Some of the world’s biggest ships are about to get even bigger and more efficient, thanks to a blast of air and a monster engineering project.
Just under a century ago the world of shipping changed forever.
On 7 January 1914, an old French crane boat called the Alexandre La Valley chugged into the Pacific ocean marking the first complete journey through the newly constructed Panama canal.
Now, ships were able to make the journey from the Atlantic to the Pacific in record time, bypassing the need to round the Cape Horn at the foot of South America and shaving 8000 nautical miles off their journey.
But the opening of the canal had a much more profound effect on shipping – effectively dictating the size of most ships for the next century. The width of the channel and its locks placed a limit on the width – or beam, as it is known - of ships passing through the canal at 32.3m. Any bigger and you simply could not squeeze through its narrow channels.
As a result, notwithstanding oil-carrying super tankers and some naval supercarriers, ship owners rarely built ships larger than this “Panamax constraint” as it is known, in case one day they had to make the journey.
“Trades through the canal are actually fairly minor – they are 2.5 to 3% of the total of world trade,” says Paul Stott, a naval architect from Newcastle University in the UK recently told me. “But the issue is that you have to meet that constraint as a ship owner to maintain the value of your fleet.”
But now all that is set to change. The canal is undergoing a major facelift, widening the beam to 49m, and ushering in a new era of shipbuilding. Boat builders are bracing for orders as shipping companies look to buy wider, bigger vessels. And at the same time maritime engineers are being given the chance to start with a clean sheet and design ships from scratch.
Research published in the International Journal of Maritime Engineering shows that the wider canal is likely going lead to new cleaner, greener, more fuel-efficient ships.
“The larger the ship, the less fuel it uses per ton mile of cargo it carries,” says Stott. “If you get up to 110,000 dead weight tons you can get up to 16% reduction in fuel use per ton mile shipped.”
But it is not just a bigger beam that is going to make them more efficient. Engineers have a few tricks up their sleeves that could make these behemoths slip through the seas faster and more efficiently than ever before.
One of the most promising technologies is something called air lubrication – a cloak of air bubbles that encase the hull of the ship, reducing drag and saving fuel.
“What you’d like to do, in the simplest terms, is to separate the liquid (water) from the metal surface of the ship. If you can put gas between the liquid and the metal, you get benefits,” says Steven Ceccio, Chairman of the Naval Architecture and Marine Engineering department at the University of Michigan, in the US.
In practice this means blowing air out of holes in the ship’s hull to act as a lubricant between the vessel and the water, reducing drag by up to 80%.
“The density of the gas is much less, so the resulting friction is a lot less,” says Ceccio.
It is an idea that has been around for some time. Russian scientists tried it in the 60s and 70s and over the years there have been a number of significant sea trials. But there has never been significant take-up – partly because of the cost of retrofitting old ships with the technology, but also because engineers wanted to understand the impact it could have. For example, whilst it could reduce friction, the bubbles could also reduce the efficiency of the turbines used to propel the ship. Or, if the ship’s hull is the wrong shape, the gas just escapes.
In addition, engineers needed to ensure they fully understand the so-called boundary layer physics – the places where the ship, bubbles and water meet.
“The ironic thing is that even though the ships are very large, the region near the metal surface that actually ends up making up a lot of the skin friction is on the order of less than one tenth of a millimetre. That ‘very near wall flow’ is where all the bad stuff happens to cause friction” says Ceccio
The physics is complicated, and has taken a long time to perfect. But the set-up itself is physically pretty simple though. Engineers install openings on a flat-bottomed hull connected to a compressor on the deck. The trick is then injecting just enough air. Too little and there is no improvement, too much and you get no extra benefit. Get it right and the gas starts to collect under the ship allowing it to glide along.
Recently Mitsubishi Heavy Industries have started to commercialize what it calls the “Mitsubishi Air Lubrication System”. Sea trails have shown a 10% reduction in CO2 emissions, whilst computer models of more efficient hull designs suggested there could be a reduction of up to 35%. And already orders have been placed for huge new ships using the technology. Late last year, grain conglomerate Archer Daniels Midland ordered three giant dry-bulk carriers with innovative hull shapes, propulsion systems and the lubrication technology. It claims the designs will help reduce CO2 emissions by up to 25%.
The trio will be launched in 2014, some of the first ships of the post-Panamax era. Exactly 100 years after the Panama canal first revolutionized shipping, its redesign looks set to do it again.