Generating electricity from tidal flows
and wave action
Tidal turbine. The first of 100 turbines planned for New York's
East River is lowered into the water. When completed, the project
is expected to generate enough electricity to power 8,000
Harnessing the constant motion of waves, tides, and currents to
generate electricity has long been one of the holy grails of energy
futurists. Now, thanks to advances in technology and a nationwide
push for renewable energy, that dream appears to be closer to
reality than ever before — with East Coast residents likely
to see the greatest gains in Florida and Maine.
"It's really a confluence of the fact that these technologies are
basically borrowing technology and components from other industries
— the offshore oil industry, wind, and submarine. All these
things come together in our designs," says Chris Sauer, president
and CEO of Miami-based Ocean Renewable Power Company. "Number two,
there is such a tremendous influence on renewable energy that we
are actually able to attract investors."
Driven largely by small start-up companies, there are projects in
the water or in the development and permitting stages in Hawaii,
Alaska, Oregon, Washington State, California, New York, and Rhode
Island, says the Ocean Renewable Energy Coalition, a trade
association founded to promote energy technologies from clean,
renewable ocean resources.
But efforts differ sharply on the two coasts. With large, regular
waves, the West Coast is considered ideal for turbines or other
mechanisms that generate electricity from waves, so "wave farms"
are among planned projects there. Waves along the Atlantic coast,
by contrast, are small and irregular, a result of west-to-east
global wind flow. That leaves tides and currents as the main
available sources of East Coast ocean energy.
Late last year, Verdant Power became the nation's first to tap
tides when the company placed a turbine in New York's East River.
The 35-kilowatt turbine affixed to the river bottom on the eastern
shore of Roosevelt Island generates power for a grocery store and
parking garage. Verdant says the project will eventually have at
least 100 turbines and generate 10 megawatts of electricity, enough
to power nearly 8,000 homes.
Enthusiasts say the Verdant project is just the start. The really
promising spots for tidal and current energy have yet to be tested,
they explain. Oddly, such sites lie at the coast's two most distant
points: South Florida and northern Maine.
The Gulf Stream, the narrow but powerful ocean current that carries
water north from the Gulf of Mexico to Newfoundland and on to
Europe, flows within sight of Fort Lauderdale and Miami beaches,
making that area ripe for current-driven turbines. Meanwhile,
Maine's Bay of Fundy, where tides can vary as much as 40 feet in a
single cycle and islands act as funnels to accelerate water flow,
suggests a huge energy resource.
"We have the Gulf Stream going past the state 24/7, so that makes
it attractive," says Manhar Dhanak, professor and chairman of
Florida Atlantic University's department of ocean engineering. "If
we could harness a fraction of the energy of the ocean, then that
could be a significant contribution to Florida's energy
Florida lawmakers last fall gave $5 million to FAU to create the
Center of Excellence in Ocean Energy Technology to explore just
that possibility. Dhanak and other FAU researchers hope to have a
1- to 3-meter, and at least 50-kilowatt prototype turbine placed in
the Gulf Stream by the end of the year, Dhanak says.
Meanwhile, more than 1,800 miles north in Eastport, Maine, Ocean
Renewable Power is working on a small demonstration turbine the
company says it will place in the Bay of Fundy's Western Passage by
November. The unique turbine is designed to turn the same direction
no matter which way the water flows, maximizing energy efficiency
throughout the tidal cycle, Sauer explains. If successful, "We
believe we can build a 20-megawatt [plant], and we believe we can
build that for $38 to $40 million," Sauer claims.
From Prototype to Production
Sauer and Dhanak are the first to admit, however, that growing the
prototypes into production facilities won't be easy. Corrosive
saltwater remains an issue despite improvements to technology.
Underwater cabling is another challenge: the deeper and more
distant the site, the harder and more expensive it is to move the
power to land efficiently.
Currents move relatively slowly and meander somewhat, meaning any
Gulf Stream production power facility would likely have to be quite
large and expensive, with many turbines spaced over a relatively
wide area. Tides move more quickly but are intermittent, so they
will never provide the steady supply available from nonrenewable
sources such as coal and nuclear energy.
