MAN embraces hybrid future & decreased ferry emissions by 15% through the hybrid process.

MAN Diesel & Turbo’s 32/44CR engine is part of a successful hybrid diesel-electric propulsion solution employed by Scandlines Ferries on a busy route between Denmark and Germany.
Scandlines' 'Prinsesse Benedikte' employs a hybrid propulsion system that incorporates a MAN Diesel & Turbo 32/44CR engine
Scandlines' 'Prinsesse Benedikte' employs a hybrid propulsion system that incorporates a MAN Diesel & Turbo 32/44CR engine

In times of great need for more intelligent fuel use in marine applications and flexible propulsion systems is great, one of the world’s leading designers of marine diesel engines is already invested in a future that increasingly embraces hybrid solutions.
As the industry saw at MEPC 70 last month, emissions regulations are getting stricter. For the time being, MAN Diesel & Turbo believes that primary methods (modifications to diesel engine design) and secondary methods (emission solutions integrated into the engine, such as Exhaust Gas Reduction and Selective Catalytic Reduction) currently suffice to meet these. However, the future – when higher fuel prices become more likely – will demand more innovative and flexible solutions.
Projects featuring diesel engines and battery hybrid solutions are already notching up a number of noteworthy references. One such example is the Danish ferry Prinsesse Benedikte, which features an MAN 32/44CR engine as part of the vessel’s innovative hybrid-propulsion solution.
Ole Grøne, senior vice president of low-speed promotion & sales, MAN Diesel & Turbo, says: “For many ships within a wide range of marine segments, a hybrid diesel-electric system offers significantly lower fuel consumption, improved manoeuvrability and lower emissions compared to other, existing systems. Noise and vibration levels are also reduced, providing comfort to the crew and the immediate environment. There is no doubt but that diesel engines will continue to play a central role in ship propulsion in the future as they are ultra-reliable and embody a wealth of technology that is invaluable for modern vessels. The ease with which they can work in train with other propulsion methods, such as electric hybrids, is also key to their future.”
Since September 2013 Prinsesse Benedikte, the largest hybrid vessel ever built, has transported its 900 passengers and 300 vehicles with the aid of a new lithium-polymer battery system that has reduced ferry company Scandlines’ fuel costs and the vessel’s environmental impact. As part of its hybrid propulsion system, the Danish ferry features an in-line six-cylinder MAN 6L32/44CR engine.
Scandlines employed energy solutions provider Corvus Energy to provide the electrical-systems expertise that enables the 124m Danish ferry to sail the Rødbyhavn to Puttgarden route with her hybrid system.
Ultimately, Prinsesse Benedikte’s conversion to hybrid running was a simple affair, with one of its engines was replaced with the battery pack to run with the MAN 32/44CR engine. With its advanced lithium-polymer battery solution, the hybrid system reduces maintenance costs, fuel consumption, greenhouse gas emissions and noise production, while increasing revenue and technical efficiency.
The energy storage system aboard Prinsesse Benedikte is capable of delivering the high peak-discharge outputs required for vessel starts. The vessel’s battery modules can recharge in 30 minutes from shore or generator power, offering the ferry the option of re-charging from the shore-based electrical grid – which in Denmark is often fed by green energy from renewable sources such as windmills/wind power – or diesel power from the vessel’s generators when necessary.
This solution does not require a cooling system, reducing engineering costs and potential failure points. It is also highly fuel efficient as the system has a load-levelling functionality that minimises the periods that Prinsesse Benedikte’s diesel engines run at a non-optimal load. Reducing the reliance on diesel fuel significantly reduces operating costs as fuel can account for 60% or more of a vessel’s total operating budget.
As well as its load-levelling ability, the battery system can drive the 16,000-tonne ship for half an hour or so without diesel fuel, dramatically reducing air and noise pollution close to port. Furthermore, the battery modules are a reliable, cost-effective alternative for hybrid ferries and almost triple diesel driveline lifetimes as the vessel can now operate on full electric propulsion while in harbour.
Since the successful conversion of Prinsesse Benedikte to hybrid running, Scandlines has similarly re-built each of its four ferries that sail between Rødby and Puttgarden. The subsequent reduction in weight and switch to electric has allowed each vessel to slash its fuel consumption by 1.2 million litres a year. The lithium-polymer battery pack aboard each ferry delivers 2,900kWh.
With the battery pack on board, the main diesel engine runs constantly at 85% load, including when tied up in port between journeys – 85% is considered the ideal load at which combustion is optimal relative to power and emissions. One diesel engine has proven to be enough to maintain a normal operational speed in good weather, and the battery pack is used to take the top off the power demand. Each ferry can sail for 30 minutes at 14 knots, or for an hour at a lower speed on battery power alone.
The Scandlines vessels represent the world’s largest battery installations in operation at sea. The experience gathered thus far shows that each ferry can manage on just one diesel engine and the battery pack in good weather. With the knowledge gained from the Rødby-Puttgarden route, it became obvious that Scandlines could have even removed a further engine from each ferry, in the process reducing the weight of the ferry even further. Scandlines has decreased ferry emissions by 15% through the hybrid process.