By: Bill Streever, ECO Contributor

The roll-on, roll-off vessel M/V Estraden carries trailers, cars, and trucks between Rotterdam and England, making three roundtrips each week. Ignoring a simple control panel on her bridge and two vertical cylinders protruding 18 m above her decks, she looks like other ships of her class. But that control panel and those cylinders are not, at this time, to be found on any other vessel of her class afloat.

Soon after getting underway, the captain of the M/V Estraden pushes a button in the control panel that sets the cylinders spinning. And just like that, the ship reduces her fuel consumption, on average, by more than 6%. Likewise, just like that, the ship reduces her emissions, on average, by just more than 6%. This is the story of the secret of the M/V Estraden—and, by extension, this is a story of curveballs, sails, and the future of shipping.

The Decline of Sails

Mariners have taken advantage of wind since the days of ancient Egypt. In contrast, mechanized shipping is a recent innovation, with steam engines finding their way onto inland and coastal vessels late in the 1700s. Often, steam engines supplemented sails, acting as somewhat untrustworthy auxiliary engines prone to both failure and explosions. For the most part they were only useful for short distances and in tight quarters.

Over time, steam engines improved. Paddle wheels were replaced by propellers to increase efficiency beginning around the late 1830s. Internal combustion engines entered the marketplace and petroleum replaced wood and coal. Most recently, gas turbines took to the sea.

Along with improved shipboard technology, the opening of the Suez Canal in 1869 gave mechanized vessels a shortcut around the Cape of Good Hope. In 1914, the opening of the Panama Canal offered a similar shortcut around Cape Horn. Sailing vessels could not compete. But the age of sail-powered shipping never quite died. There are sailing yachts, but in underdeveloped corners of the world there are also working dhows and junks and wooden boats resembling skipjacks—all powered by sails as they carry goods from place to place. Even in wealthy corners of the world, traditional sailing ships still seek out niche markets—the Brigantine Tres Hombres, for example, continues to carry organically grown products across the Atlantic. In fact, due to financial necessity or as an operational and marketing strategy, some of these vessels that trade under sail do not carry an engine of any kind.

In October 2008, Military Sealift Command chartered the world's first modern kite-powered cargo ship, MV Beluga SkySails, to move U. S. Army and U.S. Air Force equipment from Europe to the United States. Photo credit: U.S. Navy.

In October 2008, Military Sealift Command chartered the world's first modern kite-powered cargo ship, MV Beluga SkySails, to move U. S. Army and U.S. Air Force equipment from Europe to the United States. Photo credit: U.S. Navy.

Still, as alluring as they are to the historian, sailing vessels carry no more than a fraction of a fraction of the world’s cargo…and some would say they are floating anachronisms, looking toward the past rather than the future.

Sails Resurrected

In the 1980s, Japanese ship designers saw a new future in wind. They installed rigid sails made with canvas-covered steel frames on coastal tankers, such as the Shin Aitoku Maru. In what might be thought of as a role reversal from the early days of steam power, the engines provided the primary thrust while the sails provided auxiliary power.

The 1980s sailing renaissance in Japan failed. Despite scattered claims of 50%gains in fuel efficiency, the sails on Japanese tankers fell victim to low fuel costs and—according to some sources—the challenges of maintenance, operations, and safety.

Nonetheless, the potential value of wind in the modern shipping industry was not forgotten. In 2008, a giant kite was attached to a ship. Similar in appearance to a paraglider, but about the size of a baseball diamond, the kite was marketed as a SkySail. Believers claimed as much as a 30% reduction in fuel use. While SkySails have not been abandoned, they remain rare on the world’s oceans, possibly reflecting challenges with deployment and retrieval.

Meanwhile, back in Japan, researchers remained reluctant to give up on the potential advantages of sails attached to masts. The Wind Challenger Project envisioned a rigid wing-shaped sail made from steel-reinforced fiberglass. Recognizing the need for operational safety, designers wanted a retractable system. The mast with its rigid sail attached would telescope up and down, so that it could be lowered during adverse weather or mooring. In January 2014, in Sasebo, Nagasakiken, Japan, the Wind Challenger Project built a half-scale version of the retractable sail on land. Fully extended, it stands seven stories tall. Since then, researchers have used it to test design concepts and measure the complex forces of wind moving across their invention.

Dr. Kazuyuki Ouchi of the University of Tokyo estimates that four Wind Challenger sails, each standing 50 m tall and with a total area of 4,000 sq. m, will drive an 84,000 dry weight tonnage bulk carrier at 14 knots under ideal wind conditions. Current research focuses on automated controls that integrate wind information with rudder and sail controls. The Wind Challenger Project is also assessing methods to reduce the cost of manufacturing large fiberglass sails. The land-based prototype remains active, providing demonstrations and additional research opportunities, but at this time the project is searching for a ship. Dr. Ouchi and his colleagues would like to begin full-scale sea trials as early as 2017. The most suitable ships for Wind Challenger sails, he says, are bulk carriers, tankers, and cruise ships.

