In-depth
effect’ after German physicist Heinrich windward, in order to tack the rotor has consumption in cargo ships. Greenwave
Gustav Magnus who discovered it in 1852, to be stopped and its rotational direction leaders are targeting fuel savings of around
had its maritime potential demonstrated reversed as the vessel comes about through 13% on vessels up to the size of bulk carriers,
by another German, engineer and inventor the wind. Bearing arrangements have to be but the technology is scaleable and could
Anton Flettner, when his converted schooner engineered carefully so as to avoid vibration assist much smaller ships. For modest
Baden-Baden arrived in New York in 1926 at rotational speeds and to minimise power ship sizes, the technology might better suit
after rotoring its way across the Atlantic. lost through friction. An objection in the new-build rather than retrofit applications
Propulsion was provided not by masts and early Flettner days was that net power because of the need for adequate deck space
sails, but by two 15.24m high rotors visually could sometimes be such that it would have on which to mount the rotors.
resembling tall smoke stacks. Flettner been almost as useful to apply the power Greenwave spokesman Colin Whybrow
reckoned the force generated by his rotors used to drive the rotors directly to the ship’s says the WASP project is proceeding well
to be about ten times what could have been propellers. Rotor drive power must be and is attracting increasing interest from
produced by an equal area of canvas sail. minimised so that the power extracted from major shipping groups as research and
Since then, several experimental craft, the wind exceeds it by a useful margin. demonstrations progress. In the summer of
such as the American 12.8m yacht Tracker Flettner’s rotors died a death as fossil- 2008 Greenwave carried out performance,
in the 1980s, have further demonstrated the fuelled combustion engines came to rule stability and handling tests of a WASP system
efficacy of the concept. In 18kts of wind, the world. However, ‘wind engines’ are once on the lake at Solent University’s Warsash
Tracker could sail at 6kts propelled by its again being considered. A keen proponent is Maritime Academy. Whybrow reports that
rotors alone. Rotor-sailors sail best on a Greenwave, a maritime charity promoting four rotors installed temporarily on a scale
broad reach, when the wind is coming from the development of sustainable shipping. tanker propelled the vessel at up to some
the side of the vessel and the thrust developed Among the organisation’s key projects is 17kts, ‘earning us the Academy’s unofficial
is aligned with the vessel’s longitudinal axis. Wind Assisted Propulsion (WASP), which speed record for these vessels on its lake’!
One drawback is that when sailing to is developing rotors as a means to cut fuel More recently, Greenwave has tested
Leaves others in its wake
SBI_MarApr10_p20-21-22.indd 21 26/02/2010 12:21:12
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