Dynamics of Pitching Wave Energy Converter with Resonant U-Tank Power Extraction Device

Afonja, Adetoso J.

Dynamics of Pitching Wave Energy Converter with Resonant U-Tank Power Extraction Device

dc.contributor.author	Afonja, Adetoso J.	en
dc.contributor.committeechair	Brizzolara, Stefano	en
dc.contributor.committeemember	Paterson, Eric G.	en
dc.contributor.committeemember	Woolsey, Craig A.	en
dc.contributor.department	Aerospace and Ocean Engineering	en
dc.date.accessioned	2020-06-08T21:06:56Z	en
dc.date.available	2020-06-08T21:06:56Z	en
dc.date.issued	2020-05	en
dc.description.abstract	This research revolves around the concept design and theoretical validation of a new type of wave energy converter (WEC), comprising a pitching floater integrated with a resonant U-tank (RUT) and a Wells turbine as power take-off (PTO). Theoretical formulation of a fully coupled multi-body dynamic system, incorporating the thermodynamic processes of the RUT air chamber, its interaction with the PTO dynamics and their coupling with the floater is presented. Inaccuracies of the dynamic modeling of RUT based on Lloyd's low order model, which assumes constant hydrodynamic parameters irrespective of the frequency, are demonstrated by a series of high fidelity CFD simulations. These simulations are a systematic series of fully viscous turbulent simulations, using unsteady RANSE solvers, of the water sloshing at different frequencies of oscillation. Calibration of Lloyd’s model with CFD results evidenced that the RUT hydrodynamic parameters are not invariant to frequency. A numerical model was developed based on Simulink WEC-Sim libraries to solve the non-linear thermo-hydrodynamic equations of the device in time domain. For power assessment, parametric investigations are conducted by varying the main dimensions of the RUT and power RAOs were computed for each iteration. Performance in irregular sea state are assessed using a statistical approach with the assumption of linear wave theory. By superimposing spectrum energy density from two resource sites with RAO, mean annual energy production (MEAP) are computed. The predicted MEAP favorably compares with other existing devices, confirming the superior efficiency of the new proposed device over a larger range of incident wave frequency.	en
dc.description.abstractgeneral	This study present results of an investigation into a new type of wave energy converter which can be deployed in ocean and by its pitch response motion, it can harvest wave energy and convert it to electrical energy. This device consist of a floater, a U-tank (resonant U-tank) with sloshing water free to oscillate in response to the floater motion and a pneumatic turbine which produces power as air is forced to travel across it. The pneumatic turbine is used as the power take-off (PTO) device. A medium fidelity approach was taken to carry out this study by applying Lloyd’s model which describes the motion of the sloshing water in a resonant U-tank. Computational fluid dynamics (CFD) studies were carried out to calibrate the hydrodynamic parameters of the resonant U-tank as described by Lloyd and it was discovered that these parameters are frequency dependent, therefore Lloyd’s model was modelled to be frequency dependent. The mathematical formulation coupling the thermodynamic evolution of air in the resonant U-tank chamber, modified Lloyd’s sloshing water equation, floater dynamics and PTO were presented for the integrated system. These set of thermo-hydrodynamic equations were solved with a numerical model developed using MATLAB/Simulink WEC-Sim Libraries in time domain in other to capture the non-linearity arising from the coupled dynamics. To assess the annual energy productivity of the device, wave statistical data from two resource sites, Western Hawaii and Eel River were selected and used to carrying out computations on different iterations of the device by varying the tank’s main dimensions. This results were promising with the most performing device iteration yielding mean annual energy production of 579 MWh for Western Hawaii.	en
dc.description.degree	M.S.	en
dc.format.medium	ETD	en
dc.identifier.uri	http://hdl.handle.net/10919/98782	en
dc.language.iso	en	en
dc.publisher	Virginia Tech	en
dc.rights	Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International	en
dc.rights.uri	http://creativecommons.org/licenses/by-nc-sa/4.0/	en
dc.subject	Wave Energy Converter (WEC)	en
dc.subject	Pitch Resonance Tuning Tanks	en
dc.subject	Ocean Energy Technology	en
dc.subject	Non-linear Motion in Waves	en
dc.subject	Renewable Energy	en
dc.subject	Pitch Resonant Point Absorber	en
dc.title	Dynamics of Pitching Wave Energy Converter with Resonant U-Tank Power Extraction Device	en
dc.type	Thesis	en
thesis.degree.discipline	Ocean Engineering	en
thesis.degree.grantor	Virginia Polytechnic Institute and State University	en
thesis.degree.level	masters	en
thesis.degree.name	M.S.	en