Trey Taylor, Verdant's president and head of marketing and business development, estimates his company's turbines have a "water to wire" efficiency of about 40 percent, meaning that 40 percent of the overall water-flow energy turning the turbines is converted into electrical power on the grid. For the RITE demonstration the power generated was provided to two locations on Roosevelt Island—a local supermarket and a parking garage.
Taylor likens his work at Roosevelt Island to another famous first step in the history of technology: "The East River is like our Kitty Hawk," he says, "but eventually it will lead to our 747."
Verdant would like to place additional turbines in the waters around New York City. The U.S. Coast Guard has even mentioned possibly placing turbines in the United Nations's security zone in the East River, Taylor says. "The U.N. seemed to like that because the turbines might discourage boats from driving into that zone, where there aren't supposed to be any boats," Taylor says. Verdant has obtained a preliminary permit from FERC to study the site for an installation that could produce up to five megawatts. The water depth in that area could allow Verdant to install turbines that are seven meters in diameter, which Taylor estimates would translate into 110 kilowatts of power per turbine. "Once we have studied the site and have applied project and economic modeling to the site," he says, "we will engage the U.N. in discussions about building a project in its security zone.
The East River is just the beginning, according to Taylor, who says that the deeper, faster-flowing waters of the Saint Lawrence River that forms part of the border between New York State and Ontario, Canada, have the potential to produce three times as much energy as the RITE project. A key distinction is that the Saint Lawrence is a steadily flowing river, unlike the East River that depends on a tide that flows either north or south depending on the time of day.
Taylor is hoping to be able to sell river-based power to Ontario in 2012, giving his company two successful projects that might attract additional investors. In a third key project, Verdant will work with the U.S. Navy in Puget Sound. The Navy is studying Verdant's triframe turbines for their potential to provide energy to naval bases worldwide, Taylor says. Longer term, Taylor would like to install his company's technology in developing countries, something that will require additional capital. All together, Verdant expects to be producing 22,000 megawatts of power from its various installations by 2018.
A test at a lock-and-dam system
Houston-based Hydro Green Energy likewise make hydrokinetic power systems that generate electricity from river currents, tidal currents and ocean currents. The company struck a deal with City of Hastings, Minn., in late 2008 to test Hydro Green Energy's turbine technology at a U.S. Army Corps of Engineers lock-and-dam system on the Mississippi River.
Hydro Green CEO Wayne Krouse's goal was to develop a technology that could generate electricity without the need for more dams and that could be done at a cost comparable with electricity produced by burning fossil fuels. That meant coming up with a compact, low-cost technology that required a minimal number of parts. "In an offshore or saltwater environment, the more parts you have the more that could go wrong," Krouse says. Making the blades from plastics and carbon-fiber components rather than metal alloys was one solution.
Hydro Green is still working toward its goals. The company's prototype turbine operating in the Mississippi is about 3.7 meters in diameter with blades made from cast aluminum, which Krouse says is fine for freshwater but could pose a problem in salty ocean water.
The Hydro Green turbine uses flow from the nearby hydroelectric lock-and-dam system to simulate the marine tidal environment where the company wants to eventually operate. About 30 cubic meters of water per second flow through the turbine at any given time.