Tugs are being built with hybrid-electric propulsion and NOx abatement technology to meet tougher environmental rules
There is a revolution coming in tug design owners need to prepare for. Changes in towage and environmental requirements this decade will shape the future design of tugs for harbour and terminal operations, coastal and deepsea towage, salvage and emergency response.
Owners can expect more pressure from ports to include green propulsion in next-generation tugs to reduce emissions in harbours and terminals, particularly where these are close to residential areas.
As more ports introduce shore-based ship charging, there will be a greater push for hybrid-electric propulsion. With increasing awareness of the health issues associated with emissions from diesel engines, tugowners will be required to remove harmful compounds, such as nitrogen oxides and particulate matter.
Tugs will need to be built to comply with IMO Tier III, or US Environmental Protection Agency (EPA) Tier 4, requirements with emissions abatement technology or alternative fuels.
But these environmental adaptations must not impact tug performance, including bollard pull and manoeuvrability. Nor should there be any detrimental effect on tug stability.
Below we highlight the most technically advanced tugs ordered in the past 12 months by early adopters of greener propulsion and environmental technologies.
Gisas Shipbuilding Industry took a bold step towards minimising its environmental footprint when the world’s first all-electric tug was delivered at the end of 2019. Gisas Power has become a symbol of what the future holds, demonstrating performance from tugs powered by batteries and shore power. Other owners and authorities are following, with Port of Auckland ordering an electric-powered tug from shipbuilder Damen Shipyards.
In the US, the Port of San Diego in California has been given US$2M funding from US EPA, along with US$17.6M funds from public and private partners, to order an electric-powered escort tug. This will replace an elderly tug powered by diesel engines, saving 204 tonnes of NOx, 5,220 tonnes of CO2 and three tonnes of particulate matter.
Gisas Power was built at TK Tuzla Shipyard to a Zero Emissions Electric tug (Zeetug) design by Navtek Naval Technologies who collaborated with Turkish power systems integrator BMA Technology, drive and converter supplier ABB and energy storage systems provide Corvus Energy on this industry-first project.
Istanbul-based Navtek general manager Ferhat Acuner explained the technology on Gisas Power during Riviera’s Maritime Hybrid, Electric and Fuel Cell Webinar Week and Tug Technology Webinar Week in Q3 2020.
“This is a new era for the shipping business,” Mr Acuner said. “Zero-emissions boats and ships are the future of the shipping business.”
Gisas Power is the first built to a Zeetug30 design. It has an overall length of 18.7 m, beam of 6.7 m, hull depth of 4.7 m and design draught of 3.5 m.
Its propulsion generates bollard pull of 32 tonnes and gives this tug a service speed of 10 knots.
Gisas Power draws its power from two Corvus Energy 1,450-kW lithium-ion battery packs. For safety, the tug has two redundant battery rooms, one fore and one aft, maintained at a constant temperature by a cooling system.
A full charge for the tug can be accomplished in an hour by a quick-charging station designed by Navtek. It also designed the Smart Tug Energy Management System (STEMS) to optimise electric power consumption, analyse the operational profile and extend the range of the electric tug.
As compared with similar-sized, diesel-mechanical tugs, Mr Acuner said the all-electric Zeetug30 is expected to save 210 tonnes in CO2 emissions and 9 tonnes of NOx emissions in a year.
There are also operational cost savings, as Mr Acuner said expenses for the Zeetug will be 15% of that of a similar-sized diesel tug. He explained the vessel’s batteries will have a life of 10 years.
First hydro-mechanical hybrid
There are rare examples of tugs powered by batteries in a hybrid system. Port of Luleå’s hybrid propulsion ice-breaking harbour tug Vilja was delivered in 2019.
Most hybrid propulsion tugs built so far have power take-in or power take-out motors and shaft generators, supplementing power to propulsion and onboard generators.
Examples of these include the fleet of tugs Great Lakes Towing is building at its own shipyard in Cleveland, Ohio US, with hybrid propulsion mechanics on board. The latest of these to be completed is Pennsylvania, which started operations in Q4 2019.
Great Lakes launched the fifth in this series of ice-class tugs, Wisconsin, in Q3 2020 and has started a sixth of these vessels.
They are built to a Damen Stan tug 1907 Ice design with more than 30 tonnes of bollard pull. These are powered by two MTU 8V4000 Tier III diesel engines and a Logan-supplied hybrid power system, installed by Canal Marine & Industrial.