Wind Challenger Project’s retractable rigid sail in Japan, built to test and improve the technology before being deployed on ships. Photo credit: Wind Challenger Project.

Conceptual drawing of a Vindskip®, which do not carry sails on masts. Instead, the ship’s hull is shaped like an airfoil, giving it characteristics of a sail. Image credit: Lade AS.

While Dr. Ouchi and his colleagues worked on their telescoping rigid winged-shaped sails, what many may think of as a radical new approach emerged in Norway. A research-and-development company called Lade AS, supported by private capital and Norwegian government funding, developed the Vindskip® concept. Vindskips® do not carry sails on masts. Instead, the ship’s hull is shaped like an airfoil, giving it characteristics of a sail. On the right course relative to the wind, the hull itself will use the power of moving air to improve fuel efficiency. Terje Lade, the man behind Vindskip®, believes that the world may see one of his unique designs afloat as early as 2020.

Curveballs

What does all of this have to do with curveballs? To answer that question, we have to return a time when sails were a common sight on ships. We could return to the age of Isaac Newton, for example, who observed tennis balls curving after being, as he wrote, “struck with an oblique racket.” But for a more direct explanation, we turn to Heinrich Gustav Magnus, the German physicist who described what became known as the Magnus Effect in 1852.

The Magnus Effect explains the curved paths of spinning projectiles and the curved paths of spinning baseballs, golf balls, and tennis balls. Most often, the effect is described as the result of different wind speeds experienced on two sides of a spinning object, which lead to different pressures. The spinning object is pushed by the higher pressure exerted on one side. In the case of a baseball, this effect is magnified by the raised seams on the surface.

For example, say a baseball pitcher snaps his wrist while throwing, which puts topspin on the baseball. This spin increase the amount of pressure on the top of the spinning sphere—which deflects it downward—so that it drops at a rate faster than it would via gravity. On the other hand, a ball thrown with backspin will drop at a rate slower than it would via gravity. In both cases, the force generated by spin is great enough that batter may be fooled by the discrepancy in expected movement. As result, the Magnus force has been effective against batters for 150 years—ever since the curveball was invented by pitcher “Candy” Cummings in 1867.

Sketch of Magnus Effect. Image credit: Wikimedia Commons.

The Flettner-Rotor Ship Buckau. The rotor ship could tack (sail into the wind) at 20 to 30 degrees, but the rotors were not as efficient as propeller systems. Image credit: Wikimedia Commons.

Enter Anton Flettner, born 33 years after Magnus described his effect. It was Flettner who realized that the Magnus Effect could move ships. In 1924 (the year of Cummings death), he removed the masts from a schooner and replaced them with two vertical cylinders, each standing 15 m tall and with diameters of about 3 m. The cylinders could spin with the assistance of a motor. Using the spinning cylinders to take advantage of Magnus Effect, he sailed from Poland to Scotland in 1925. The following year, he took his ship across the Atlantic. The spinning cylinders became known as Flettner Rotors.

If Flettner Rotors worked, why did they fail to appear on the world’s cargo fleet? Because they did not work well enough. The clumsy metal rotors required constant attention to produce only slightly more thrust than could be generated with sails. There was no place for them in the early decades of mechanized shipping.

Flash forward to the M/V Estraden. The cylinders on deck are modernized Flettner Rotors. The control box on the bridge is part of that modernization.

Tuomas Riski of the Finnish company behind the M/V Estraden’s rotors provides some background. The company Riski runs, Norsepower, opened its doors near the end of 2012 with the goal of designing and installing modernized Flettner Rotors. Just months later, in the first half of 2013, a ship owner expressed interest. Eighteen busy months after that, in November 2014, the M/V Estraden’s first rotor was installed. After a year of single-rotor experience, the ship’s second rotor was installed. The rotors, 3 m in diameter, stand 18 m tall.

The ship could be thought of as a demonstration vessel. Many mariners know of Flettner Rotors from their training, but they have never seen them in action. Potential clients often request tours of the M/V Estraden.

“The crew,” says Riski, “keeps getting questions about the rotors.”

When asked about the difference between Norsepower’s product and the rotors used by Anton Flettner, Riski points out that modern rotors are seen as providing auxiliary power, not primary power. But Riski also points to the rotors themselves. “They are made from very lightweight composite materials,” he says, “so they can be rotated with high RPMs using a small amount of electricity.”

