Retrofitting a portion of the US shipping fleet from internal combustion engines to battery-electric systems could significantly reduce greenhouse gas emissions and be largely cost-effective by 2035, according to a new study from Berkeley Lab researchers recently published in Nature Energy.
Shipping represents three of total US greenhouse gas emissions from transportation, making it an important target for decarbonisation.
However, electrifying ships is more challenging than electrifying cars from both a technical and a market perspective. A ship is a much bigger capital investment than a car and has a lifespan of several decades. While better battery technology in recent years has meant EVs with longer ranges, ships are vastly heavier than cars and can travel very long distances between ports. These heavy weights and long distances have led some to think that electrifying shipping isn’t
feasible.
The researchers decided to test that assumption, said Won Young Park, the study’s lead and an energy policy researcher at Berkeley Lab.
“Our analysis includes the feasibility of electrification for 100 percent of all trips, while also exploring excluding a small percentage of very long single trips, which could be potentially addressed through optimised operations across multiple vessels,” he said.
“Declining battery costs coupled with increasing battery energy densities, cleaner grids, optimised vessel operations, and valuing the battery’s second life create a unique electrification opportunity in domestic shipping.”
The researchers analysed US-flagged ships with less than 1,000 gross tonnage, which includes primarily passenger ships and three types of tugboats. They identified 6,323 such ships.
Of those, 2,722 had enough data from the Automatic Identification System, an automatic tracking system for vessels, to understand the length and
patterns of the trips they made.
Park and his colleagues found that excluding just one percent of the longest trips made electrifying the ships much more feasible, allowing for batteries two-thirds smaller than would be needed for the longest trips. For passenger ships, the size could be reduced by 85 percent, they found.
How much electrification reduces emissions depends on the carbon intensity of the electricity used for charging. These 6,323 ships contribute 9.5 percent of the total US domestic shipping emissions, according to the paper.
The researchers looked at three scenarios for the carbon intensity of the electrical grid over time. Scenario one was the status quo, scenario two was 95 percent electricity decarbonisation by 2050, and scenario three was a more aggressive 95 percent decarbonisation by 2035.
Retrofitting these ships could reduce maritime CO2 equivalent
emissions by 34-73 percent in 2035, with the highest reduction reached through the third scenario.
The researchers also looked at how electrifying shipping could be cost-effective, meaning that retrofitting to battery electric costs the same or less as operating an equivalent internal combustion engine vessel.
For internal combustion engine ships, the total cost included fuel, operations and maintenance, and the social cost of CO2 equivalent emissions and air pollution.
For the battery-powered ships, the total cost included batteries, charging, operations and maintenance, the cost for charging infrastructure, the social cost of CO2 equivalent emissions, and the battery’s second-life value at the end of first life.
The researchers compared these costs under scenarios again including the percentage of total trips, carbon intensity of the electrical grid, and different cost scenarios for the battery system and charging costs.
In
the 95 percent electricity decarbonization by 2035 scenario, electrifying up to 85 percent of these ships covering 99 percent of annual trips would be cost-effective in 2035, they found.
The researchers also studied how much charging energy the ships would need for successful electrification. They found about half of the charging needs could be concentrated at 20 US ports.
"The electrification potential is concentrated at relatively few ports, including New York–New Jersey, New Orleans, and Houston,” said Hee Seung Moon, a Berkeley Lab postdoctoral researcher and first author of the paper.
“This implies that focusing infrastructure investments on these ports will facilitate vessel electrification."
“Our analysis offers an essential first step in understanding battery-electric shipping options,” Park said.
“It lays a foundation for future research and policy development to identify optimal locations for prioritising battery electrification based on individual ship activity and local grid emissions.”
This research was supported by the Maritime Administration (MARAD) of the U.S. Department of Transportation.