Sea transport is still of great importance worldwide today. Precisely for this reason, naval engineering is constantly working to innovate, in an era in which the main objective is to reduce the environmental impact of transport.
Let’s take the example of Fincantieri: it is an Italian company that is among the largest and most specialized in the world when it comes to the construction of highly complex ships. Fincantieri has set itself a goal: to build the first ship with net zero emissions by 2035, ahead of the European target set for 2050. Already today, it must be said, their ships have achieved the goal of consuming approximately 50% less than 20 years ago, thanks, among other things, to systems capable of thermally recovering up to 20% of the energy contained in the fuel. But what frontiers are being tested and will be tested in order to reach the goal of zero emissions?
The electric solution
A first frontier is electricity. There are already many modern ships that can provide electricity for ancillary services, even by connecting to shore sockets when in port. Many of these ships are in fact equipped with lithium batteries which come into operation during stops, thus avoiding the use of diesel generators and eliminating emissions near cities. At the moment, however, the energy necessary for propulsion, i.e. to make the ships move, combined with the on-board utilities (which in a large cruise ship consume from 20 to 70 MW) is too high to think about replacing the engines with batteries only. The latter would weigh too much, take up enormous volumes and would not be able to guarantee the same autonomy, not to mention the logistical difficulties of recharging them. The major investments in this field have therefore been aimed at smaller ships, such as small ferries, which sail during the day and stop at night to change the batteries, leaving the exhausted ones on land to recharge.
Liquefied natural gas
Another possible solution for powering large ships is LNG, or liquefied natural gas. LNG has a great advantage, that of polluting less than diesel, reducing CO2 emissions. The downside is the lower calorific value which, together with a more complex storage system based on cryogenic tanks, leads to greater space on board ships and, consequently, a reduction in the payload. Fincantieri has led the way in this field, building both small and large LNG ships, up to around 180 thousand tons in tonnage and capable of accommodating up to 7,000 people including passengers and crew members.
Green fuels
Another solution is “green” fuels. This term refers to fuels of a biological nature, i.e. derived from biomass or from synthetic processes using renewable energy (solar, wind, etc.). Fincantieri has long since begun studying new ships with energy systems modified to allow the storage, treatment and use on board of bio-methanol or renewable diesel (HVO) in the future.
Fuel cells
Few will have heard of the fourth solution: we are referring to fuel cells, powered by hydrogen. They are devices that generate electricity and heat by combining an oxidizer, oxygen, with a fuel, hydrogen, which is naturally carbon-free. It is a technology that, in fact, does not produce polluting substances. This system is currently tested on board a laboratory ship, approximately 25 meters long, called Zeus, built by Fincantieri in collaboration with the CNR, the ENR and the universities of Genoa, Palermo and Naples. For the moment this ship has a limited power, around 130 kilowatts, but its objective is precisely to acquire information on the behavior of fuel cells in the real environment. Another experimental module, with a nominal power of 100 kW, was installed on board the Viking Neptune, with the aim of investigating the rules and regulations on the use of hydrogen in cruise ships.
The green future of large ships will be a mix of solutions
If we therefore wanted to make a prediction of a ship of the future, we could imagine a combination of all these solutions, integrating the advantages in terms of power, space and emissions of each of them. In other words we could see hybrid ships, perhaps even exploiting fourth generation nuclear power.
And then be careful, we talked about fuels, engines, but not about on-board energy optimization and digitalisation. In fact, this too is an aspect in which ships have evolved: today on board the most modern ships the lighting, air conditioning and heating systems and in general everything that can be powered by electricity have been optimised. Systems capable of recycling up to 90% of the waste produced have been implemented. Artificial intelligence will also play its role: ships of the future will in fact be equipped with self-learning mechanisms, so as to identify any waste of energy in the various processes and search for the best solution. The equation is quite obvious: the less energy needs a ship has, the lower its fuel consumption and emissions will be.
