Oceans

Exciting “far horizon” energy opportunities exist with the motions of the oceans. Experts estimate that only 0.2 percent of this kinetic energy would meet the entire planet’s power requirements. The renewable energy is there—the problem is capturing it. And it is not a trivial problem.

Ocean-motion energy has three components: tides, currents, and waves. The earliest patents for harnessing these power sources came in the early 19th century. Few attempts, however, translated into practical use.

Tides are the best-known oceanic energy source. Wherever there is a tide range of at least 15 feet, there is potential for energy production. The first commercial-scale operations have used dams that trap the water once the maximum tidal difference has occurred. Then, as the water level on one side of the dam decreases, the high water behind it is released through a set of power-generating turbines. Tide times and heights are predictable for years in advance, so this type of power supply is reliable.

The oldest and largest tidal power station is La Rance in France’s Bay of Biscay, where the average tidal range is 26 feet. Since 1966, La Rance has supplied 4 percent of Brittany’s power at less cost than nuclear energy. In Canada’s Bay of Fundy, where the tidal range is 55 feet, a smaller tidal station generates energy equal to about 10 percent of La Rance. About a dozen other nations have tidal energy-generation facilities. Most are experimental.

Tidal-power barrages pose environmental problems, as do dams everywhere. A more recent means to capture tidal energy is to use seafloor-mounted “watermills” with rotating blades that turn generators. The units are mounted so they rotate facing into the direction of water flow. In this way, most of the water movement can be captured.

A similar scheme is used in places where the current flow is primarily in one direction. From 2006–2008 six 35-kilowatt turbines were operating in New York’s East River. There are proposals to site turbines on the seafloor in the Gulf Stream off Florida that could supply the state’s entire electricity needs. Similar projects are being studied for major rivers such as the Mississippi.

The greatest ocean-energy potential is in its wave motions. A wave 4 feet high with a 10-second period will produce energy equivalent to 35,000 horsepower per mile of coastline. The best U.S. regions for wave power are along the Northwest, Northeast, and Hawaiian coasts.

The kinetic energy of wave motion is converted to electrical energy by use of mechanical devices. A recent survey report listed more than 15 different experimental machines. One of them claimed a conversion efficiency of 81 percent.

Today, the world’s most advanced programs for renewable ocean energy are in Scotland. For more than a decade the British government has provided encouragement, funding, and facilities through its European Marine Energy Center. A major goal is to fulfill 20 percent of the United Kingdom’s power needs. Such alternative-energy pioneering also develops new international business opportunities for British companies.

Harnessing energy from motions of the oceans is a concept still very much in its infancy. Government support is both critical and appropriate, and must attract the private investment needed to form profit-making businesses.

Time and patience will be essential in getting to the point where oceanic motion can produce energy that’s cost-competitive with carbon-based fuels. The theory is there, and the needed experiments are taking place. All of it needs to be done more rapidly.

Finally, the problems are not just with science, technology, and investment developments. Environmental concerns and poorly conceived government regulations create authorization problems that seriously delay timely approvals. Rules and regulations are needed, but they must be tailored to this new field.

Renewable energy from the oceans can help move the United States to greater energy independence. The surf’s up—and it’s there to be used.

 

Dr. Walsh, a marine consultant, is a retired naval officer and oceanographer. During his naval career he served at sea in submarines and ashore in ocean-related research-and-development assignments.
 

 
 

Conferences and Events

Maritime Security Dialogue

Fri, 2015-03-13

Please join us for a Maritime Security Dialogue event:A Cooperative Strategy for 21st Century Seapower:Forward, Engaged, Ready A...

2015 U.S. Naval Institute Annual Meeting

Why Become a Member of the U.S. Naval Institute?

As an independent forum for over 135 years, the Naval Institute has been nurturing creative thinkers who responsibly raise their voices on matters relating to national defense.

Become a Member Renew Membership