A closer look
Letting a mega-ship idle its massive marine diesel engines in port is roughly equivalent to leaving tens of thousands of heavy-duty trucks running in a parking lot. To stop asphyxiating nearby coastal neighborhoods with sulfur dioxide, modern maritime regulations require 'cold ironing.' Ships must completely kill their combustion engines upon docking and forcefully plug into colossal, high-voltage shore power cables, essentially treating a 100,000-ton vessel like a giant, floating iPhone.
