The Promise of Wave Power (Invited)

The solutions to today's energy challenges need to be explored through alternative, renewable and clean energy sources to enable diverse energy resource plans. An extremely abundant and promising source of energy exists in the world's oceans: it is estimated that if 0.2 % of the oceans' untapped energy could be harnessed, it could provide power sufficient for the entire world. Ocean energy exists in the forms of wave, tidal, marine currents, thermal (temperature gradient) and salinity. Among these forms, significant opportunities and benefits have been identified in the area of ocean wave energy extraction, i.e., harnessing the motion of the ocean waves, and converting that motion into electrical energy. Ocean wave energy refers to the kinetic and potential energy in the heaving motion of ocean waves. Wave energy is essentially concentrated solar energy (as is wind energy). The heating of the earth’s surface by the sun (with other complex processes) drives the wind, which in turn blows across the surface of the ocean to create waves. At each stage of conversion, the power density increases. Ocean wave power offers several attractive qualities, including high power density, low variability, and excellent forecastability. A typical large ocean wave propogates at around 12 m/s with very little attenuation across the ocean. If the waves can be detected several hundred kilometers off shore, there can be 10 hours or more of accurate forecast horizon. In fact, analysis has shown good forecast accuracy up to 48 hours in advance. Off the coast Oregon, the yearly average wave power is approximately 30 kW per meter of crestlength (i.e., unit length transverse to the direction of wave propagation and parallel to the shore.) This compares very favorably with power densities of solar and wind, which typically range in the several hundreds of Watts per square meter. Globally, the wave energy resource is stronger on the west coasts of large landmasses and increases in strength toward the poles. This phenomenon is due to the prevailing west to east global winds known as the "westerlies" found in the Northern and Southern hemispheres between 30 and 60 degrees latitude. Correspondingly, the west coast of the United States, the west coast of Australia, and the coastal regions of Europe have seen the greatest wave energy industrial activity to date. Ocean wave energy has great potential to be a significant contributor of renewable power for many regions in the world. For the West coast of the US alone, the total wave energy resource is estimated at 440 TWh/yr, which is more than the typical total US annual hydroelectric production (270 TWh in 2003). For US west coast states, a fully developed wave energy industry could be a significant contributor to renewable energy portfolio standards. Within the next few years, several utility-scale wave energy converters are planned for grid connection (e.g., Ocean Power Technologies and Columbia Power Technologies in Oregon, USA), with plans for more utility-scale development to follow soon after. This presentation will cover the physical basics of wave energy, examples of commercial technology, challenges opportunities for research, and an update on the wave energy research and developments at leading commercial, industrial, and academic institutions around the world.