Situated 8 to 12 miles (14 to 20 kilometers) off the west coast of Denmark, the Horns Rev wind farm is the world's largest. The 80 turbines are spread across 7.7 square miles (20 square km), with blades stretching 360 feet (110 meters) into the air. Completed in 2003, the project added 160 megawatts (MW) of power-generating capacity to the country's electrical grid, and it is expected to produce nearly 2 percent of the nation's electric power. European nations have plans to add nearly 5,000 MW of wind power production in the coming years, and nearly 50 wind farms have been proposed for U.S. waters. (Elsam A/S.)
An engraving by J.W. Barber from the 1840s shows the coastline of Provincetown, Massachusetts, dotted with wind-powered salt mills. The artist noted: "The numerous wind or salt mills, and the elevations of sand, give the place a novel appearance."
The Judah Baker gristmill (center) and a salt mill (left) stood near the coast of South Yarmouth, Massachusetts, in 1866 at the height of a boom in "dry-land sailing." The wind powered nearly 1,300 salt- and gristmills along the shores of Cape Cod in the 19th century. The Baker gristmill has since been moved inland and serves as a tourist attraction. (William Quinn.)
Sources: U.S. Department of Energy; California Energy Commission.
Recent advances in the design of wind turbines, as well as government incentives, have made the cost of wind power production comparable to other forms of energy. But calculating their true power-generating impact is tricky. Wind farms often cite total capacity, but average production is typically 70 percent lower because winds do not always blow at optimal strength. (© Elsam A/S.)