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SunEdison, a company that grew from making chemicals and components for solar modules to become one of the leading developers of solar farms, is making an acquisition that will give it a foothold in the wind power business.

SunEdison and its publicly traded power plant subsidiary, TerraForm, said on Monday that they would buy First Wind, a leading developer and operator of wind farms, for $2.4 billion.

SunEdison said the purchase would make it the world’s largest renewable energy development company. The deal would increase the generating capacity of the renewable power plants SunEdison is capable of completing in 2015 to about 2.2 gigawatts, from roughly 1.7 gigawatts.

“We felt that having wind would help us double down on our strategy,” said Ahmad Chatila, SunEdison’s president and chief executive. “We feel that electrons are electrons — solar or wind really doesn’t matter for our customers. Our customers are demanding that we have a more comprehensive solution.”

First Wind, based in Boston, is operating or building renewable energy projects in the Northeast, the West and Hawaii. It said its projects had a combined capacity of nearly 1,300 megawatts, or enough to supply more than 425,000 homes each year.

The two companies will pay $1.9 billion upfront for the company and another $510 million if First Wind completes projects in its backlog.

The acquisition fits with Sun-Edison’s growth strategy, Mr. Chatila said. He said the company had been growing at 90 percent a year since 2009.

Over the last couple of years, SunEdison undertook a successful turnaround plan. Two years ago, the company’s stock was sagging as low-cost Chinese solar panels undercut American offerings.

But with the help of a new plan pushed heavily by Steve Tesoriere of Altai Capital, an activist hedge fund that SunEdison surprisingly welcomed into its boardroom, SunEdison has built both solar panels and power-generating projects around the world. SunEdison held a successful initial public offering for TerraForm in July.

The acquisition will help TerraForm satisfy investors looking for a bigger pipeline of projects, Shayle Kann, an analyst with GTM Research, wrote in an email. He added that First Wind had “made a successful foray into solar project development over the past couple years.”