From pv magazine USA
Researchers from the University of California, Berkeley, and Lawrence Berkeley National Laboratory have released a study which examines “the technical outlook, economic feasibility, and environmental impact of battery-electric containerships.”
Breaking from previous studies, the researchers have classified the volume of space housing the batteries as an opportunity cost, rather than a fixed technical constraint. After modelling a wide variety of containership sizes, as well as 13 major world trade routes, the research suggests that more than 40% of the world’s fleet of containerships could be electrified “cost-effectively and with current technology,” by the end of this decade.
TCP (total cost of propulsion) by ship type, route length, current (a) and future (b) battery pricing:
In graph ‘a’, (above left), the authors show the current viability of containership electrification, based on ship size and length of voyage. The grey and white areas of the graphs represent the shipping routes where the electrification of containerships would immediately lower shipping costs.
Using only technology available for purchase today, nearly all ships with routes shorter than 2,000 kilometres are economically advantageous, and ships with routes as long as 3,000km are economically viable.
Graph ‘b’, (above right), projects that price reductions to “near future“ battery technology are expected to roughly double the economic viability and range of electrified containerships.
Crucially, this research demonstrates that electrified containerships have an economic advantage over the internal combustion engine (ICE), even when the costs of environmental and health damages are excluded.
The differences in TCP are contrasted in graph ‘a’ (ICE) vs graph ‘b’ (electrified):
The authors present estimates of air pollution damages and the social cost of carbon for both ICE, (above left), versus electrified containerships, (above right). The grey bars in the chart above show that ICE containerships cause damages equal to or greater than three times the ship’s costs.
An electrified containership will also cause some environmental damage, however, the estimates of electrified ship’s air pollution, and the social cost of carbon, are only 1/12th that of an ICE ship.
In a future in which the costs of large ICE containerships will continue rising, as electrified containerships become increasingly cost effective, the authors posit that ICE ships (below, left) will be grossly more expensive than electrified containerships (below, right).
The authors show that at current battery prices, the electrification of trade routes less than 1,500 km is economical, and has minimal impact to ship carrying capacity. And when the authors include environmental costs, the economical range skyrockets to 5,000 km.
A 5,000 km containership would require approximately 6.5 GWh of LFP batteries.
The average cost of lithium-ion batteries has plummeted 89% since 2010, and is expected to reach US$50 per kWh in the near future. Assuming a battery cost of US$100 per kWh, the TCP for a battery-electric containership is already lower than that of an ICE equivalent, for routes less than 1,000km. And when battery prices reach US$50 per kWh, which is predicted for the near future, electrified ships will be cost-effective on routes as long as 5,000km.
The key technical constraint for battery-electric container shipping is the volume of the battery system and electric motor relative to the volume occupied by a vessel’s existing engines, fuel storage and mechanical space. The extra weight of the BES system is, however, non-trivial in determining a vessel’s power requirements.
Battery chemistry is another key factor in configuring electric cargo ships. Vessels that take short, frequent trips have lower power requirements, but would need to recharge quickly. These vessels should benefit from the high charge rates and long life cycles of lithium iron phosphate (LFP) batteries. Long range ships already spend more time docked in each port – typically well over 24h – and could take advantage of the relatively low cycle life and high energy density of nickel manganese cobalt oxide batteries.
The Yara Birkeland is an 80m long, 7MWh electrified autonomous containership that can hold 120 twenty-foot equivalent units (TEU), which makes 12 nautical mile trips.
For ‘Neo-Panamax’ containerships, (sized to fit through the Panama canal), routes less than 3,000km actually require LESS space for batteries and motors than the volume currently occupied by combustion engines and fuel tanks.
If this class of ship were to travel 20,000km on a single charge, the batteries and motor would require 32% of the ship’s carrying capacity, or 2,500 TEU.
We find that as carrying capacity increases, the percentage of total carrying capacity volume occupied by batteries decreases because larger ships typically have lower energy requirements per unit of carrying capacity.
The charging infrastructure for a containership traveling less than 10,000km can be accomplished using less than 300 MW. Containerships holding 1,000-3,000 TEUs typically spend an average of 31 hours waiting in line and berthing. The largest ships, holding 10,000-20,000 TEUs, spend an average of 97 hours waiting and berthing.
The infrastructure required to support such massive charging capacities is surprisingly affordable, largely due to the efficient logistics of ports, since berths are typically occupied more than 50% of the time. At 50% utilisation, the researchers modelled that the levelised cost of a 300MW charging station comes to mere US$0.03 per kWh.
None of this technical viability would exist if it were not for recent and ongoing improvements to batteries, inverters and electric motors. For instance, in their models, the researchers assumed ICE “tank-to-wake efficiency” of 50%, and electric motor and inverter efficiencies of 95% each. Electrified containerships are 80% more efficient than their ICE counterparts, and use 30% less energy overall.
For inquiring minds: one gallon of heavy fuel oil (HFO) contains approximately 150,000btu, equivalent to roughly 44kWh. But since even the most efficient internal combustion ship engines are no more than 50% efficient, a gallon of HFO produces no more than 22kWh of actual propulsion. Most modern electric motors are now over 90% efficient, and the most advanced prototypes are approaching 99% efficiency.
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