Numerical Investigation on Hydrodynamic Performance of a WEC Array Integrated Into a Pontoon

Zhao, Xuanlie (Dalian University of Technology) | Ning, Dezhi (Dalian University of Technology) | Johanning, Lars (Dalian University of Technology, University of Exeter) | Teng, Bin (Dalian University of Technology)

OnePetro 

ABSTRACT

High construction-cost is one of the barriers that limited the developments of wave energy utilization. Integrating wave energy converters (WECs) into other marine structures may reduce the construction cost of WECs effectively. In this paper, an integrated system with a medium array (11 devices) of heaving point absorber WECs (PAWECs) arranged at the weather side of a fixed pontoon-type structure is proposed. The hydrodynamics of the PAWECs are investigated numerically by using higher-order boundary element method (HOBEM) code package (i.e., WAFDUT), which is developed based on linear potential flow theory. The hydrodynamic performance (including interaction factor, wave exciting force and heave response) of the WEC array with the rear pontoon is investigated with focus on the influence of the spacing between the WEC array and the pontoon (WEC-pontoon spacing). For sake of comparisons, the results corresponding to the isolated WEC array, i.e., without the pontoon, are presented. Results show that the performance of the pontoon-integrated WEC array performs better than that without the pontoon.

INTRODUCTION

One obstacle that limits the wave energy utilization is the high construction cost. Integrations of wave energy converters (WECs) and other marine structures (such as breakwaters, offshore wind turbine, offshore platforms, etc.) have attracted much attention for its advantage of cost-sharing (Mustapa et al., 2017; Astariz and Iglesias, 2015; Favaretto et al., 2017). The cost reduction of WECs caused by the integration scheme may enhance the competitiveness of the wave energy converters. Pontoon-type structures are very common in offshore engineering, such as breakwaters, floating docks, ships, etc. In addition to the sharing of the infrastructures of both aspects, the WEC devices can provide power to the offshore operation in a convenient way.

It is understood that, for the pontoon-type structures, the wave conditions at the weather side can be described as the superposition of the incident waves and the reflected waves caused by the pontoon. Thus, it is expected that the energy conversion efficiency of the WECs can be improved. There are some cutting edge studies on improving the efficiency of WECs (mainly including oscillating water column WECs and heaving point absorber WECs) by using the reflection of costal structures. The detailed investigations can be found in Howe and Nader (2017), McIver and Evans (1988), Mavrakos et al. (2004), Schay et al. (2013) and Zhao et al. (2017).