Experimental investigation of wave-to-force modelling uncertainty for wave energy converters

Abstract

Achieving an accurate yet analytically and computationally simple mathematical model to describe the dynamical behaviour of wave energy converters (WECs) in realistic (experimental) conditions, is fundamental for optimising their performance, in particular via suitable control design procedures. Within the literature, these models are virtually always obtained by leveraging a set of simplifying assumptions on the WEC system, based on small motion about a natural equilibrium position, which does not reflect a realistic behaviour under operating controlled conditions, inevitably introducing uncertainty in the overall representation. Motivated by such an issue, this paper aims to enhance the current understanding of so-called wave-to-force WEC dynamics and to address a proper quantification of the uncertainty associated with adopting small motion assumptions in a generic form. The proposed experimental framework includes definition of the necessary tests to characterise any given WEC prototype, synthesis of representative mathematical models from the data collected, quantification and modelling of dynamical uncertainty, and consequent robust performance assessment, able to provide robust estimates of the capabilities of any (developed/novel) WEC concept at prototype stage. The methodology is illustrated by means of an experimental case study, with a small-scale prototype of the Wavestar system. Overall, the proposed framework provides valuable insights for improving WEC performance, efficiency, and reliability in practical applications, supporting decision making at early stages.