It might surprise you to learn that using the right data in the right way is the number one expert tip for small cruise ship operators who want to decarbonise. Resident expert Maikel Arts has four more top decarbonisation tips – whether you’re sailing discerning guests to stunning arctic landscapes or delicate island paradises.
The cruise industry as a whole has seen huge growth in passenger numbers in recent years, with figures in 2023 surpassing even the pre-COVID levels of 2019. The market is very diverse too, with ships of all shapes and sizes plying their trade around the world. The small cruise ship segment has followed this growth trend and is also actively investigating new ways to address another megatrend: decarbonisation.
The small cruise ship segment serves a niche market, with well-appointed, intimately sized ships sailing passengers to far-flung destinations where the mega-sized cruise liners simply cannot go. The superyacht-like luxury experience these ships can offer has proven very popular.
Operators in this segment offer bespoke experiences like luxury eco-cruises to the polar regions, or nature-themed adventures around paradises like the Galapagos Islands. In practical terms, global shipping services provider Clarksons defines a small cruise ship as one that is either below 60,000 gross tons or carries 1,000 passengers or fewer.
Just like the rest of the maritime industry, the small cruise segment is facing up to the urgent need to reduce greenhouse gas emissions. However, the small size of these vessels means that the ways available to decarbonise might be a little different compared to larger vessels. Space is at a premium on small cruise ships, so space efficiency is a top priority. They also often sail to remote destinations, so any technology and equipment the operator installs on board needs to be proven, reliable and have redundancy built in.
Maikel Arts, General Manager, Innovation, Cruise & Ferries at Wärtsilä gives us his top five tips to help small cruise ship operators make rapid progress on their decarbonisation journey:
Let’s take a look at each of these tips in more detail.
This is the number one tip because it’s a one of the easiest (and cheapest) ways to reduce emissions and it provides a very fast return on investment. Modern route-planning systems will allow you to use global weather data to plan the optimal route for your small cruise ship. Route optimisation will help your ship to arrive at its next port of call safely and just in time – and minimise the amount of energy expended during the voyage. This in turn minimises both fuel consumption and emissions.
Handpicked related content: Discover how to turn your onboard data into a powerful voyage optimisation tool with the Wärtsilä fleet optimisation solution.
The more data you collect, the more you can do to reduce your vessel’s overall carbon emissions by keeping systems operating optimally. Even exchanging a filter or cleaning an air cooler at the right time can cut fuel consumption by around 2% – and data can tell you when that time is.
While 2% might sound small, it means a lot in terms of your fuel bill – especially when these efficiencies can be achieved for a relatively small cost. You can learn more about how marginal gains like this can be a gamechanger for cutting emissions in this Insights article: One simple secret that will make your emissions strategy look awesome.
When planning newbuild small cruise vessels and upgrading existing ships, every operator needs to think carefully about fuel flexibility.
Some alternative fuels, for example methanol, take up more valuable space on board than traditional maritime fuels like diesel. This is of particular concern to vessel operators in the small cruise segment, where space is at a premium. Converting a vessel to run on methanol requires approximately double the fuel tank volume to maintain the same level of fuel endurance as diesel.
Handpicked related content: Methanol as marine fuel – is it the solution you are looking for?
Another challenge is that it is going to take a long time before alternative fuels like methanol will be available in the kinds of ports that small luxury cruise vessels typically visit. This is why having fuel-flexible engines that can switch seamlessly between fuels with no loss in performance is a big advantage.
If your small cruise ship is currently using diesel, switching to methanol will reduce CO2 (tank-to-wake) emissions by up to 7%. When running on green methanol the reduction can be as much as 80% on a well-to-wake basis. Green methanol also reduces SOx emissions by up to 99% and NOx emissions by up to 60% compared to HFO operation. An efficient, fuel-flexible engine like the Wärtsilä 31 will mean your small cruise ship is ready to sail on cleaner alternative fuels whenever they are available while still being able to burn regular fuel when necessary.
If you’re building a new small cruise ship, smart planning will reward you with big gains in propulsion and auxiliary efficiency. Instead of over-dimensioning – specifying engines and auxiliary gensets based on how much power you think you might need – expert advice assisted by data-driven simulations can help you design a system that provides just the right amount of power. This will optimise your fuel use and minimise your vessel’s emissions.
Installing an energy-efficient engine such as the Wärtsilä 25 or Wärtsilä 31 will give you a great platform to work from.
The size of small cruise vessels means that they are great candidates for hybrid operations. Hybrid ships combine a conventional engine with a rechargeable battery bank. Running a hybrid ship can provide fuel savings of up to 10% compared to an equivalent diesel-powered vessel. This makes it easier to comply with strict emissions regulations in environmentally sensitive areas. A hybrid system also enables zero-emission operation for short periods and smokeless engine starts, which can make your small cruise ship more attractive for eco-conscious passengers.
Many exciting developments are on the cards for hybrid vessels. The trends you’ll want to hear about are all covered in this Insights article: Seven fascinating hybrid ship trends that everyone needs to know about.
Another popular method for maximising the overall efficiency of small cruise ships is heat recovery. This method works by capturing waste heat from the engines on board and using it to power other processes, for example the laundry systems, freshwater production, gallies or onboard heating systems. The Wärtsilä 31 engine can be equipped with a Smart Heat recovery system that can almost double the amount of usable heat from the engines for onboard use.
While space on board might be at a premium, there are two proven energy saving technologies that are perfect for small cruise ships.
The first is hull air lubrication. This technology can cut fuel consumption and emissions by as much as 10%. It works by creating a carpet of microbubbles on your cruise ship’s hull that reduces frictional resistance without impacting your ship’s operational profile in any way.
The second is wind-assisted propulsion. One operator of small luxury cruise vessels, Orient Express Silenseas, is installing rigid sails shaped like traditional canvas sails on board two luxury vessels. These sails will work alongside fuel-efficient Wärtsilä 25DF (dual-fuel) engines, providing propulsive power and adding to the romance of the cruise experience by echoing the sailing ships of old.
Almost every new small cruise vessel being built today will have a shore power connection on board. This means you can plug your ship into the onshore power grid when in port to cover onboard power needs – known as the hotel load – as well as to charge the batteries if your ship has them. Doing so avoids the need to burn fuel and generate emissions by running auxiliary gensets and can reduce your ship’s fuel consumption and emissions by as much as 10%.
From 2030 all passenger and container ships will be required to connect to shore power when they are at berth for more than two hours in a Trans-European Network port. So if your small cruise ship is sailing within the EU, shore power is essential – but even if you are not sailing within the EU it is likely that shore power will become more common.
If you operate a small cruise ship, my top five decarbonisation tips are: use data, build in fuel-flexibility, maximise overall efficiency, install energy saving technologies, and use shore power.
How many ways to cut greenhouse gas emissions of your vessels could you list? Three? Ten? Don’t worry if you can’t come up with more ideas. The 50 best ways are all collected in this go-to eBook to inspire you: 50 great ways the maritime industry could reduce its greenhouse gas emissions.
Image: ©PONANT-Daniel Ernst
