Effect of mooring-line stiffness on the performance of a dual coaxial-cylinder Wave-Energy Converter |
| |
| Institution: | 1. The University of Naples “Parthenope”, Department of Science and Technology, Centro Direzionale Isola C4, 80143 Naples, Italy;2. The University of Naples “Parthenope”, Department of Engineering, Centro Direzionale Isola C4, 80143 Naples, Italy;1. State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China;2. College of Engineering, Mathematics and Physical Sciences, Exeter University, Cornwall TR10 9FE, UK |
| |
| Abstract: | A point-absorber-type Wave-Energy Converter (WEC) consisting of a floating vertical inner cylinder and an annular outer cylinder that slides along the inner one is considered. The two cylinders heave differently under wave excitation, and wave energy can be harnessed from the relative heave motion between the two cylinders using a Permanent Magnet Linear Generator (PMLG) as the Power Take-Off unit. A mooring cable is attached to the bottom of the inner cylinder. This paper aims to examine the effect of the stiffness of the mooring cable on the performance of the coaxial-cylinder WEC system. The two limiting cases of no mooring cable (freely floating inner and outer cylinders) and an infinitely stiff mooring cable (fixed inner cylinder) were also considered. To perform the analysis, hydrodynamic and interference coefficients of the two heaving cylinders were computed semi-analytically using the method of matched eigenfunction expansions. Experimentally determined viscous corrections on damping were also included in the model in order to have more realistic predictions. The performance of the system in terms of motion responses and capture width were predicted and discussed for both regular and irregular waves. The results of the analysis indicate that both the freely floating design and the design with rigidly moored inner cylinder are viable. The two limiting cases show similar optimal performances, albeit with very different optimal generator damping. However, an ill-chosen mooring-cable stiffness may cause the inner and the outer cylinders to have the same resonance frequency, eliminating the relative heave motion and leading to almost no energy extraction. This situation needs to be avoided when designing the mooring system for a coaxial-cylinder WEC. |
| |
| Keywords: | Wave-energy extraction Dual coaxial-cylinder Mooring-line stiffness Linear generator damping Capture width |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
