PORTLAND — The U.S. Department of Energy is awarding another $3.7 million to a University of Maine-led offshore wind power pilot project, a sign of confidence in the project, officials said Monday.

The DOE found enough promise in the project’s progress to spend the additional money, bringing the total investment to $6.7 million and allowing the consortium to complete engineering and design work and to address remaining technical concerns, David Danielson, assistant secretary, wrote in a letter to Sen. Angus King.

Habib Dagher, leader of UMaine’s offshore wind research team, said the DOE was impressed by the Maine project’s low cost. It’s also the only project with a power purchase agreement in place.

“The big goal is to close together all of the pieces that you need to be construction ready. That means closing on financing for the project. Certainly our project is in good shape with the power-purchase term sheet,” Dagher said Monday. Financing will be a combination of public money, private investment and borrowing, he said.

Last year, the U.S. Department of Energy passed over the Maine Aqua Ventus project for a $47 million grant, but provided $3 million to keep the project alive. The winning proposals in Virginia, New Jersey and Oregon are currently behind on project milestones, creating the opportunity for Aqua Ventus to leapfrog the other projects.

Aqua Ventus, which would put a two-turbine, 12-megawatt project off the coast of Monhegan Island, is unique because it’s the only one to use concrete for the floating platforms.

The DOE is impressed by the design because it holds the potential to drive down costs while moving construction closer to project sites, spreading out the economic impact, Dagher said. The technology can be used to access more than half of the offshore wind resources in deep waters within 50 miles of the coast, as well as to create jobs, Dagher said.

UMaine already has tested a scaled-down version. A 65-foot-tall turbine deployed off Castine, Maine, performed as engineers expected, even as waves reached the equivalent of 75 feet.

Hopes for an offshore wind project are pinned on Aqua Ventus after Norwegian company Statoil spiked its plans to put four three-megawatt wind turbines 12 miles off Maine’s coast. Statoil’s decision followed maneuvering by Republican Gov. Paul LePage’s administration to reopen competitive bidding.

UMaine, which was selected as an alternative, is waiting in the wings if any of the winning proposals fail to meet milestones by May 1. Those programs with the greatest likelihood of success will be selected to move forward after May 31, Danielson wrote.

As part of the effort, UMaine will unveil a $13.8 million expansion of the Advanced Structures and Composites Center next week. The new structure will allow scientists to produce wind and waves of varying intensity, recreating the fury of the North Atlantic in a controlled setting on campus in Orono, Dagher said.