8 – Wave directionality monitoring

This chapter illustrates design of piece of equipment to measure correctly the directions of wave travel and the amount of energy available to a wave extraction device. It also demonstrates that the analysis of data should not be considered as trivial or straightforward. The assessment of the British wave energy extraction devices was based on projected units of electricity costs and a demonstration of their power take-off capability. Theoretical studies based on inviscid free-surface hydrodynamic theory and generalized frequency domain equations of motion were used to predict the power take-off of a device subject to regular wave excitation. The monitoring system was initially required to be sensitive to wave periods of 1–4 s at least and was to provide a measure of the spectral density function and its directional spread. Once the monitoring system was installed, records from the system were analyzed for each set of three probes and the unidirectional spectrum for each heading were plotted. The mathematical analysis presented in the chapter developed under highly pressurized face saving conditions. This chapter indicates the need to understand the principles of spectral analysis in the context of the situation to be investigated.