On the Generator Constraint Design of a Wave Energy Converter at a Pre-Sizing Stage

Abstract

International audienceThis paper deals with the constraint pre-design of the energy conversion chain for a wave energy converter application. At the first step, and because the control input is the torque (or the linear force) delivered by the generator, we start by limiting mechanically the nominal velocity. For that purpose, we introduce a new quantity based on short-term wave analysis, namely the maximum expected relative velocity. It may be evaluated when both the wave energy converter is controlled or not. Using long-term wave analysis, based on a known local wave climate, we can constraint the maximum relative velocity that the system have to handle. It appears that because of the constraint applied on the torque, it has to be chosen when no loading is applied. Once it have been chosen, we can then determine the generator nominal power rating based on a time-domain analysis. In this context we use two simple criteria (i) one based on the maximisation of the produced electrical energy, (ii) the second on the maximisation of the annual profit. From numerical investigation, it appears that it exists a point which make a compromise between these two antinomic criteria