Time-Span of future information necessary for theoretical acausal optimal control of wave energy converters

Optimal control of a wave energy converter (WEC) in polychromatic seas is possible only with accurate future knowledge of wave elevation, excitation force or WEC state. The required future knowledge is related to the bandwidth of the radiation damping, while the available future knowledge is related to the bandwidth of the wave spectrum. A new concept called premonition time is introduced, which is defined as the time by which the time-span of the required future knowledge exceeds that of the available future knowledge. The effect of the size of a WEC on the premonition time, and suitable methods for prediction of future state, are also discussed.