Wind Assisted Ship Propulsion: Back to the Future

 ^ USS Constitution: A Sailing Frigate & the Legend of the War of 1812 is Still Afloat
   Image Courtesy of Todd Stevens at
   Retrieved From

It is not the strongest or the most intelligent who will survive, but those who can best manage change. (wrongfully attributed to) Charles Darwin

Winds of Change in the Traditionalist Shipping World

May you live in interesting times. So goes an ancient, apparently Chinese, curse. The implication is clear. You are more likely to find peace and tranquility during stable, uninteresting times. Upheavals, though interesting, create precarious times.

Presently, we are living in interesting times. The global economy is yet to shrug off the lethargy injected by the global economic slump of 2008. Add to that the harrowing prospect of another slowdown – over the past fifty years, the global economy has slipped into a recession every eight years.

Then, there is what Professor Joseph Schumpeter in 1942 called Creative Destruction, a phase when pioneering innovation replaces established technologies and work cultures.

Over the long term technological advance does facilitate qualitative and quantitative economic growth. But you can’t escape the turmoil. And, for every winner there is a loser.

Change is Essential, Lest this be the Reality of the Shipping World Image Courtesy of Cartoonresource at

Change is Essential, Lest this be the Reality of the Shipping World
Image Courtesy of Cartoonresource at

Your outlook will depend very much on which side you are on. Change however is the natural order of things. As General Shinseki aptly put it, “if you don’t like change, you’re gonna like irrelevance even less.” And, it is precisely change that is interesting.

Shipping is among the most globalised of industries – ships sail across the globe transporting over 90% of the internationally traded cargo, the owners are of some nationality, the ship is registered in another country, and the crew members may hold diverse nationalities.

Not for nothing do investors regard the Baltic Dry Index (BDI) as among the prime barometers on the health of the global economy – the BDI indicates the global demand for raw materials that rises when the global economy is on the upswing and vice versa.

Currently, the BDI is not indicating great news. The prophecies of a recession every eight years might well come true. But this creates the need for an acceleration of the efforts by the shipping industry to cut costs and survive.

Technologically, shipping may not exactly be cutting edge. Many regard it as largely conservative. But the necessity to survive under the onslaught of unpredictably fluctuating fuel prices, commercial pressures, and tightening regulations is propelling genuinely useful innovation.

Wind Assisted Ship Propulsion

Wind assisted ship propulsion is one such innovation. Or is it the revival of an old concept? For in the Age of Sail stretching roughly from about the 16th to the mid-19th century, our ancestors relied on natural winds to propel ships.

Heavily Listing Ship Image Courtesy of Herve Cozanet at Retrieved From

Heavily Listing Ship
Image Courtesy of Herve Cozanet at
Retrieved From

Sailing ships list heavily during high winds. Listing is the movement of a ship towards its sides – starboard or port. This and their total dependence on winds ensured that a superior technology – steam ships – replaced them.

The way sailing ships had replaced oar-powered galleys before them. And the way diesel powered ships would soon replace the steam powered ones.

Now, shipping is a largely conservative industry. This might have something to do with the investment paradox of shipping – while the risk is high, the returns are low. Only a destined few make it big. But when they do, they make it really large, colossal.

The point is, the investment paradox may deter adoption of a maverick course of action as the winners fear losing their hard earned gains. Without change however you risk stagnation. The aforementioned pressures are triggering positive change in the world of shipping.

Established in 2014, the International Windship Association (IWSA) seeks to develop wind assisted propulsion for commercial shipping over the world. It provides valuable data about and financially supports investments into such technologies.

And if the Ship Efficiency Awards of 2015 are anything to go by, wind assisted propulsion technologies seem to have arrived. The top performers of this year bear testimony:

  • Finnish marine engineering company Norsepower Oy won the Energy Efficiency Solution Award for its successful rotor sail solution
  • IWSA made it to the finals in the Initiative of the Year category as Deltamarin did to the finals of One to Watch
Flettner Rotors @ the Buckau in 1925 Image Courtesy of the U.S. Library of Congress at

Flettner Rotors @ the Buckau in 1925
Image Courtesy of the U.S. Library of Congress at Buckau_Flettner_Rotor_Ship_LOC_37764u.jpg

Design Parameters & Technologies

Simply speaking, wind assisted ship propulsion involves the use of a wind capture device – such as a sail – in order to lower the fuel consumption of a ship.

