Unveiling the potential of using a spar-buoy oscillating-water-column wave energy converter for low-power stand-alone applications

Applications including the offshore aquaculture, remotely operated vehicles, data acquisition systems, and desalination can be either supplemented or completely powered by renewable energy. The spar-buoy oscillating-water-column wave energy converter concept, typically studied for large scale wave energy production, can be re-designed to meet the power requirements of such applications, which results in a much smaller device working outside resonance conditions under typical sea states, and therefore with a smaller energy conversion efficiency. Experimental results are presented for a 1:10th scale model of a spar-buoy oscillating-water-column, undertaken in a wave channel. Calibrated orifice plates were used to model the flow characteristic of an impulse turbine, which will be used in the full-scale system. The system performance is examined for regular and irregular wave conditions. The results show the presence of non-linear effects, caused by viscous flow and turbine damping. A capture width ratio matrix is generated through stochastic modelling using regular-wave data and the performance of the device is assessed for two locations with different wave energy resource. The device presents an annual-averaged power of approximately 1kW for an Atlantic wave climate, and an annual-averaged power of approximately 0.4kW for a Mediterranean wave climate, which makes it adequate for the supply of specific oceanographic equipment in the first location, while for the second location a larger buoy should be considered.