WARWICK — Governor Carcieri on Friday signed into law legislation that could pave the way for offshore wind farms in Rhode Island.

The bill, passed by both chambers of the General Assembly earlier this month, allows electrical utility National Grid to enter into long-term contracts to purchase “green” energy. For Deepwater Wind, the company proposing more than 100 wind turbines off the Rhode Island coast, the law means having a guaranteed buyer for its energy, a crucial selling point to investors. The legislation will also benefit other clean-power proposals, including a plan to build a solar farm in Coventry.

Carcieri signed the bill at a green-economy conference organized by the Rhode Island Economic Development Corporation and designed to spur an industry that lawmakers say will create thousands of new jobs in a state with the third-highest unemployment rate in the nation.

In remarks before the conference’s 120 attendees, Carcieri said the legislation is coming at a “pivotal point for our state” and the renewable-energy industry throughout the country.

“We are positioned to show the nation this can work,” he said of offshore wind power. “Once we start, you will see this develop up and down the East Coast. My goal is for Rhode Island to become the focal point and the leader to make that happen.”

This was not the first year the long-term contracting legislation had come up for consideration. Last year, the governor vetoed a different version of the bill after it had been approved by both the House and the Senate. The sticking points then included key provisions governing solar power and markups on the power National Grid buys from renewable sources.

There were no such disagreements this year. Despite concern late in the session that the bill had stalled, it eventually passed smoothly through the legislature.

Carcieri was joined at the signing by House Majority Leader Gordon Fox, Sen. Joshua Miller, a chief sponsor of the bill, and Michael F. Ryan, president of the Rhode Island distribution company for National Grid.

Fox spoke of the cooperation with the governor’s office to work out new language in the legislation.

“We have to do this together,” he said. “Our economy is dependent on it.”

Also present were executives from Deepwater, the New Jersey company that is not only pursuing a plan in Rhode Island but was also recently selected by federal regulators to move forward with proposals in its home state and in Delaware.

Ever since Carcieri last year chose Deepwater to develop a wind farm in Rhode Island, representatives of the company have said that the long-term contracting bill was key to advancing the project. Without it, they said, the company would have struggled to tie up the remainder of the financing for the $1.5-billion project.

In an interview after the formal ceremony, Paul Rich, Deepwater’s chief development officer, said that it would have been a major setback if the legislation had failed to pass. But he said the company would not have walked away.

“If we didn’t get this, we would have been back here fighting,” he said.

Carcieri was asked whether the Deepwater project could have been realized without the legislation.

“No. In order to get financing they need to have a buyer for their power,” he said.

Fox was even more blunt, saying that without a contract with National Grid, Deepwater’s energy would have been “worthless.”

Allen Durand, business manager of Local 99 of the International Brotherhood of Electrical Workers, came to the event in support of the legislation. The union says that Deepwater’s wind farms and similar renewable-energy projects would generate many new jobs in Rhode Island. He likened the potential for growth to the auto industry when Henry Ford started production of the Model T.

“It’s going to generate an awful lot of jobs,” Durand said.

The next step in Deepwater’s plan will come Monday, when the board of directors of the Quonset Development Corporation is expected to approve leases for 117 acres in the Quonset Business Park, in North Kingstown, that the company would use as a staging area for its project.

akuffner@projo.com