The Power of the Tides

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 wind[turbines], 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.

Salvatore Salamone is a guest editor for Energy Central's, EnergyBiz Insider. This article originally appeared in the March/April 2007 issue of EnergyBiz magazine and is republished with permission from CyberTech, Inc. EnergyBiz Insider is published three days a week by Energy Central. For more information about Energy Central, or to subscribe to EnergyBiz Insider, other e-newsletters and EnergyBiz magazine, please go to http://www.energycentral.com.