Of all the developed nations, few have pushed harder than Germany to find a solution to global warming. And towering symbols of that drive are appearing in the middle of the North Sea. They are wind turbines, standing as far as 60 miles from the mainland, stretching as high as 60-story buildings and costing up to $30 million apiece. On some of these giant machines, a single blade roughly equals the wingspan of the largest airliner in the sky, the Airbus A380. By year's end, scores of new turbines will be sending low-emission electricity to German cities hundreds of miles to the south. It will be another milestone in Germany's costly attempt to remake its electricity system, an ambitious project that has already produced striking results: Germans will soon be getting 30 percent of their power from renewable energy sources. Germany's relentless push into renewable energy has implications far beyond its shores. By creating huge demand for wind turbines and especially for solar panels, it has helped lure big Chinese manufacturers into the market, and that combination is driving down costs faster than almost anyone thought possible just a few years ago. The changes have devastated its utility companies, whose profits from power generation have collapsed. The word the Germans use for their plan is starting to make its way into conversations elsewhere: energiewende, the energy transition. Worldwide, Germany is being held up as a model, cited by environmental activists as proof that a transformation of the global energy system is possible.