Kinetic hydropower

There's no question that climate change poses one of the greatest threats to the integrity of the world's ocean ecosystems. At the same time, the oceans are also a source of significant renewable energy resources that can potentially play a major role in addressing climate change. Wind, waves and tides -- fueled by radiation from the sun and the gravitational pull of the moon have the added benefit of being in close proximity to the world's major population centers (and electricity demand). The question is: can these resources be tapped in ways that do not compromise the marine environment or conflict with other commercially and culturally important uses of the oceans?

Offshore wind has received the lion's share of headlines of late, due in large part to the incredible trials and tribulations of the Cape Wind project. But wave and tidal technologies have been quietly making progress amidst the clamor of the more high-profile initiatives. (GW)

Power of the Tides
By Salvatore Salamone
Energy Biz
March/April 2007

A pilot project in New York's East River is evaluating the use of underwater turbines to generate electricity. If the project bears fruit, the technology could have widespread applications.

The effort, formally called New York's Roosevelt Island Tidal Energy Project, is being conducted by Verdant Power and the New York State Research & Development Authority. As part of the project, Con Edison is using the electricity produced by the turbines to power a grocery store and parking garage on Roosevelt Island, which sits adjacent to midtown and upper Manhattan in the middle of the East River.

With the project, three-bladed turbines from Verdant Power are used. Each turbine can generate from 16 to 32 kilowatts of electricity. In December, two turbines were put into place. One was pushed to its limit to gather operational data. Its blades collapsed. The other remains operational. And the companies plan to deploy about a half dozen more turbines in the spring.

There is great interest in the in-stream power generation. The water current driven turbines offer some characteristics that might make them more appealing or more practical than some other renewable power sources.

"Compared to other sources of distributed generation, this technology is not episodic," said Trey Taylor, president of Verdant Power. He noted that you can look at a tidal chart and know what the currents will be on any given day in the future. This means utilities using the technology would be able to predict and forecast exactly how much power they could derive on a regular basis from a group of turbines. That is not something that utilities can do with solar or wind generation systems, which depend on the weather conditions on any particular day.

Additionally, the fact that the turbines are underwater eliminates a problem many wind generation projects have faced. To be precise, many wind projects around the country have encountered stiff local "not-in-my-backyard" resistance.

Like windmills, the underwater turbines still have to go through a licensing process. One aspect of the project will be to determine the environmental issues with using the technology, such as the impact of the turbines on marine life.

New York's East River, thanks to its incredible currents, is turning out to be a great place to test in-stream hydropower generation. In a separate project funded by the U.S. Department of Energy, the New York City Department of Parks and Recreation is in the early stages of developing a system that combines solar, wind, and tidal-power units. Another firm, Natural Currents Services, which develops hydro, tidal, and ocean energy systems, will build the hybrid plant, according to the New York Post.

The Technology's Potential

Underwater turbines can be driven by currents in oceans, rivers, and even canals. The energy produced by tides or in-stream currents driving an underwater turbine is called dam-less, small-scale, or kinetic hydropower.

There are many regions of the United States that are well suited to using this technology including most major rivers and areas with strong ocean tides, such as the northeast, Pacific northwest, particularly in the Puget Sound, parts of Alaska and California, particularly in the Golden Gate area.

Additionally, there are many other places where the technology could be useful. For instance, underwater turbine technology "could enable economic in-stream hydropower generation from free-flowing sources of water, such as canals, waste water treatment plant outfalls, power plant cooling towers and ocean tides," according to the financial industry research firm SNL Financial.

SNL Financial adds that the U.S. Department of Energy estimates that U.S. rivers could generate 30,000 megawatts using this in-stream technology and the devices could potentially produce another 10,000 megawatts from industrial flows and canals.

Interest in these forms of power generation is gaining industry appeal. The Electric Power Research Institute has recently published a number of reports and is involved with a number of tidal and in-stream energy-generation projects.

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