As a concept, wind assisted ship propulsion goes back to the 1920s. First devised in the 1920s, the Flettner Rotor technology is the market leader in wind assisted ship propulsion technologies of the present day.

These devices, according to Lloyd’s Register are, ‘one of the few technologies that offers double digit fuel savings.’ Retrofits can save 10% to 30% fuel while new builds can slash 50%.

Although the price of bunker fuels has currently tanked, it won’t be there forever. And when it rises, wind-assisted ships will be more viable. It’s better to start early – in real life, there are no second prizes for late birds.

Maximizing cargo space that, in turn, maximizes revenues, is the main design parameter of present day commercial ships. Engineers however design sailing ships to have sails of the largest possible surface area.

This is a fundamental contradiction in adapting present day ships to wind assisted ship propulsion. Furthermore, the design of a wind assisted commercial ship has to be such that it minimizes crew requirements while maximizing stability.

Such design parameters have led to the development of three main concepts for wind assisted ships:

Principle of Operation of Flettner Rotor Image Courtesy of NASA at Retrieved From

Principle of Operation of Flettner Rotor
Image Courtesy of NASA at
Retrieved From

  • Wing Sail
  • Kite Sail
  • Flettner Rotor

First invented in the 1920s, the Flettner Rotor is the leading technology for wind assisted ship propulsion at present. They did not however find wide application during the last century.

It consists of a large and tall cylinder mounted vertically aboard ships. When mechanically spun, it makes the wind around generate thrust for the ship. The system requires very little supervision because you only need to control the speed of the rotor’s rotation.

Enercon’s E-ship1 is among the largest ships employing a four Flettner rotor prototype system. The company does not disclose the vessel’s operational data but has reported 25% savings after sailing 170,000 nautical miles

Magnus Force Schematic Image Courtesy of Rdurkacz at

Magnus Force Schematic
Image Courtesy of Rdurkacz at with_streamlines_and_turbulent_wake.svg

Norsepower’s Rotor Sail solution is an advanced version of the Flettnor Rotor. Operating as a spinning cylinder, it uses the Magnus Effect to tap wind power for ship propulsion.

Magnus Effect is the generation of sideways force on a sphere or cylinder immersed inside and rotating in a flowing fluid. The force causes its deviation from the straight path. The effect is a specific case of Bernoulli’s Theorem.

In 2015, the Rotor Sail demonstrated a 20% reduction in fuel use for two trials on the MS Estraden, a 9,700 DWT Ro-Ro carrier. This was the case when using multiple, large rotors on routes with favorable wind conditions. Overall, it provided around 5% savings.

What makes the Rotor Sail technology interesting is that it is the first wind-assisted propulsion system in the market that is practicable, verified, and class-approved.

You can use it aboard new build tankers, ferries, bulk carriers, and ro-ro vessels and also retrofit them onboard such vessels. And, hold your breath, installation time is a meager seven hours! For average bunker fuel prices of $250 per ton, payback periods commence from three years.

Kite Sails consist of a colossal kite flying from the bow of the ship. Wind speeds are much greater and more consistent at higher altitudes. The kite uses this wind to generate thrust and pull the ship.

You can also use multiple kites to amplify the thrust. An alternative to this arrangement is getting the kite to drive an electric generator and using the power for propulsion.

With low cost of retrofitting, kite sails create minimum interference in the ship’s existing structure. And you can automate it with computers that figure out the optimum position and angle of the kite sail.

Recently, a vessel chartered by the U.S. Military Sealift Command – MS Beluga Skysails – installed a kite sail system in order to analyze the fuel saving benefits that come with it.

Commercial Vessel with Kite Sail Image Courtesy of Reederei Vessels at

Commercial Vessel with Kite Sail
Image Courtesy of Reederei Vessels at

Friction with the earth’s surface is an important reason for why winds near the surface slow down and why winds at higher altitudes are faster. This layer where winds slow down is the planetary boundary layer.

Wing Sail concept emerged out of the U.S. government commissioned study in the 1980s that went into the economic feasibility of wind assisted propulsion in response to soaring fuel prices.

