Xuewei Zhang

Research on Coupling Prediction of Mooring Line Tension and Motion Response of Vertical Axis Floating Tidal Energy Converter

ABSTRACT Ma, Y.; Li, T.; Zhang X., and Zhang L., 2015. Research on coupling prediction of mooring line tension and motion response of vertical axis floating tidal current energy converter. In order to predict mooring line tension and motion response of vertical axis floating tidal energy converter, ANSYS ICEM and ANSYS CFX softwares are used to simulate stress of vertical axis water turbine and formulas are fitted to determine added mass and damping of rotation water turbine in wave environment. Based on ANSYS AQWA software, numerical time-domain coupled prediction method for the prediction of mooring line tension and wave effect of vertical axis floating tidal energy converter in terms of rotation of water turbine and motion response are constructed. Mooring line tension and motion response are predicted and the result is compared with the experiment result. According to the result, the predicted value of mooring line tension and motion response of vertical-axis tidal energy converter obtained by the numerical time-domain coupling prediction method in the paper corresponds with the experiment result. Feasibility and validity of the numerical time-domain coupling prediction method in the paper are confirmed. The research offers theory foundation and technical support for design and construction of vertical axis floating tidal energy converter.

Semi-Analytical Solution of Optimization on Moon-Pool Shaped WEC

Abstract In order to effectively extract and maximize the energy from ocean waves, a new kind of oscillating-body WEC (wave energy converter) with moon pool has been put forward. The main emphasis in this paper is placed on inserting the damping into the equation of heaving motion applied for a complex wave energy converter and expressions for velocity potential added mass, damping coefficients associated with exciting forces were derived by using eigenfunction expansion matching method. By using surface-wave hydrodynamics, the exact theoretical conditions were solved to allow the maximum energy to be absorbed from regular waves. To optimize the ability of the wave energy conversion, oscillating system models under different radius-ratios are calculated and comparatively analyzed. Numerical calculations indicated that the capture width reaches the maximum in the vicinity of the natural frequency and the new kind of oscillating-body WEC has a positive ability of wave energy conversion.

Optimal Configurations of Wave Energy Converter Arrays with a Floating Body

Abstract An array of floating point-absorbing wave energy converters (WECs) is usually employed for extracting efficiently ocean wave energy. For deep water environment, it is more feasible and convenient to connect the absorbers array with a floating body, such as a semi-submersible bottom-moored disk, whose function is to act as the virtual seabed. In the present work, an array of identical floating symmetrically distributed cylinders in a coaxial moored disk as a wave energy device is proposed The power take-off (PTO) system in the wave energy device is assumed to be composed of a linear/nonlinear damper activated by the buoys heaving motion. Hydrodynamic analysis of the examined floating system is implemented in frequency domain. Hydrodynamic interferences between the oscillating bodies are accounted for in the corresponding coupled equations. The array layouts under the constraint of the disk, incidence wave directions, separating distance between the absorbers and the PTO damping are considered to optimize this kind of WECs. Numerical results with regular waves are presented and discussed for the axisymmetric system utilizing heave mode with these interaction factors, in terms of a specific numbers of cylinders and expected power production.