Student Research Projects
Characterization of an Oscillating Bristol Cylinder Wave Energy Converter Prototype Using Image Analysis
Andrew Waldron, Midshipman First Class
Major: Mechanical Engineering
Abstract: Ocean waves possess an abundance of energy that can be harvested by wave energy converters (WECs), but the ocean's dynamic state makes extracting wave energy cumbersome and inefficient. Research into heaving WEC prime movers such as the Salter Cam and the Bristol cylinder show that these shapes have an antenna effect on incident waves at a small range of frequencies, resulting in higher efficiencies and power outputs. The goal of this research is to observe and measure the interaction between an oscillating Bristol cylinder prototype and waves. Image Analysis was also conducted to confirm free surface and WEC characteristics.
WEC Simulation and Test
Sabrina Spracklen, Midshipman First Class
Major: Mechanical Engineering
Abstract: Wave energy converters (WECs) lack a prominent design that dominates the field. This project attempts to reproduce a theoretical cylinder that is 100% efficient in simulation and experimentation. The simulated cylinder is modeled in Capytaine, a BEM, from which hydrostatic and hydrodynamic data is rendered. That hydrodata will be used to create an *.h5 file to be used with WEC-Sim, a MATLAB Simulink packaged. WEC-Sim will permit the cylinder to be more accurately simulated through simulated dampeners, springs and power takeoff devices (PTOs). The physical experiments were performed and compared to the simulated data.
Wave Power Absorption by Oscillating Bodies
Matthew Peshek, Midshipman First Class
Major: Mechanical Engineering
Bowman Research Scholar
Abstract: Wave energy is a promising renewable energy resource, but currently lags other renewable energy technology due to the dynamic and nonlinear nature of the ocean. One type of wave energy converter, a fully submerged Bristol cylinder, was restricted to oscillate in heave motion only in order to measure the amount of incident wave absorption in one degree of freedom and to test the cylinder in more realistic conditions outside of the linear wave approximation. The goal of this research was to create a proof of concept model to find the frequencies it absorbed the most energy and its natural frequency.
Modeling Surface Waves To Tune Wave Energy Converters
Brendan Neal, Midshipmen First Class
Major:
Abstract: In the critical search for renewable energy, many researchers have overlooked harnessing the ocean’s waves as a source of energy. Control of wave energy converter (WEC) devices may one day be improved if given accurate measurements and forecasts of the wave height and frequency spectra as it interacts with the device. To aid this process, this project uses tools from computer vision to process camera images of a wave train, extract the free surface height, and estimate characteristics of the wave. Previous studies have produced either frequency-energy spectra models for individual waves or large-scale region-based models for wave height/tidal direction. None of these models include the required tuning parameters or are too large in scale in order to effectively tune the USNA WEC on a wave-by-wave basis. Using video from trials in the USNA 120 and 380 ft tanks, we fit a 5th order polynomial to estimate the free surface. Results indicate accurate estimates of the wave group speed, frequency, and amplitude.
Experimental Determination of Energy absorption Characteristics of a Cylindrical Wave Energy Converter in Linear and Nonlinear Waves
Ryan Conway, Midshipmen First Class
Major:
Abstract: Wave Energy Converters (WEC’s) are devices that extract the energy stored in ocean waves and convert it into useful energy, like electricity. A cylindrical WEC was tested in both 1-degree-of-freedom (DOF) and 2 DOF configurations. The first set of experiments were performed with a 1 DOF system featuring mechanical springs which provided passive restoring forces. The second set of 1 DOF experiments and all of the preliminary 2 DOF trials were done with an actuated gantry. This gantry allowed for the control forces applied on the cylinder to be changed via software rather than by switching out mechanical hardware. During trials with wave amplitudes ranging from 0.75 inches to 1.5 inches and wave periods between 0.5 and 2.5 seconds, the hydrodynamic forces acting on the cylinder caused it to oscillate and absorb a fraction of the incident wave energy. The maximum energy available for extraction from the oscillator was 35% in the mechanical 1 DOF configuration, which occurred at the resonant wave period of 1.48s and a wave amplitude of 0.75in. Measurements of available energy for 1 DOF and 2 DOF tests with the gantry system are in the initial stages, as the presence of significant system frictional damping caused all experiments to have an overdamped response. However, the addition of a second degree of freedom caused an increase in available energy by a factor of around two (as compared to the 1 DOF gantry tests). Future work will consist of deducing an accurate model of gantry friction to allow the control system to properly account for it during experiments.
