Rolls-Royce Solutions is developing methanol-combustion engines for tugboats and other maritime applications following studies to determine the most cost-effective decarbonisation solution. In a technical presentation at ITS 2022, Rolls-Royce Solutions director for applications in marine engineering Tobias Kohl explained how the company made this decision while working with Svitzer on future propulsion technologies.
Fuel For The Future
By 2026, Rolls-Royce expects to have developed a methanol-burning mtu engine for tugboats, which will reduce carbon emissions. These engines could be developed from mtu 4000 Series diesel or gas-burning engines that Rolls-Royce already supplies for new tugs. “Our cylinder tests have been successful, and we are currently developing mtu 4000 Series methanol engines,” Mr. Kohl said. These engines will comply with the latest IMO Tier III and US Environmental Protection Agency Tier 4 emissions standards for minimal SOx, NOx and particulate matter.
“In the long term, we need to work towards overcoming the challenges associated with hydrogen and fuel-cell integration to improve the feasible usage of decarbonised fuels,” he further added. For the medium term, Rolls-Royce’s focus is on developing combustion engines and hybrid propulsion. Mr Kohl expects the costs for green diesel and green methanol to remain relatively high in the short to mid-term. Hence, battery-powered tugs have the potential to gain market share, but only if operators are able to live with reduced operational requirements.
A Case Of Fuel v/s Battery
Svitzer group head of technical innovation Thomas Bangslund spoke about balancing propulsion selection, the tug operating profile, infrastructure and operational realities. “The current flexibility of tugs in terms of operation and location might need to be sacrificed, especially when thinking about hydrogen and battery propulsion,” he said. Batteries would be efficient for propulsion, but there is not enough power in the grid and not enough infrastructure for fast and timely charging. In the future, tugs will need to be design-optimized for the intended operating location and operational profile.
Svitzer worked with Robert Allan Ltd (RAL) to design the TRAnsverse tug with a unique towing arrangement, increased stability and enhanced maneuverability.“The idea for the tug started with an innovative new type of towing staple that would allow for 180˚ free movement of the tow line while also generating a high righting moment,” said Mr Bangslund. This allows the tug to safely generate high steering forces without compromising the stability of the tug. This is then coupled with the concept of a double-ended tug to enhance the capabilities of the overhead guide staple with increased maneuverability. This design could be scaled for all types of harbor and terminal operations, especially ship escort.
The Canadian naval architects developed 3D computerized and physical models for thorough assessment, using finite element modeling and computational fluid dynamics. RAL then used HSVA’s ship modeling basin in Hamburg, Germany to “determine which hull appendages would give the best performance and also the optimal placement of the new staple” said Mr Hyslop, Project development director of Robert Allan Ltd. TRAnsverse tug was optimized for four basic operational modes in harbor towage and ship escort. These were push-pull on a ship’s side; center-lead forward; center-lead aft and indirect escort pull at speeds between 6 to 12 knots.
Challenges That Lie Ahead
Svitzer head of decarbonisation Gareth Prowse explained how the Maersk subsidiary plans to achieve its ambitious decarbonisation targets, with the TRAnsverse tug one of the strategy components. He said the scale and challenge of the task of getting to zero carbon emissions is huge as there is a global fleet of around 20,250 tugs, almost all running on diesel. He does not expect the tug industry as a whole, or Svitzer, to be able to decarbonise these fleets through newbuild investments. “The global fleet will need 715 new tugs per year to meet the 2050 target,” he said. Svitzer would need to order 24 new tugs each year, where it currently takes delivery of around 10 per year. Being an early adopter brings advantages, such as being ahead of potential regulations such as the European Union’s Emissions Trading System, which could cover vessels over 300 gt in future years. But there are investment risks and the potential for making an incorrect decision.
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