In a context where sustainable development should be a priority, Orazov \emph{et al.} have proposed in 2010, an excitation scheme for buoy-type ocean wave energy converter. The simplest model for this scheme is a non autonomous piecewise linear second order differential equation. The goal of that paper is to give a mathematical framework for this model and to highlight some properties of its solutions. In particular, we will look at bounded and periodic solutions, and compare the energy performance of this novel WEC with respect to the one of wave energy converter without mass modulation.
