Study of a Pelamis-Like Wave Energy Converter in Regular Waves
- Yulin Zhao (Stevens Institute of Technology) | Yufei Ai (Stevens Institute of Technology) | Yao Liu (Wuchang Institute of Technology)
- Document ID
- International Society of Offshore and Polar Engineers
- The 28th International Ocean and Polar Engineering Conference, 10-15 June, Sapporo, Japan
- Publication Date
- Document Type
- Conference Paper
- 2018. International Society of Offshore and Polar Engineers
- Multi-floating bodies, Pelamis-like WEC, Capture power, Hinge joint, Waves
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- 14 since 2007
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In this paper, the power capture performance of a Pelamis-like wave energy converter (WEC) is studied. The Pelamis-like WEC is simplified as three floating cylindrical pontoons which are hinged together. And the relative motion is converted into electricity by the power take off (PTO) system which is simplified as a linear damper. Frequency domain method which is based on linear potential theory is used to establish the equations of motion of the floating system. Considering the displacement constraints between pontoons, the dynamic response of the Pelamis-like WEC can be analyzed in regular waves. Based on the calculated results, the effects of wave frequencies, wave directions, the damping coefficient of the PTO system, as well as the geometric quantities on the power capture performance of the Pelamis-like WEC are studied in detail. It is found that for a given Pelamis-like WEC, there exists an optimum combination of damping coefficient, wave direction, wave frequency, hinge axis inclination to make the maximum power capture.
In recent years, wave energy utilization has been a hot topic of ocean energy development. In order to capture wave energy, various types of wave energy device have been proposed and studied, such as oscillating water column (OWC), floating structure wave energy converter (WEC) and overtopping WEC, etc. The Pelamis-like WEC, as a kind of floating WEC, consists of several floating-body modules which are hinged together. And the relative angular motion between adjacent floating elements is converted into electricity by the power take off (PTO) system. In spite of a lot of researches focusing on Pelamis-like WEC, only a few of them are concerned with hydrodynamics. Dalton (2010) has investigated on the performance and economic viability of the Pelamis-like WEC over a 20-year project time period using 2007 wave energy data from various global locations: Ireland, Portugal, USA and Canada. Palha (2010) described the study of the impact of energy absorption by wave farms on the near shore wave climate and, in special, the influence of the incident wave conditions and the number and position of the wave farms, on the near shore wave characteristics is studied and discussed; Henderson (2006) described the hydraulic power take-off system employed in the Pelamis wave energy converter. He presented the process of the system’s development, including simulation and laboratory tests at 1/7th and full-scale, as well as results of efficiency measurements. O’Connor (2013) presented the results of a case study comparing the performance of two wave energy devices at various scaled power ratings deployed at several European wave energy locations. Yemm (2012) introduced the Pelamis-like WEC in detail, and pointed out that pitch axis and yaw axis were not designed horizontal and vertical but with a certain offset angle. Thiam (2010) studied the power generation efficiency of the Pelamis systematically. He focuses on a simplified model of the Pelamis wave energy converter, with the model consisting of a modified Euler-Bernoulli beam oriented head-on to incoming ocean waves and with energy conversion accounted for by a damping term, where the additional bending moment is proportional to the time derivative of the beam curvature. But no literature exists to study the efficiency of power generation from the aspect of the hydrodynamic model. Multi-body floating model is supposed to be a more accurate method to analyze this problem. He (2013) utilized the AQWA hydrodynamic software to calculated swing angles, hydrodynamic coefficients, and wave exciting forces, but he didn’t mention the efficiency of power generation. Gou (2004, 2014) studied the hydrodynamic interaction effects between wave and two connected floating structures by the boundary integral method. This method is used to study the performance of a Pelamis-like WEC.
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