PORTLAND — A Maine tidal power company is partnering with a Canadian project developer to break into a much larger market by installing underwater turbines off the coast of Nova Scotia, the parties said Monday.

Portland-based Ocean Renewable Power Co. and Nova Scotia-based Fundy Tidal Inc. plan to install underwater turbines in the Petit Passage off western Nova Scotia in the fall of 2012, about six months after installing Ocean Renewable’s turbines off eastern Maine, the companies said.

The partnership would get Ocean Renewable into a lucrative market, one that’s subsidized by Nova Scotia’s government as it seeks to make the province a world leader in tidal power.

Maine shares the Bay of Fundy with Canada, and development potential in Canadian waters “is 10 times larger” than it is in Maine, said John Ferland, Ocean Renewable’s vice president.

Ocean Renewable formed ORPC Nova Scotia Ltd., a subsidiary that will do business in Nova Scotia. The goal in the Petit Passage is to install about 15 to 20 of Ocean Renewable’s tidal power units, said Dana Morin, president of Fundy Tidal Inc.

Ocean Renewable, which has tested its system in the waters off Eastport and Lubec, also plans to install a similar-sized system off eastern Maine. That project, aimed at producing 3.2 megawatts for the power grid, was pushed back from this fall until May 2012 because of delays of regulatory approvals and a desire to avoid installing turbines in the winter, said company spokeswoman Susy Kist.

More than 160 billion tons of water flow in and out of the Bay of Fundy each day, and it’s estimated that as much as 2,500 megawatts of energy could be tapped safely, officials say. That’s roughly the same amount of electricity as three nuclear power plants the size of Maine Yankee could produce, when it was operating.

“With the establishment of ORPC Nova Scotia Ltd., Eastport and Lubec are now located in the epicenter of one of the largest tidal energy markets in the world,” said Ocean Renewable CEO Chris Sauer.

Tidal power, like power produced by wind turbines, has ebbs and flows as tides come and go, twice a day. But tidal-energy proponents note that tides, unlike wind, are predictable. And water’s greater density than wind means fewer turbines are needed to create the same amount of power.

Because they’re underwater, the turbines don’t produce complaints about aesthetics, but the harsh marine environment produces its own challenges for engineers.

Ocean Renewable’s tidal power units use rotating foils that have the appearance of a manual reel mower.

The Canadian project is getting assistance from the government of Nova Scotia, which has established a special rate of 65.2 cents per kilowatt hour for tidal power to be paid by utilities to promote community-based tidal energy projects. The so-called feed-in tariff is about six times the typical rate for electricity.

Also, Nova Scotia’s government is making $750,000 available to support the assessment and evaluation of underwater sites for small tidal projects like the one announced by Ocean Renewable and Fundy Tidal.