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Redefining Fuel Efficiency


4 March 2010


The challenging economic climate means that the push to cut energy emissions has become less of a priority for cruise lines, but as Sauli Eloranta of STX Europe tells Shirley Accini, fuel efficiency measures can lower costs, helping cruise operators turn the downturn to their benefit.


There is no doubt that reducing emissions is a crucial factor in cruise operations today. While emitting fewer pollutants into the environment should be motivation in itself, for operators the main driver in recent years has been the rising cost of fuel.

However, according to Sauli Eloranta, STX Europe’s vice-president of product development and innovation, cruise and ferries, the tough economic conditions have helped the environmental cause.

"The high cost of fuel has always been a concern for the cruise industry: the less fuel consumed the better the results for the cruise lines, and the more value they can give their passengers," he says. "Cruise ship energy management today is developing with greater emphasis on operational cost efficiency."

Implementing technologies to reduce emissions is expensive and, in a tough economy, cruise lines understandably want to keep expenditure to a minimum. But streamlining operations can result in the added bonus of keeping costs and emissions at low levels. "Cruise lines are responding to the downturn by improving their cost efficiencies where they can and this, in turn, is leading to less energy being used," says Eloranta.

Back to the drawing board

For shipbuilders such as STX Europe, the most effective way that operators can improve efficiency and reduce emissions begins at the drawing board. "When looking to reducing emissions, many people focus on technical solutions, but the most effective way is to start at the concept design phase, by finding out how you can minimise the ship’s overall energy demand," Eloranta says. "When you know this, you then work to meet that demand with technology."

"For shipbuilders such as STX Europe, the most effective way that operators can improve efficiency and reduce emissions begins at the drawing board."

A ship’s body is a major factor in fuel consumption. STX has pioneered a wave-dampening aft body, a hull form that dampens the wave system and results, Eloranta claims, in substantial energy savings.

"In the last ten years, we have improved the efficiency of propulsion power by 10-15%," he says. Weld-seam grinding and covering the bulk thruster tunnel openings also achieves resistance savings. "Streamlining the performance of the hull is a question of dimension optimisation and correctly working with measurements to look at the waterline length, the length to beam ratio and hull fullness," explains Eloranta.

Keeping the hull clean through the use of silicon paints reduces marine growth, which can add up to 40% resistance. "Even the slime on the surface can increase resistance by 1-2%," Eloranta adds. "Using podded propulsion technology rather than the traditional shaft propulsion can create propulsion efficiency savings of up to 15%."

The next generation

STX’s ideas incorporate a common sense strategy: ships, no matter how large, have limited space, and a cruise ship design that is based on simplicity and versatility is key. In March 2009, Eloranta introduced his company’s latest concept: the xpTRAY, where all public passenger areas and activities are based in one location, on a wide ‘tray’, reducing ship volume by up to 15%, resulting in higher space ratios and more efficient service operations.

"Centralising all the restaurants means you have a central galley that is more efficient in energy and size," says Eloranta. "When you use less energy there is less weight; less weight means less displacement and less resistance, which in turn means less power and less energy consumption."

The xpTRAY offers economies of scale, but with a lower gross tonnage compared with a standard post- Panamax cruise vessel – 130,000t rather than 160,000t – which results in substantial savings in building costs, electrical load and propulsion power.

The xpTRAY has similarities with STX’s Eoseas vessel concept, part of the company’s new Ecorizon project. The five-hulled ship boasts a new architectural design, uses renewable energy and incorporates environmental technical solutions to reduce carbon dioxide (CO²) by 50% and nitrogen oxide (NOx) by 90%, while sulphur oxide (SOx) and particulate matter are completely eliminated, claims STX.

The ship’s other technical energy saving solutions include:

  • five sails covering a 140,000ft² surface to harness wind energy
  • natural gas to drive generators and supplying heating and cooling needs
  • solar panels to provide the ship with electricity and that act as a natural air conditioning system
  • an advanced heat recovery system that turns waste heat into energy; water is recycled through a waste and water recycling system; rainwater is recovered from the upper decks
  • an air lubrication system that enhances hydrodynamic efficiency by injecting air beneath the hull
  • an innovative propulsion system that helps improve the ship’s efficiency.

The multi-hulled design also provides added stability at sea and opportunities for creating new passenger areas and amenities. Inside the cabins, the décor and furnishings are made from recycled materials.

Burning issues

Within the Eoseas’s engine room, a trigeneration liquefied natural gas (LNG) energy plant supplies heating, electricity and cooling needs. "LNG produces less CO² and no SOx, but there are practical problems in having it on board a ship," Eloranta explains. "Its storage requires large tanks because of its low density." While such fuel efficiencies are attractive, Eloranta points out that LNG is still a fuel of the future. "It is not widely available enough for cruise lines to base their consumption needs on it exclusively," he says. "An LNG vessel can be operated easily in areas such as Norway because the fuel is available in that country, but this is not the situation in the rest of the world."

The same issues arise with biodiesel and low-sulphur fuels. "These fuels have availability and cost problems," Eloranta says. "Once regulations shift towards less sulphur content in fuels, the availability will improve, but today the 0.1% fuel is extremely expensive, so one possibility is a scrubbing system, which would clean sulphur exhaust gases. But it requires a lot of investment to install the equipment and for the volume of energy they consume when in operation."

Wide-scale approach

A true push for sustainability requires a holistic approach and most ships have adopted energy management programmes including power management, automation, energy-efficient LED lighting, timers and motion detectors, and environmentally friendly materials and practices. "It’s important to fine-tune the energy consumption of vessels in different situations and find out what can be done to reduce consumption," says Eloranta.

STX built Royal Caribbean’s 225,000t Oasis of the Seas, which boasts the latest energy-efficiency technology. When vessels reach such proportions, economies of scale mean that the ratio of fuel consumption per passenger is reduced.

"Royal Caribbean’s 225,000t Oasis of the Seas boasts the latest energy-efficiency technology."

While vessels of this size are hard to beat with their 30% potential energy savings compared with smaller vessels, the main challenge today is how similar efficiencies can be made in vessels that are half the size.

However, the Oasis has set a hard-to-beat benchmark in energy efficiency for any future vessel design. "The greatest potential for energy savings is in the larger size of ship, but the downturn might force operators to acquire smaller vessels, and in these cases, the energy management plan is the best option," says Eloranta.

By building a new ship or making adjustments to existing vessels, every company can do something to reduce their fuel consumption.

When the downturn is over and the economy improves, the industry will no doubt focus on sustainability again, but whether the driver is cost or sustainability, both ideals are heading in the same direction.