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Energy and ClimateECEnergyComputational Modeling & SimulationUpgrades to SNL-EFDC: A Tool to Balance Marine Hydrokinetic Energy Generation Efficiency with Environmental Response

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.

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