Early in Q1 2020, an alternative approach to hybrid propulsion was demonstrated on a tug newbuilding. Sanmar Shipyards built Boğaçay XXXVIII to a Robert Allan design with the world’s first advanced variable drive (AVD), which reduces emissions.
This is a unique application of hydro-mechanical hybrid propulsion in the marine segment, with technology supplied by Caterpillar. A primary advantage an AVD is the continuously variable transmission, which can modulate propeller speed down to zero revolutions by a slipping clutch.
AVD can also spin the propeller faster than would be possible if the engine was directly coupled to the drive. This enables engines to operate in their peak efficiency zone instead of operating along the propeller demand curve at higher fuel oil consumption resulting in significant fuel savings.
With a fixed-pitch propeller pitched for bollard conditions at zero knots, this feature enables full power to be taken from the engine when free running, much like controlled-pitch systems.
Boğaçay XXXVIII was built to a RAmparts 2400-SX design and ABS class for an A1 towing vessel with 70 tonnes of bollard pull.
It has an overall length of 24.40 m, moulded beam of 11.25 m, a hull depth of 4.38 m and a maximum draught of 5.40 m.
EPA Tier 4 compliance
In the US, several harbour tugs have been built with propulsion systems compliant with EPA Tier 4 emissions reduction requirements. It is a legislative rule and increasingly expected by US ports for new escort and harbour tugs.
Owners such as Brusco Tug & Barge, Crowley Maritime, Bisso Offshore, McAllister Towing & Transportation and Moran Towing have ordered new tugs to EPA Tier 4.
Foss Maritime, part of the Saltchuk Marine family of companies, ordered a series of EPA Tier 4-compliant escort tugs for assisting ships into US west coast ports.
At least four of these were ordered from Nichols Brothers Boat Builders in Freeland, Washington state, of which the first two – Jamie Ann and Sarah Averick – have been completed. The other two will be Leisa Florence and Rachael Allen.
These azimuth stern drive ASD-90 class tugs are built to Jensen Maritime’s Valor design, to US Coast Guard’s Subchapter M regulatory standards and with ABS’ Loadline certification.
They each have two MTU series 4000 main engines driving Kongsberg’s US255 azimuth thrusters. For Tier 4 compliance, they have selective catalytic reduction (SCR) systems for removing NOx emissions.
Foss’ ASD-90 tugs have an overall length of 31.7 m, moulded beam of 12.2 m and moulded hull depth of 5.2 m, plus 90 tonnes of bollard pull.
LNG dual-fuel propulsion
Outside North America, owners and port operators have invested in LNG-powered tugs and bunkering infrastructure. PSA Marine has been operating dual-fuel tugs in Singapore for more than a year with PSA Aspen providing the operator with significant LNG fuelling experience.
In China, Ningbo Zhoushan Port has also gained LNG bunkering experience with dual-fuel tug Yong Gang Xiao Tuo 60. This 750-gt tug was built to a Robert Allan RAstar 3800-DF design by Jiangsu Zhenjiang Shipyard, delivered at the end of 2019. It has China Classification Society (CCS) notation for port and coastal operations and for fire fighting.
Dual-fuel Niigata 8L28AHX-DF main engines provide 2,389 kW of power at 800 rpm to Kongsberg US 255 controllable pitch (CP) Z-drives. These give the tug a top speed of 13.5 knots and bollard pull ahead of 80.3 tonnes.
Gloryholder Liquefied Machinery supplied the fuel gas system and deck-mounted LNG tank with gross storage capacity of 55 m³, giving this tug a range of more than 700 nautical miles in gas mode. This can be supplemented by an additional range of nearly 1,700 nautical miles when the engines are in diesel mode, from fuel oil storage of 83.3 m³.
Also in China, shipyards are completing tugs to a new CCS notation denoting their intelligent online systems. This is a growing trend in tug construction and operation with more monitoring, alert and intelligence deployed in tugs. At the end of 2019, Sanlin Shipyard of Shanghai Harbour Fuxing Shipping Service delivered two tugs, Jin Gang Lun 33 and Jin Gang Lun 34, to Tianjin Port. These have CSS class notations for coastal services, ice class B and Rules for Intelligent Ships. This I-ship consists of N – intelligent navigation; M – intelligent machinery; E – intelligent energy efficiency management; and I – intelligent integrity platform.
