It has seemed a visionary idea, but it could now happen.

Ocean Renewable Power Co., of Boston, Mass., in November will test a prototype of a tidal power turbine the company is developing, and is on track for installation of a larger commercial-scale test unit in Knik Arm near Anchorage in September 2008, company president Chris Sauer told an Arctic technology conference in Anchorage Oct. 17.

ORPC is still working to raise the estimated $1.5 million that will be needed for the Knik Arm demonstration, Sauer said.

The prototype test in November will be done in East Port, Maine, but the 2008 demonstration would be in Knik Arm, near Anchorage. If those tests are successful a commercial tidal generation unit could be operating in Knik Arm in 2012, Sauer said.

Meanwhile, another test next year of a river-flow turbine system at Eagle, on the Yukon River, is planned by Alaska Power and Telephone, which operates the local electric utility. AP&T is working with UEK Corp. of Maryland on the project, and has secured the needed $1.6 million of funding in place.

ORPC's turbine generator is new technology but all other systems, such as mooring devices, are conventional, he told the conference. ORPC Alaska LLC, formed for the Alaska project, is working with PND Inc. Consulting Engineers on a design for the anchor system, he said. The Federal Energy Regulatory Commission has issued a preliminary permit for a tidal energy site. A FERC operating permit will eventually be needed, Sauer said.

Sauer said the company has developed a proprietary underwater turbine generation unit that could be a breakthrough in generation of electric power from tidal action, river flow and possibly deep ocean currents

ORPC worked with U.S. Navy scientists in development of its “OCGen” technology, for which patents have been applied. The design calls for turbines designed to rotate in one direction with outgoing and incoming tides, and to work with a single shaft with a magnet generator.

Navy scientists advised ORPC to keep the turbine unit mechanically simple and rugged and with minimal moving parts. It would be placed below the water surface to avoid ice and debris. A power and control system would connect the power unit to an underwater transmission line that would connect with an electrical substation on the shore.

Each 60-foot power generating unit would generate 250 kilowatts if current speeds are 6 miles per hour. An array of four units would generate 1 megawatt, Sauer said. At a small scale generation costs are estimated at 10 cents per kilowatt hour. With a larger arrangement costs could be as low as 4 cents per kwH, he said.

ORPC is working on potential projects in Cook Inlet and the Bay of Fundy in Maine, which have the strongest tidal currents in North America. Two sites in Cook Inlet are being examined, one in Knik Arm, the site of the first installation, and a second location off Fire Island.

If fully commercial installations are done, they would probably have to be at least 10 megawatts, built in modules over time, to justify the cost of the transmission line and other infrastructure.

“The advantages are that there are no discharges into the environment and no visibility issues, since the equipment is deployed underwater. There are no impoundments that are required, unlike hydro power, because the units are installed in free-flowing currents,” Sauer told the conference.

Since they are underwater, the units will not interfere with shipping or recreational boating, he said.

In Alaska there are always concerns about fish, but Sauer said preliminary tests have indicated that the current and the rotating turbines seem to create a pressure buildup in front of the turbine that would cause fish to be deflected around the unit.

“The fish would sense it as a solid object,” Sauer said in the presentation.

Another issue in Knik Arm will be the effects of silt on the turbines. One previous investigation of Cook Inlet tidal power, by the Europe-based Rothschild group in the 1970s, concluded that the heavy silt load of the inlet's tides would cause turbines to disintegrate.

Rothschild envisioned a turbine fixed on the bottom, however, while ORPC's unit would be held in position between the bottom and the surface, where silt may be less of a problem.

A major uncertainty is what effect a possible listing of Cook Inlet Beluga whales as endangered could have on ORPC's project, as well as other Cook Inlet projects. Federal agencies are now considering a request to list the belugas as endangered, which could trigger restrictions.

Sauer is bullish on the technology, but also cautious.

“This isn't the silver bullet to the world's energy problems, but it's part of the answer,” he said.

If the unit performs as is hoped it could have application in rivers, and in the deep ocean. Sauer envisions units installed at depths of 1,000 feet off Florida, where they would generate power with gulf stream currents, which move at about 3 miles per hour.

Those would be large applications, possibly hundreds of units, to pay back the high costs of underwater transmission lines, but ocean current systems of that scale could reliably generate large amounts of power.