Norway’s state oil company, Statoil, is considering a massive project that would convert unwanted offshore oil platforms into pollution-free power plants that derive electricity from the movement of ocean waves. Oil platforms in the deep waters off Norway include some of the world’s tallest structures, and dismantling them could cost billions of dollars. At the same time, constructing tidal power plants from scratch would be quite expensive. So Statoil’s idea, still in very preliminary stages, is to tow the platforms to land, convert them into power plants, then tow them to areas with strong tidal currents, where waves would turn the plants’ waterwheels and generate electricity.