Performance of large arrays of point absorbing direct-driven wave energy converters

J Engström,M Eriksson,M Göteman,J Isberg,M Leijon

doi:10.1063/1.4833241

Abstract

Future commercial installation of wave energy plants using point absorber technology will require clusters of tens up to several hundred devices, in order to reach a viable electricity production. Interconnected devices also serve the purpose of power smoothing, which is especially important for devices using direct-driven power take off. The scope of this paper is to evaluate a method to optimize wave energy farms in terms of power production, economic viability, and resources. In particular, the paper deals with the power variation in a large array of point-absorbing direct-driven wave energy converters, and the smoothing effect due to the number of devices and their hydrodynamic interactions. A few array geometries are compared and 34 sea states measured at the Lysekil research site at the Swedish west coast are used in the simulations. Potential linear flow theory is used with full hydrodynamic interactions between the buoys. It is shown that the variance in power production depends crucially on the geometry of the array and the number of interacting devices, but not significantly on the energy period of the waves.

Highlights

For large-scale utilization of wave power from the oceans, it is required that a large number of Wave Energy Converters (WECs) operate simultaneously
We study the performance in terms of power production and smoothing for a large array of directdriven point absorbers of the Uppsala University WEC system
The shadowing effect of the buoys can clearly be seen in Figs. 2(a) and 2(b), with the non-shadowed WECs receiving the highest Capture Width Ratio (CWR)

Summary

INTRODUCTION

For large-scale utilization of wave power from the oceans, it is required that a large number of Wave Energy Converters (WECs) operate simultaneously. As the individual units in such wave power arrays interact by scattered and radiated waves, the complexity of the modeling increases rapidly with the number of interacting structures, and the numerical simulations are a challenge that call for new methods and theories. We study the performance in terms of power production and smoothing for a large array of directdriven point absorbers of the Uppsala University WEC system. The positions of the WECs are not exact, but tend to drift slightly off their mean positions These realistic randomized geometries are taken into consideration in this paper.

THE LYSEKIL WAVE POWER PROJECT

THEORY

MODELL SPECIFICATION

RESULTS

DISCUSSION AND CONCLUSION