The Ocean as an Energy Source: Wave Energy in California

Wave energy conversion takes advantage of the ocean waves caused primarily by interaction of winds with the ocean surface. Wave energy is an irregular and oscillating low-frequency energy source that must be converted to a 60-Hertz frequency before it can be added to the electric utility grid.

Although many wave energy devices have been invented, only a small proportion have been tested and evaluated. Furthermore, only a few have been tested at sea, in ocean waves, rather than in artificial wave tanks.As of the mid-1990s, there were more than 12 generic types of wave energy systems. Some systems extract energy from surface waves. Others extract energy from pressure fluctuations below the water surface or from the full wave. Some systems are fixed in position and let waves pass by them, while others follow the waves and move with them. Some systems concentrate and focus waves, which increases their height and their potential for conversion to electrical energy.

A wave energy converter may be placed in the ocean in various possible situations and locations. It may be floating or submerged completely in the sea offshore or it may be located on the shore or on the sea bed in relatively shallow water. A converter on the sea bed may be completely submerged, it may extend above the sea surface, or it may be a converter system placed on an offshore platform. Apart from wave-powered navigation buoys, however, most of the prototypes have been placed at or near the shore. The visual impact of a wave energy conversion facility depends on the type of device as well as its distance from shore. In general, a floating buoy system or an offshore platform placed many kilometers from land is not likely to have much visual impact (nor will a submerged system). Onshore facilities and offshore platforms in shallow water could, however, change the visual landscape from one of natural scenery to industrial.

The incidence of wave power at deep ocean sites is three to eight times the wave power at adjacent coastal sites. The cost, however, of electricity transmission from deep ocean sites is prohibitively high. Wave power densities in California's coastal waters are sufficient to produce between seven and 17 megawatts (MW) per mile of coastline

According to the European Union, "Among the different converters capable of exploiting wave power, the most advanced is unquestionably the Pelamis Wave Energy Converter, a kind of "undulating sea serpent" developed by Ocean Power Delivery. This technology is the object of a commercial contract for installation of a farm in Portugal. In 2007, three machines, with a total capacity of 2.25 megawatts are in installation phase, and should be joined by 27 others in the years to come. Another 5 MW project is being studied for England this time."

None of these plants are located in California, although economic feasibility studies have been performed for a 30 MW wave converter to be located at Half Moon Bay. Additional smaller projects have been discussed at Fort Bragg, San Francisco and Avila Beach. There are currently no firm plans to deploy any of these projects

As of the mid-1990s, wave energy conversion was not commercially available in the United States. The technology was in the early stages of development and was not expected to be available within the near future due to limited research and lack of federal funding. Research and development efforts are being sponsored by government agencies in Europe and Scandinavia

Many research and development goals remain to be accomplished, including cost reduction, efficiency and reliability improvements, identification of suitable sites in California, interconnection with the utility grid, better understanding of the impacts of the technology on marine life and the shoreline. Also essential is a demonstration of the ability of the equipment to survive the salinity and pressure environments of the ocean as well as weather effects over the life of the facility.

Now this may sound like a grand new plan for a source of energy, but the truth is, like all technological advances, wave energy comes with a price. One such problem is the destruction of marine lifeincluding changes in the distribution and types of marine life near the shore. This would be caused by the building of wave energy converters. Another problem is the possible threat to navigation from collisions due to the low profile of the wave energy devices above the water, making them undetectable either by direct sighting or by radar. Also possible is the interference of mooring and anchorage lines with commercial and sport-fishing. Lastly, as stated a little earlier, these wave energy devices would not look good to many people.

Now there are other types of ocean energy conversion such as tidal wave energy which is when tides comes into the shore, they can be trapped in reservoirs behind dams. Then when the tide drops, the water behind the dam can be let out just like in a regular hydroelectric power plant. A third type of ocean energy is ocean thermal energy conversion which is The idea of using the temperature of water to make energy. These are also viable options for energy sources but have not been tested and studied as much as waver energy.

Energy Innovation Institute & EPRI Report on Assessment Offshore Wave Energy Conversion Devices, June 2004. (Acrobat PDF file, 52 pgs, 1 MB)

Wave Energy - European Union website page.

Ocean Energy Recovery: The State of the Art, American Society of Civil Engineers, 1992.

Natgerman, George, "Wave Power," in Encyclopedia of Energy Technology and the Environment, John Wiley & Sons, 1995.