People have been using wind power to accomplish tasks for centuries. Wind turbines convert the energy of moving air into electricity. The wind spins the turbine's curved blades, creating torque that turns a geartrain and drives a generator. The generated electric current can be stored in batteries or sent via transmission lines into the electric grid. Huge, utility scale turbines and wind farms power whole cities or neighborhoods, while smaller residential-scale machines can power an individual home or building.
Since 2000, the total installed electric capacity from wind turbines exploded from 2,000 to 37,000 megawatts (as of March 2011). All of these turbines have been installed on land, but the U.S. Department of Energy estimates that the country's coasts are windy enough to meet the nation's power needs many times over. Cape Wind in Massachusetts will be America's first offshore wind farm, and a project called Deepwater Wind in Block Island, Rhode Island, will test a "jacketed design" (similar to deepwater oil rigs) that allow turbines to be sited up to 20 miles offshore.
Since June 2011, the Museum of Science has drawn 100% of its electricity from green energy. Renewable Energy Certificates (RECs) from wind energy facilities across the U.S. match all of the Museum's electricity usage.
One of the biggest challenges of wind power is that the wind is variable. Wind power systems are often connected to the electric utility grid to share clean energy across a large region; the utility provides electricity when the wind isn't blowing. Wind power can also generate electricity at remote sites off the grid or can charge batteries — such as those in plug-in electric vehicles — for later use.