Naval architects design LNG and IMO Tier III-compliant tugs as owners opt for greener propulsion or fuels
Naval architects have designed a new generation of tugs with lower emissions using alternative fuels or exhaust gas cleaning systems as owners show a greater interest in trialling different fuels and electric-driven tugs.
Liquefied natural gas (LNG) is the main alternative fuel currently used on tugs. The latest design for an LNG-driven tugboat comes from a consortium in Italy.
Marine Engineering Services (MES) teamed up with Engys and Università degli Studi di Trieste to design Tuga, an escort tug powered by gas. They have been working on the design since the project was officially launched in October 2018. As an added complication, Tuga was designed to operate in shallow waters.
This project received funding of €614,000 (US$729,480), out of a budget of €937,000 (US$1,133,000) from the European Regional Development Fund as part of the Regional Operational Program (2014-2020). With these funds, the partners drafted a 36-m vessel with propulsion based on a modular LNG fuel system.
“In this regard, the layout of the fuel system container will be optimised both in terms of shape and size while meeting all the safety requirements on board,” says Engys.
Its design was optimised using high-fidelity computational fluid dynamics (CFD) and validated using a set of towing tank experiments.
When Tuga is built, it will be equipped with real-time control system software to assess the dynamic equilibrium of the hull body during escort trial operations, based on the input provided by hydrodynamic and propulsion forces calculated during CFD studies.
Tuga has a breadth of 14 m, can store 80 m3 of LNG, accommodate up to eight workers and has a fixed-point pulling capacity of 60 tonnes.
MES was responsible for arranging the fuel containment system and optimising the hull and topside geometries, while considering the safety requirements.
Other naval architects have also designed LNG-powered tugs, with more than 10 LNG tugs in operation including small fleets in Norway, Singapore and China.
A new fleet of LNG-driven tugs is being built for Canadian operations. Sanmar is building dual-fuel escort tugs to a RAstar 4000-DF LNG design for Seaspan partnership HaiSea Marine. Sanmar and Robert Allan Ltd will update tug owners on progress of this project during Riviera Maritime Media’s TUGTECHNOLOGY 2021, to be held 25-26 October in London.
In Japan, Mitsui OSK Lines’ (MOL) subsidiary Nihon Tug-Boat loaded the nation’s first carbon-neutral LNG (CNLNG) fuel on its Ishin tug.
Daigas Energy supplied the fuel at Sakai Senboku Port, Osaka from a lorry on 1 September 2021. Nihon Tug-Boat has a memorandum of understanding with Daigas covering CNLNG supply over several years.
Its carbon-neutral designation means all greenhouse gases generated throughout the lifecycle, including natural gas extraction, liquefaction, transport, production and combustion processes, were offset by carbon credits.
Carbon offset credits are a tradeable form of quantified greenhouse gas reduction and absorption, though the introduction of renewable energy, energy-efficient equipment, or forest management.
Nihon Tug-Boat estimates its use of LNG reduces CO2 emissions by 25% compared with amounts from similar tugs run on fuel oil. MOL expects this industry-first delivery will enable wider adoption of CNLNG in the future as vessel fuel.
Ishin has been operated by Nihon Tug-Boat since February 2019. This 247-gt tug uses LNG to power two Yanmar 6EY26DF dual-fuel main engines, generating speeds of 16.4 knots. It has an overall length of 43.6 m, breadth of 9.20 m and draught of 3.15 m.
Hydrogen has also gained greater interest from tug operators and naval architects. OSD-IMT has partnered with Nedstack to design a fully electric harbour tug, fuelled by pure hydrogen. This Azistern design will use proton-exchange membrane (PEM) fuel-cell technology. The partners’ goal is to develop a zero-emissions vessel to meet operational and safety requirements. They will provide more details during TUGTECHNOLOGY 2021.
New IMO Tier III design
Despite these projects, most global tugboats operate on diesel with an IMO Tier II rating. Some operators are adopting IMO Tier III, where NOx and particulate matter emissions are vastly reduced.
Naval architects at OSD-IMT have developed a new tug design with IMO Tier III-compliant propulsion for smaller harbours. It worked with Voith to develop a tractor tug with an overall length of 23.82 m and bollard pull of 70 tonnes.
Cyclostern 2370 is a compact harbour tug with a shallow draught of 3.5 m, breadth of 12.82 m and the manoeuvrability of a Voith tractor tug. “This powerhouse is able to do the work of a larger vessel for the price of a smaller one, and it can squeeze itself into the tight corners of ports and locks,” says OSD-IMT.
Cyclostern 2370 will have top speed of 11 knots, accommodation for four workers, capacity to store 80 m3 of fuel oil and 9.3 m3 of fresh water.
This design has two Voith Schneider VSP 32 propellers powered by two main engines, each developing 2,525 kW at 1,800 rpm. Cyclostern 2370 is designed with a selective catalytic reduction unit and urea storage of 6.4 m3 for IMO Tier III emissions requirements.
OSD-IMT’s design includes two auxiliary engines producing 98 kW each and a double-drum towing winch, with a pull of 25 tonnes, speed of 30 m/min and a full load of 200 tonnes.
