Gearboxes with power take in and take out motors can reduce requirements for gensets and even cut engine loads
Demand is growing for gearboxes designed with hybrid propulsion in mind, as tug owners seek to cut fuel consumption and emissions, while reducing the number of generator sets on board.
A new generation of gearboxes are being developed for four-stroke engines to meet the requirements of hybrid propulsion systems on harbour, escort and coastal towage tugs.
These units can be installed on new vessels or retrofitted to existing tugs, helping reduce fuel consumption, engine load and running time and emissions.
During Riviera Maritime Media’s recent Gearboxes: gearing up for hybrid propulsion applications webinar, executives from two gearbox manufacturers outlined the latest developments in this area. Katsa gearbox business sales manager Mikko Happonen outlined the latest gearbox technology for four-stroke engines and how these can reduce requirements on gensets.
This event was held on 22 February 2021 as part of Riviera’s Marine Propulsion Webinar Week. The debate looked at typical hybrid applications involving power take in and take out (PTI/PTO) motors when combined with marine engines and gensets.
During the discussion, Mr Happonen outlined developments in the Katsa L350 and L490 gearbox series. These are compact, clutched power PTI/PTO gearboxes designed for marine hybrid applications.
“These gearboxes combine two power inputs to one main output with flexible clutch options,” said Mr Happonen.
The two main applications are for driving thrusters on workboats, offshore support vessels and tugs, and for propulsion drivetrains. The L350 has a power range of 200-1,000 kW and the L490 range spans 1,000-2,500 kW. These gearboxes have an integrated wet running, multi-plate clutch.
“PTO or PTI electric motors can be connected for running either as a generator or as a driving motor,” said Mr Happonen.
“Our standalone hybrid PTO/PTI clutch gearboxes have compact designs enabling the selection of main engine or propulsion gearbox as standard,” he said, adding, “They are easy to handle, assemble and maintain.”
These gearboxes enable hybrid propulsion to be integrated with thruster-based propulsion, reducing emissions from tugboats. They can be controlled by a vessel master from the bridge.
Katsa’s hybrid PTO gearbox has a hydraulic clutch dynamic torque of up to 16,000 nautical miles. It has independent oil circulation, with pump and integrated oil sump, hydraulic clutch control system with proportional valves and a clutch protection system with a remote bridge control. These PTO gearboxes also have flexible gear ratios for optimal engine and pump revolutions.
Mr Happonen anticipates higher demand for these hybrid gearboxes as more owners select them for different vessel types to reduce emissions and fuel consumption, and increase periods between engine and generator set maintenance.
“Hybrid is the main technical solution for the future,” he said. “We are focusing our research on developing smart hybrid gearboxes and ensuring the electric power fits well with the mechanical side.”
Mr Happonen said most of the applications for Katsa hybrid gearboxes were on newbuild vessels with thruster-based propulsion, although these products are available for retrofits if required.
“Retrofit projects would be challenging because of the limited space in enginerooms,” he said. “This is why we make [gearboxes] as compact as possible.”
Katsa is also developing new winch gears and winch electric powerpacks, incorporating permanent magnet motor technology. For the marine and offshore sector, these could be used for demanding applications such as escort winches on tugs.
Still, there has been some reticence among shipowners as regards investing in hybrid propulsion gearboxes for newbuildings.
“Many projects are being postponed as system engineers wait for better electric motor components,” said Mr Happonen.
Mr Happonen was joined on the webinar panel by RENK sales and project engineer for marine propulsion systems Dominik Elskamp, who presented the benefits of hybrid gearboxes for two-stroke engines.
Rival transmission manufacturer ZF has expanded its range to include electric power and hybrid drivelines. ZF also said it can supplement its existing scope of supply with electric motors, power electronics and controls.
ZF Marine’s parallel hybrid systems enable installation of electric drives with power levels of 150-750 kW. It can be a complete hybrid driveline from a single source, which some shipyards prefer for newbuildings, said ZF head of sales of commercial and fast craft Wolfram Frei. “We provide standardised overall solutions,” he said.
ZF hybrid transmission is part of a propulsion solutions portfolio. It enables full-electric operation, or supplements the engine load, reducing operating hours and maintenance costs.
Electric motors have minimal noise and can provide a boost function augmenting power from engines when tugging heavy cargo.
Engines and gensets ready for EU Stage V and IMO III applications
Volvo Penta introduced new gensets in its D16 range for IMO Tier III and European Union’s Stage V marine emissions requirements.
The Swedish builder will begin supplying diesel engines below 300 kW with aftertreatment systems to comply with stricter European emissions regulations.
This year it will begin supplying four-stroke D8 and D13 engines for diesel inboard, marine genset and auxiliary ranges that comply with EU Stage V emissions regulations.
The EU Stage V standards put stricter limits on emissions of particulate matter, impacting engines greater than 37 kW used in inland waterway vessels for propulsion and engines greater than 560 kW used in inland waterway vessels for auxiliary power.
In the power range below 300 kW, the Volvo Penta D8 and D13 engines use aftertreatment –selective catalytic reduction (SCR) technology – to meet the stricter emissions standards. Volvo Penta says the diesel engines are designed to cope with high back pressure and high-sulphur fuel – up to 1,000 ppm. This ensures high engine power and efficiency while simultaneously reducing NOx.
SCR solutions have been specifically adapted to commercial marine conditions. They have been tested at Volvo Penta’s own facilities and through customer applications, accumulating some 35,000 hours in operation before the 2018 launch.
Designed with a reduced footprint, the SCR can be mounted on the engine, engineroom ceiling, or floor, providing the shipyard with flexible aftertreatment installation options. Volvo Penta says the SCR solution will reduce NOx levels by up to 75%. With this SCR technology, diesel exhaust fluid (DEF) is infused into the exhausts, and gases are mixed inside the SCR unit.
The ammonia content of the DEF/urea transforms NOx into nitrogen and water. An intelligent level-sensor in the urea tank controls the level and quality of the urea. The systems allow for an aqueous urea solution of 32% or 40%, according to Volvo Penta.
The first marine diesel inboard models available will be Volvo Penta’s inline six-cylinder, 7.7-litre D8 MH IMO Tier III/EU Stage V, with a power range of 154 to 261 kW and 296 kW at between 1,800 and 2,200 rpm. These engines use common-rail fuel injection, double overhead camshafts and a twin-entry turbo.
For applications of 294 kW, Volvo Penta will make available the D13-MH six-cylinder, 12.8-litre diesel engine for IMO III and EU Stage V inline applications. This uses a high-pressure unit injector system, overhead camshaft and twin-entry turbo, with a water-cooled exhaust gas manifold and miller timing.
For marine genset applications, Volvo Penta will supply two versions of the inline, six-cylinder common-rail D8 MG and D13 MG diesel to IMO Tier III/EU Stage V requirements, covering 50 Hz at 1,500 rpm and 60 Hz at 1,800 rpm.
The engines will also be available as marine auxiliary engines, in variable speed and constant speed models.
Riviera Maritime Media will provide free technical and operational webinars in 2021. Sign up to attend on our events page