EASTPORT, Maine — Months of underwater testing in Cobscook Bay of experimental, tidal-based electrical generation technologies were not without its challenges, according to a research report recently filed with the Federal Energy Regulatory Commission.

The Portland-based Ocean Renewable Power Co. said in its 653-page, 2012 environmental monitoring report on its Cobscook Bay Tidal Energy Project that research to date demonstrates “improved knowledge of our TidGen power system’s installation, operation and interaction with the marine environment,” according to Nathan Johnson, ORPC’s director of environmental affairs.

Years in development at a test site in the Washington County community of Eastport, ORPC’s underwater turbine resembles the blades on a hand-pushed rotary lawnmower. The device is 98 feet long, 17 feet wide and 17 feet high and is anchored on a frame that positions it 15 feet above the sea floor. It was engineered to be installed at depths of 60-150 feet, using the force of tidal ebbs and flows to power turbines that are now generating electricity for underwater transmission to an onshore Bangor Hydro Electric Co. substation.

After being submerged since mid-September at a 60-acre Cobscook Bay test site at a depth of less than 100 feet, ORPC’s turbine array was pulled from the water in late October for an onshore quarterly inspection, which is required under the terms of a $10 million Department of Energy federal research grant.

That inspection showed a number of issues that needed to be addressed while the turbine was in dry dock in Eastport for about six weeks. It was determined that electromagnetic “noise” from the turbine’s operation had compromised the integrity of data collection and that misalignment of submerged connectors had compromised data from water speed sensors.

The dry dock inspection also showed that loose bolts required replacement and the need for alternative approaches to preventing future bolt loosening caused by vibration. At one point a failed resistor in the circuit controlling the turbine’s brake “effectively locked out the tidal generating unit.”

Those fixes in place, the turbine was again submerged in the test area on Dec. 12, 2012.

Congratulating ORPC on its first year of testing was U.S. Sen. Angus King, Jr., an advocate and one-time investor in wind energy, who issued this statement Wednesday:

“Maine is a leader in the country in the area of tidal power generation and deep water offshore wind,” King said. “The Ocean Renewable Power Company turbine which was installed last summer is a great example of the potential of clean renewable marine based industry. This is a project where government worked hand in hand with the private sector around regulatory issues and in the end it was to the benefit of the public.”

A next-generation of ORPC’s technology now being planned for deployment in Western Passage will operate in fast-flowing waters at depths ranging from 150 to 400 feet and will be tethered to the bottom, not anchored. In some areas, turbine arrays will be stacked vertically.

Unlike Cobscook Bay, the Western Passage is a busy commercial shipping lane and an active fishery that is also populated by a variety of whales, dolphins and seals.

Initial research at the Cobscook Bay test site included environmental impact monitoring by state and federal agencies, including the U.S. Fish & Wildlife Service and the Maine Department of Marine Resources. That monitoring showed the Cobscook Bay test site, including its installation, showed no significant impact on marine mammals, the fishery or migratory seabirds.