Electric Shipping — Looking at the Numbers, Where We Are Today

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A recent article by Zachary Shahan, “Largest Battery-Electric Container Ship Now Operating — You Know Where,” represents an interesting case study for electric shipping. It refers to earlier articles in which Michael Barnard reported on the case of the COSCO Green River 01 electric ship a year ago. The COSCO ship is a 700 TEU river transport vessel with a max of 80 MWh battery capacity and 1,000 km of range. TEU is a standard unit of measure equivalent to 20 feet. It is an approximate standard for a shipping container size, 20 ft x 6ft x 6ft.

Some Observations on Green River 01

Here’s some more info: “the electric container ship is powered by a large-capacity battery combining for over 50,000 kWh. However, COSCO says the number of battery modules can be configured depending on the length of the voyage at sea. For example, additional 20-foot battery boxes offering 1,600 kWh of electricity can be loaded onto the container for extra range.

“This ship’s captain, Wang Jun, told CCTV that when the Green Water 01 is equipped with 24 battery boxes, the electric container ship can complete trips that consume 80,000 kWh of energy, equivalent to approximately 15 tons of fuel for a similar journey in a traditional container ship. COSCO Shipping also shared that the new Green Water 01 can save 3,900 kg (8,600 pounds) of fuel for every 100 nautical miles traveled, cutting carbon dioxide emissions by 12.4 tons. Following the successful launch, the Green Water 01 has commenced weekly service between Shanghai and Nanjing.”

There are a number of points here.

• Each energy storage container is 1.6 MWh.
• The maximum speed is 19.4 km/h, only 10.48 knots, less than ocean going container ships, which typically travel at 15 to 24 knots.
• According to the captain, 80 MWh is equivalent to 15 tons of fuel for a similar journey, and the Green Water 01 could consume 3.9 MT (metric tons) of fuel for every 100 nautical miles traveled.
• Weekly service between Shanghai and Nanjing is a distance of approximately 194 nautical miles, and at 10 knots, takes 0.8 days.
• Given 45MJ/kg diesel or GMO, and 1MJ = 0.2777 kWh, 3.9 MT × 1,000 kg/MT × 40 MJ/kg × 0.2777 kWh = 43,300 kWh, or 48 MWh.

The COSCO Green River 01 can be used for river and coastal shipping.

There are some important results here guiding estimates of further electric shipping opportunities. Expanding from these we can explore longer range electric shipping. Let us start with some calculations of energy for one of the longest non-stop maritime container routes, China to LA, a relatively worst case scenario.

Total Energy Required for a 7,000 TEU Vessel
China to LA

Let us start with some energy calculations for one of the longest non-stop maritime container routes, China to LA, a relatively long-range scenario. The total amount of energy for shipping from existing diesel-powered ships shows some interesting results. Calculation of the values shows to what extent container ships can now be used, trip lengths, and carrying capacity. At present, container ships of 6,000 to 8,000 TEU are typical. Let us consider the amount of energy required for a 7,000 TEU container ship traveling from China to LA nonstop at 19 knots, a distance of some 6,500 nautical miles and 12,500 km. “For instance, while a container ship of around 8,000 TEU would consume about 225 tons of bunker fuel per day at 24 knots. At 21 knots, this consumption drops to about 150 tons per day, a 33% decline,” The Geography of Transport Systems writes. Source: adapted from Notteboom, T. and P. Carriou (2009) “Fuel surcharge practices of container shipping lines: Is it about cost recovery or revenue making?”. Proceedings of the 2009 International Association of Maritime Economists (IAME) Conference, June, Copenhagen, Denmark.

For cross reference check on fuel consumption, panamax ships can consume 63,000 gallons of fuel per day. At 3.7 kg/gallon bunker fuel, that is 233,000 kg.

That is roughly 512,000 lb or 256 tons. As a check, the numbers line up well with 225 tons at 24 knots, roughly the same TEU as the first example, about 8,000–14,000 TEU for panamax ships.

Ships may travel at 19 knots, a fuel consumption compromise between slow (15 knot) and fast (24 knot) operation. Fuel use is computed at 19 knots to be 112.5 tons per day, according to a cubic curve established by the proportionality given in the reference.

The required time is 352 hours or 14 and ⅔ days. At 112.5 tons bunker fuel per day, that comes in at 1,650 tons of bunker fuel for the journey at 19 knots.

• Bunker fuel has a gravimetric energy density of 40 MJ/kg. 1,000 kg = 1.102311 ton
• 1,650 tons × 1000 kg/1.102311 ton = 1,497,000 kg or 1,497 metric tons
• 40 MJ/kg × 1,497,000 kg = 59,874,000 MJ
• At an efficiency of 50 percent, we have 30 M MJ delivered
• 1 MJ = 0.27777 kWh
• To deliver 30M MJ, an electrical system must deliver: 30M MJ × 0.2777 kWh/MJ = 8.331M kWh, or 8,331,000 kWh

Thus, including electrical efficiency of 0.81, the required electrical energy is 10,285,000 kWh.

