PORTLAND — A Maine-based tidal energy company brought a prototype underwater turbine the size of a school bus to the city’s waterfront on the eve of an international ocean energy conference, and the company’s president and CEO declared Monday that tidal energy’s time has come.

At 46 feet long, Energy Tide 2 is described as the largest tidal energy turbine ever deployed in the U.S., and it underwent extensive testing last year off Maine’s eastern tip.

Ocean Renewable Power Co. is in the process of building a larger unit – about 90 feet long – that will be deployed this fall and connected to the Bangor Hydro-Electric Co. grid by year’s end.

“Tidal energy has come to Portland, and it’s here to stay,” Chris Sauer, Ocean Renewable’s president and CEO, said before opening its vessel up for tours.

The 35-ton research vessel and tidal power unit arrived in Portland for the EnergyOcean International Conference, which is expected to draw more than 400 people today through Thursday. Christopher Hart, offshore wind manager with the U.S. Department of Energy, will deliver the keynote address.

Ocean Renewable’s research vessel is essentially a barge loaded with electrical equipment and monitoring devices, and with the capability of raising and lowering the turbine unit.

On board, researchers can monitor the speed of the ocean current, the revolutions of turbines and voltage and power output, as well as underwater cameras. The entire system is sturdy enough to operate on its own, and it did so during a two-week period in December when the weather was too rough for workers to reach the device off Eastport.

Ocean Renewable, which holds permits for three sites in the waters off Eastport, where the tide rises and falls 20 feet, isn’t the only U.S. company harnessing the power of the ocean’s tides. New York-based Verdant Power intends this year to put new underwater turbines in New York City’s East River, where they’ll connect to the grid.

Verdant’s design looks a lot like a wind turbine. Ocean Renewable uses rotating foils that lend the appearance of a manual push reel lawnmower. Both companies are awaiting federal approval to proceed.

Depending on the location, Ocean Renewable’s turbines will generate 60 to 150 kilowatts, enough electricity to power 25 to 60 homes, said John Ferland, vice president of project development. The goal is to have up to 3 megawatts of capacity, or about 21 of the units, deployed by 2014, Ferland said.

Monday’s event on the Portland waterfront came nearly a month after Gov. Paul LePage splashed some cold water on offshore wind power, saying that creating jobs through “corporate welfare” is not a sustainable way to stimulate the economy. “The majority of these ‘green jobs’ are temporary,” he added.

Sauer said Monday the governor may have concerns about some forms of renewable power, but he said the governor has supported tidal energy efforts.

Ocean Renewable already has created or retained 100 or more jobs, so the jobs aren’t theoretical, Sauer said. And while it has obtained $14 million in federal funding and $3 million in loans from the state, Ocean Renewable has raised more than that – about $20 million – in private equity, he added.

“This isn’t theory because we’re actually doing it. We have equipment in the water, so it’s a fact,” he said. “We think this is a highly desirable new industry for the state of Maine.”