General Electric’s giant new wind turbine, which can produce enough power to light up a small town, is stoking a renewable energy arms race. This wind turbine is so large, it is difficult to photograph; the turning diameter of its rotor is longer than two American football fields end to end. When assembled in arrays, the wind machines will have the potential to power cities, supplanting the emissions-spewing coal- or natural gas-fired plants that form the backbones of many electric systems today. They will be deployed at sea, where developers have learned they can plant larger and more numerous turbines than on land to capture breezes that are stronger and more reliable. GE’s innovation has “shaken the industry” and is causing competitors to try to catch up.