The Successful Marriage of Gas and Electrics


The ferry route from Bergen in southwest Norway to Kirkenes in the north has no less than 34 stops that traverse some of the country’s most cherished and environmentally sensitive coastline.

Currently, diesel-driven ferries run this historic service, but that will change from January 2021 when Hurtigruten switches to gas and electric-powered engines in a progressive conversion of its existing fleet. This is happening partly in response to official pressure but also because of the desire of Hurtigruten chief executive Daniel Skjeldam that the fleet make an environmental statement.

“This is an investment for the future, and a historic day for us, for the environment and for the whole, long Norwegian coastline,” he said in April when Hurtigruten signed a letter of intent with Rolls-Royce. “The combination of battery packs with the most environmentally friendly and effective gas engines in the market will provide a huge gain for the environment.”

The main engines on up to nine of Hurtigruten’s cruise ships will be replaced with two of Rolls-Royce’s latest B36:45L&PG power units that achieve exceptionally low emissions of NOx, CO2, SOx and particulates. Not only will these lean-burning engines keep the Norwegian Government happy because the tender for the route specified the lowest-possible emissions, their development also shows how engine makers are rising to the environmental challenge as regulators tighten the screws on the maritime industry.


In many cases the authorities are under pressure from local communities lobbying for not just cleaner air but for a quieter environment. And it is happening everywhere. That is one of the reasons why Canada’s Blue Heron Cruises’ latest ferry, launched in May, is powered by three MTU Series 2000 M72 engines mounted on a form of shock absorber. “The Series 2000 is undetectable in the [ferry’s] passenger lounge and dramatically reduces the noise that carries to waterfront residential neighbours,” the company reports.

Blue Heron operates out of Tobermory on the northern tip of Ontario’s Bruce Peninsular, a UNESCO-designated area where environmental sensitivity also includes not making too much noise. That is why the engines in the ferry, Blue Heron 8, are installed on pre-engineered rubber mounts that reduce vibration and noise. Even pushing the ferry at up to 40 knots, they meet the local community’s requirements for peace and quiet.

As in the Bruce Peninsular, the increase in the number of designated sensitive areas is serving as a catalyst for cleaner propulsion in passenger ships. One of the challenges is to make engines clean and fast, as on Lake Constance in southern Germany, where MTU is developing for city authorities a purely gas-powered unit to be installed in a rapid ferry due to hit by water in 2019. The new eight-cylinder engine, based on the Series 4000 diesels much used in workboats, will have a rated output of 750 kW.

This is a closely watched pioneering project. No passenger vessel plying inland waterways in Europe has yet met the certification standards that MTU has been asked to reach on Lake Constance.

As MTU informed Passenger Ship Technology, by comparison with a diesel engine that has not been fitted with after exhaust gas after-treatment technology, the gas engine will emit no soot particles, no sulphur oxides, 90% less NOx and 5-10% less greenhouse gas. These virtues mean the engine satisfies the IMO III emission standards in force since 2016, without the need for after-treatment systems. Even better from the viewpoint of the authorities, the emissions “will be significantly lower than the limits specified in the EU Stage V regulations applying from 2020.”

The authorities also want quick crossings. The Lake Constance ferry will be the first on Europe’s inland waterways to be powered by a high-speed, pure gas-driven unit. Its dynamic acceleration will match that of a diesel engine, but the unit promises to lift the bar in other ways. The engine map will be able to display all propulsion modes. The rpm range is so wide that fixed propellers can be used to provide low-cost drive systems. And its power to weight ratio might set new standards – most gas engines on the market are medium-speed units.

Gas power

Gas power is becoming de rigueur in Europe in just about every place deemed to be of ecological importance. This year, Dutch shipping company Rederij Doeksen will launch two new catamaran ferry services on the Wadden Sea, a massive expanse of water in the southeastern part of the North Sea covered in tidal flats and wetlands. Both of the 70 m long vessels will be powered by 16-cylinder Series 4000 gas-driven units, each with an output of 1,492 kW.

As Rederij Doeksen head of operations Richard de Vries explained “On the Wadden Sea it is very important for us that we operate our ferries in a very eco-friendly manner.” The area is listed as a UNESCO world heritage site.

Also built by MTU, these engines are pre-production models. The production versions only started rolling off the assembly line in 2018. The engine manufacturer expects to follow up with the eight-cylinder version currently under development for the Lake Constance ferry. Highly versatile, the eight-cylinder power plants will be suitable for tugboats and special-purpose vessels as well as for ferries.

