Advances in energy storage, control systems, electric drives and supporting systems are driving the adoption of hybrid- and all-electric propulsion
Powered on by giant strides being made in battery, electric drive, and system technology and a push to reduce greenhouse gas (GHG) emissions, there has been a global surge in orders for new and converted hybrid- and all-electric vessels. Over the last four years, the number of vessels fitted with battery technology – either hybrid, pure-electric or plug-in hybrid – has almost doubled, climbing from 168 to 330, with another 191 under construction or on order, according to DNV Alternative Fuels Insight.
Advancements in electric-drive technology, DC grid systems and benefits of simulation technology were among the topics tackled by panellists during Riviera Maritime Media’s webinar Electric Propulsion – steering towards efficiency, part of Marine Propulsion Webinar Week, held 1 June.
As panellist Philipp Fedorov, head of sales for marine at Denmark-headquartered Danfoss Editron, explained, the manufacturer is riding a fast-developing market as the costs of electrification continue to fall and regulators clamp down on particulate pollution.
Danfoss Editron is a specialist in DC systems for electric hybrid marine applications and Mr Fedorov explained the main advantages of these systems are that, “They offer big savings in fuel, space, power, weight and cabling”.
The group’s systems are built around a synchronous reluctance-assisted permanent magnet (SRPM), a liquid-cooled technology designed for robust working conditions. Additionally, SRPM motors are generally smaller, lighter and considered to be more efficient.
These motors deliver maximum torque from any speed, even standstill. “Our generators and motors show more than 90% efficiency in all operational modes,” he said. Similarly, Danfoss’s electric converters are designed for a higher power-to-weight ratio – a box weighing 15 kg can provide up to 300 kw conversion power.
The robust, compact and light-weight nature of the motors translates into onboard space savings. “There is no need for large, electrical rooms,” insisted Mr Fedorov. “Everything can be placed in the machinery room.”
Simulation becomes indispensable
Delegates showed considerable interest in the observations of panellist Dr. Christoph Priestner, manager multi-body and NVH (open environment) simulation at Austria-based AVL List, a specialist in advanced simulation technology that has a foot in the doors of the automotive and marine industries.
As he explained, in the design of electrically-powered systems, simulation technology has become indispensable. “Simulation is an enormous help,” he said, noting it can even replace harbour tests. “You need reliable virtual models from the very beginning to the hardware phase,” he said.
During a poll taken during the webinar, delegates clearly agreed, with nearly half voting that virtual technologies – essentially simulation – will account for 75% of the development and optimisation of electric powertrains. Just 9% of those responding to the poll, however, believe it will account for all the development process.
However, in a seeming contradiction, an overwhelming 95% of respondents went a big step further by agreeing that virtual models will be used to tweak future electric drives all the way up to the hardware phase.
During the Q&A session, the questions posed by delegates revealed a hunger for information about all-electric and hybrid propulsion, with some of the experts’ responses clearly startling the audience. For instance, asked whether remote-controlled electric propulsion may be a possibility in the near future, Mr Fedorov pointed out that it is happening right now: “We see this as one of the market trends. It’s a reality nowadays and Danfoss is already delivering systems.”
Similarly, asked about the redundancy available in electrical power compared to diesel propulsion in the event of a total shutdown, Dr Priestner was in no doubt about which is the superior technology. “Electricity has more redundancy,” he explained. “There are at least eight independent power sources available if there’s a black-out.”
Also, he said, all-electric power is generally a much more efficient form of propulsion than diesel. It is possible to pull full torque from zero, which is much better for manoeuvrability and operational performance. Under electric power, the vessel’s behaviour is better and fuel savings are of course superior.
Meantime the insights provided by the two experts are corroborated by outside events, as other sources confirm. A late-2020 study by OECD’s International Transport Forum reported slightly less rosy numbers than DNV for the global fleet of all-electric and hybrid-powered vessels, with around 250 including ships on order. Most of these vessels are passenger vessels – water taxis, inner-city and coastal ferries – tugs and offshore support vessels.
“Electricity has more redundancy; there are at least eight independent power sources available if there is a black-out”
Supporting the experts’ contention that all-electric technology is steadily becoming more powerful, in March the 144 -m all-electric ferry Bastø Electric began sailing the main Oslo fjord. With a capacity for up to 200 cars, 24 trucks and 600 passengers, it is the world’s largest all-electric ferry to date. So encouraged is owner Bastø Fosen by the performance of the 7,200-kwh battery system, that the company will convert two more ferries to all-electric propulsion by 2022.
As class society DNV GL foresees: “Bastø Electric is a paradigm shift for the route, the shipowner and arguably the wider passenger ship segment in Norway and beyond. Battery technology is now finding its way into cruise ships, tankers, roros, container ships and bulk carriers.
Mr Fedorov expects hybrid-powered systems to have a strong future for the next five years or so, with improvements in battery technology eventually underpinning an increase in the number and size of vessels in the all-electric fleet.
Snapshot polls taken during the webinar presentations revealed a mounting conviction among delegates about the future of all-electric and hybrid power. For instance, although 24% of respondents “strongly agreed” that hybrid-driven vessels will dominate all-electric ones for the next five years, a surprising 53% only “agreed” in a response that suggested growing support for battery power.
And nearly everybody wants more bang for their buck. A substantial 97% voted for increasingly efficient, space-saving electric motors.
Meantime, delegates continue to put their faith in DC-powered grids, with more than two thirds maintaining there was “no chance” that AC grids would completely replace the former.