Cruise lines are paying considerable attention to sustainability. Just this week, the Cruise Lines International Association (CLIA) released its 2019 Environmental Technologies and Practices Report, and Carnival Corporation announced an agreement to install the world's largest battery storage system for a passenger ship.

CLIA highlighted a number of "pioneering innovations to advance environmental sustainability" in the worldwide oceangoing cruise ship fleet. They include:

  • Half of current ships are fitted with exhaust gas cleaning systems, although most operate the systems only when in port or in other emission-control areas. 29 of the 88 new ships on order, representing 42% of the on-order passenger capacity, will have the systems.
  • 26 of those 88 new ships will use low-emission liquified natural gas as their primary propulsion fuel.
  • Both ships and ports are beginning to adopt shore-side electricity systems allowing ships to plug into the electric grid for their energy needs while in port instead of running their engines to generate electricity.
  • More than half of current ships have advanced wastewater treatment facilities onboard. All new ships on order will have them.

Cruise ships use electric motors for propulsion. To power those motors, they generate electricity with diesel engines, gas turbine engines, or both. The diesels are generally less polluting than the types of diesels used in cargo ships, but more polluting than the gas turbines.

Carnival's announcement trumpeted the installation next year of a 10 megawatt-hour lithium-ion battery system aboard the AIDAperla, a ship in its Germany-based AIDA Cruises fleet. (Carnival owns nine cruise lines: AIDA, Carnival Cruise Line, Princess Cruises, Holland American Line, Seabourn, P&O Cruises Australia, P&O Cruises UK, Costa Cruises, and Cunard.)

AIDA has been a sustainability pioneer among cruise lines. Since 2000, every ship built for the line has had a shore-side electricity system ("cold ironing," in cruise-line lingo). In December 2018, AIDA introduced the first cruise ship to run on liquefied natural gas both in port and at sea.

"The integration of innovative battery technology into our green cruising strategy is another important practical step we are taking on our path toward emission-neutral ship operation," said Felix Eichhorn, president of AIDA Cruises. He was quoted in a Carnival news release.

At sea, the battery system will allow the ship to operate more efficiently and consume less fuel. It will do that through peak shaving (feeding supplementary power to the propulsion motors during peak demand) and load leveling (storing power during light loads and delivering it when loads are heavier).

The batteries will also prevent blackouts in case of the fossil-fuel engines shut down.

The ship will be able to cruise on pure battery power for short periods in emission-control areas, such as some Norwegian fjords. It can also use pure battery power when entering or leaving port and use the batteries to run the electrical systems while the ship is in port.