Spinning sail technology is poised to bring back wind-powered ships

March 21, 2017 by George Aggidis, The Conversation
Credit: Norsepower

Over 200 years after steamships first began crossing the ocean, wind power is finding its way back into seafaring. Global shipping firm Maersk is planning to fit spinning "rotor sails" to one of its oil tankers as a way of reducing its fuel costs and carbon emissions. The company behind the technology, Finnish firm Norsepower, says this is the first retrofit installation of a wind-powered energy system on a tanker.

Yet the idea of using these spinning cylinders on ships to generate thrust and drive them forward was first trialled in 1924 – and shortly after disregarded. So why do Norsepower and Maersk (and the UK government, which is providing most of the £3.5m of funding), think this time the technology will be more of a success?

The sail was invented by German engineer Anton Flettner. It is effectively a large, spinning metal cylinder that uses something called the Magnus effect to harness and propel a ship.

How does it work?

When wind passes the spinning rotor sail, the air flow accelerates on one side and decelerates on the opposite side. This creates a thrust force that is perpendicular to the wind flow direction. Although it takes energy in the form of electricity to spin the sail, the thrust it produces means the engines can be significantly throttled back, so it reduces overall use and emissions.

Flettner built two rotor vessels, one of which managed to sail across the Atlantic to New York in 1926. But this modern attempt to harness the wind for ocean travel failed to compete with diesel power. Rotor sails were too heavy and the costs too high for them to yield the expected fuel savings and become successful with shipping operators.

The first Flettner rotor-powered ship. Credit: Library of Congress

But technology improvements and the rise of environmental regulations have led to renewed interest in rotor sails. Wind power firm Enercon launched a new rotor ship in 2008, while in 2014 Norsepower added its first rotor sail to a cargo ship owned by sustainable shipping firm Bore. Promising lightweight and relatively cheap materials and designs, combined with higher oil prices and the need to reduce emissions, mean rotor sails could now take off.

The 240 metre-long Maersk tanker will be retrofitted with two modernised versions of the Flettner rotor that are 30 metres tall and five metres in diameter. In favourable wind conditions, each sail can produce the equivalent of 3MW of power using only 50kW of electricity. Norsepower expect to reduce average fuel consumption on typical global shipping routes by 7% to 10%, equivalent to about 1,000 tonnes of fuel a year.

The rotor sail project will be the first installation of -powered energy technology on this type of tanker. This will provide insights into fuel savings and operational experience and help to reduce their environmental impact. Each rotor sail is made using the latest intelligent lightweight composite sandwich materials, and offers a simple yet robust hi-tech solution, although they could still cost more than £1.5m to install. That is the equivalent of around 5.5% of the cost of a typical used ship of that size, but a significantly lower percentage for a new tanker.

Greener technologies

The rotor sails that Maersk will be testing might be its most promising yet, but it has also been exploring other efficiency measures. Shipping is entering a brave new era with accelerating advances in big data, artificial intelligence, smart , robotics and automation. Maersk is testing drones to deliver ship supplies instead of traditional barges, special paints on its hulls that would cut down on algae and other microorganisms that increase drag, solar-powered sails, kites that tow a vessel, batteries, and biofuels.

What will force more shipping firms to adopt these kind of measures are the new pollution rules that will come into effect at the end of the decade. From 2020, shipping companies will be required to reduce the sulphur content of their fuel, which could come at a significant cost. This potentially makes investment in technologies such as rotor sails much more worthwhile. Wind propulsion for commercial vessels appears to be gaining mainstream industry support and perhaps, in the not too distant future, might even become commonplace.

Explore further: Researchers are looking to wind power for the next generation of ships

Related Stories

Lifting mechanism for mounting huge rotor blades

September 25, 2014

Siemens has created a special mechanism for mounting its 75-meter-long rotor blades for offshore wind farms. The lifting system makes assembly work safer and lets construction take place at higher wind speeds than was previously ...

Wind turbine with record-breaking rotors

July 30, 2012

Siemens has produced the world's longest rotor blades for wind turbines. Measuring 75 meters in length, the blades are almost as big as the wingspan of an Airbus A380. Beginning this fall, the B75 rotor blades will be installed ...

A software 'detective' for wind power generation

August 31, 2016

Advanced detection of wind anomalies could help prolong the lifespan of wind turbine components and reduce the cost of wind energy generation. In this context, European researchers have developed smart control software

Recommended for you

Galactic center visualization delivers star power

March 21, 2019

Want to take a trip to the center of the Milky Way? Check out a new immersive, ultra-high-definition visualization. This 360-movie offers an unparalleled opportunity to look around the center of the galaxy, from the vantage ...

Ultra-sharp images make old stars look absolutely marvelous

March 21, 2019

Using high-resolution adaptive optics imaging from the Gemini Observatory, astronomers have uncovered one of the oldest star clusters in the Milky Way Galaxy. The remarkably sharp image looks back into the early history of ...

When more women make decisions, the environment wins

March 21, 2019

When more women are involved in group decisions about land management, the group conserves more—particularly when offered financial incentives to do so, according to a new University of Colorado Boulder study published ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.