Marine HydroKinetic (MHK) energy is a largely undeveloped renewable energy source with great potential. Energy recovery from freestream flows such as rivers, tidal passages, and ocean currents may eventually make a significant contribution to U.S. power, but we currently lack understanding of how to recover this energy in an environmentally-safe way. Because of the highly concentrated nature of the resource and the environmental sensitivity of most, if not all, of the high-energy-density sites, successful recovery of MHK energy depends critically on finding answers to the most pressing environmental concerns. Specifically, we do not yet understand how the operation of MHK devices alters the local flow environment and resulting sediment dynamics, nor do we have the methods to quantify these effects. Redistribution of sea floor sediment by the wake of the turbine or its support structure could potentially change the character of the benthic ecosystem. Resuspension of sediment may reintroduce contaminants that had otherwise settled out of the freestream, and the momentum deficit in the wake of the turbine could lead to enhanced deposition. For marine hydrokinetics to become a viable energy resource in the U.S. and the rest of the world, we must understand the environmental effects of these devices.
In this EAGER project, Laboratory-scale demonstration experiments will be performed on models of MHK turbines to model the different environments where MHK energy recovery is currently being evaluated. A novel two-phase particle image velocimetry (PIV) technique developed at UMD will be used to quantify the suspended load dynamics of both the carrier fluid and the sediment particles. Bed profiling will be used to assess changes in the local erosion and deposition. The long-term of the PIs is to characterize and quantify the two-phase flow-physics of the interaction between the sea floor geophysical environment and the wake of an MHK turbine, with a specific interest in the redistribution of sediment.
Intellectual Merit The intellectual merit of this work lies in the fundamental nature of non-equilibrium sediment dynamics that occur as a result of a complex flow characterized by high levels of turbulence and vorticity. First, the PIs will quantify the effect of the near wake of a MHK turbine on sediment uplift and transport in laboratory-scale experiments, primarily with the goal to produce demonstration data that illustrates the capabilities and utility of the facility and techniques. Based on the enhanced understanding of the relevant flow-physics gained through these experiments, the PIs will start the initial investigations of the scaling conditions and modeling that will allow the creation of new models for sediment transport induced by MHK flow fields.
Broader Impacts The broader impacts of this work will extend to both the educational and industrial arenas. The proposed research will enable MHK energy to be assessed in a fair, timely and efficient manner, over a broad range of potential operational sites and conditions. Thus, it could open the doors to a new source that could quickly impact the percentage of renewable energy produced in the United States, displacing non-renewable and polluting sources.
