wind farm
n. A collection of generators that convert wind power into electricity.
The sandy shoals about two miles off Skegness' beaches provide the ideal foundation for one of the world's first offshore wind farms, which will convert the strong air current into hundreds of megawatts of electricity. Due to begin construction late next year, the Skegness farm will consist of 60 steel towers, each standing in about 30 feet of water and jutting nearly 200 feet into the sky. The structures will be topped by powerful 2-plus megawatt turbines driven by massive rotor blades with wingspans wider than a Boeing 747. Strung across the water in long rows, the towers will be linked by an undersea cable that will send the electricity they produce to an onshore substation, then to about 150,000 homes near England's eastern seaboard.
—Alex Markels, “Sea Change,” Wired, March 01, 2002
1978 (earliest)
The state Energy Commission has predicted that by 1995 "wind farms," groupings of 3,000 small windmills, could provide up to 10 percent of the electricity utilities sell homes and businesses.
—Jennifer Kerr, The Associated Press, January 31, 1978
Using wind as a source of power first became popular after the OPEC oil crisis of the mid-70s. So it's not surprising that the earliest citation for this phrase is from around that time.