The Tides are Turning for Alternative Energy

A New York City company is converting the East River’s tidal currents into electricity.

December 12, 2008

Roosevelt Island resembles a simpler past. Its sole commercial drag, Main Street, is lined with a series of generic storefronts: “The Restaurant,” “Flower Shop,” “Beauty Salon” and “Hardware Store” – the last sharing its retail space with “Video Store.” So, it may come as a surprise that this two-mile sliver of land wedged between Queens and Manhattan is actually ahead of its time. Home of the first major tidal power project in the United States, Roosevelt Island represents a sustainable future.

The electric currents that illuminate the grocery aisles in the island’s Gristedes Supermarket, and the adjacent Motorgate parking garage, originated in the Atlantic Ocean.

Two years ago, when Verdant Power plugged in its “underwater windmill” at the bottom of the East River, a tidal strait surrounding Roosevelt Island, the alternative energy company became the first in the world to transmit dam-less hydropower to a grid-connected customer. This prototype tidal turbine had already spent four years in underwater development. Now, with a fifth-generation turbine, Verdant Power’s technology continues to evolve.

“There is such promise for this embryonic industry. There’s moving water everywhere,” says Trey Taylor, president of Verdant Power, whose office overlooks the East River.

The river’s east bank is a short walk off Main Street, just steps from Gristedes Supermarket. While not as well manicured as the Manhattan-facing west side of the island, the rocky shoreline is pleasant enough. In fact, without knowing that six 20-foot tall turbines were tethered to the bottom of the river, you might miss the three red and white buoys bobbing in the offshore current. Upon further inspection onshore, however, you will likely spot several long yellow cables emerging from the water below a series of “DANGER: KEEP OUT” signs.

That near invisibility is one of tidal power’s advantages as a sustainable energy source and may partly explain why, according to Taylor, Roosevelt Island residents “wanted it in their backyard.” Solar and wind power have the potential to produce more energy, but their greater visibility, cost and irregularity remain deterrents.

“What we love about tides is that they are very predictable,” says Taylor. “We can look at a clock and a tidal chart and know exactly when power is coming on and going off.”

During the approximately six hours each day that the East River tide is “off” — when the direction of the current is reversing — the local electricity company, Con Edison, takes over.

“The lights never flicker,” says Taylor. And the supermarket’s cash registers never miss a “ka-ching.”

Verdant Power’s underwater design started with basic modifications on the wind industry’s model. However, rather than facing upstream, against the current, the blades face downstream. As water hits the blades, the propeller orients its back end toward the current, similar to a weathervane, and begins turning at about 35 rpm’s — fast enough to feed a generator connected to the grid, but per federal mandate too slow to harm passing fish.

“It’s a passive system, not mechanical,” Taylor explains. “It senses when the current is changing.”

Energetic waters, like those ebbing and flowing past Roosevelt Island, touch many of the world’s most populated locations. Global and national companies have already begun to take advantage. France has had a tidal power plant in place since the 1960’s, and Ireland recently became the home of the world’s largest tidal turbine. Other technologies are now being tested in Scotland and Australia, and more locally in places like Maine and Washington State.

“If you look at a picture of the U.S. from space at night, you see the distribution of lights clearly shows the distribution of people,” explains John Miller, a marine energy expert at the University of Massachusetts, Dartmouth. Where there are people, there is a need for electricity.

Given the scattering of these dense pockets of lights – and people – Miller recommends that each region use the energy most readily available, giving new meaning to the term “decentralized power.” For some parts of the country, like Arizona, that power source may be solar. Iowa, in contrast, could use wind.

The brightest spots on the map are East Coast cities. “Marine renewable energy is literally right on [New York City’s] doorstep,” says Miller.

On a hot and humid summer day, New York City uses about 11,500 megawatts of electricity, according to Steve Hammer, director of the Urban Energy Project at Columbia University. “Right now, we have fewer than two megawatts of renewable energy capacity,” he says, which is enough to provide electricity for only about 1,600 homes.

Solar power alone, thanks to a lot of roofs, has the potential to contribute at least 6,000 megawatts to the city. However, the costs of this technology are huge.

Hammer believes “tens of megawatts” of potentially cheaper energy are waiting to be tapped in the Hudson and East Rivers.

While tidal power would provide a far smaller harvest than solar, Hammer recommends utilizing all viable sources, while weighing important considerations: “What we need to ask ourselves is, ‘How much do we want? How much do we want to pay for it? And where do we want it?’”

About the Author

Lynne Peeples

Lynne Peeples is a freelance journalist focusing on health and the environment. She graduated from NYU’s Science, Health and Environmental Reporting Program, where she was the editor-in-chief of Scienceline. She has also written for Scientific American online, Audubon Magazine, The Harvard Gazette and Amstat News. Before NYU, Lynne worked at Harvard University crunching numbers for HIV clinical trials and environmental health studies, while teaching an introductory biostatistics course. She also holds an M.S. in Biostatistics from Harvard and a B.A. in Mathematics from St. Olaf College. Her resume and clips can be found at: http://www.lynnepeeples.com



I’m sorry but I fail to see what is innovative about a tidal turbine that produces nothing a few hours around slack water.

Readers may be interested to know that a Scottish invention, Gentec WATS, using wave and tidal stream power, generates at full power continuously even during slack water and does not require any sub-sea cables.

The strategy of generating in ‘real time’ from any renewable is a seriously flawed one – out of time load following electricity from renewables is the only way that carbon emissions can be reduced.

Luna says:


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