The world’s oceans hold the potential for producing at least 2 terawatts of electricity—a little over 10 percent of the world’s energy consumption. The Pacific coast of the U.S. is one the prime locations for wave-based power generation, which has led to several research efforts aimed at harnessing the potential. Columbia Power Technologies (CPT) teamed up with Oregon State University and Ershigs, Inc., a fiberglass-reinforced plastics manufacturer, to develop a buoy—a wave energy converter code-named Manta—that can generate an average of 400 kilowatts of electricity.
Once constructed to utility scale, the buoy will have two, 18 meter long wings, each attached to a central shaft within a single nacelle measuring 9 meters in diameter and 16 meters high. The wings react to the shape and amplitude of passing ocean swells and transfer rotational energy to each central shaft. The rotation of each central shaft drives dedicated rotary generators. As each wing moves up and down, it generates electricity, which is then transmitted to the electrical grid on shore.
The body components in the Manta are made out of fiber-reinforced plastic, which provides the strength and corrosion-resistance necessary for use in the ocean. “A composite approach to the Manta will have distinct corrosion advantages over metallic alternatives for long term seawater service,” says Steve Hettick, vice president of manufacturing at Ershigs.
Several manufacturing processes are to be used in making the Manta components, including filament winding, contact molding, and vacuum infusion methods. Ershigs specializes in the filament winding of large diameter cylindrical structures. According to Hettick, the company worked with Columbia Power to optimize various buoy components in order to reduce manufacturing complexity. Columbia Power then ran extensive wave modeling simulations to ensure power-generating capacity was maintained with the most efficient manufacturing configurations. The Manta is being designed to withstand waves associated with 100-year storm events, says Hettick. When tested in the Oregon State University wave tank at scaled sizes, prototype wave energy converters survived the stresses created by such a storm event, and performed well.
Wave-generated power offers several advantages over other forms of renewable energy, according to experts at Columbia Power. Wave-power farms, can produce more power on smaller footprints than photovoltaic, solar thermal, or wind farms. Finally, the generating capacity of waves can be predicted several days in advance with a high degree of accuracy using satellite imagery and offshore weather buoys allowing wave farms to be scheduled like a base load.