This system was designed as an automated mechanism of solid, rectangular sails on a framework of cylindrical masts. They would adjust automatically to changes in wind direction and would need minimal handling.

Despite the fact that trials of the wing sail fitted aboard a small freighter demonstrated fuel savings of between 15% and 25%, the concept failed to make it big. You will not find the wing sail aboard any commercial vessel at present.

Upcoming technologies:

  • Fen Pollux will operate Eco Flettner in 2016
  • A partnership of Skysails and the Irish Navy will field test Kite Sails
  • S. naval ships will test the Submaran S10 by Ocean Aero in 2016
  • Windchallenger is a large wind propelled cargo vessel partly financed by Japan’s Ministry of Land, Infrastructure, and Transport. The vessel is scheduled to enter service in 2017
Eco-Flettner Rotors @ the Wind Hybrid Coaster Image Courtesy of MariTIM at

Eco-Flettner Rotors @ the Wind Hybrid Coaster
Image Courtesy of MariTIM at


As rosy as the prospects might look at first glance, all is not hunky dory. The road ahead for wind assisted propulsion technologies is not a cakewalk. Far from it, the path is dotted with umpteen pitfalls such as:

  • Conservative Mindsets
  • Limited Finance
  • Exclusion from Climate Change Agreements

As mentioned, shipping is largely conservative. This is the number one enemy of innovation. Things are changing, but the pace is pitifully slow. Survival in the 21st century demands express adaptability.

Such entrenched outlooks mean that not many are ready to divert funds for research and development. And without finance, innovation is as good as dead. Please note, research is a supremely dicey area. You need large investments but cannot guarantee if and when you can give results.

The Globalized Nature of Shipping Makes it Tough to Impose Geographically Uniform Emission Caps Image Courtesy of Atiketta Sangasaeng at

The Globalized Nature of Shipping Makes it Tough to Impose Geographically Uniform Emission Caps
Image Courtesy of Atiketta Sangasaeng at

We have already noted the investment paradox of shipping. While this does not limit the flow of funds into shipping as a whole, the total investment in innovative shipping technology is grossly inadequate at present.

Coming to the issue of climate change agreements, the Paris Agreement did not dare include international shipping and aviation within its ambit – just like its predecessor agreements at Kyoto and Copenhagen.

This is because ships and airplanes move through diverse zones each with its separate set of emission regulations. Something, that makes it near-impossible to set uniform ship emission standards.

But that does not mean shipping will forever remain immune from emission regulations. Sooner or later regulations will catch up with shipping. And its better if we are prepared for it.

For example, ships plying in the Emission Control Areas (ECAs) cannot burn fuel with more than 0.1% sulphur by mass. There are four such areas at present. By 2020 or 2025, ships will not be able to use fuel with over 0.5% sulphur – anywhere in the world.

If you cut down on fuel use, emissions drop automatically. We have technologies available that can cut both without compromising on the power output. Or compromising very little. A win-win situation. And there is ample reason to cut both.

According to IMO estimates for 2007 to 2012, international shipping discharged about 2.8% of the annual global greenhouse gas emissions and around 3.1% of carbon dioxide after guzzling between 250 and 325 million tons of

Ships Emit 3.1% of the Global Annual Average of Carbon dioxide  Image Courtesy of Arvydas Kniuksta at

Ships Emit 3.1% of the Global Annual Average of Carbon dioxide
Image Courtesy of Arvydas Kniuksta at


IWSA is working with a cross section of the shipping world in order to tide over these pitfalls. Towards this end, the IWSA provides valuable information and financial support packages to those who are willing to risk investment in wind assisted ship propulsion technologies.


Innovations gain ground very slowly. But once they cross the threshold of popular credibility, there is no turning back. From then on, nothing succeeds like success.

Right until the moment the same becomes true for another, superior innovation that replaces it. And the cycle continues. Charles Darwin may or may not have said the opening quote, but there is no denying the truth of it – only the flexible survive.

As and when wind assisted propulsion comes into its own, we will witness an explosion in the use of devices harnessing this technology. That time is not very far.

For once, interesting times might be benevolent too . . . immediately that is!

Want to know more of such groundbreaking, ultra innovative concepts? Visit our blog.

If you wish to experience top notch marine fabrication services, marine pipe fitting, and large scale custom metal fabrication, contact Kemplon Engineering.