A new breed of gearbox has been produced for four-stroke and two-stroke engines to develop hybrid propulsion systems
Executives from two gearbox manufacturers outlined the latest developments with hybrid gearboxes and their benefits to vessel owners during Riviera’s Gearboxes: gearing up for hybrid propulsion applications webinar.
This event was held on 22 February 2021 during Riviera’s Marine Propulsion Webinar Week, where Katsa gearbox business sales manager Mikko Happonen outlined the latest gearbox technology for four-stroke engines. He was joined on the panel by RENK sales and project engineer for marine propulsion systems Dominik Elskamp, who presented the benefits of hybrid gearboxes for two-stroke engines.
They debated the typical hybrid applications involving power take in and take out (PTI/PTO) motors when combined with marine engines and generator sets.
Mr Happonen outlined developments in the Katsa L350 and L490 gearbox series, which are compact clutched PTO/PTI 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 is 1,000-2,500 kW. They have an integrated wet running, multi-plate clutch with all input for engaging or disengaging the main engine.
“PTO or PTI electric motors can be connected running either as a generator or as a driving motor,” said Mr Happonen. “Our standalone hybrid PTO/PTI clutch gearboxes have compact designs enabling a selection of main engine or propulsion gearbox as standard. They are easy to handle, assemble and maintain.”
Hybrid propulsion can be integrated with thruster-based propulsion, reducing emissions from vessels in ports, coastal and inland applications and during deepsea operations. “Maritime will be going for hybrid as this is the main technical solution for the future,” said Mr Happonen. “We are focusing our research on developing smart hybrid gearboxes and to ensure the electric power fits well with the mechanical side.”
Mr Elskamp introduced the RENK MARHY and Integrated Front-end Power System (IFPS) gearboxes for two-stroke engines during the webinar. MARHY is a geared PTO/PTI/PTH system, mounted on the propulsion shaft line with a power rating 500-3,000 kW. It has a propeller shaft clutch and lubricant oil station, frequency converter, elastic coupling and tunnel gear box.
“Its most important mode is PTO as it is more efficient than using the generator set to improve the Energy Efficiency Design Index of the ship,” said Mr Elskamp.
This energy generating mode has lower operating costs than using heavy fuel oil and LNG fuel in engines and generator sets, and reduces maintenance costs due to lower running hours of gensets.
MARHY also operates in PTI mode, where an electric motor boosts output from the main engine for higher power demands. “Ships can have smaller engines and supplement with electrical power from the genset,” said Mr Elskamp.
The PTH mode disconnects the main engine with just electric propulsion from the genset. “This could be for electric propulsion only in restricted areas or as redundancy for a single-screw vessel,” he said.
The IFPS package includes a geared PTO system on the front of a two-stroke engine. This is mounted at the engine free end with power ratings of either 500 kW, 1,000 kW, 1,500 kW or 2,000 kW. They have an elastic coupling, frequency converter and a generator.
With all of these developments, shipowners have been reluctant to invest in hybrid propulsion gearboxes for newbuildings, said Mr Happonen.
“Many projects are being postponed as system engineers wait for better electric motor components,” he said, “some are waiting for 2022.”
Many of the webinar attendees were in general agreement. When asked whether ongoing fast development of hybrid systems, electric motors and components is postponing their decision making, 54% agreed and 6% strongly agreed, while 40% disagreed.
In a second poll question, attendees were asked whether they agreed that there are technically suitable and reasonably priced marine hybrid PTO gearbox solutions on the market. Of those who responded, 47% agreed, 39% disagreed, 11% strongly agreed and 3% strongly disagreed.
Gearboxes: gearing up for hybrid propulsion applications webinar panel consisted of Katsa gearbox business sales manager Mikko Happonen (left) and RENK sales and project engineer for marine propulsion systems Dominik Elskamp
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