Still, Sauer says he thinks ocean power could one day produce 10%
to 20% of the East Coast's energy needs. Dhanak estimates the Gulf
Stream and other South Florida ocean energy projects could provide
20% of Florida's demand.
"It's not the silver bullet," Sauer says. "It's one of many
solutions that, when combined with wind and other resources, will
basically wean us from imported oil." — Aaron Hoover
As if hurricanes weren't bad
Seismic sensor. Six tsunami-detecting buoys like this one have
been deployed in the Gulf of Mexico. If the warning system works as
intended, coastal municipalities may have an hour or more to
prepare before the wave washes ashore.
Thousands of people cavort on Daytona Beach on a hot Sunday in
August when, out of nowhere, a 15-foot wave floods the beach. The
water swamps the sun worshippers and rushes into buildings along
Emergency managers in Daytona's home of Volusia County sought to
prepare for just such an event during a drill earlier this year.
Their morning-long exercise was part of a growing effort by local,
state, and federal officials to plan for a catastrophe so rare on
the East Coast that few hurricane-hardened residents have pondered
it: a tsunami.
"The thing about a tsunami is, it's a low probability, high-impact
event," says Daniel Noah, a Ruskin, Fla.-based warning coordination
meteorologist for the National Weather Service. "We've had them
before, and we're going to have them again."
Many tsunamis occur when an earthquake causes rapid movement of the
ocean bottom, displacing vast quantities of water. Others well up
from underwater landslides or volcanoes. Most tsunamis happen
within the seismically and volcanically active "Ring of Fire"
surrounding the Pacific. An 8.0-magnitude quake there was the
source of the tsunami that left 52 dead in the Solomon Islands in
early April 2007.
Although recent tsunamis have struck Asia, they are not unheard of
in Europe and the U.S. Perhaps most famously, a massive 1755
earthquake off the coast Lisbon, Portugal, caused a tsunami that
killed tens of thousands of the city's 275,000 residents. Modelers
believe that earthquake, which occurred in the Azores-Gibraltar
fracture zone near Portugal, spurred successive tsunamis that raced
across the Atlantic — striking Florida with a series of 7- to
10-foot waves, Noah explains. Florida and other southeastern states
are also threatened by undersea earthquakes in the Caribbean's
Puerto Rico Trench and by the Cumbre Vieja volcano in the Canary
Islands. A fracture zone between Cuba and the Yucatan could cause a
The largest tsunami to strike the East Coast in recent memory came
in 1929, when a likely underwater landslide on the Grand Banks
created a 6- to 23-foot tsunami in Newfoundland and reported as far
south as South Carolina, according to the U.S. Geological Survey.
Overall, there are probably one to two tsunamis every century along
the East Coast, Noah estimates. But the hugely devastating Indian
Ocean tsunami of December 2004 prompted U.S. officials to expand
the warning system already in place for Alaska and Hawaii —
the U.S. states most prone to tsunamis — to the Atlantic
coast, Noah said.
Today, the National Weather Service's Alaska Tsunami Warning Center
monitors the East Coast's seismic hotpots. Because not every quake
causes a tsunami, the service has a total of six tsunami-detecting
buoys — most installed in 2006 — in the Gulf,
Caribbean, and Atlantic. If seismologists detect an earthquake of
at least 6.8 magnitude, the center may issue a tsunami warning,
while also seeking to confirm the tsunami via the buoys. That
warning goes to the service's Melbourne office and then to other
coastal offices, which issue flood warnings to emergency managers
and the media.
The weather service believes East Coast communities could face a
maximum of a 15-foot wave extending 300 feet inland. On much of the
Gulf Coast, where the extensive underwater continental shelf would
dissipate the wave's energy, the biggest wave would be about 18
inches, accompanied by strong currents.
If the warning system works as intended, coastal municipalities may
gain an hour or more to prepare, which with efficient evacuation
procedures could go a long way toward getting everyone off the
beach before the tsunami arrives. — A.H.