When battery-hybrid power first arrived in the maritime
industry in the early 2010s, it was billed as a great way to make diesel
ferries and workboats more fuel-efficient. The value proposition was
straightforward with fuel savings of 10-20 percent, depending on the
application.
That’s still an important advantage, but hybrid power has
turned out to be much more than an efficiency-booster for existing technology.
For the evolution beyond diesel, hybrid is an essential tool for
electrification, fuel cell power and the transition to zero-carbon shipping.
Stop-and-Go Operations
Battery-hybrid propulsion is ideal for stop-and-go operating
cycles, and ferries are strong candidates.
Ferry operators in Europe, North America and Asia have been
testing and deploying hybrid propulsion systems for nearly a decade, beginning
with the Scottish ro/pax ferry Hallaig in 2013. The technology has caught on
for passenger vessels of all sizes, all the way up to the 3,200-dwt Color
Hybrid, a ro/pax ferry operated by Color Line between Norway and Sweden.
Scandinavian ferry operators led the way, but the North
Americans are quickly catching up.
Ferries are ideal for plug-in hybrid technology, according
to EBDG principal John Waterhouse, the longtime dean of American ferry design.
These vessels have a predictable duty cycle, and their regular routes and fixed
terminals are perfect for installing charging infrastructure.
“Hybrid is well past the early adopter stage for ferry
applications, and we owe thanks to our friends over in Norway who have taken
the lead in developing and deploying it," says Waterhouse. "Operators
can think of this as a mature technology and a viable option for their fleets. Perhaps
the real question is whether you want to be the last adopter.”
Decarbonizing Domestic Vessels
According to the Getting to Zero Coalition, domestic vessels
like ferries, tugs and OSVs have an important early role in the effort to
reduce shipping's carbon emissions.
Cutting domestic vessel emissions by just 15 percent could
reduce the entire shipping industry's greenhouse gas footprint by three percent
by 2030. That may not sound like much, but the coalition says early steps (even
small ones) are essential to get the process of decarbonization started.
Hybrid propulsion is a great option for these vessel
classes, and it’s a bigger step than one might think towards getting to zero.
Any hybrid vessel has a big battery pack, and if that pack is big enough the
vessel can be converted to run all-electric with a diesel engine as ballast.
“You can order a hybrid vessel today and it will reduce your fuel consumption
immediately,” Waterhouse explains. “Then you can build shoreside charging
infrastructure and run the same vessel on plug-in electric power in the
future."
On routes that are tough to electrify because of their
length or limited grid capacity, hydrogen fuel cells may have an important edge
over battery-electric designs. The higher energy density of hydrogen fuel means
the designer can fit more of it on board for a long trip. However, fuel cells
have a drawback: It takes a while to move the throttle, particularly for the
solid-oxide fuel cells that work well with ammonia and other hydrogen-based
fuels.
A battery pack can smooth over that throttle lag by
delivering power instantly when it's needed for maneuvering, giving the fuel
cell time to catch up. With this synergy between battery power and fuel cell
power, today’s battery-hybrid vessels are great candidates for a fuel cell
retrofit down the road, and many are being designed with this upgrade in mind.
Stay tuned, says Strupp, as fuel cells will likely be an accessible commercial
option within the next five years.
Decarbonizing the Supply Chain
In the offshore wind vessel sector, the charterers are wind
farm developers, and they work every day on decarbonizing the world’s power
supply. So it’s no surprise they’re actively interested in decarbonizing their
own supply chain including their service vessel fleets. As a transition
solution, battery-hybrid propulsion fits that need well: The engines give
enough range for transits to and from the site, and stored battery power can be
used for station-keeping and loitering, saving fuel and reducing wear and tear.
This combination is an attractive solution for U.K.-based
crew transfer vessel operator CWind, a division of Global Marine Group. Working
with wind farm developer Ørsted and naval architect ESNA, CWind set out to make
a super-fast, super-efficient, first-of-its-kind vessel.
Its new crew transfer vessel (CTV) CWind Pioneer combines a
hybrid powertrain with the design of a surface effect ship (SES), a hovercraft
built with catamaran hulls instead of a rubber skirt. CWind Pioneer looks like
a standard catamaran at first glance, but when her electric lift fan turns on
she rises up out of the water for a cruising speed of 40-plus knots.