Sustainable Energy Blog

Hi all,

A piece on sustainable shipping I originally wrote for the RMIT student magazine ‘Catalyst’ in semester 1. Feedback welcome.

Christian

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Its recently been revealed that a serious source of air pollution comes from the cargo ships currently sailing the worlds oceans. I had heard this before and a claim that apparently you could trace the worlds shipping lanes by the brown haze above them but I hadn’t realized that ships actually contribute more pollution then the rest of the worlds transportation sector combined! A bit of research soon uncovered some startling statistics including this extract:

“…although emissions from road vehicles has declined sharply in recent decades, emissions from large ships have changed little while the volume of worldwide shipping has steadily increased. Those two factors have allowed pollutants from ships, estimated at 6 million metric tons in 2001, to surpass road vehicle emissions estimated at 2.2 million metric tons.

If no stringent international ship emission regulations are adopted by the International Maritime Organization, the study warns, ship emissions of sulfur dioxide and nitrogen oxides will soon surpass those of not just land vehicles, but all land sources, including power plants, factories and refineries.”

The funny thing is that for thousands of years we have explored and colonized the globe, fought grand sea battles and reaped a bountiful harvest from the sea all using a completely sustainable and zero emission power source. I am referring to, of course, the sailing ship. These probably had their apogee in the great clippers that plied the competitive tea routes route just before the steam age. One of the most famous of these great multi-masted sailing ships; the ‘Cutty Sark’ once posted an Australia to England time of just 67 days! It also holds a 24 hour record of 360 nautical miles, averaging over 15 knots! The great sailing ships, despite being marginally faster than the steamships that replaced them nevertheless lost out due to the fact their schedules relied so much on the vagaries of the weather.

But what if we were to reassess the sailing ship for use in the 21st century? With rising oil prices and the worry of carbon emissions could sail-power once more make economic and environmental sense? Theres a strong case to be made that sailpower could once more play a role in global shipping. In the 120 odd years since powered ships replaced wind there have been dramatic advances in sail and rigging technology. New sail and hull designs allow us to sail ever closer to the wind and modern lightweight and strong materials give vastly improved response and performance to weather conditions.

Some interesting ideas that have been floated (pardon the pun) include large solid composite fins that are in effect wings that power the boat and can have their angle changed in order to provide ‘lift’ that is then transferred to the hull. This has yet to be tried on commercial boats but the famous explorer Jacques Cousteau’s yacht Calypso was powered by such an arrangement.

However, the most exciting development in the sailing world has to be that of kites. Kite-surfing has taken off in the last ten years and many of us who’ve tried it understand just what amazing thrust is generated by these aerofoils. Kites have the advantage of being able to sail high above the boat they towing at altitudes of up to 500 meters where the wind is much stronger and consistent than at sea level and because they are not attached to a solid mast but rather flexible kite lines they can swoop and follow the wind thus generating up to 10 times as much thrust as a standard sailing rig! An added benefit is they would take up very little room on the deck of the boat thus leaving it free for cargo and could be retrofitted to existing vessels at relatively little expense. Some drawbacks of kites include that they are not suitable for harbour use due to the massive amounts of room they need, they are relatively ineffective in very light winds and they are difficult to launch and retrieve.

Of course a wind powered ship still lies at the mercy of the weather to some degree but it would remain appropriate for shipping much of what we ship today where a day or two either side of schedule would not matter so much. After all, if scheduling was of such importance to these goods we would air freight them. But the obvious thing to do is have a hybrid wind/engine powered ship. There are many new technologies under development including low-emission diesel and hydrogen powered engines and new types of batteries that could be charged by use of windmills, wave actuated generators built into the hull or solar panels on the deck or incorporated into container sides. The attraction for hydrogen of course is that you are literally floating on a massive fuel tank of the stuff.

The lack of regulation amongst international shipping and the conservatism of ship-owners means we may not see many of these radical developments soon but they are all out there and they could make a huge difference to the environmental and economic cost of shipping in a relatively short time.