Propulsion manufacturers are developing drives and thrusters for a growing fleet of diesel-electric, hybrid and all-electric vessels
Maritime battery usage, either for hybrid-electric or all-electric propulsion, has skyrocketed over the last five years, more than tripling the size of the electrified fleet to 331. Some 47% of these vessels are hybrids, 26% are pure electric, 22% are plug-in hybrids and 5% are not known, according to DNV’s Alternative Fuel Insights. With another 191 newbuilds on order, it won’t be long before the global fleet eclipses 500 hybrid and all-electric vessels.
As emission regulations tighten, this trend is only expected to accelerate in the years ahead, particularly in the offshore energy market, where batteries on board are becoming standard on most newbuilds. Charterers, too, are increasingly showing a preference for offshore support vessels that are fitted with batteries in their tenders, whether they are for offshore oil and gas or renewable projects.
Recognising the uptake in hybrid and electric vessels, propulsion manufacturers are developing thrusters specially designed to meet the needs of owners, designers and builders in this growing market.
One such manufacturer is Germany’s Schottel, which announced in April the availability of its latest thruster with an electric motor aimed at diesel-electric or battery-powered vessels. Schottel believes its embedded L-drive (LE-drive) will enable naval architects to introduce more variants into their vessel designs, compared with conventional Z- and L-drives.
LE-drives are available for Schottel RudderPropellers (SRP) and EcoPellers, with options to use either fixed-pitch or controllable-pitch propellers. Built with highly efficient nozzles and steerable through 360 degrees, SRPs have been around for about 70 years. EcoPellers are optimised for open sea and coastal operating conditions, with powerful DP operation.
Notable, says Schottel, is the compact nature of the LE-drive, which has an installation height comparable to that of a Z-drive despite the incorporation of an electric motor on top. It is also energy efficient, reducing losses from conversions between electrical and mechanical forces.
Omission of the upper gearbox results in several benefits, explains Schottel, including increasing mechanical efficiency by approximately 3%. At the same time, fuel consumption is reduced, resulting in lower operating costs, it says. Additionally, both vibration and noise levels are reduced, improving comfort for crew on board, according to the company.
These electric drives enable SRPs to achieve high bollard pull values and optimum efficiency on medium-speed vessels, says Schottel.
On the EcoPeller, the company says: “It ensures high propeller performance in terms of overall efficiency and enables course stability for more demanding applications at higher speeds.”
Some of the most powerful SRPs in the company’s portfolio will be supplied for a trio of LNG-fuelled multi-purpose vessels being built by Abeking & Rasmussen shipyard in Lemwerder for the German Waterways and Shipping Administration (WSV).
Each of the 90-m sister ships will be equipped with two Schottel RudderPropellers, type SRP 750, each rated at 4,500 kW at 750 rpm. This will provide a service speed of over 15 knots and a bollard pull of at least 145 tonnes.
For manoeuvrability, each vessel will have a Schottel PumpJet, type SPJ 520, rated at 2,990 kW. Installed flush to the hull, the PumpJet will allow the vessel to operate in shallow water, while its elastic mounting reduces noise and vibration levels on board and underwater noise.
All three of the vessels will be equipped with a Schottel MariHub data acquisition system that records and analyses signals from onboard sensors, machinery and other components for evaluation. Combined with the condition monitoring service ProCMS, MariHub allows for early detection of irregularities in the drive train, facilitating a predictive maintenance approach that can lower maintenance costs and improve service planning.
Built as replacements for existing vessels, the newbuilds will operate in German coastal waters in the North and Baltic Seas, with deliveries scheduled from 2023 to 2025.
Two newbuild cable-layers under construction for different owners will both be equipped with propulsion solutions from Brunvoll. In March, the Norwegian propulsion specialist was selected by shipbuilder Vard Brattvåg and Dutch family-owned marine contractor Van Oord for the project, which will see Brunvoll provide a complete propulsion and manoeuvring system for a 130-m cable-laying vessel.
Based on the VARD 9 02 design, this hybrid vessel will have ‘future fuel-ready’ engines with built-in flexibility to be powered with e-fuels when it enters operation in the offshore wind market in 2023. It will have a large battery pack, a shore supply connection and an energy management system. This sustainable set-up will result in higher energy efficiency, reducing CO2, NOx and SOx emissions, says Vard.
