The Power of Water

The motion of the ocean may help power your home in the not-too-distant future
November, 2012
  • future energy sources
  • power of water
  • ocean energy
  • If rolling waves make you seasick, consider this: someday soon they could help charge your car and light your house.

    “The potential for ocean energy is huge,” says Jason Busch, executive director of Oregon Wave Energy Trust (OWET), a nonprofit that hopes to see enough green wave electricity created by 2030 to power 3,000 homes.

    Waves and tides alone could produce one-third of the nation’s electricity if all their potential were realized, according to The U.S. Department of Energy. Realistically, they’ll make up part of the 15 percent of total electricity generated from water power over the next 20 years.

    Waves required.
    To create wave power, you need waves, which are “always biggest on the west side of continents,” says Dr. Belinda Batten, director of the Northwest National Marine Renewable Energy Center (NNMREC) at Oregon State University. Why? Westerly winds consistently blow over vast stretches of ocean. This makes Northern California, Oregon, Washington, Alaska and Hawaii ideal spots, as a well as Scotland, Portugal, Chile and Western Australia.

    How does it work?
    Converting wave energy is still in the “toddler” stage, Dr. Batten says. Devices rely on waves’ up-and-down, back-and-forth or right-to-left movement, or a combination of all three. Some sit on the seabed; others float under the water or on its surface. They are designed for use offshore or near shore, and to power everything from remote ocean sensors to public utilities.

    In the U.S., the project closest to supplying a public utility involves a 150-ton buoy that will be deployed 2.5 miles off the coast of Reedsport, Ore., in early 2013. The 40-foot-wide, 146-foot-tall device, most of it sitting underwater, uses the vertical motion of waves to move a float up and down on a stationary spar and spin a generator. Scientists will monitor the buoy for a year before it’s hooked up to the electrical grid. Eventually, 10 buoys will generate 1.5 megawatts of power.

    Last summer, NNMREC evaluated a device that captures all three wave movements at its new Newport, Ore., test site. Looking a bit like a football goal post with cylindrical float on the cross bar, it was hooked to a test buoy, which gave feedback on power generation and wave profiles.

    Near Fort Pierce, Fla., students from Florida Institute of Technology’s ocean engineering program are testing two designs for harvesting near shore wave energy abundant in coastal areas similar to Florida.

    The power of tides.
    Another renewable energy source is tidal power, which uses wind-turbine-like devices anchored to the sea floor. “Instead of trying to harness the power of fast moving wind, you’re harnessing the power of fast moving water,” explains Dr. Brian Polagye, co-director of NNMREC at University of Washington.

    Tides are a “very predictable, high intensity resource” and installations can be scaled to a given location, Polagye says. But they require high tides and narrow channels –you want a lot of water flowing through a small area – like in Washington, Maine and Alaska. Marine turbines need 4 knots of water speed to operate efficiently.

    An underwater turbine in Cobscook Bay, Maine, delivered electricity to the public utility in September. It is the first grid-connected tidal project in the U.S. and will generate enough electricity to power 25 to 30 homes annually. Two additional turbines will be installed next fall.

    A demonstration project with Washington’s Snohomish County Public Utility District will test an underwater turbine in Admiralty Inlet, a narrow channel at the mouth of Puget Sound. It should go online in late 2013.

    Energy from slow-moving water.
    For areas without big waves or tides – typical ocean currents are slower than 3 knots, rivers less than 2 knots – scientists have found other ways to harness energy.

    The VIVACE system relies on vortex-induced vibrations. Think of the swirls and eddies that form around dock pilings. Vortices can cause structures like bridges to fatigue and collapse, but also help schools of fish propel through the water. VIVACE’s horizontal cylinders, which even sport a fish-scale-like surface for improved efficiency, sit on the seabed and oscillate up and down with the frequency of the vortices.

    Left: This buoy in Newport, Ore. captures the back-and-forth, up-and-down and left-to-right movements of the waves. Copyright NWEI 2012. Right: The PB150 PowerBuoy, developed and manufactured by Ocean Power Technologies, Inc. (OPT), deployed in Reedsport, Ore. PowerBuoy®, Ocean Power Technologies, Inc.

    This movement creates power. VIVACE generates 14,600 times more power per volume than the two largest U.S. wind farms at equivalent speeds, says creator Dr. Michael M. Bernitsas of the University of Michigan. Rated speed for wind farms is 12 meters per second; the equivalent speed in water is 1.3 meters per second or 2.6 knots, well within normal offshore current speeds.

    Fish easily navigate the cylinders, tested in Michigan’s St. Clair River and a Netherlands canal. Portable units for charging autonomous underwater vehicles should be available in 2014.

    Baby steps for the environment.
    While an OWET survey found 78 percent of Oregon coast residents support wave energy development, organizations are taking pains to “avoid the mistakes of our forefathers” and not adversely affect the environment, Jason says.

    OWET has spent more than $1 million on studies to evaluate the impact of wave devices on whale migration and sediment transport, as well as how electromagnetic force from electricity flowing through cables impacts marine life.

    The main goal of the Admiralty Inlet tidal project is learning the long-term impact on marine creatures, ocean habitats, water quality, acoustics and even derelict fishing gear. Devices and their placement in the ocean will be adjusted based on the data gathered.

    “That’s not an opportunity we’ve had with other types of renewable or traditional energy generation,” Polagye says. This scrutiny also makes for a slower road to development.

    Uncertain future?
    At this stage, ocean energy relies heavily on federal support.

    In many ways, it’s where wind energy was 30 years ago, explains Dr. Batten of NNMREC, a “neutral voice of science and engineering” and one of three centers funded by government to help commercialize ocean energy. The U.S. led the world in wind technology, but backed off when incentives, research funding and budgets were cut. Today, European wind turbines are being installed here.

    “In wave energy we have the opportunity to be a world leader.” It’d be a shame to have that pulled out from under us, Dr. Batten says.

    By Anne Nagro



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