Sailing Back Into the Future?
By Bill Moore
Posted: 25 Mar 2010The Kathleen and May is up for sale. She's a 136 ton wooden three-mast, top sail schooner built in 1900. For some seven decades, she plied the waters of the Irish Sea and the Bay of Biscay, mostly as a coal hauler She was restored in the late 1990's to her original specifications, and was briefly employed last year in shipping 30,000 bottles of wine from France to Dublin and Bristol. She is, in effect, the last of her kind. In the age of mega ships propelled by diesel engines weighing more than the Kathleen & May, itself, its tiny hatches and cramped holds are an unprofitable anachronism.
But are ships like her due for a renaissance as we move deeper into the end of the age of oil? The crew at Puget Sound's Sail Transport Company certainly seem to think so. They are experimenting with using even smaller sailboats to haul fresh, organically-grown vegetables from the tip of the Olympic Peninsula down the Sound to Ballard and Seattle's farmer's market, using not a drop of petroleum. The trip, however, takes anywhere from around 12 to 24 hours depending on winds and tides, covering a straight-line distance of around 45 miles, though obviously it is further by water. By truck, the trip could take as little as 2 hours, depending on ferry schedules.
Like the Kathleen and May with its small holds, carrying several dozen cardboard boxes of produce a relative short distance seems pretty impractical, though it is admirable. While I like the idea of using as little petroleum as possible to deliver wholesome produce to nearby customers -- they use an electric cargo bike to move their vegetable from the wharf to the local farmer's market -- and I really love the idea of doing it by sail. I also know that looking backward isn't the answer to moving forward beyond the petroleum age. I once owned a tiny Banshee sailboat and know a little bit about sailing -- I am also a fan of the late Patrick O'Brian's Jack Aubrey series of "age of sail" novels -- and while clipper ships served the needs of a growing global commerce a hundred and fifty years ago, I don't think cloning the Cutty Sark is going to cut it in the mid-2000s.
So, how could we make shipping in the 21st century sustainable and oil-free? Sail will, I believe, play an important role. A German company called SkySails have developed a giant tow kite that can, in their current state, tow between 8 and 16 tons. A 130 ton capacity kite is in development. The first cargo ship to be fitted with the 160 sq. meter SkySail system is the Theseus, a 90 meter long, 3,700 ton Rhine class vessel, which is powered by a 1,500 kW MaK marine diesel engine. For cruising speed, the Theseus needs 11 tons of thrust. The Skysail provides up to 8 tons, over 70% of the force needed to move the ship through the water. The company estimates that a ships average fuel consumption can be cut by 10-35 percent, and in optimal wind conditions, it can cut diesel consumption by as much as 50 percent.
One of the key reasons why a system like the SkySail tow kite works so well is because the crew can fly it above the layer of calmer air at the water's surface in stronger, steadier breezes high up. The reason tall ships evolved into tall ships was in order to get their primitive sails as high up as mechanically possible. In fact, in order for sails to work, they must operate just like an airplane's wing, creating a low-pressure zone on the lea side of the sail. The higher the pressure differential between the back of the sail and the front, the more "lift" the sail produce, in effect pulling the vessel through the water, not pushing it. The exception is when the ship is running before the wind as the old Windjammer's did. However, this turns out to be one of the slowest tacks a vessel can be on, because the force of the wind from behind has to overcome the drag of the air in front of the sail. Sailors always, when possible, prefer to sail across the face of the wind because it offers faster sailing conditions. That was -- and is -- the advantage of a gaff-rigged, top sail schooner like the Kathleen and May. Her crew could, when necessary, deploy a set of square-rigged top sails above her mail sails to take advantage of a trailing wind.
Beyond better sails and tow kites, are several interesting experiments, including the late Jacques Cousteau's Turbosail in the early 1980s. According to Wikipedia..
"When compared to the thrust coefficient of the best sails ever built (Marconi or square types, i.e. ships of the American Cup or the Japanese wind propulsion system) that of the Turbosail is 3.5 to 4 times superior and gives the system a unique advantage for the economical propulsion."
A similar concept was developed sixty years earlier by a German engineer Anton Flettner that used what is called the Magnus effect. Again large cylindrical tubes replaced conventional masts and sails. The rotor ship Baden Baden crossed from Europe to North America in 1931. The concept used a 37kW electric motor to spin the ship's twin rotors. However, in practice, it was discovered that the system wasn't all that efficient, so the rotors were removed; and the Baden Baden was lost in a storm in the Caribbean later that year.
In 2008, the Enercon, the world's third largest wind turbine manufacturer, commissioned the construction of the E-Ship 1 [bottom image], a 10,000 ton cargo ship propelled by four Flettner rotors that will be used to transport its wind turbines worldwide.
In addition to using wind, which historically has also been the bane of merchant shipping as sailor found themselves becalmed for weeks at a time, solar energy is finding a role by turning photons into electrons to run electric motors. To date, the most ambitious attempt to use the rays of the sun to propel a ship is Planet Solar, a European enterprise that seeks to sail around the world in 120 days on solar energy alone. The tri-hulled catamaran measures 31 m in length, 15 meters in width, stands 6 meters in height and weighs 60 tons. She has room for up to 200 guests while docked. Her top deck is covered with 500 sq meters of 22% efficient solar panels, producing a maximum of 103.4 kW, or the equivalet of 138.7 hp. Her average speed is 8kt and her maximum speed is 14 kts. She will be launched next month in Keil, Germany, where she was built.
In addition to solar and wind, other firms are looking to hydrogen to power vessels from luxury yachts to North Sea supply ships, though producing the hydrogen in a sustainable manner that doesn't utilize fossil fuels will remain a challenge. In addition to hydrogen, biofuels are also likely to play an important role as an auxilary power source. Marine diesel engine maker Yanmar has approved the use of B5 biodiesel in its sailboat engines. Less promising, at least from my perspective, are discussions by Chinese shipping firms of using nuclear power for bulk cargo haulers.
In summary, I believe that we have a number of exciting options moving forward that will enable sea-borne commerce to sail beyond petroleum towards a new era, one that doesn't involve "wearing" the future back into a muscle-powered past, but a smarter, more intellegent tack into the future.
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