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From 2018, the Dutch shipping company Doeksen will use two aluminium catamarans, each equipped with the new MTU gas engines, as ferries in the Wadden Sea.
© MTU Friedrichshafen / Strategic Marine
Gas engines replace ship diesel
05.10.2017

New low-emission marine engines

The operation of ships causes considerable pollutant emissions. Future ship propulsion systems must therefore be more environmentally friendly. One possible way is to operate engines with natural gas rather than diesel. They have lower emissions when compared with current diesel engines without exhaust after-treatment. Researchers are developing and testing components and control instruments for this economical new generation of engines. They are aiming to reduce the engines' CO2 emissions and halve them in future.

Established marine propulsion technology consists of variable-speed diesel engines with mechanical propeller drives. In future it is intended that large gas engines will drive the ships as a more environmentally and climate-friendly alternative. Researchers are adapting the engines to the requirements of ship propulsion systems. In further developing the technology of the variable-speed gas engine they are focusing on charging and regulation as the core components in making the engine more efficient.

In further steps, internal and external engine measures are aimed at further reducing the system-related release of greenhouse gases such as methane. The gas engine will then subsequently be integrated into a drive system that combines an advanced liquid gas system, electrical support and intelligent networking.

Project Manager Dr Michael Hönl from MTU Friedrichshafen explains: „The new charging and control concepts enable us to reduce the CO2 emissions by two per cent with gas engines. We have already achieved up to thirteen per cent savings compared with current diesel engines. Later we want to achieve additional savings of up to 25 per cent.“

Conventional gas engines are only suitable for ships to a limited extent

Current stationary gas engines are large diesel engines adapted for gas operation. They are used as continuous power motors for generating electricity. This is why they are mainly designed for the rated power point and high efficiency. Engines for ships' main propulsion systems are operated at variable speeds. They also often work in the lower load range at low to medium speeds. During partial load operation, the efficiency of gas engines drops. The low temperatures can also cause sedimentation and deposits to form, for example on the pistons.

Because ships' propulsion systems have to fulfil completely different requirements than stationary engines designed for uniform power output, it is necessary to re-design components and the control system. Even technologies from the commercial vehicle or passenger car sector can only be transferred to a very limited extent, since the utilisation and operational times of marine engines are significantly greater.

Development steps for optimising the gas engine

In Phase 1 of the project, MTU Friedrichshafen is developing a new gas engine for the propulsion of ships. The first engines will go into operation in 2018. One of the first projects will be a ferry in the Dutch Wadden Sea, where natural gas will be stored on board as LNG (liquefied natural gas). The system is capable of meeting the IMO III emission level without exhaust gas after-treatment. Changing the fuel from diesel to gas reduces the CO2 emissions. However, the equivalent CO2 reduction is diminished by methane slippage. There is a remaining reduction of up to 11 per cent compared with diesel propulsion. The Stadtwerke Konstanz municipal utility company will begin operating a new ferry boat on Lake Constance from 2019. It will be powered by two 8-cylinder gas engines from MTU Friedrichshafen, each with a capacity of 746 kilowatts.

New charging and control concepts make gas engines more efficient

In order to adapt and further improve gas engines to meet the special requirements of marine propulsion, researchers are working on these focal points in Phase 2 of the GAMMA-1 project (Efficient Gas Engines for Next Generation Maritime Applications):

  • A new, highly efficient two-stage exhaust gas turbocharger with a low-pressure axial turbine improves the engine efficiency. It is being designed with new simulation and development tools. The charging group is very compact, which reduces heat losses and gas volumes. This improves the dynamics of the charging process and thus the overall engine.
  • The innovative control concept finds the optimal system setting values independently and in accordance with the statutory, mechanical and thermal boundary conditions. The development of the concept will permanently enable efficiency-optimised operation and thus increased efficiency of the drive system.

Based on the current research and development, the technologies are to be networked to form an intelligent, fully integrated drive system solution. By means of exhaust after-treatment, the researchers are planning to reduce the methane released and – by further increasing the efficiency – to halve the equivalent CO2 emissions of the drive. Renewably generated fuel gas would enable nearly CO2-free marine propulsion. Using Power-to-Gas, CO2 equivalent emissions could be reduced by 95 per cent.

After testing the new charging and model-based control system for mobile maritime applications, the researchers want to investigate whether it can be applied to other mobile gas and diesel engines, for example in the rail or mining industries.

Research for new maritime technologies

The German Federal Ministry for Economic Affairs and Energy is supporting innovations, research and development for low-emission propulsion technologies with 32.2 million euros of funding as part of its "Next Generation Maritime Technology" funding programme. The German federal government sees good market prospects for climate and environmentally friendly products and technologies from the shipbuilding industry („green shipping“). In its „Maritime Agenda“, it stresses that the development of alternative drives and the establishment of new marine fuels can help to meet the more stringent air pollution requirements. In addition, the German Federal Government is promoting the use of hydrogen in inland waterway and maritime transport with the „e4ships“ flagship project as part of its National Programme of Innovation for Hydrogen and Fuel Cell Technology.

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Addresses

Project management, gas engine charging and control
MTU Friedrichshafen GmbH

Optimisation and design guidelines for centrifugal compressors
TU Darmstadt, GLR

Automated networking, integration and coupling
NUMECA Ingenieurbüro

Parametric modelling and integration
FRIENDSHIP SYSTEMS AG

Links

GAMMA-1
Project website of Friendship Systems AG

Energy transition in the transport sector
Federal Ministry for Economic Affairs and Energy funding initiative

Maritime Agenda 2025
The future of Germany as a maritime industry hub

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