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Computer-Controlled Cargo Sailing Vessels Go Slow, Frugal
An anonymous reader writes "Big container ships are taking it very slow these days, cruising at 10 knots instead of their usual 26 knots, to save fuel. This is actually slower than sailing freighters traveled a hundred years ago. The 1902 German Preussen, the largest sailing ship ever built, traveled between Hamburg (Germany) and Iquique (Chile): the best average speed over a one way trip was 13.7 knots. Sailing boats need a large and costly crew, but they can also be controlled by computers. Automated sail handling was introduced already one century ago. In 2006 it was taken to the extreme by the Maltese Falcon, which can be operated by one man at the touch of a button. We have computer-controlled windmills, why not computer-controlled sailing cargo vessels?"
I don't expect sail power would scale to the size of modern container ships.
Sure, a sail array may not be the best solution for getting a container ship underway from a standstill, but once the ship reaches open ocean, and a course is set, sails can be used to replace some of the engines' thrust, saving fuel.
Considering that container ships consume 100-400 metric tons of fuel per day, even a 5-10% savings would be pretty damn significant.
(Of course, 100-400 is a very broad range - the 4,250-TEU Arafura consumes ~65 MT / day, while the 11,000-TEU Emma Maersk chows down on 350 MT per day, so yeah, YMMV).
Marine Diesel is about $ 420-450 per metric ton right now.
As an intellectual exercise, let's take a 6,000-TEU ship consuming 100 MT/day, making the Shanghai-Long Beach run at express speed (15 days), and let's take the cost of MDO at $ 435.00 per metric ton.
At 5% savings, the sail array will save $ 2,175 / day. Multiply by 15 days = $ 32,625 saved per trip.
To put this into even more of a perspective, the average lifetime of a container ship is 27 years. Assume it's running 75% of the year. (27*365)-25% = 7,391 days. Take $ 2,125 saved per day * 7,391 days = $ 15,705,875 saved.
Is $ 15.7 million enough to pay for the sail array + computers? Seems like it to me.