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Speaking at the CIMAC Congress in Helsinki last week, Harry Robertsson, Technical Director at Stena Teknik, said: "In the future there will be a 'fuel mosaic'."

Robertsson, who has been with Stena Teknik since 1999, was outlining Stena's vision for future ship design. He advised delegates that in fifteen years' time Stena Group's fleets are likely to be driven by heavy fuel oil cleaned by scrubbers but with other fuels playing a growing role.

"Our approach to fuels is driven by the 0.1% sulphur limit in the North European ECA, as our activities for Stena Line and Stena RoRo are very much in this area," said Robertsson. "I agree that we will have a fuel 'mosaic' in the future: different ships on different routes in different parts of the world will be running on different fuels."

Currently, the company has four scrubbers installed and a further three units are planned, but it is potentially complicated work - and expensive at a cost of US$5-10 million per installation.

Other than for the group's LNG carriers, retrofitting for LNG has also been discounted for the time being. The expense of conversion - around US$30 million for a ro-pax vessel - and the loss of power, which Stena estimates could be up to 20%, making it difficult for the ships to keep to schedule, have precluded it.

Commenting on the results of in-depth research Stena has carried out, Robertsson said that LNG could be an option for newbuild vessels, particularly in regions where the infrastructure is in place and the price makes it feasible.

The company's research produced interesting results, Robertsson told delegates in his wide-ranging speech. "What surprised us in this study was that batteries could be an attractive option for short sea shipping (under 100 nautical miles).

"And in the longer term, biofuels and fuel cells will enter the market. But today, marine batteries are three times as expensive as car batteries, and so far the capacity and lifespan of fuel cells are too small."

The company is keen to explore the potential of battery power, initially by looking at battery-powered bow thrusters which may eliminate the need to start the two generator sets when ships enter port - one that powers the thrusters and one for redundancy.

Going forward, the company will also explore options to replace two of the four engines on its ferries with electrical motors. Utilising shore-charged batteries, this will allow emission-free sailing in ports and within the Stockholm archipelago.

Methanol is also firmly in the group's sights following conversion work on the Stena Germanica, which is in the process of having the third of its four medium-speed Wartsila engines converted to run on methanol. The group has also designed a concept vessel - the ro-pax Stena Elektra - which features methanol propulsion and energy storage and which Robertsson suggested could be a reality by 2030.

The future of ship design was a key component of Robertsson speech along with highlights of the company's approach in three core areas - safety, cost efficiency and environmental performance.