Hi International Shipping Goes Green:
The world's economy continues to be buoyed by its oceans. Approximately 90 percent of all international trade is exchanged by vessels, and between tankers and intermodal container transport ships, they represent 65 of the 68 largest ships in operation.
Of course, the negative environmental effects of huge shipping vessels are well documented. International Maritime Organization predicts that carbon dioxide emissions from shipping would constitute 72 percent of human-made emissions by the year 2020. Considering cargo weight and transport distance, shipping via sea is the most efficient and economical, but annual increases in the amount of tonnage traded and distances traveled mean most efficiency gains are offset by increased usage.
A variety of engineering solutions have been implemented to keep mega-ships financially afloat.
Wind power returns:
In 2007, German shipping company Beluga Group launched MS Baluga Skysails, a 433 ft. long container ship. Notably, the ship receives auxiliary power from a paraglider attached to the front of the ship that reduces fuel consumption between 20 and 30 percent. The largest of the paragliders, up to 6,500 ft.², can exert as much towing power as a 6,800 hp engine. A pod-based logic controller system links the canopy and the towline to determine the optimal flying height (up to 1,600 ft.), wind direction, and speed.
Overall, Skysails have been slow to catch on, though the company says 40,000 container ships can be retrofitted with the system.
Dual props, slower speeds:
International shipping operator Maersk operates the current largest ships in the world, their Triple E class of container ships, of which there are 20. The handful of vessels larger than their Triple E Class have all been retired and dismantled because they weren't sustainable enough. So when Maersk launched their first Triple E in 2013, they knew that many operational changes were necessary in order to keep the ships viable.
Despite being the largest ships ever, Maersk claims there is a 20 percent improvement in operational efficiency over their second largest fleet of ships, the E class. This savings comes primarily from reduced throttle speeds. Most of Triple E transit is conducted at 19 knots, and the ship have maximum speed of 23 knots. This is considerably slower than other container ships (up to 28 knots), but it is considered the optimum operating speed which reduces power consumption. This adds 2-6 days to each journey.
Efficiency also stems from a unique twin propeller arrangement. Most container ships utilize just a single propeller, as they're more efficient because the dueling draughts of two propellers often result in parasitic drag. But the Triple E class has two 9.8 m four-bladed screw propellers, compared to the single 9.9 m six-bladed screw propellers, contributing 4 percent better efficiency and better pressure distribution. In this instance, the significantly larger disc area of the propellers compensates for conflicting vortices. The ship is also fitted with an innovative, $10 million waste heat recovery system, and Maersk is considering adding exhaust treatment systems as well.
LNG tankers run via boil-off:
While the Triple E is the largest container ship, the Q-max is the largest liquefied natural gas tanker, as it's 80 percent larger than most LNG carriers. Just as LNG trade has increased, LNG carriers have become more prominent. But it would be an oxymoron for a ship that provides for essential services for a booming green industry to also be an emissions giant. As such, the ship uses two low power diesel engines to power a dual propeller arrangement. Since the natural gas needs to be supercooled, the vessel maintains an internal membrane which waffles or compresses to minimize thermal effects on the vessel hull. Naturally, some of the gas transitions to vapor, where a system captures it and returns it to a liquefied state. Most LNG carriers recapture LNG at rates of 99 percent or more.
But the tankers can also run on the boil-off gas from its recapture system. The company that owns the 14 Q-maxs has initiated conversion on its fleet, so the diesel engines can also run via recaptured LNG. The result is a tanker that has a significant reduction in emissions, engines that require less periodic maintenance, fuel supply flexibility, and ultimately risk reduction.
Like many industries, international shipping businesses are adjusting to new environmental regulations that determine in which nations they can do business. Efficiency equals increased profitability, so it's ultimately a business decision to create a new generation of shipping vessels. Until a true bridge-over-the-ocean engineering project comes true, even more efficient ships are needed to offset the increasingly global marketplace.
!!!Hi GREEN DISCLOSURE!!!
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