Recent Advances in Wave Energy Utilization

After many decades of study, two wave energy conversion systems have been shown to be the most effective in producing either electricity or potable water at remote location, such as the over 100,000 inhabited islands of the world. Those systems are the McCabe Wave Pump (MWP) and the Backward Bent Duct Barge (BBDB). Both of these are floating systems with well defined missions for remote locations. The BBDB is primarily designed to provide electricity, while the MWP's primary mission is to provide potable water. Both systems are resonant systems, in that they are designed to operate most efficiently in the neighborhoods of specific wave periods. In random seas, the operational ranges of each are within the half-power bandwidth of the center band resonant periods. The BBDB is an oscillating water column system in which a horizontal column of water, with its mouth facing aft and its internal free,-surface facing upward through a 90° bend at the bow of the floating structure, excites a pneumatic turbogenerator above the internal free-surface by the wave-induced motions of the water column. In other words, the water column acts as a flexible piston. The MWP is a mechanical-hydraulic system which provides high-pressure, pre-treated water to reverse osmosis desalination systems by the motions of hinged barges. The BBDB is now operational in Japan and China, while a prototype of the MWP is now deployed in the Shannon Estuary in Ireland. The operations of these two systems, as related to the hull dynamics, are discussed.