HELIGOLAND, Germany — 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. Many smaller countries are beating that, but Germany is by far the largest industrial power to reach that level in the modern era. It is more than twice the percentage in the United States.