    A comparison of power coefficient between experiment and CACTUS simulation.

    CACTUS can also be coupled with Sandia’s optimization code, DAKOTA, allowing users to semi-automatically optimize the hydrodynamic performance of hydrokinetic turbine designs. It simulates arbitrary geometries, including cross- and axial-flow rotors.

  • Joint Sandia-DOE-HMRC Testing of a Floating Oscillating Water Column Wave Energy Converter Device

    From September 8th–20th, Diana Bull (in Sandia’s Water Power Technologies Dept.) worked with the team from Ireland’s Hydraulics and Maritime Research Centre (HMRC) to complete testing of Reference Model 6, a backward-­bent duct buoy (BBDB) oscillating water column wave energy converter design.

    Testing was completed in both the flume as well as Ireland’s Hydraulics and Maritime Research Centre (HMRC) basin. A backward-bent duct buoy (BBDB) floating oscillating water column (OWC) wave energy converter (WEC) device in HMRC 's wave basin.

    Testing was completed in both the flume as well as Ireland’s Hydraulics and Maritime Research Centre (HMRC) basin. A backward-bent duct buoy (BBDB) floating oscillating water column (OWC) wave energy converter (WEC) device in HMRC ‘s wave basin.

    The team from HMRC included Tom Walsh, Brian Holmes, Florent Thiebaut, Neil O’Sullivan, Tony Lewis, Ray Alcorn, and Brendan Cahill. The team from the U.S. included Alison LaBonte and Jeff Rieks (DOE) and Daniel Laird, Diana Bull, and Vince Neary (all in Sandia’s Water Power Technologies Dept.).

    This testing was completed under a memorandum of understanding between Ireland and the U.S. Discussions began approximately one year ago and planning began approximately four months before this test. Testing was completed in both the flume as well as the basin at HMRC. Data capable of verifying the Sandia-developed BBDB performance model was collected and is currently being analyzed.

  • Post-Processing and Analysis of Wake Measurements Around a Scaled Turbine
    Photo of test set-up showing skiff and array of catamaran-mounted acoustic Doppler current profilers.

    Photo of test set-up showing skiff and array of catamaran-mounted acoustic Doppler current profilers.

    Sandia and the Univ. of Washington recently (jointly) reprocessed data from a UW wake-measurement campaign to include power-performance (Cp-TSR) and thrust (Ct-TSR) data for comparable velocity conditions obtained in the September 2012 field campaign. Their reanalysis shows that normalized wake-recovery metrics (i.e., velocity deficit vs turbine diameters downstream) suggest that wake recovery is independent of inflow velocity (in the range of 1–2 m/s) and largely independent of the turbine’s operating state (i.e., position on the Cp-TSR curve relative to peak performance). In comparison with wake studies behind turbines in flume facilities, the wake generated during the tow test generally recovered more quickly. However, additional analysis will reveal the nature of the recovery and the best ways to compare test results. Additionally, this data set is being evaluated for use as a Sandia-EFDC validation test case.

    In September 2012, the UW collected wake data behind a scaled, vertical-axis cross-flow turbine using an array of catamaran-mounted acoustic Doppler current profilers. The test turbine was attached to a small skiff and towed by a larger boat in a lazy figure-eight pattern on Seattle’s Lake Washington. However, this test involved an incomplete characterization of associated turbine performance and turbine thrust.

  • Sandia-NREL Wave Energy Converter (WEC)-Sim Development Meeting

    Kelley Ruehl and Sam Kanner (both in Sandia’s Water Power Technologies Dept.) hosted a three-day meeting onsite at Sandia that was attended by Yi-Hsiang Yu, Michael Lawson, and Adam Nelessen of the National Renewable Energy Laboratory to further develop WEC-Sim, a multiple-year, DOE-funded, joint NREL/Sandia project to develop an open-source WEC modeling tool.

    A heaving two-body point absorber modeled in WEC-Sim.

