Installation of an exhaust gas scrubber aboard a DFDS ferry in Bremerhaven, Germany.

Green Ship of the Future

A group of Danish maritime companies initiated the Green Ship of the Future project to develop and demonstrate green technologies within shipping and shipbuilding to reduce air emissions.

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This unique initiative has been met with great interest globally and received the International Environmental Award from the Sustainable Shipping organisation in July 2009 for being the most environmentally friendly shipping initiative.
The following is a summary of the particular projects MAN Diesel is involved in. More details can be found at: www.greenship.org.
Exhaust Gas Scrubbers
Future regulations regarding sulphur emissions from ships demand the use of low-sulphur fuel. However, exhaust gas scrubbers are accepted as an alternative.
Aalborg Industries’ newly developed scrubbing system can in principle be compared to a large shower cabinet placed in the funnel of a ship. This makes it possible to reduce sulphur emissions to as low a level as if low-sulphur fuel had been used, but in a more economic fashion.
A scrubber’s major environmental benefit is that it can use both seawater and freshwater mixed with caustic soda, making the scrubbing process more environmentally friendly than using chemicals.
The scrubbing system underwent extensive testing during the winter of 2008/09 at MAN Diesel’s test facility in Holeby, Denmark with good results; it was possible to remove almost 100% of the sulphur and up to 80% of the particles from exhaust gas. The first scrubber installation is being installed aboard a DFDS Ro-Ro cargo vessel with completion and commissioning expected this winter.
Lower Ship Speeds within Certifications
The majority of main engines aboard ocean-going ships are low-speed, two-stroke diesel engines designed for a certain power output corresponding to ship speed. As propulsion power decreases, fuel-oil consumption drops, lowering CO2 emissions and improving the engine’s overall performance. This leads to optimised low-load operation of the engine but affects the environmental certification of the engine, especially with regards to NOx.
This project has found two solutions with the potential for low-load optimisation of the existing vessel fleet within the current certifications. The first is sailing at low-load using electronically controlled engines. This enables optimum sailing at far lower speeds than normal, reducing fuel consumption and air emissions accordingly.
The second solution involves cutting out a turbocharger on ships with multiple turbocharged engines; this can be used on both electronically controlled engines and mechanical engines.
Turbocharger cut-out has already been implemented on the A.P. Moller – Maersk Line 8,000 TEU container ship “Maersk Salalah” with a MAN B&W 12K98ME main engine. Tests show that lower ship speeds cut CO2 emissions by 25% per sailed nautical mile, while turbocharger cut-out contributes another 3% reduction.
Auto-Tuning of MAN Diesel Engines
Currently, ship engines are tuned manually to enable safe running within recommended load limits, but leaving a margin for performance optimisation because operating conditions and fuel-oil properties change over time. Auto-tuning enables this margin to be harvested continuously and automatically, resulting in reduced fuel consumption, CO2 emissions and carbon particles.
The auto-tuning concept is based on online measurements of the combustion pressures in the cylinder chambers. An engine control system has been developed that constantly monitors and compares measured combustion pressures to the reference value. The control system then automatically adjusts the fuel-injection timing in accordance with the deviation between the measured value and the reference value to reach the optimal combustion pressure during the next firings.
Auto-tuning reduces fuel consumption for an average vessel by >1%, with a potential reduction of >3% for some vessels. Installing auto-tuning on the >10,000 MAN Diesel two-stroke engines in service would reduce total fuel consumption by an estimated 2 million tons, equivalent to 5 million tons of CO2, or about 10% of the total annual Danish emission of CO2.

Emission Reduction Using Exhaust Gas Recirculation
MAN Diesel has developed an Exhaust Gas Recirculation (EGR) system for low-speed, two-stroke engines that can reduce harmful NOx emissions from ships by 80%.
The EGR system reduces NOx by directing part of the exhaust gas back into the engine’s scavenge air. This reduces the oxygen content of the air in the combustion chamber, thereby reducing the combustion temperature and, as a result, the formation of NOx.
Tests on MAN Diesel’s test engine in Copenhagen have been very promising and show that compliance with the IMO’s forthcoming NOx emission requirements is possible with EGR alone.
A. P. Moller - Maersk is providing a ship for a service test of the prototype EGR system, with the system currently being installed aboard the container ship “Alexander Maersk”.

Optimisation of CO2 Emission and Fuel Efficiency

This project combines MAN Diesel’s Variable Turbine Area (VTA) turbocharger with an MAN B&W ME-B main engine with electronically controlled fuel injection.
Unlike a conventional turbocharger, the VTA turbocharger’s turbine area can be continuously controlled to increase the scavenging air pressure at part-load. This offers significant improvements in fuel efficiency and typically leads to a reduction in soot and smoke.
The MAN B&W ME-B main engine combines electronic fuel-injection control with mechanical control of exhaust valve timing. As such, the engine provides an extremely flexible solution with regards to fuel optimisation and meeting emission regulations.
The first installation of a MAN B&W 6S50ME-B8, combined with a MAN Diesel TCA66 with VTA turbocharger, took place in conjunction with TORM. The initial engine performance test showed an improvement in SFOC at part-loads where the VTA can be optimised. Based on an average load profile, this equates to an annual saving in fuel oil of 95 tonnes, and reduced CO2 emissions of 300 tonnes.
Source:Dieselfacts 4/2009