Brunvoll’s workscope will be the supply of two tunnel thrusters, each of 2,100 kW, a combined retractable azimuth/tunnel thruster of 1,500 kW and two azimuth propulsion thrusters with propeller in nozzle, each with a power of 2,500 kW.
With this package of propulsion and manoeuvring equipment, the dynamic positioning class 2-capable (DP2) vessel will be able to operate and maintain its position even in extreme weather conditions.
The tunnel thrusters and the combined azimuth/tunnel thruster will be installed in the foreship. All units are controllable pitch and all run at variable speeds. By using simultaneous control of speed and propeller pitch – so-called combinator control – several benefits are achieved, including lower noise and vibration levels on board, less noise into the sea, and lower energy consumption, says Brunvoll.
Under a separate contract, Brunvoll recently delivered similar thruster systems for the DP3 cable-laying vessel Nexans Aurora for Nexans Subsea Operations. Designed by Skipsteknisk, Ålesund, Norway, Nexans Aurora is nearing completion at Ulstein Verft in Ulsteinvik, Norway. The DNV-classed vessel has an overall length of 149.9 m and beam of 31 m, with accommodation for 90, with a cable capacity of 10,000 tonnes.
There are numerous advantages of a fully thruster-based propulsion system for Nexans Aurora; it will ensure optimal vessel positioning capacity during cable/umbilical installation operations, with layers of redundancy and flexibility. The flexibility of the retractable thruster will also allow the vessel to adapt to near-shore operations in shallow water and still maintain excellent propulsion capacity.
“Nexans is leading the charge of the energy transition by providing connected, sustainable, and decarbonized energy. There is a lot at stake when a vessel like the Nexans Aurora is undergoing operations for customers and Nexans Aurora is tailormade for the risks we are involved in,” says Nexans project manager Frode Beyer.
The Brunvoll thrusters incorporate the latest in barrier technology and use certified biodegradable lubricants to ensure zero emissions during operations, in keeping with Nexans’ environmental commitment. This, coupled with electric drives and the latest in power generation and management technology, will ensure a minimal environmental footprint.
DeepOcean’s 2016-built cable-layer Maersk Connector was recently serviced by Danish shiprepairer Fayard Shipyard, where two service engineers from Berg Propulsion overhauled the vessel’s six thrusters – two MTA626, three MTT625 and one MTT419 models – in seven days.
Maersk Connector can deliver all the capabilities of a DP2 installation vessel without sacrificing shallow-water workability. Equipped with a seven-point mooring system, the vessel can manoeuvre on a comprehensive anchor spread, allowing close approach for shore-end installations, and is certified to ground fully loaded for beach operations.
In recent months, the shipyard’s thruster shop overhauled the thrusters and shaft equipment for Wind innovation and Esvagt Bergen.
Portable DP system
Jack-Up Barge BV’s JB117 now has DP2 class capability, following its refit with a portable DP system. Veth Propulsion reports DP sea trials were recently completed for the Dutch-owned jack-up barge. Four diesel-electric-driven Veth Propulsion modular retractable L-Drives give the jack-up barge DP2 capability, allowing it to hold position without the use of anchors. Additionally, this retrofit means only one tug is required for mobilising to the project location, since JB117 can move and position itself autonomously at the area of operation.
Built in 2011 at Labroy Marine Limited in Singapore, the MSC SEA-3250 design vessel was originally equipped for mooring operations, with four 6.5-tonne Delta Flipper anchors and four 44-tonne line pull, 500-m winches.
As the system is modular, the refit was relatively straightforward, requiring an azimuth thruster to be installed at each corner of the jack-up barge, along with a power-supply container. An additional 30-ft container housing the DP controls was placed on deck. The entire propulsion package, including thrusters, power supply and control room, can be removed and shipped for potential use on other vessels.
According to technical details disclosed by the Dutch owner, each of the four Veth VL-900 L-Drive units has a thrust of about 15t, with a rating of 900 kW at 900 rpm. The DP system is Kongsberg K-pos, including the laser-based position reference system Cyscan.