When the Ever Ace – one of the world’s largest container ships – left Yantian port, China, on August 14, 2021, maneuvering cautiously across the South China Sea, it set out to set a new world record.
So far, no other ship has carried such a large volume of containers – the equivalent of 21,710 6-meter (20 ft) containers!
The Ever Ace, 399.9 meters long and 61.5 meters wide, is huge, but there are dozens of similarly sized container ships sailing today. And more is being built.
Two of these ships, stacked vertically, will be roughly the height of the world’s tallest building, the Burj Khalifa, in Dubai, United Arab Emirates.
If you look at the list of the largest container ships in the world, you will notice that they are 400 meters in length, or a little less, and about 60 meters in width. It is somewhat the current limit of this type of ship.
The number of reasons for this limit is staggering – and you’ll likely never see container ships much larger than these. but why?
There are about 5,500 container ships worldwide. Together, they will be able to load 25 million TEUs (20-foot equivalent units for containers). That if all of these ships were fully loaded at the same time.
George Griffiths, Global Container Markets Editor at S&P Global Commodity Insights, explains that global orders for new container ships are expected to increase this total capacity by a staggering 25% within a few years.
“We’re seeing huge numbers of huge container ships being built,” he says. “The number of ships capable of carrying more than 14,000 containers is enormous.”
In the past decade alone, the average capacity of container ships has increased from less than 3,000 to about 4,500 TEUs. There are currently more than 50 vessels with a capacity of 21,000 TEUs or more. Almost all of them were built in the last five years.
But these ships transcend port boundaries — even the largest in the world, according to Griffiths.
To load and unload containers, cranes must reach the entire vessel.
Container ships also have to turn aside, and pass through locks and canals, including the Suez and Panama Canals, which have size restrictions.
In addition, it is necessary to prevent ships from stranding. In some ports, large ships touch the bottom and glide through gravel rather than floating on the water, says Stavros Karamperidis, head of the shipping research group at the University of Plymouth in the UK. It is a maneuver that requires great care.
Accommodating ships much larger than those in existence today would require an overhaul of the port’s infrastructure, which would be very costly.
Griffiths asks: “Why would you invest in bigger ships if, for that, you would also need to invest huge sums in ports?”
Karamperidis also notes that larger ships still face restrictions on their navigation routes, as they are quite vulnerable to weather conditions. They do not often cross the Pacific Ocean, for example, with its violent storms. Medium-sized ships sometimes lose hundreds of containers in the Pacific Ocean.
“So, ships [ultragrandes] Sail close to the coast, so as not to encounter rough waves. It’s a matter of stability.”
Karamperidis adds that most US ports are not large enough to accommodate the largest container ships. Only a few ships with a capacity of about 20,000 TEUs have docked in US ports.
With all this said, it is possible to see that the constraints on the size of ships have little to do with the daunting engineering challenges of building huge ships – but rather with the economics and logistics needed to run these giants.
“Financially, there is virtually no limit,” says Rosalind Blazejczyk, a marine architect and managing partner at Solis Marine Consultants. But it does indicate that there is indeed a limit to the number of containers that can be stacked on top of another on a ship before the container at the bottom of the stack begins to sag under weight.
Containers are also strapped together so that they stay in place inside the ship — and these systems have limits on the number of boxes that can be securely strapped, according to Jon Simpson, Blazejczyk’s Fellow at Solis.
Another question is how these wide and long ships face the waves.
When navigating directly through a wave sequence, ships can experience a phenomenon known as parametric rolling.
This is because when waves pass along a very large container ship, its bow and stern can be above the water when the crest of the wave is in the middle of the ship.
This leaves the top of the bow and stern without the necessary support from the water underneath. Variation of this support, as the waves continue to pass, can cause the ship to awkwardly shake from side to side.
“You have great rotation angles with not very high waves,” Blazejczyk says.
Large ships face greater risks in the face of this phenomenon. Container ships also have very large deck openings. This means that their overall hull is weaker than other ships – and more prone to bending or twisting.
“They’re like a shoebox without a lid,” Blazejczyk explains.
On calm seas this is fine, but deciding when and where a ship can sail can be another factor limiting its usefulness.
Another type of climate to consider is economical. Griffiths points out that the price of oil is currently very high, and that the largest container ships consume huge amounts of fuel.
Investing in larger ships may not be the smartest financial decision in the future – although those costs are currently more than covered by astronomical shipping rates around the world, given the current demand for cargo handling.
Karamperidis says that for container ships with a capacity of more than 25,000 TEU to be viable, the economics of their operation need to change.
The Suez Canal will likely always be the bottleneck for ships heading from Asia to Europe. But, according to him, it is not impossible to imagine a ship with 30,000 TEUs (or something similar) one day traveling along a route from China to a thriving African port, for example.
“Maybe we can see this kind of ship traveling between Asia and Mombasa [o maior porto do Quênia]”, He says.
The current ceiling of 24,000 TEU of container vessel capacity is a reflection of the economic frontier, port infrastructure, and configuration of the world’s busiest shipping lanes and engineering.
But there is always the possibility that one day, someone with enough money somewhere on the planet will order a ship that will turn even today’s giant container ships into dwarves. It will definitely be amazing to watch.
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