PROVIDENCE — In a near-unanimous vote, the state Senate on Wednesday approved a bill that will allow electricity utility National Grid to sign long-term contracts to purchase power from alternative-energy suppliers.

Passage came after the chamber amended the bill to make it identical to the version approved by the House Tuesday. Even though there is no difference between the two bills, one chamber must pass the other’s, without amendment, before it can go to the governor, who is expected to sign it.

The vote means that both chambers are on the same wavelength on renewable energy. Approval would open the door to large renewable-energy projects in the state, guaranteeing their developers a market for the power they produce.

A solar farm is already on the drawing boards for Coventry. Deepwater Wind is planning an offshore wind farm near Block Island and seeks to move rapidly enough to make it the first such offshore project in the United States.

The only dissenting Senate vote was cast by J. Michael Lenihan, D-East Greenwich, who questioned the need for National Grid to make a 2.75-percent profit on its long-term contracts.

He said the company is already guaranteed a 10.5-percent return on equity, which should be sufficient, and is asking for an 11-percent rate increase.

“In a year filled with financial trouble, I’m afraid I cannot vote for a bill which contains a provision adding a cost of two-and-three-quarter percent to [customers when] that same provider has already been guaranteed, in law, a generous return on its investment, and has a guarantee that covers every dime of cost in acquiring that power,” he said.

Sen. Leo Blais, R-Coventry, said he also objected to the bill, alleging that “the industry has been less than forthcoming in answering questions.”

But he said he would vote for it anyway because it was “a necessary step” toward “green” power and because the solar farm would be in his district.

Sen. V. Susan Sosnowski, D-South Kingstown and chairwoman of the Environment and Agriculture Committee, said National Grid won’t profit from the long-term contracts “until the power is humming.”

She said “most everything [about the bill] has been thoroughly vetted in the committee process and by the PUC [Public Utilities Commission, which must oversee its implementation] and I think it’s a go.”

gemery@projo.com