Modern materials offer one advance, but computers also play a critical role. Upon leaving port, a computer integrates information about wind speed and direction. “When it makes sense,” Riski says, “the computer turns on the rotors. A 90° true wind angle offers the maximum benefit.”

To a sailor, this would mean that the rotors are most efficient when the ship sails on a beam reach.

“Optimal wind speeds are about 25 m/second,” he says— a whopping 48 knots, a Force 10 gale on the Beaufort Scale. But the rotors provide thrust at lower wind speeds too. Wind speed and direction changes constantly, and the computer responds without rest, adjusting rotor rotation to match ever changing conditions.

“It is a dynamic optimization problem,” Riski says. But it is a problem addressed by a computer rather than a problem requiring a captain’s attention.

One other ship, the E-ship 1, is equipped with Flettner Rotors. The E-ship 1 belongs to Enercon, one of the world’s largest wind turbine manufacturers, and while Enercon sees value in Flettner Rotors its focus is not on development of a world market for Flettner Rotors. And E-ship 1 is not a roll-on, roll-off cargo vessel—perhaps making a statement about Enercon’s commitment to wind, E-ship 1 transports wind turbine parts.

According to Riski, about 20,000 currently active ships would benefit from Flettner Rotors, even at today’s low fuel prices. The target vessels include tankers, bulk carriers, ferries, cruise ships, and roll-on, roll-off vessels. Many of them burn bunker fuel, the heaviest and dirtiest fuel component found in crude oil. While rotors can pay for themselves in fuel savings in less than 5 years, the additional benefit of emissions reductions cannot be overlooked, Riski says.

Riski acknowledges that routes impact the usefulness of rotors. In the waters plied by the M/V Estraden, between Rotterdam and England, the wind often blows hard. The ship’s rotors provide thrust during about 80% of a typical voyage.

Rotors can be retrofitted to existing ships in a matter of days. Crew training can be completed in a matter of minutes. Despite what might be thought of as market inertia, Riski believes that as many as a thousand ships will be equipped with rotors in the next 10 years.

The E-Ship from Magnuss uses a retractable Flettner Rotor called the Vertically-Variable Ocean Sail System (VOSS™).

Norsepower is not the only company promoting the virtues of modernized Flettner Rotors. There is, for example, Magnuss Services corporation based in New York. When asked about Magnuss’ approach to the market, Magnuss co-founder Ted Shergalis explains that ship owners understand the physics and the economics of Flettner Rotors. But, he says, they do not want the rotors on deck. They do not want rotors creating obstacles during loading and unloading or creating unwanted windage when not in use. With that in mind, Magnus markets what it calls the Vertically-Variable Ocean Sail System (VOSS™). The VOSS™ is a retractable Flettner Rotor. When it is not needed—in port, when the wind comes from the wrong direction, or when the wind simply fails to blow—the VOSS™ disappears into the ship’s deck, retracting much like the Wind Challenger Project’s sails retract.

The Future

In the increasingly complex world of wind-assisted shipping, confusion is inevitable. In addition to rigid sails and skysails and Flettner Rotors, there are wing sails, turbo sails, solar sails, soft sails, Dynarigs, and others—each with advantages and disadvantages, each vying for a place in the market somewhere in the world.

Wind-assisted shipping companies have joined forces to form the International Windship Association. Gavin Allwright, the Association’s Secretary, sees both higher fuel prices and requirements for lower carbon emissions impacting shipping. Fuel, even at today’s prices, constitutes the highest operating cost for most vessels. And, as is often pointed out, if the shipping industry were a nation it would rank somewhere around number six for carbon emissions, between Japan and Germany.

By itself these realities do not ensure the success of wind-assisted shipping. A recent academic study assessed survey responses about wind technologies. All respondents were in the shipping industry, but some had no knowledge of recent wind technology development. Others perceived wind technologies as less safe, less reliable, or less effective than available alternatives. Wind technologies scored poorly against approaches such as waste heat recovery and enhanced propeller designs.

Confronted with realities like these, Ted Shergalis of Magnuss Services provides a response that could, in one form or another, come from anyone maneuvering in the uncharted waters of wind-assisted shipping. “There is always resistance to change,” he says, “but we have history on our side. Technology that improves performance will be adopted.” It is, he believes, a matter of when rather than if.

Whether the future lies with one wind technology or many, including some not yet envisioned, the world’s cargo fleet seems poised to use wind to its advantage.

“The deck,” Shergalis quips, “is stacked in our favor.”

Bill Streever wrote the best-seller Cold and the award-winning Heat. His most recent book, release in 2016, is And Soon I Heard a Roaring Wind: The Natural History of Moving Air.