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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 rotor 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 wind power 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 fuel use and emissions.
(Score: 2) by bzipitidoo on Wednesday March 22 2017, @03:08PM (6 children)
The past few days, I've been watching the iceberg collision and sinking of the Titanic as depicted in the 1997 movie. Why? Maybe it's that at a subconscious level I'm worried about the Trump presidency? Anyway, I found the steam power tech of that time fascinatingly primitive and gross, and wondered how modern cruise ships are powered.
Learned that there is still one ship, the Queen Mary 2, that does transatlantic trips. Takes a week and costs $1500 per person, one way. The QM2 is basically a diesel electric, much like a modern train engine. It's built for speed more than lazy cruising, with propellers front and rear, and a maximum speed of 35 mph. Has a bulbous bow projection under the water line, to reduce drag, and I read it was repainted with drag reducing paint in 2008. But no sails of any sort, and I wondered why not?
(Score: 0) by Anonymous Coward on Wednesday March 22 2017, @03:26PM (4 children)
The chances are low that a suitable wind would be available to propel a ship at anything like that speed, constructed like that.
You can get extremely fast sailing vessels, but they're as far on the bleeding edge of materials science and dynamics as, say, Formula 1 cars.
Tankers don't travel as fast as the Queen Mary. They cruise at (depending on various factors) somewhere between 15 and 20 knots, with oil prices playing a role in how fast they cruise.
The big problem with the spinning cylinder approach is that you can't trim it (other than reversing direction), so you're dependent on a suitable wind, after the added vector of induced wind, to be useful, and that's hard to guarantee. However, if you have a wind that is, after induced wind, off your beam, then it can be useful, but given that the net wind will only be off your beam less than half the time, the real world usefulness of this remains to be seen.
(Score: 2) by massa on Wednesday March 22 2017, @03:34PM
20 knots = 37 km/h according to Google.
(Score: 1, Redundant) by massa on Wednesday March 22 2017, @04:01PM (2 children)
QM2's maximum speed is 30 knots and cruising speed is 26 knots, not mph (not a large difference)
(Score: 1, Funny) by Anonymous Coward on Wednesday March 22 2017, @05:49PM
Knot a large difference.
ftfy
(Score: 0) by Anonymous Coward on Wednesday March 22 2017, @07:40PM
30 knots = 35 mph.
(Score: 0) by Anonymous Coward on Thursday March 23 2017, @03:15PM
Inserted a jab at Trump into a story that is completely unrelated? Success! We are all now aware that you dislike the president even though none of us asked. Good job!