Moon-driven tides, ocean currents and waves generate more oomph than wind, are more consistent that solar

A drama is unfolding in New York City’s East River. This summer the Popsicles at a Gristedes supermarket on Roosevelt Island, midstream between Manhattan and Queens, will be kept icy by power generated just a stone’s throw from the riverbank. Anchored 30 feet down, six underwater turbines will turn day and night, driven by the tidal flows in the channel. At a fish-friendly 35 rpm, the propellers will crank out up to 200 kilowatts of clean power, or roughly half the peak needs of the supermarket.

Projects like this one are still small fry. But hydropower, the granddaddy of green energy, is making a comeback. Think Hoover Dam, but less visible and a whole lot easier on the environment. This born-again breed of clean energy isn’t yet on the agenda for George W. Bush, who is out barnstorming the nation on behalf of renewable power. The President is pointing to the earth for plant-based ethanol, to the sky for wind power, and to the sun for photovoltaics. But he should also be pointing to the moon, say fans of the new hydropower, and to the seas that lie below it. Tugged by lunar gravity and stirred by wind and currents, the oceans’ tides and waves offer vast reserves of untapped power, promising more oomph than wind and greater dependability than solar power.

The appeal of next-generation hydropower is hard to miss. “It’s local, reliable, renewable, and clean. Plus, it’s out of sight,” says Trey Taylor, president of Verdant Power LLC, the Arlington (Va.) startup developing the East River site. Adds Roger Bedard, ocean energy leader at the Electric Power Research Institute (EPRI), the industry’s research-and- development arm: “Offshore wave and tidal power are where wind was 20 years ago, but they’ll come of age faster.” By 2010, Bedard predicts, the U.S. will tap about 120 megawatts of offshore wave energy — enough to power a small city — up from virtually zero today.

GROWING DEMAND

The planets are certainly in alignment for hydro. Prices for natural gas and coal are high, making renewables more cost-competitive. And in an effort to halt climate change and cut energy imports, 19 states have mandated that a share of their power come from green sources. Demand for alternatives is soaring: U.S. wind capacity surged by nearly 2,500 megawatts last year, up 35%, and solar is sizzling.

Wind and solar won’t be able to satisfy all the green-power mandates. So more than two dozen companies worldwide are developing systems to unlock the power of waves and currents. The first to sell devices to a commercial project is Edinburgh’s Ocean Power Delivery Ltd. Its Pelamis system is a snake-like steel tube that floats, semi-submerged, in the ocean.

In its Scottish factory, OPD is putting the finishing touches on three of these 400-foot-long machines. This summer they’ll be towed to a site three miles off Portugal’s northwest coast and hooked into the power grid. Lying low in the water, the snakes are invisible from a distance, unlike offshore wind farms that are causing “not in my backyard” complaints across the Atlantic, in Cape Cod. Initially the project will supply 2,500 kilowatts of juice, enough to run 1,500 Portuguese homes. OPD hopes to have 30 units at the site by 2008, pumping out enough current to power a town of 15,000 homes.

With its vast stretches of shoreline, the U.S. has some 2,300 terawatt-hours of potential near-shore wave power, estimates EPRI. That’s more than eight times the yearly output of the nation’s existing fleet of hydroelectric dams — “a very significant resource,” says Bedard. What’s more, since water is heavier than air, marine systems pack a bigger punch than wind power. Because they work not by impounding rivers behind costly bulwarks but by tapping water’s energy as it ebbs, flows, rises, or falls, upfront costs are lower than for dams. Maintenance to keep away barnacles and similar “biofouling” generally runs higher than for wind. Still, on balance, wave energy will evolve to be cheaper than wind was at similar levels of development, Bedard believes.

The power is more predictable, too. Unlike dam-based hydroelectric generators, which depend on rain or snowpack to keep current flowing and which shut down during droughts, newer “hydro- kinetic” systems exploit less capricious natural forces. “Lunar power” is the term offered by experts such as George Hagerman, a senior research associate at Virginia Tech and co-author of a recent EPRI marine-energy study. “You can’t know if the wind will be up in an hour,” he says, “but you can predict the tide 1,000 years from now.”

Hydropower already propelled one revolution in the U.S. Starting in the Great Depression, the government erected thousands of dams, spreading cheap power across many states. Today they supply 7% of U.S. demand, some three times the combined share of wind, solar, and other renewables. Yet even as existing dams are being upgraded, environmental concerns thwart new building.

EUROPEAN EMBRACE

Before the U.S. fully taps tidal power, it will have to play catch-up. Marine-energy R&D was born in the energy programs of the Carter and Reagan eras, but these experiments lost their funding in the 1980s. “We were the leaders when I started out. Now Britain is entreating us to set up there,” says Verdant’s technology director, Dean Corren. He dreamed up the East River project in the mid-1980s while investigating alternative power at New York University. But then “power got cheaper, and research stopped,” he says.

Across the Atlantic there is a long history of subsidies for renewable energy. For example, the EU-backed European Marine Energy Center Ltd. in Orkney, Scotland, is a one-stop shop for lunar startups. Entrepreneurs can get a test rig in the water and get hooked up to the grid quickly, says EMEC managing director Neil Kermode.

Ocean Power Technologies Inc. in Pennington, N.J., opted for a London stock listing because of stronger interest from European backers, says CEO George W. Taylor. Both the U.S. Navy and Iberdrola, a utility in Spain, have signed contracts to test OPT’s PowerBuoy, which generates energy by bobbing up and down.

In the U.S., last year’s energy bill raised hopes in the hydropower community. By unifying the licensing of offshore wind- and marine-energy projects under the jurisdiction of the Interior Dept.’s Minerals Management Service, “it sets the stage for faster approvals,” says Carolyn Elefant, co-founder of the Ocean Renewable Energy Coalition. But the bill failed to recognize ocean energy as eligible for the sorts of production tax credits that jump-started wind power investment in the ’90s.

At the East River, Verdant is confident its compact submarine turbines are ready for the long haul. Once an 18-month trial is completed, Verdant hopes to get the O.K. to install up to 300 turbines. That would generate enough power to supply some 8,000 New York homes. “It’s our flight at Kitty Hawk,” says Taylor.

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