ABSTRACT
The contributions of this paper are twofold with regard to the technological development of the Ocean Grazer: (I) the analysis of the wave energy extraction through a simple floater blanket system; and (II) the control design of the adaptable piston pumps for optimal energy extraction for arbitrary wave profiles. The first case focuses on the energy extraction of an array of floaters connected to pumping systems. In this analysis, we consider the dynamical interactions between buoys, pumps and storage elements. This also includes the radiating waves between buoys. In the second case, we propose a Model Predictive Control (MPC) strategy in order to maximize the energy capture from the waves. The proposed solution relies on mathematical optimization (Bertsekas 1999, Papalambros & Wilde 2000), which aims at maximizing the extracted energy from the waves. In (Li, Weiss, Mueller, Townley, & Belmont 2012) the applicability of MPC for optimizing a single nonadaptable WEC is discussed-by non-adaptability we mean that the WEC operation is restricted to a certain wave height. In (Feng & Kerrigan 2013) optimization-based techniques were also used for
1 INTRODUCTION
Increased renewable energy penetration in countries’ energy mix has become a worldwide priority, evidenced, for example, by the Kyoto Protocol, and the more recent COP 21 held in Paris. Wave energy is one renewable energy source that shows great promise and is a viable alternative to facilitate the aforementioned energy mix goals. This can be achieved by converting the latent untapped energy of the ocean waves into electrical energy through a device known as a Wave Energy Converter (WEC). There are diverse operating principles of WECs such as oscillating water columns, connected structures, overtopping devices, and point absorbers (Drew, Plummer, & Sahinkaya 2009, Koca, Kortenhaus, Oumeraci, Zanuttigh, Angelelli, Cantu, Suffredini, & Franceschi 2013, Ringwood, Bacelli, & Fusco 2014). A comprehensive exposition of different types of WECs can be found in (Ringwood, Bacelli, & Fusco 2014) and the references therein from a control engineering perspective, and in (SI-Ocean 2012) from a broader perspective.
