Construction for a solar array at Katama Farm is set to begin this winter, now that the Edgartown planning board approved a special permit for the project this week, clearing the last hurdle for what will be the Island’s largest installation of photovoltaic panels.

The six-acre project will hold four acres of solar panels and produce 1.2 megawatts of electricity to help power the town’s municipal buildings, roughly the equivalent of 150 homes. Combined with two other projects, one at the old landfill and another at Nunnepog, a town well off Edgewood drive, the panels will provide 4.5 megawatts of electricity.

About 2,500 solar panels will be installed at Katama Farm. They are expected to last 30 years.

A special permit was needed for the project because the site is located in the Katama Airfield district of critical planning. The panels will sit in the corner of a parcel nestled in between Aero avenue and Mattakesset Way that abuts the airpark and the Farm Institute, an educational farm.

The site will be surrounded on four sides with an eight-foot green chain-link fence and a three-foot berm with six-foot trees to block the visual impact of the panels.

Edgartown signed a 20-year lease in July with the Cape and Vineyard Energy Cooperative for operating the panels. The energy cooperative subcontracted out construction to American Capital Energy Inc., a six-year-old engineering company based in Chelmsford.

Heavy construction must be completed before June 15, 2012 or after Oct. 15, 2012.

The energy comes clean and cheap to the town — the $6 million project is completely financed through ACE and the cooperative. The town will be the beneficiary of about $269,000 in energy savings between the Katama Farm array and the two other sites.

The project comes as the option to take advantage of federal tax credits nears expiration on Dec. 31. The town of Aquinnah inked a deal this week with Vineyard Power to install a solar array at the town landfill.

Tisbury is also part of a contract with ACE and will be building solar arrays at their landfill, producing 1.25 megawatts.

There were some areas of concern with the Edgartown project, including taking active farmland out of use.

Some abutters have also opposed the project.

“I favor solar energy but I am concerned that enough research has been given to the project,” John Osborn wrote to the planning board. “How many people would approve of solar panels being directly in front of their house, especially when they could be located in areas on the property away from impaired view?”

Paul and Christine Crotty were concerned with the effect on their view and property values.

“One of the primary attributes of our property is an unobstructed pastoral view across the fields of the Farm Institute and the Katama grass airfield with a distant view of the Atlantic Ocean,” they wrote.

Another issue involved rare species that live on the Katama plains. An assessment prepared for the Massachusetts Natural Heritage and Endgared Species Program found that the grasshopper sparrow and the Northern harrier live at Katama, but the report said the area was not found to be a good breeding habitat for either.

Mr. Smadbeck said the panels would pin Edgartown as a leader in the alternative energy field.

“I think I would hope that every community in America would at some point embrace this kind of thinking,” he said. “We’re one of the very first communities to take advantage of this.

“I did want to say we’re proud of what we’re all doing. It’s a good example to set for the rest of the world.”

The vote was unanimous. The planning board is expected to sign the special permit in the next two weeks, after which an appeal period begins for the next 20 days.