Taking the Heat Out of Big Marine Diesels & Putting it to Work

By George Backwell at November 29, 2013 21:38
Filed Under: Marine Diesel Engines

Waste Heat Recovery Systems (WHRS) from specialist suppliers are becoming increasingly popular to boost the overall plant efficiency of large container ship propulsion installations, reducing fuel consumption and thus carbon dioxide emissions. This is evidenced by ABB’s recent US$23-million order to supply no less than fourteen new 8,800 TEU ships with their WHRS package.

MSC Container Ship: Photo credit ABB

The first seven post-panamax vessels will be built at Dalian Shipbuilding Industry Co. Ltd., (DSIC) and the other seven vessels at New Times Shipbuilding Co. Ltd., for China International Marine Containers Group Co. and Mediterranean Shipping Co. S.A (MSC). ABB say that their scope of supply includes power turbines with control valves, alternators, reduction gears and dynamic compensators. The package also includes two of their latest generation of turbochargers. The electrical output of the system is 1.65 megawatt (MW).

The combination of large main engine size and high onboard electricity requirement (due to power supply demands of refrigerated containers) makes container vessels particularly well suited for WHRS technology and the take-up is mainly by this type of vessel.

Waste Heat Recovery System (WHRS)
 In marine propulsion plants, around 50 percent or more of the energy from fuel is lost to heat when converted to mechanical work by the main engine. By supplementing a ship’s main propulsion plant with a waste heat recovery solution, up to 4 percent of the lost fuel energy can be recovered and converted into electricity. More efficient energy use also reduces CO2 emissions in relation to the engine’s mechanical power output.

Waste Heat Recovery System Energy: Schematic courtesy of ABB

ABB’s improvements in the efficiency of main engine turbochargers allows a proportion of the exhaust gas to be diverted to a power turbine whose rotational energy is used to produce extra electricity for the vessel via a reduction gearbox and generator, reducing fuel consumption and exhaust gas emissions by up to 4%.

After leaving the turbo units, the gasses are channeled into the exhaust gas boiler which uses this energy source to produce steam. The steam is fed into a steam turbine connected to the same generator as the power turbine. This more than doubles the output of electricity from this generator, which can then be fed into the vessel’s electrical grid. The combined output of this recovery method adds at least 10% to the energy efficiency and thus decreases the overall fuel consumption onboard.

ABB mention that these new ships, due for delivery in 2015 and 2016, and equipped with their WHRS propulsion package will serve under a long-term charter agreement to MSC, one of the world’s largest container ship owners.



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