Wave energy converters (WECs) face many technical challenges before becoming a cost-competitive source of renewable energy. The levelized cost of electricity could be decreased by implementing real-time control strategies to increase average power produced by a WEC. These control strategies typically require knowledge of the immediate future excitation force, caused by the waves. This paper presents a disturbance prediction methodology that is independent of the local wave climate and can be implemented on a wide range of devices.
A time-domain model of a generic heaving WEC is developed with the Cummins equations. The model is simulated with measured water surface elevation data collected off the Oregon Coast. A simplified linear frequency-invariant state-space model is used in conjunction with a Kalman filter to estimate the current excitation force with measurements of the WEC’s motion. Future excitation forces are then predicted multiple steps in the future with a recursive least squares filter. The results show this approach makes accurate predictions of excitation force over short time horizons (up to 15 seconds), but accurate predictions become infeasible for longer horizons.
If wave energy technology is to mature to commercial success, array optimization could play a key role in that process. This paper outlines physical and numerical modeling of an array of five oscillating water column wave energy converters. Numerical model simulations are compared with experimental tank test data for a non-optimal and optimal array layout. Results show a max increase of 12% in average power for regular waves, and 7% for irregular waves between the non-optimized and optimized layouts. The numerical model matches well under many conditions; however, improvement is needed to adjust for phase errors. This paper outlines the process of numerical and physical array testing, providing methodology and results helpful for researchers and developers working with wave energy converter arrays.
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