    This meeting’s accomplishments included restructuring the code into a more user-friendly form and integrating the following subsystems

    • time-domain simulation modules,
    • hydrodynamic force calculation block,
    • power take-off module,
    • the six degree of freedom multiple-body solver, and the
    • mooring module

    into the new WEC-Sim model structure. A simple heaving two-body point absorber was then simulated using the new framework.

    The WEC-Sim team feels confident that the new WEC-Sim model structure will allow for a more user-friendly interface and relatively seamless avenue to model a vast array of WEC designs, ones that operate in different degrees of freedom, with different power-conversion trains, mooring configurations, etc.

  • New Mexico Small Business Assistance (NMSBA) Program Collaborations Recognized

    Phil Kithil, left, CEO of Atmocean Inc. of Santa Fe, and Phillip Fullam, chief engineer of Reytek Corp. of Albuquerque, worked with Sandia National Laboratories modeling specialist Rick Givler to assess the feasibility of their pump system that turns wave power into electricity. Givler’s findings helped Atmocean attract a six-figure investment for continued product testing and component manufacturing. (Photo by Norman Johnson)

    Ten NMSBA projects that achieved outstanding innovations last year were honored at the program’s annual Innovation Celebration Awards event. “NMSBA has been bringing small businesses together with scientists and engineers from Sandia and Los Alamos for more than 12 years. We are grateful to the principal investigators who work with New Mexico’s small businesses,” said Jackie Kerby Moore, manager of Technology and Economic Development at Sandia. “Together they are implementing innovative ideas and stimulating our state’s economy.”

    Phil Kithil (Atmocean Inc.) partnered with Phillip Fullam (chief engineer of Reytek Corp.) to produce a pump system that converts wave power into electricity. Kithil and Fullam worked with Sandia’s Rick Givler (a specialist in modeling physical systems in Sandia’s Fluid Sciences and Engineering Dept.) to assess the feasibility of their waves-to-electricity concept. Givler proved that, using typical waves and a set number of seawater pumps, considerable pressurized water would reach the onshore array of Pelton water impulse turbines.

    Givler’s findings helped Atmocean attract a six-figure investment to continue product testing, add staff, and boost component manufacturing at Reytek. “Rick’s work was absolutely essential to our moving forward with the business model,” Kithil said. “We think our system is very viable and we’ll do more testing this summer.” This collaboration received the first Honorable Speaker Ben Lujan Award for Small Business Excellence as the honoree that demonstrated the most economic impact.

    Since its inception, the NMSBA program has provided 2,036 small businesses with more than $34M worth of research hours and materials. The program has helped create and retain 2,874 New Mexico jobs, increase small companies’ revenues by $145M and decrease their operating costs by $72.6M. These companies have invested $43M in other New Mexico goods and services and received $52M in new funding and financing.

  • Sandia–Univ. of Minnesota (UMN) Floating Offshore Wind Collaboration

    From August 27th–September 27th Sandian Kelley Ruehl hosted Toni Calderer, a Ph.D. student from UMN. UMN and Sandia are currently collaborating on a 3-year DOE-sponsored offshore wind Funding Opportunity Announcement on high-resolution offshore wind turbine/farm modeling. UMN’s contribution is experimentation and wind turbine numerical modeling; Sandia’s contribution is floating-platform modeling. The month-long collaborative effort between UMN and Sandia was to couple the wind-wave models.

    As a result of the collaboration, UMN and Sandia made significant progress toward an integrated, high-resolution wind-wave model. A wave boundary condition was successfully implemented in UMN’s code and simulations were run in the combined wind-wave model of a simple floating platform when subject to regular waves of various wave periods. These results were then compared to Sandia’s results for the same platform using boundary element methods. Initial results are promising, but refinement of the combined wind-wave model is necessary before moving onto more complicated geometries, like a semisubmersible platform.

    Experimental testing of the floating platform is planned to begin at UMN’s St. Anthony Falls Laboratory flume this winter.

