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| Fig. 1: Visualization of a common Transpacific Route from Hong Kong to Los Angeles. (Image source: L. Taylor) |
In this increasingly globalized world, long-distance shipping remains a crucial method of connecting economies, industries, and consumers. According to the 2018 United Nations Conference on Trade and Development, maritime transport is responsible for 80-90% of world trade by volume, and 70% of world trade by value. [1] Perhaps unsurprisingly, however, our global reliance on long-distance shipping has recently come under much scrutiny due to its environmental impacts, primarily the greenhouse gas emissions and energy expenditure associated with each trip. Currently, the vast majority of cargo ships are fuel powered.
Fairly recently, supplementing cargo ships with wind-power has emerged as a potential resolution. Given the intricacies and time-sensitive nature of the industry, we wonder if the reduction in CO2 emissions achieved through this supplementation outweigh the potential compromises in reliability, efficiency, and speed. To address this question, our exploration delves into the cost implications, the broader energy dynamics, and the projected competence of wind-powered cargo ships.
The transpacific route is one of the busiest trade routes for long-distance shipping, connecting East Asia to North Americas West Coast. [2]
The International Maritime Organization reported all fuel consumption data submitted to their database in 2020. They reported that the 4,480 registered containerships consumed a total of 56,882,591 tons of fuel over the year, and were actively traveling for a combined 23,261,474 hours. [3] From this we can estimate that the ships, on average, use 2.5 tons of fuel per hour.
The transpacific shipping route is estimated to be about 6000 nautical miles, which is equivalent to 6905 miles. [2] 20 knots is equivalent to 24.16 miles per hour, so 6905 miles / 24.16 miles per hour = 285.8 hours. Therefore, we can estimate the fuel consumption for this trip to be 285.8 hours * 2.5 tons per hour = 715 tons of fuel.
In 2019, the International Energy Agency reported the price of marine oil to be $71/barrel. [4] With a standard barrel of 42 gallons, and 300 gallons of oil per ton, that is $507 per gallon. $507 per ton * 715 tons = $362,505 worth of fuel for a one-way transpacific trip, assuming that the ship takes the most direct route, has no delays, and experiences normal weather conditions. In reality, this price is likely much higher.
Burning 715 tons of fuel (equivalent to 726,474 kg) creates a considerable amount of greenhouse gas emissions. Knowing that burning 1 kg of fuel oil generates 3.14 kg of CO2, we can calculate that the burning of 726,474 kg of fuel releases 2,281,128 kg of CO2.
WindWings is an example of new technology that harnesses wind energy to provide propulsion in conjunction with traditional fuel-burning engines. [5] Structurally similar to sails, this process is based on the Bernoulli Principle: as wind blows across the wing, a pressure difference forms across its surface, resulting in a motive force.
The costs associated with retrofitting a cargo ship with a system like WindWings are nontrivial. Pyxis Ocean, a 751-foot vessel operated by Cargill, was retrofitted with WindWings for $4 million dollars. [5] There are other costs associated, such as the time the ship is non-operational during the retrofitting process, and any cargo space that might be lost due to the placement of the wings. Is it worth it?
Due to the unpredictability of wind, the WindWings technology is intended to supplement, not replace, power from fuel. Therefore, it is estimated that these wind power- supplemented ships can use 30% less fuel than they normally would. [6] If fuel use was reduced by 30%, 1,596,789 of CO2 would be generated by the same transpacific route. Financially, reducing the amount of fuel needed by 30% would save $108,751 on this one-way transpacific route. To put this into perspective, in order to recover the $4 million retrofitting cost, the vessel would need to sail this route nearly 37 times. While this seems like a good investment, note that these calculations assume that the wind-supplemented vessel is able to maintain the same speed as the fully fuel-powered vessel. Although the companies that create these inventions make no mention of reduced speed, that has yet to be proven, and is likely one of the main reasons why the industry has been slow to buy into this technology.[5]
It remains to be seen if wind-supplemented ships can help save money on fuel costs and reduce emissions while still providing a reliable and fast long-distance shipping method. The concept might seem promising, but notably variable factors such as weather, lost cargo space, manufacturing time, and maintenance are still undefined and perhaps not given enough attention in the advertising period.
© Lauren Taylor. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the dauthor.
[1] "Review of Maritime Transport 2018," United Nations Conference on Trade and Development, 2018.
[2] C.-K. Yeh et al., "Real-Time Energy Consumption and Air Pollution Emission During the Transpacific Crossing of a Container Ship," Sci. Rep. 12, 15272 (2022).
[3] "Energy Efficiency of Ships," International Maritime Organization, August 2021.
[4] "Oil Market Report" International Energy Agency, September 2019.
[5] S. Neuman, "New Technology Uses Good Old-Fashioned Wind to Power Giant Cargo Vessels," NPR, 5 Oct 23.
[6] F. Tillig and J. W. Ringsberg. "Design, Operation and Analysis of Wind-Assisted Cargo Ships," Ocean Eng. 211, 107603 (2020).