Marine Energy Technology Symposium

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https://hdl.handle.net/10919/49096
The Marine Energy Technology Symposium, http://www.globalmarinerenewable.com/mets/, is held in conjunction with The Global Marine Renewable Energy Conference (GMREC). All METS papers are peer-reviewed and authors whose papers are accepted to METS will have the opportunity to give a technical presentation at METS. Note that authors must present their paper in-person at METS in order to have their work included in the conference proceedings.

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Browsing Marine Energy Technology Symposium by Subject "Energy conversion"

Now showing 1 - 3 of 3
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    Discrete Element Modeling of Blade–Strike Frequency and Survival of Fish Passing Through Hydrokinetic Turbines
    Richmond, Marshall C.; Romero-Gomez, Pedro (2014-04)
    Evaluating the consequences to fish from blade-strike on marine hydrokinetic (MHK) turbine blades is important for incorporating environmental objectives into the integral optimization of machine performance. For instance, experience with conventional hydroelectric turbines has shown that innovative shaping of the blade and other machine components can improve hydraulic performance while reducing negative impacts to fish and other aquatic life. In this work, we used unsteady computational fluid dynamics (CFD) simulations of turbine flow and discrete element modeling (DEM) of particle motion to estimate the frequency and severity of collisions between a horizontal axis MHK tidal energy device and drifting aquatic organisms or debris. Two metrics are determined with the method: the strike frequency and the survival rate estimate. To illustrate the procedure step-by-step, an example case of a simple runner model was run and compared against a probabilistic model widely used for strike frequency evaluation. The results for the example case showed a strong correlation between the two approaches. In the application case of the actual MHK turbine flow, turbulent flow was modeled using detached eddy simulation (DES) in conjunction with a full moving rotor. The CFD-simulated power and thrust were satisfactorily comparable to experimental results conducted in a water tunnel on a reduced-scale (1:8.7) version of the turbine design. A cloud of DEM particles was injected into the domain to simulate fish or debris entrained into the turbine flow. Because various studies have pointed out the importance of fish volitional behavior, an assumed avoidance rate of 90% was applied to the particle sample. The strike frequency was the ratio of the count of colliding particles to the crossing sample size. The fish length and approaching velocity were test conditions in the simulations of the MHK turbine. Comparisons showed that DEM-based frequencies tend to be greater than previous results from Lagrangian particles and probabilistic models, mostly because the DEM scheme accounts for both the geometric aspects of the passage event —which only the probabilistic method does— as well as the fluid-particle interactions —which only the Lagrangian particle method does. With the full particle sample (0% avoidance), the DEM-based survival rates were generally high (above 90% in all studied cases), and comparable to previously reported laboratory results for small fish but not for mid-size fish mainly because of the considerable differences in rotor design between the CFD and laboratory models. With an assumed avoidance rate of 90%, the survival rates increased to nearly 99% across all scenarios. These results point to the need for further research and development of field monitoring methods for operating turbines to better understand the potential interaction between fish and MHK devices. The modeling framework can be used for applications that aim at evaluating the biological performance of MHK turbine units during the design phase and to provide information to regulatory agencies needed for the environmental permitting process.
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    A Framework for Optimizing the Placement of Current Energy Converters
    Roberts, Jesse; Nelson, Kurt; Jones, Craig; James, Scott C. (2014-04)
    This study investigates the potential environmental impacts and performance of a small array of tidal energy converters (TECs) in Cobscook Bay, ME; TECs are a subset of current energy converters (CECs) that are specifically deployed in tidal channels. A previously constructed coarse-grid, regional-scale hydrodynamic model of Cobscook Bay was coupled to a refined domain centered on a proposed TEC deployment location. All models were developed with Sandia National Laboratories-Environmental Fluid Dynamics Code (SNL-EFDC). An optimization framework was then constructed that used results from the refined model to determine optimal device placement locations that maximize array performance and minimize potential environmental effects. Within the framework, environmental constraints can be included to limit CEC-induced changes in flow, sediment transport, or other physical phenomena that might affect the health of aquatic species (i.e., altering fish-swimming behavior and sediment-transport trends that could affect benthic habitat or the stability of the CEC infrastructure). Simulation results were compared between model runs with optimized array configurations, and the originally proposed deployment locations. The optimized array had roughly a 17% increase in power generation. The framework developed also provides regulators and developers with a tool to assess environmental impacts and device-performance parameters for the deployment of CEC devices.
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    Spatio-Temporal Resolution of Different Flow Measurement Techniques for Marine Renewable Energy Applications
    Lyon, Vincent; Wosnik, Martin (2014-04)
    Marine hydrokinetic (MHK) energy conversion devices are subject to a wide range of turbulent scales, either due to upstream bathymetry, obstacles and waves, or from wakes of upstream devices in array configurations. The commonly used, robust Acoustic Doppler Current Profilers (ADCP) are well suited for long term flow measurements in the marine environment, but are limited to low sampling rates due to their operational principle. The resulting temporal and spatial resolution is insufficient to measure all turbulence scales of interest to the device, e.g., "blade-scale turbulence." The present study systematically characterizes the spatial and temporal resolution of ADCP and Acoustic Doppler Velocimetry (ADV). Simulations were used to quantitatively investigate the flow scales that each of the instruments can resolve in low and high turbulence intensity flows. For comparison, measurements were conducted at the UNH Tidal Energy Test Site in Great Bay Estuary at General Sullivan Bridge. The purpose of the study is to supply data for mathematical modeling to improve predictions from ADCP measurements, which can help lead to higher-fidelity energy resource assessment and more accurate device evaluation, including wake measurements.