Publications

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The pace of research and development efforts to integrate renewable power sources into modern electric utilities continues to increase. These efforts are motivated by a desire for cleaner, cheaper and more diverse sources of energy. As new analyses and controls approaches are developed to manage renewable sources and tie them into the grid, the need for these controls to be tested in hardware becomes paramount. In particular, hydrokinetic power is appealing due to its high energy density and superior forecastability; however, its development has lagged behind that of wind and solar due in part to the difficulty of acquiring hardware results on an integrated system. Thus, as an alternative to constructing an elaborate wave-tank or locating a power lab riverside, this paper presents a method based on electromechanical emulation of the energy source using a commercially available induction motor drive. Using an electromechanical emulator provides an option for universities and other laboratories to expand their research on hydrokinetics in a typical laboratory setting. © 2013 MTS.

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Increasing interest in marine hydrokinetic (MHK) energy has spurred to significant research on optimal placement of emerging technologies to maximize energy conversion and minimize potential effects on the environment. However, these devices will be deployed as an array in order to reduce the cost of energy and little work has been done to understand the impact these arrays will have on the flow dynamics, sediment-bed transport and benthic habitats and how best to optimize these arrays for both performance and environmental considerations. An "MHK-friendly" routine has been developed and implemented by Sandia National Laboratories (SNL) into the flow, sediment dynamics and water-quality code, SNL-EFDC. This routine has been verified and validated against three separate sets of experimental data. With SNL-EFDC, water quality and array optimization studies can be carried out to optimize an MHK array in a resource and study its effects on the environment. The present study examines the effect streamwise and spanwise spacing has on the array performance. Various hypothetical MHK array configurations are simulated within a trapezoidal river channel. Results show a non-linear increase in array-power efficiency as turbine spacing is increased in each direction, which matches the trends seen experimentally. While the sediment transport routines were not used in these simulations, the flow acceleration seen around the MHK arrays has the potential to significantly affect the sediment transport characteristics and benthic habitat of a resource. Evaluation Only. Created with Aspose.Pdf.Kit. Copyright 2002-2011 Aspose Pty Ltd Evaluation Only. Created with Aspose.Pdf.Kit. Copyright 2002-2011 Aspose Pty Ltd

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The structure of turbulence in an oscillating channel flow with near-sinusoidal fluctuations in bulk velocity is investigated. Phase-locked particle-image velocimetry data in the streamwise/wall-normal plane are interrogated to reveal the phase-modulation of two-point velocity correlation functions and of linear stochastic estimates of the velocity fluctuation field given the presence of a vortex in the logarithmic region of the boundary layer. The results reveal the periodic modulation of turbulence structure between large-scale residual disturbances, relaminarization during periods of strong acceleration, and a quasi-steady flow with evidence of hairpin vortices which is established late in the acceleration phase and persists through much of the deceleration period.

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Marine hydrokinetic (MHK) projects will extract energy from ocean currents and tides, thereby altering water velocities and currents in the site's waterway. These hydrodynamics changes can potentially affect the ecosystem, both near the MHK installation and in surrounding (i.e., far field) regions. In both marine and freshwater environments, devices will remove energy (momentum) from the system, potentially altering water quality and sediment dynamics. In estuaries, tidal ranges and residence times could change (either increasing or decreasing depending on system flow properties and where the effects are being measured). Effects will be proportional to the number and size of structures installed, with large MHK projects having the greatest potential effects and requiring the most in-depth analyses. This work implements modification to an existing flow, sediment dynamics, and water-quality code (SNL-EFDC) to qualify, quantify, and visualize the influence of MHK-device momentum/energy extraction at a representative site. New algorithms simulate changes to system fluid dynamics due to removal of momentum and reflect commensurate changes in turbulent kinetic energy and its dissipation rate. A generic model is developed to demonstrate corresponding changes to erosion, sediment dynamics, and water quality. Also, bed-slope effects on sediment erosion and bedload velocity are incorporated to better understand scour potential.

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