Post Access Report: Numerical simulation and analysis of the MADWEC wave energy converter

TY - RPRT
TI - Post Access Report: Numerical simulation and analysis of the MADWEC wave energy converter
AU - University of Massachusetts
AB - The wave energy converter (WEC) developed at the University of Massachusetts Dartmouth is called MADWEC, which stands for maximal asymmetric drag WEC. MADWEC is a point absorber device and designed to be low-cost, low-maintenance, and easily deployable. The main MADWEC components are the buoy, power take-off (PTO), and tethered ballast system. A major cost-saving has been achieved through the tethered ballast system (US Patent 11,156,200 B2), which is a lightweight alternative to heavy and costly steel spars commonly used in point absorber WECs. The tethered ballast system is a series of nested hollow cylinders. At the bottom of each hollow cylinder, there are louvres that open as the ballast system moves in a downward direction, allowing the device to quickly drop in water and position itself properly relative to the free-surface waves. On the ascending half-cycle of the wave period, when the ballast system is forced to move in the upward direction, the louvres close, trapping water in the hollow cylinders and creating significant added mass that keeps the PTO relatively stationary while the buoy continues to ascend. As a result, a relative motion between the buoy and PTO is developed, which is captured by the PTO. This TEAMER support had two major objectives: 1) Optimization of the tethered ballast system design to maximize the total added mass; and 2) Building a WEC-Sim model of the MADWEC prototype and analyzing the tethered ballast and PTO performance under linear waves. Using the boundary-element method (BEM) and WAMIT software, the optimal distance between the nesting cylinders were determined to achieve the highest total added mass. The results were then used in a WEC-Sim model developed to evaluate the performance of MADWEC under various wave conditions. The WEC-Sim model also includes Simulink models of the PTO that follow the bench-top prototype model of UMassD. The preliminary WEC-Sim results suggest that the total added mass of the ballast system, which plays a key role in the system dynamics, can be increased to enhance the performance. The WEC-Sim analysis also helped capture the natural frequency and resonance phenomenon found in the multibody WEC system.
DA - 2023/10//
PY - 2023
SP - 52
UR - https://teamer-us.org/report/university-of-massachusetts-dartmouth-numerical-simulation-and-analysis-of-madwec-wave-energy-converter/
LA - English
KW - Wave
KW - Point Absorber
KW - Modeling
KW - Hydrodynamics
KW - Mooring
KW - Performance
KW - Power Take Off
KW - Structural
KW - Substructure
ER -

Export Citation to RIS

Abstract

The wave energy converter (WEC) developed at the University of Massachusetts Dartmouth is called MADWEC, which stands for maximal asymmetric drag WEC. MADWEC is a point absorber device and designed to be low-cost, low-maintenance, and easily deployable. The main MADWEC components are the buoy, power take-off (PTO), and tethered ballast system. A major cost-saving has been achieved through the tethered ballast system (US Patent 11,156,200 B2), which is a lightweight alternative to heavy and costly steel spars commonly used in point absorber WECs. The tethered ballast system is a series of nested hollow cylinders. At the bottom of each hollow cylinder, there are louvres that open as the ballast system moves in a downward direction, allowing the device to quickly drop in water and position itself properly relative to the free-surface waves. On the ascending half-cycle of the wave period, when the ballast system is forced to move in the upward direction, the louvres close, trapping water in the hollow cylinders and creating significant added mass that keeps the PTO relatively stationary while the buoy continues to ascend. As a result, a relative motion between the buoy and PTO is developed, which is captured by the PTO. This TEAMER support had two major objectives: 1) Optimization of the tethered ballast system design to maximize the total added mass; and 2) Building a WEC-Sim model of the MADWEC prototype and analyzing the tethered ballast and PTO performance under linear waves. Using the boundary-element method (BEM) and WAMIT software, the optimal distance between the nesting cylinders were determined to achieve the highest total added mass. The results were then used in a WEC-Sim model developed to evaluate the performance of MADWEC under various wave conditions. The WEC-Sim model also includes Simulink models of the PTO that follow the bench-top prototype model of UMassD. The preliminary WEC-Sim results suggest that the total added mass of the ballast system, which plays a key role in the system dynamics, can be increased to enhance the performance. The WEC-Sim analysis also helped capture the natural frequency and resonance phenomenon found in the multibody WEC system.