Concerns over the high amount of fuel and carbon emissions by cruise ships have become more prominent in recent years, causing many of the world’s leading cruise lines to look for ways to cut their emissions levels. This has led to the introduction of solar-diesel hybrids, pure-solar cargo ships, and even several oversized sailing ships. One of the most successful emissions-limiting ships in the cruise world, however, is an LNG cruise ship.
By Michael LoCascio (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia CommonsNew LNG and hybrid designs
One of the newest models in this line of ships is Viking Line's Viking Grace; a 700 ft cruise ship which operates with LNG (liquid natural gas). Using this fuel has helped the ship to reduce its carbon emissions by 30% compared to a standard cruise ship. With a ship of this size using an estimated 60 tons of fuel per day, a cut like this in emissions has the potential to greatly reduce carbon emissions across an entire fleet.
Cruise ships with similar fuel sources have been designed and are now being utilized by other cruise lines. In Europe, a cooperation deal between French STX Europe and Stirling Design starting in 2007 resulted in a design known as EOSEAS.
The EOSEAS relies on a hybrid propulsion system that combines solar power, LNG, biogas recovered from the waste treatment system onboard, and five large sails. The main propulsion system relies on four dual fuel 8MW LNG diesel electric gensets, supplemented by 88,800 ft2 of photovoltaic panels to produce up to 1.08 MW with and average of 270 kWe. While the design has not been fully implemented on any ship, many components of the design are showing up on LNG cruise ships all over the world.
Retrofitting existing ships
In fact, many cruise lines, including Carnival, are ordering new LNG cruise ships or retrofitting old ships in order to comply with new, more stringent, environmental regulations in countries all over the world. Swapping liquid natural gas for the traditional heavy fuel oil or marine gas oil can help meet the requirements of these regulations and provide a hedge against fluctuating oil prices.
In order to make this swap, the existing cruise ship must be taken out of operation for several weeks. Installing new LNG tanks and handling systems often reduces the number of cabins available, since these tanks require more room than most HFO and MGO fuel tanks. In order to mitigate this, prefabricated, LNG mid-body sections have been produced that can be inserted into the space. These designs incorporate the new equipment into the passenger and public spaces, making it possible to actually increase the number of cabins being offered.
As an increasing number of countries, and therefore ports of call, implement tighter regulations on the carbon emissions of cruise ships, it will become increasingly necessary for cruise lines to replace or retrofit their existing ships. With a 30% or more reduction in carbon emissions from LNG ships and their hybrids, this propulsion method is sure to become more common.