Frequency dependence in a power take-off mechanism means that power generated does not have a one-to-one correspondence with power available in the waves. Viewing wave power resources from the perspective of the power takeoff device leads us to question the assumption that waves carrying the maximum power are the best target for resource development. We explore this power take-off perspective for a heave device fitted with an electric generator and find that power is preferentially produced from higher frequency waves.

While globally most wave power is concentrated in low frequency swells, when power production is dependent on velocity, as when driving an electrical generator, an energy-harvesting device gathers more power from higher frequency waves. We examine spectral data from the Pacific Ocean and the Gulf of Mexico and find that the peak frequency for heave velocity, and hence for power production, can be as much as twice the peak frequency of the resource power in the waves.

Furthermore, Response Amplitude Operator (RAO) considerations demonstrate the need for small, ‘nimble’ devices to access the most easily available wave power. We compare the total energy capture from the empirical wave spectra using devices tuned to different natural frequencies and find the most energy is captured, regardless of geographic location, with devices that have natural frequencies around 0.2 Hz, far above the swell frequency.

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