Cruise ship engines: how they work, diesel, gas or hydrogen

Cruise ships have doubled in size over the last quarter century, from 2000 to 2024. If they continue to grow at this rate, by 2050 the largest cruise ships could reach 345,000 gross tons, nearly eight times greats of the Titanic. This would be enough to make us understand how fundamental it will be to think about intelligent propulsion for giants like the one in the opening photo: Icon of The Seas. Measuring 365 meters long and 65 meters wide, it has a gross tonnage of 250 thousand tons and is divided into 20 decks accessible to passengers, the engines, in this specific case six Wärtsilä powered by LNG (liquefied natural gas) which generate 67,500 kW (90,520 HP) of power – must also be used to generate energy for the services of 7,600 fully loaded passengers plus 2,300 crew members. An obvious comparison with the Titanic: the ship that sank in the Atlantic in 1912 carried 2,500 passengers and had a tonnage of 46 thousand tons. Another impressive fact: in 1970, only 21 cruise ships sailed on the seas of the world with a total tonnage of 103 thousand tons, in 2025 there will be more than 515 units for 30 million tons of tonnage. In short, there will be a lot of work to do for those involved in propulsion. In order not to consume too much (think of how much is spent to move ships of this size) and not to pollute too much. Decarbonizing the shipping sector is becoming a political priority, as the sector accounts for around 3% of global CO2 emissions, and a 2020 study by the International Maritime Organization predicted that they could increase by up to 130% by 2050. compared to 2008 levels. Unbearable obviously and not only for politics. While we wait for the future, let’s see how propulsion works for today’s ships.