  • Bernadette Hernandez-Sanchez


    Bernadette A. Hernandez-Sanchez is the project lead for the Advanced Materials Program and DOE’s Marine and Hydrokinetic Technology Database (MHTDB). The Advanced Materials Program focuses on understanding the properties and performance of materials and coatings being investigated for potential marine hydrokinetic (MHK) and ocean thermal energy conversion (OTEC) technologies as well as developing novel anti-biofouling and anti-corrosion coatings. Sandia also supports the update and maintenance DOE’s MHTDB that provides up-to-date information on marine and hydrokinetic renewable energy, both in the U.S. and around the world. Bernadette earned her B.S. in Chemistry from New Mexico Tech and her Ph.D. in Solid State Inorganic Chemistry from Colorado State University. She joined Sandia as a student intern and returned in 2004 as a postdoctoral researcher. In 2008, she became a member of technical staff in Sandia’s Ceramic Processing & Inorganic Materials Department.

  • Sandia Adds Water Power to Clean Energy Research Portfolio

    [singlepic id=637 w=320 h=240 float=right]ALBUQUERQUE, N.M. – Sandia National Laboratories will receive more than $9 million over three years from a Department of Energy competitive laboratory solicitation for the development of advanced water power technologies.
    Sandia, through a partnership with several national laboratories and academic institutions, will lead two of the four topic areas awarded under the grant and will provide technical support in a third topic area. The topic areas are Supporting Research and Testing for Marine and Hydrokinetic Energy, Environmental Assessment and Mitigation Methods for Marine and Hydrokinetics Energy, Supporting Research and Testing for Hydropower, and Environmental Assessment and Mitigation Methods for Hydropower.

    “We will perform fundamental research to develop and assess technology breakthroughs and help promote a vibrant industry that is currently in its beginnings,” said Jose Zayas, manager of Sandia’s Wind and Water Power Technologies group.

    “Water power technologies contribute to the diversification of our nation’s energy mix,” Zayas said, “by providing clean energy in areas near high population centers as well as enhancing our nation’s energy security. Water power technologies could leverage an indigenous resource in parts of the country where other technologies may not be viable.”

    Zayas will add the water power research to the department’s wind energy portfolio. He will oversee a multidisciplinary team drawn from many areas of lab expertise, including materials and manufacturing research, environmental monitoring and stewardship, performance modeling, and testing. The department will pursue a diverse research agenda in marine hydrokinetics (MHK) systems and will collaborate with Argonne and Oak Ridge national laboratories on conventional hydropower.

    Technology evaluation

    Rich Jepsen, a specialist in water resources engineering, will lead the project to examine the cost-effectiveness and reliability of technology for MHK technologies, which include wave, current/tide and thermal energy conversion. Jepsen’s water power research will also evaluate the use of Sandia’s lake facility, used for large-scale wave testing.

    In partnership with Oak Ridge National Laboratory (ORNL), Pacific Northwest National Laboratory (PNNL) and the National Renewable Energy Laboratory (NREL), activities will evaluate new device designs and conduct basic research in materials, coatings, adhesives, hydrodynamics, and manufacturing to assist industry in bringing efficient technologies to market.

    The research will focus on developing and advancing the science and tools needed to bring new water power technologies to market and evaluating methods designed to improve the performance of existing hydropower facilities.

    Sandia will also work with NREL, the other lead in the technology area, in the direct design and testing of new technologies.

    Environmental stewardship

    Jesse Roberts, a specialist in sediment transport and hydrology, will lead Sandia’s research to describe and quantify environmental impacts caused by new and existing marine and hydrokinetic technologies. The team will evaluate environmental factors including rates of sediment transport, water flow, water quality and acoustic changes. The results will help quantify the types and magnitude of environmental impacts for various new and existing technologies. Researchers will collaborate with industry to develop criteria for selecting locations for projects and select technology to monitor and mitigate such impacts. Sandia will partner with ORNL, PNNL and ANL in this work.

    In both areas, Zayas said, Sandia will work with universities to leverage its existing world-class facilities for research to provide students and faculty the opportunity to work on water power problems and technologies.

    “Sandia will work to bridge the gap between research institutions and industry by helping to develop technologies that deliver cost-effective and reliable energy while also committing to the importance of environmental stewardship,” he said.


    Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.

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