Sailing cargo

You might question why an IP firm concerned with innovation is writing about the use of sails in shipping – a technology that had its heyday well over a hundred years ago. The answer, of course, is that sailing ships for goods transport are seeing a resurgence. The drivers being (as with many things nowadays) sustainability and cost. 

While shipping is actually somewhat more sustainable than other forms of transport on a per tonne-kilometre basis, it is still estimated to contribute to about 3% of worldwide greenhouse gas emissions. The IMO has sought to address this with the introduction this year of the new EEXI and CII rules. That, and the desire to reduce operating costs wherever possible, are providing motivation for operators to seek more fuel-efficient ways to move their ships across the world.  

Sail power + fuel power

While the eventual goal may be ships that don’t require any fuel, many current technologies have the more practical aim of providing sails as assistance to fuel power to improve fuel efficiency. Michelin’s technology (WISAMO) is a great example of this. WISAMO, which stands for wing sail mobility, is an inflatable wing system that can be fitted (or retrofitted) to merchant ships as well as smaller pleasure craft. The sail, which is fitted to a telescopic mast, can be inflated by an onboard compressor to benefit from suitable wind conditions (saving up to 20% in fuel consumption) and can then be deflated to allow access into ports. 

Access to various ports around the world is, of course, an important consideration in ship design. In many locations ships must be limited in height, for example to be able to pass under bridges. This conflicts with the fact that the effectiveness of a sail is at least partly related to its height. That is why the WISAMO system can be deflated. It is also why Bar Technologies’ WindWings sail system provides means to collapse the sails to the ship. In this case, however, the (patented) the WindWings are able to fold from a vertical to horizontal orientation. 

Each WindWing sail is in fact made up of a row of three (vertically extending) aerofoil-shaped elements (i.e. shaped like the wing of a plane). Both the entire sail, and each individual aerofoil element, can rotate about a vertical axis depending on the direction of the wind. When correctly oriented the aerofoil shape of the WindWing elements provides “lift” – unlike a plane wing this “lift” is in the forward direction of the ship so that wind passing across the WindWings helps to move the ship forward. 

Lade AS’s Vindskip concept (now partly owned by Høglund Marine), takes the aerofoil concept to another level. This (once again, patented) concept involves shaping the entire hull of a ship to form an aerofoil, so that wind directed onto the hull of the ship (at a suitable angle) can drive the ship forward.

The Magnus effect

An aerofoil is not the only alternative to traditional sail design. Some “sail” technologies, known as rotor sails, instead use the Magnus effect to generate forward motion. The Magnus effect occurs when a spinning object moves through a fluid (such as air). The spin of the object creates a region of lower pressure on one side of the object and higher pressure on the other, which provides a resultant force that acts on the object in the direction of the low-pressure region. This creates, for example, the curved path of a spinning tennis ball, football, or a ping pong ball.

How can the Magnus effect be used to power a ship? 

Typically, the ship is provided with a series of tall, spinning columns. As wind passes across the ship (from port to starboard or vice-versa) the spin of the column provides a resultant force in the forward direction of the ship. This concept has been around for some time – it was first used on a ship by a German engineer, Anton Flettner, in the early 1900s. In more recent times, though, Norsepower has developed the technology for modern ships (and has filed a number of patents to protect those developments). Norsepower says that its technology, which can be controlled with the push of a button, can provide operators with 5-20% in fuel savings. 

Is zero fuel an option?

Fuel savings like this are fantastic, but what about doing away with traditional fuel altogether? This is exactly the type of thing organisations like Windcoop, Veer and TOWT propose. Instead of combining traditional fuels with sustainable propulsion, these organisations are building cargo sailing ships that are mostly powered by wind (in Veer’s case, supplemented by hydrogen). Initially, at least, these ships are likely to be on a relatively small scale – certainly, at least, compared to the largest container ships travelling the world’s oceans. This limitation means entirely wind driven marine transport is likely to be more of a niche offering (at least for the foreseeable future). 

Nevertheless, it is abundantly clear that these types of endeavours, along with the hybrid technology we discussed above, are taking shipping in the right direction on the path to more sustainable marine transport.

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