Practical limits to the power that can be captured from ocean waves by oscillating bodies

The maximum average power that can be captured from ocean waves by an idealised and unconstrained oscillating body depends on two hydrodynamic properties: the wave radiation pattern and the radiation resistance (also called added damping or wave damping coefficient). These properties depend on the body geometry and the mode of oscillation. For such unconstrained motion the limits of absorbed power are well described. Power bounds due to physical restrictions like limited volume stroke or machinery stroke length has also received some attention, but has not been sufficiently explored.This paper looks at such physical bounds to the achievable absorbed power. It is done by physical reasoning leading to analytical expressions for the upper bounds, treating heave, surge and pitch motions separately. It is shown how size, oscillation mode and volume stroke of the oscillating body inherently influence the absorption ability. Furthermore, implications for the practical and economical design of wave energy are identified and discussed.