Optimal Discrete PTO Force Point Absorber Wave Energy Converters in Regular Waves

For ocean wave energy converters (WECs) to become a cost-effective alternative in the energy production system a large increase in the conversion efficiency is needed. Fluid power technology is the leading technology for the Power Take-
Off (PTO) system of wave energy converters. However the conventional fluid power systems suffer of poor efficiency. Therefore discrete fluid power force systems have been proposed. Limited research has, however, been conducted with focus on choosing the discrete force levels and force profiles for a discrete PTO system for WECs. This paper is to support the design of discrete
force systems for PTO, by focusing on how to choose the optimal PTO force levels and force profile when seeking to increase energy harvesting. The work concerns point absorber WECs and utilises a simple float model based on linear wave theory. Utilising the principle of superposition and the Laplace transform a solution of the float movement is found when subjected an incoming wave and a discrete PTO force. Finally an optimisation leads to the force profile implying the highest harvested energy.