This summer, the Norwegian energy company, Statoil, will send a vessel to survey a triangular slice of federal waters about 15 miles south of Long Island, where the company is planning to construct a wind farm that could generate up to 1.5 gigawatts of electricity for New York City and Long Island — enough to power roughly 1 million homes. Construction on the “Empire Wind” project, with scores of wind turbines generating electricity across 79,000 acres of leased federal waters, is scheduled to begin in 2023, with construction completed in 2025.