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OCEAN SURFACE CURRENT ENERGYENERGY FROM OCEANIC RIVERS
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Ocean surface current resources are hidden from view just off the coastlines of every continent on Earth. Though vast, these incredible energy resources are almost completely unused. As shown on this Miami University Ocean Surface Current Map , the currents of the world flow in a generally clockwise direction north of the equator, and counter clockwise south of the equator. They are a form of stored solar energy. The interaction of sunlight with our atmosphere creates winds that blow across the oceans of the world. The most predominant current generating winds blow in a westerly direction towards the equator from about 30 degrees either north or south of the equator. As the wind endlessly blows across the surface of the ocean, part of its energy is given up to the waters in the form of the surface currents that circulate around the world. Like other forms of hydropower, harnessing this energy resource will involve water turbine generators. [You will need the Free Adobe Reader to access some of the documents on this page.] The U.S. Department of the Interior is involved with development of ocean current resources. They have an online OCS Energy Guide , as well as an OCS-EIS White Paper that give overviews of ocean current development so far. Most of the information in this section is from those two sources. NOTE: The U.S. Government loves acronyms and working through them can be more difficult than understanding the engineering challenges of oceanic hydropower development. The term OCS, above, refers to the Outer Continental Shelf, which is the relatively shallow ocean water immediately off our coasts. EIS refers to the Environmental Impact Statement. _________________________________________________________________ ENVIRONMENTAL FRIENDLINESS -
Used with caution, ocean surface current hydropower is easy on the environment. It produces no air pollution, no water pollution, and no greenhouse gasses. But, as with any water turbine technology, some concerns exist regarding fish safety around turning blades. Thanks to talented engineers and computer design, the turbines in use today have excellent safety records, and high operating efficiencies. The anchors and housings on these generators will almost certainly be utilized by marine life for shelter. Fish love structure, and virtually every structure placed in the water attracts a huge variety of fish. A much larger concern is the possible slowing of ocean surface currents as we harvest power from them. Ocean surface currents carry massive amounts of solar heat away from the equator and transport it to latitudes far away. If these currents stopped or slowed dramatically, the result would almost certainly be drastic cooling of latitudes far from the equator, and equally drastic heating of tropical regions around the equator. It is not wild speculation to suspect that dramatic slowing of these global thermal energy conveyors could create a global environmental disaster of unimaginable magnitude. Energy extraction will cause these currents to slow; that is not debatable. But the slow down from one, or even a few dozen turbines would be imperceptible. Would it cause environmental problems? What would be the effect of thousands of multi-megawatt turbines placed in these currents? Ocean surface currents are wind driven. Multi-story buildings on the coasts and on islands around the world affect the winds that blow across the seas. A constant flow of hundred thousand ton ships in and out of the oceanic currents also has an effect. We don’t know if harvesting energy from ocean surface currents, combined with other human activities (shipping, seashore high-rise development, etc.), will actually slow it down at all. There is, frankly, a lot we don’t know about the environmental effects of harvesting energy from ocean surface currents. But as we begin to develop this valuable resource, scientists will focus more and more resources on studying the environmental effects. _________________________________________________________________ COST -
The Department of the Interior OCS-EIS White Paper states that: Because no commercial turbines are currently in operation, it is difficult to assess the costs of ocean current energy and its competitiveness with other energy sources. Initial studies suggest that for economic exploitation, velocities of at least 2 m/s (meters per second - about 4 knots, or roughly 4 mph or 6kph) would be required (a 5-knot current has the kinetic energy equivalent of wind at more than 100 mph), although it is possible to generate energy from velocities as low as 1 m/s. Major costs of these systems would be the cables to transport the electricity to the onshore grid. There are a number of similarities between tidal current energy and ocean surface current energy. In some ways, ocean current energy will prove more economical. It isn’t intermittent like tidal energy. Its flow is constant and highly reliable. But ocean surface currents are often slower than tidal currents. As detailed on the Pros and Cons of Tidal Energy page, the U.S. Government does not believe that tidal energy can be brought on line economically. But some private business people would disagree with that. Private enterprise has repeatedly shown that they will find a way forward if there is a way to be found at all. So, it is entirely reasonable to believe that ocean current energy will be lighting homes in the very near future; and it will be doing so at a competitive price. _________________________________________________________________ AVAILABILITY - Ocean current energy is a vast resource and found off the coasts of every continent in the world. This Wikipedia Ocean Currents discussion lists 54 major currents; and there are many other, smaller currents. The United States has two major ocean current flows. The California Current runs the entire length of the West Coast. The Gulf Stream flows the entire length of the East Coast and carries a mass of water 75 miles wide and 3,000 feet deep. The OCS-EIS White Paper states, “The total worldwide power in ocean currents has been estimated to be about 5,000 GW, with power densities of up to 15 KW/m2.” If 100% of that energy resource could be harnessed 24 hours a day it could generate 43,800 TWh annually, or about 2.5 times total global electrical demand. _________________________________________________________________ AESTHETICS -
Ocean surface currents extend hundreds of feet below the surface. Most turbine generators will subsurface and unseen. Any structures that are on the surface will be several miles offshore and largely out of site. _________________________________________________________________
Ocean surface current energy offers exciting possibilities. Do we need to explore development of this resource? Probably. Should we exercise a great deal environmental caution as we develop it? Absolutely. _________________________________________________________________
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