Their main roles include harbour towing, berthing and unberthing visiting ships, ice breaking and emergency response with fire-fighting systems.
During sea trials, the 34.6-m tugs achieved a maximum bollard pull ahead of 51 tonnes and free running speed ahead of 13 knots. They each have two Daihatsu diesel engines, each rated for 1,471 kW at 750 rpm. These drive Kawasaki KST-180ZF/E Z-drive units with a 220 cm diameter propeller.
Other important deliveries
When McAllister Towing needed more towage capacity on the US east coast, it ordered a series of powerful tugs from Washburn & Doughty shipyard.
Eileen McAllister is the latest of these escort tugs and has become the most powerful tug in Port Everglades in Florida, US.
It was built to ABS class with 84 tonnes of bollard pull. Eileen McAllister comes with two Caterpillar 3516E main engines, which are compliant with US Environmental Protection Agency (EPA)’s Tier 4 emissions requirements. These engines have a combined power of 5,050 kW and drive two Schottel SRP 490 Z-drive units.
Eileen McAllister has an overall length of 28.3 m and a beam of 11.5 m. It has Markey-manufactured winches on the bow and stern for ship handling and docking.
Brusco Tug took delivery of a 307-gt escort tug from Diversified Marine in Portland, Oregon and it was chartered to Crowley Maritime to support ships on the US west coast.
This azimuth stern drive (ASD) tug was built to Robert Allan’s RApport 2500 design with bollard pull of 89 tonnes ahead and 87 tonnes astern. This was formidable power from a tug with an overall length of 25 m and moulded beam of 12.2 m.
Hercules has a full Caterpillar Marine propulsion suite, complying with US EPA’s Tier 4 emissions requirements.
This includes twin Cat 3516E main engines that develop 2,240 kW at 1,800 rpm driving Caterpillar (now Berg Propulsion) MTA 627 azimuth thrusters with 2.7 m diameter propellers, connected by carbon fibre shafts. It has a high-performance Markey winch as part of its deck machinery package.
Bogazici Shipyard completed a new escort tug for French owner Compagnie Maritime Chambon in October to support terminal operations in New Caledonia.
The Turkey-based shipyard built this 30-m ASD tug to a Robert Allan design and Bureau Veritas class.
Cyathea has a beam of 12.6 m, draught of 5.6 m, bollard pull of up to 50 tonnes and free running speed of 12 knots.
Its propulsion comes from two MTU 4000 series M63 main engines, each developing 1,500 kW at 1,800 rpm driving two Schottel 360 fixed-pitch propeller Z-drive units.
Kraaijeveld supplied the deck machinery. This includes a single split-drum escort towing winch with 35 tonnes capacity and a double-drum towing winch, also with 35 tonnes capacity, on the aft deck. Other equipment includes tow pins, hook, stern roller and knuckle-deck crane.
Caspian Offshore Construction deployed shallow-draught, ice-class tug Caspian Fauna in Aktau Port, Kazakhstan, in June.
This 30-m tug was built by Aksoy Gelibolu Shipyard with a draught of just 1.8 m and bollard pull of 25 tonnes. It is classed for unrestricted navigation, for anchor handling and with ice-class 1D.
Caspian Fauna has a beam of 11 m and hull depth of 3.20 m. Its propulsion comes from two main diesel engines with power ratings of 970 kW each. Combined, these produce 1,940 kW to power two propellers through reduction gears.
Seaplace developed the design and carried out structural engineering using subsystem V80R3.0 for naval architecture and detailed hull and internal structural engineering from Sener’s Foran V80 system.
Remontowa Shipbuilding is building a series of tugs for the Polish Navy, starting with Bolko. These were built in the B860 tug programme for towing naval ships and logistics services in the Baltic Sea. They are also available for salvage and emergency support, pollution control and removing hazardous material from the water along the Polish coast.
So far, Remontowa has completed three of a series of six B860 tugs. Bolko and Gniewko entered service during Q1 2020. Mieszko officially entered service and Semko had undergone sea trials in August. The other two tugs, Leszko and Przemko were launched in Q3 2020.
These tugs have sufficient ice class to enable them to operate in severe ice conditions accompanied by icebreakers. They have bollard pull of around 35 tonnes coming from a pair of Rolls-Royce MTU diesel engines driving two Schottel rudderpropellers.