Magnetics Business & Technology - May/June 2024 - 14

FEATURE ARTICLE
Rotor Sails Bring Windpower Propulsion Back to Maritime Vessels
Norsepower rotor sails harness the wind to help power maritime
vessels such as the latest cement carrier in the Baltrader fleet.
Adapting a century-old concept to modern technology and
green energy demands, Finnish company Norsepower is bringing
its novel rotor sails onboard a variety of marine vessels to
help propel them through ocean waters. The company recently
scored a number of contracts to place its auxiliary wind
propulsion systems with leading fleet operators as demand
mounts for greener shipping in the world's seas. Separately, a
Korean research group is investigating the use of magnetically
levitated bearings to adapt rotor sails for use in coastal waters
where wind is more variable.
The Norsepower Rotor Sail is a radically modernized, digitalera
version of the Flettner rotor. It uses a minimal amount of
the ship's electric power to actively rotate the cylinder-shaped
rotors on the ship's deck. Rotation, together with wind, packs
the air behind the sail and creates powerful thrust - saving fuel
and reducing emissions. The huge, spinning rotors are partly
manufactured from approximately 342,000 plastic bottles. The
product has already been used by customers for about 10
years and has 310,000+ operating hours on ships operated
by some of the world's best-known shipping companies and
charterers, delivering 21,000+ tons of CO2 emissions reduction
so far.
When wind meets the
surface of the visible,
spinning rotor part of
the sail, the air flow
accelerates on one
side and decelerates
on the opposite side
of the rotor sail. The
change in the speed
of air flow results in a
pressure difference.
This creates a force
that is perpendicular
to the wind flow
direction. The same
principle applies to all
rotating spheres and
cylinders. This can
In operation, a rotor
sail harnesses the wind
and allows the main
engine to be throttled
back, saving fuel and
reducing emissions.
The speed will remain
the same - and may
even increase in some
cases; for instance, on
one vessel equipped by
Norsepower, top speed
raised from 12 to 20
knots, making it one of
the most powerful sailing
ships ever built. Rotor
sails can be around ten
times more powerful
than a conventional
sail because more lift is
produced by the sail area.
A variable speed drive controlled
electrical motor is powered by the
ship's low voltage network and spins
the cylindrical rotor. VSDs typically use
induction motors.
The concept of the Flettner rotor was first devised by Finnish
inventor and architect Sigurd Savonius and German engineer
Anton Flettnerin the 1920s. The first Atlantic crossing, by a
vessel using Flettner rotors only, took place in 1926. However,
technical challenges and the market situation prevented more
widespread application.
" Our vision is to set the standard in
bringing sails back to ocean transportation,
and empower shipping towards
reaching the goal of zero carbon
emission. Our entire team is strongly
motivated by our mission to reduce
the environmental impact of shipping
with our rotor sails. " Tuomas Riski,
CEO of Norsepower.
Tuomas Riski, CEO of
Norsepower
Norsepower, based in Helsinki, was
founded in 2012 with a mission to
reduce the environmental impact of
shipping. Since then, it has raised more than $40 million to
facilitate development, piloting and commercialization. Three
significant contracts were announced in February.
Baltrader Capital GmbH of Hamburg, Germany signed for delivery
of one 24m x 4m sized Norsepower Rotor Sail in summer
2024. The product will be fitted on the newest cement carrier
of the Baltrader fleet, M/V CEMCOMMANDER, to be built at a
shipyard in China, depicted in the image at top left column.
Flettner rotors are rotating cylinders
that, when immersed in a fluid stream,
are able to produce fluid dynamic lift using
the Magnus effect. Rotor sails utilize
the Magnus effect to create thrust and
propel the ship forward.
also be observed for example in golf, tennis, or football, where
spinning balls curve in flight.
14 Magnetics Business & Technology * May/June 2024
French shipowner, Louis Dreyfus Armateurs SAS plans to
install the Norsepower Rotor Sail technology on its new lowemission
RoRo fleet to be chartered to Airbus. The vessels,
which will be used to ship aircraft components for Airbus,
will each be powered by a combination of six 35-meter tall
Norsepower Rotor Sails and two dual-fuel engines running
on maritime diesel oil and e-methanol. Routing software will
optimize the vessels' journey across the Atlantic, maximizing
wind propulsion and avoiding drag caused by adverse ocean
conditions.
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Magnetics Business & Technology - May/June 2024

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