Waste gas

In the race for cleaner propulsion, MAN Diesel & Turbo’s ethane-driven engines are opening up new possibilities. First installed on a gas carrier some 18 months ago, these units designated ME-GIE have since been developed to operate on almost any gas quality, whether LPG, methane or ethane, and possibly even waste gas in the future.

When the engine was first released, MAN reported keen interest but that fell away in the intervening period. Suddenly though, MAN informed PST, the group has received a run of orders, probably in response to the imminent Stage V emission standards.

Some of the most innovative and bespoke solutions in hybrid propulsion systems are being developed for luxury yachts. When Sailing Yacht A, the world’s biggest wind-driven yacht, was launched in mid-2017, it was powered by an MTU-devised diesel-electric system as well as by the wind. The system boasts seven different drive modes, rather like the ‘sport’ and other functions in a sports car, that enable the skipper to switch between them according to requirements, such as low-fuel consumption, high-speed or low vibration.

The yacht’s fuel-driven engine is married to an E-Drive power pack. Depending on the type of diesel engine, E-Drive can cover electric power ranges of between 100-600 kW per power train.


Dual-fuel engines continue to make progress on environmental and other levels. Wartsila’s 20DF, much-used on smaller passenger ships, operates on the lean-burn principle, meaning the unit lets more air into the cylinder than is needed for complete combustion. The result is that peak temperatures are lower and less NOx is released into the air.

When the 20DF is running in gas mode, it is fully compliant with IMO Tier III regulations without the need to tack on elaborate technology for purifying the exhaust gases. Overall, as Wartsila points out, “dual-fuel technology offers reduced SOx and CO2 emissions as well as smokeless operation [when running on gas]”.

When Spanish ferry operator Baleària launches its new roro passenger ferry in 2019, it will be powered by no less than four purely LNG-fuelled Wartsila engines, the mighty 50DF, four nine-cylinder 20DFs and two of Wartsila’s transverse thrusters. The first LNG-juiced passenger ferry on the Mediterranean, the 232 m long vessel will be able to carry up to 1,700 passengers and 331 vehicles. Baleària has also mandated tough targets relating to the reduction of noise and vibration, even at 24 knots.


Hurtigruten’s conversion to hybrid-powered vessels such as its new ice-class cruise ships caps ten years of development by Rolls-Royce of gas-powered engines. But the form of propulsion is just one, albeit vital, element of a package of technology.

As a Hurtigruten spokesperson told PST “The main technical elements include hybrid technology that makes possible periods of soundless sailing solely by electric propulsion, an energy-saving low-resistance hull, onboard energy-conservation measures, and peak shaving.” The latter describes how batteries charge and recharge under varying power loads in a way that allows the main generators to operate efficiently at a nearly constant load.

Other fuel-saving technologies include L-drive azipull thruster propellors equipped with permanent magnet motors and the latest iteration of fuel-sipping diesel generators.

When the vessels are navigating in narrow waters, in harbours or under dynamic positioniing, the batteries will be used as a ‘spinning reserve’. That is, they will have on tap enough power to eliminate the need for a diesel-driven generator running as a back-up in case the captain needs instant redundant power.

Like the latest engines from competing manufacturers, the B36:45 engines are smaller and quieter than previous models. They vibrate less, even under heavy loads, and emit less structural noise.

In yet another example of the rapid advances in electric technology, Rolls-Royce will also install its SAVe Cube system on the Hurtigruten ferries, which organises all the control systems for electrical power within a single cabinet and switchboard.

Test bed for new technology

The latest breed of hybrid engines builds on earlier developments, such as the diesel and electrical power unit that has driven the Norwegian passenger and vehicle ferry, 85 m, 1,182 tonne Folgefonn, since 2014. Retrofitted into the Norled-owned vessel, it uses Wartsila’s wireless inductive charging technology installed on land and on board. The technology allows the ferry’s batteries to be recharged without cumbersome cables.

In fact, Folgefonn has been something of a test bed for new technology that will inevitably work its way through to larger passenger vessels. Norled and Wartsila Norway are currently using the ferry to perfect auto-docking procedures – that is, berthing a vessel without the captain’s intervention. In two trials, the latest in April, Folgefonn was successfully auto-docked in the harbour in Stord, Norway.

Based on the dynamic positioning technology that has been developed for offshore oil and gas vessels, auto-docking is likely to become a standard form of propulsion in harbours. “We’ve translated our offshore dynamic positioning expertise into a new and exciting potential market for ferries and maybe for cruise ships,” enthused Wartsila dynamic positioning managing director Thomas Pedersen. “The plan is to submit the auto-docking functionality for regulatory approval to make automated docking a vital part of the new offering for the ferry and other markets. It is one of the first steps in fully autonomous shipping.”

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Source: Passenger Ship Technology


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