Cyclostern 2370 was also designed with a towing hook of 75 tonnes, forward capstan of 2.5 tonnes and a 2.5-tonne capstan or windlass on the aft.
Voith propulsion manager for research and development Dirk Jurgens says the company supported OSD-IMT in developing this design with CFD calculations for the VSPs and tug hull during bollard pull operations.
US’ first all-electric tug
In the US, Corvus Energy was selected to supply the energy storage system for Crowley Maritime’s all-electric tug eWolf.
This is a subcontract from ABB Marine & Ports, which secured the contract to deliver an integrated propulsion system and advanced vessel control technology for the first electric-powered tug in the US.
Corvus will supply Orca Energy batteries with a full capacity of 6.2 MWh for integrated electrical propulsion, enabling eWolf to complete a full day of towage work before needing to recharge.
Alabama-based shipbuilder Master Boat Builders is constructing this 25-m tug for delivery mid-2023. eWolf will then support shipping activities in the Port of San Diego in California.
ABB is supplying an Onboard DC Grid power distribution system to integrate Corvus Orca Energy for zero-emissions operations and the mechanical L-drive thrusters. The full scope of supply also includes propulsion motors, low-voltage switchboards, transformers and the ABB Ability remote diagnostics system for continuous equipment monitoring and predictive maintenance.
Alternative fuel options debated
Alternative fuel options will be discussed at a leading industry conference in October. Shipping industry leaders will debate the advantages and drawbacks of various alternative fuels and power options during Riviera Maritime Media’s Maritime Air Pollution Conference, Europe 2021, to be held in Amsterdam, the Netherlands on 12-13 October.
There will be sessions on the potential use of biofuels, LNG and LPG on various vessel types, with case studies and technical input from engine manufacturers.
During the conference, there will be a session debating ammonia development, hydrogen and methanol for marine fuels, including an update from the Port of Amsterdam and Proman Shipping.
Potential game-changers in terms of decarbonisation and emissions reduction will also be discussed during two sessions. Experts will present case studies of hybrid and electic-powered vessels and debate the potential of fuel cells, atomics and renewable energy.
Report analyses inland waterways decarbonisation
A report was published in the US analysing potential decarbonisation strategies for inland waterways transportation.
ABS and Vanderbilt University produced this landmark report evaluating the potential of future propulsion technologies and alternative fuels to reduce carbon emissions.
Decarbonization of the Inland Waterway Sector in the US demonstrates the feasibility of near-term electrification of smaller vessels operating on the inland river system. It includes a case study and designs for vessels retrofitted with electrical propulsion.
“This collaborative study evaluates the fuel and technology options that will help drive decarbonisation of the US inland waterways and support a safer and more sustainable fleet,” says ABS chairman, president and chief executive Christopher J Wiernicki. “We are at the forefront of decarbonisation efforts globally and regionally in the US.”
ABS director for global sustainability Georgios Plevrakis says the greenhouse gas emissions profile of US inland waterways was low compared with other shipping sectors. But, “the need to decarbonise operations is growing more pressing all the time.”
He says the sector faces “unique challenges and limitations and will require a bespoke emissions approach.”
This was analysed with Vanderbilt University, working in collaboration with the Vanderbilt Center for Transportation and Operational Resiliency and the Vanderbilt Climate Change Initiative (VCCI).
“While electrification clearly offers smaller inland river vessels swift CO2 gains, the report also explores the wider decarbonisation landscape that will need to be navigated to put this sector on a sustainable footing,” says Mr Plevrakis.
VCCI director Leah Dundon expects the possibilities and pathways identified in the report to be taken forward.
“We are hopeful that a pilot project based on river fleet boat electrification can be accomplished in the near term,” she says, “which would inform scalability potential and cost, as well as further research needs.”
This report is the latest in a series of ABS sustainability guidance and publications, low-carbon shipping outlooks and sustainability whitepapers.
EU maritime environmental impact report published
European Maritime Safety Agency (EMSA) published its first European Maritime Transport Environmental Report in Q3 2021 providing an overview of the sector’s impact. This report was written in collaboration with the European Environment Agency (EEA).
In 2019, maritime transport to and within the EU accounted for 13.5% of transport-related emissions in Europe. However, CO2 emissions generated by the sector in the EU have dropped by around 26% from 1990 levels.
They still account for around 16M tonnes, or 18% of global maritime emissions, according to the report. These emissions reductions are attributed to fleet renewals and greater energy efficiency.
EMSA/EEA’s study also addresses underwater noise and changes in biodiversity impact from shipping. Measurements in the last 50 years have shown noise from maritime is increasing. Organisms are transported mainly through ballast water (up to 25.5%) and hull fouling (up to 21.2%).
Also in Q3 2021, the EU Commission published its roadmap on the revision of the Combined Transport Directive. It released the Inception Impact Assessment setting out the different scenarios to be considered by the directive.
The Combined Transport Directive supports the shift from road freight to lower emissions transport modes such as inland waterways or maritime transport. The revision aims to improve existing support by extending the incentives so transport companies can increase their use of intermodal or multimodal transport.
Riviera Maritime Media will be hosting TUGTECHNOLOGY 2021 in London, UK during 25-26 October 2021 - use this link to access more information and register to attend or exhibit at the event
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