The Impacts of Marine Hydrokinetic Devices on Coastal Ocean Morphodynamics

Marine Hydrokinetic (MHK) devices provide an opportunity to expand renewable energy by harnessing waves and currents power and converting it to electricity. However, most MHK devices are in the developmental stage requiring research to understand their impacts on the surrounding environment. The impact of the devices on the hydrodynamics (wave and current) and morphodynamics (ocean floor) is of great importance to minimize future operational costs. In this study, we use the SNL-SWAN model to investigate the wave field response to MHK devices and then use wave and morphology within Delft3d to obtain the impact of different MHK arrays on wave, flow, and sediment conditions driving short-term and long-term morphologic evolution under mean and extreme wave condition.

The objectives are: (1) wave data analysis and investigation of mean and extreme condition (2) obtain equilibrium bathymetry under mean condition (3) simulate wave field response to various MHK devices using the SNL-SWAN model (4) The placement of the devices using different methods (static physical lump, energy absorption object, and a combination these two methods) into Delft3d (5) sensitivity analysis of sedimentation to different MHK array parameters (spacing, size, and number of devices).

We found that using the thin-dam obstacle inbuilt into the SWAN module of Delft3D seems to reasonably represent the wave climate and subsequent sediment transport. Representing the devices as only a physical lump within bathymetry is not enough and considering the energy absorption of the device in SWAN module makes the simulation more realistic. Representing the devices as static lumps, the sediment deposition on the downstream decrease 50%. However, by adding 30% energy absorption, downstream deposition increases around 100%. Changing MHK deployment array parameters (spacing, size and number) led to a change in the pattern and amount of the sedimentation, as well.