Pack Volume versus Load Volume

Today’s battery pack densities approach 200 Wh/kg. The BYD Blade battery pack density is 150 Wh/kg. That gives the weight of batteries required. LFP cells reach 550 Wh/liter. With a packing density of 63%, the calculated pack density is 350 Wh/l. That is 0.35 kW/l.

• 10,280,000 kWh × l/0.35 kW = 29,400,000 litre
• 1 litre = 0.001 cubic meter
• The amount of energy storage volume required is thus 29,400 cubic meters.
• A container ship of approximately 7,000 TEU, a Post-Panamax Plus, has dimensions of: 300m × 43m × 14.5m — a ship volume of 187,000 cubic meters.
• The ratio of ship energy storage volume to total volume is 29,400/187,000 = 0.1572, or 15.72%.

Pack Weight versus Max Load Weight

Given 150 Wh/kg and a required 10,280,000 kWh:

• 10,280,000,000 Wh /150 Wh/kg = 68,500,000 kg
• 1,000 kg is a metric ton,
• 68,500,000 kg × 1 MT/1,000 kg = 68,500 MT.

Thus, 68,500 metric tons of battery storage are required.

The gross mass for a TEU container is 24,000 kg or 24 metric tons. 68,500 metric tons would require 2,850 TEU containers. The ship is capable of handling 7,000 containers, so by TEU, the percentage of TEU for energy storage would be 2,850/7000 = 41%. The percentage by TEU is 41%.

Weight and volume are limiting factors for LFP batteries for distances of this extent. Weight appears to be a more critical factor than volume, at least for LFP chemistry. This assumes the ship can load containers at the max cargo weight per TEU.

Looking Further

At 150 Wh/kg, with a TEU load limit of 24,000 kg, each TEU would be capable of storing 3,600,000 Wh (3,600 kWh or 3.6 MWh). That does not include any additional weight needed for cooling or the weight of the shipping container. Calculations above are only for the pack density. The overhead for cooling is a negligible percentage of total pack weight.

The Tesla Model 3 with a 60 kWh LFP pack requires 14.6 L of ethylene glycol water mix. The radiator weighs on the order of ten pounds or 4.5 kg. Water is 1 kg/l and ethylene glycol nearly the same. 14.6L of coolant weighs about 14.6 kg. The pack dry weight is on the order of 400 kg or more.

Subtracting the tare weight of a TEU container, the cargo weight is reduced from 24 metric tons to 21.6 metric tons.

Given the above calculations, an upper estimate of the amount of energy for each TEU container would be about 15% lower, or about 3.06 MWh.

Just for fun, let’s figure and compare energy requirements for the COSCO vessel.

COSCO Vessel Comparisons

At 700 TEU, the Cosco vessel is one tenth the cargo capacity of our 7,000 TEU container vessel example. Also, we calculated energy required on the basis of a very long route — Gangzou to Los Angeles, a distance of 12,500 km. Let us compare the two. In round numbers, the cargo capacity size and range are each an order of magnitude larger, about 100×. The 80 MWh max energy of the COSCO ship may scale up by the factor of 10 × 12.5 or 125. 80 MWh × 12.5 = 10,000 MWh, very close to the direct calculation for the 7,000 TEU container ship. Power varies with speed, and the COSCO and container ships travel at different speeds, while the form resistance and other factors may also vary, so linear scaling load or TEU is not a given.

Battery Pack Swap

The 12,500 km example used represents a possible worst case scenario requirement. Just as with EVs, use cases of electric shipping can be different from FF–powered shipping (FF = fossil fuels). FF-powered shipping has no need to refuel on longer distances, but there are routes with shorter distances between ports.

One of the use patterns that would change in long distance shipping is battery pack swapping. That is, TEU energy containers could be swapped by loading and unloading. This is convenient, as port moving equipment is designed for containers. Rather than travel nonstop routes at longer distances, ships may swap energy containers along the way.

Consider that the Green River 01 is a 1,000 km, or 600 mile container ship. It demonstrates a sort of existence proof for at least that much range. That ship uses 36 out of 700 containers for energy storage, a total of 80 MWh.

Charging infrastructure, just like for electric cars, is a factor. The energy container size calculation depends on the battery chemistry. On the practical side, ship costs and charging facilities are factors. Swap allows lower infrastructure peak power needs with lower power charging over longer periods, and speeds travel times compared to fast charging an onboard pack. With days of travel time between destinations, swappable energy storage units can charge slowly. For example, an 80 MWh pack charged over two days, requires only 3.33 MW. The COSCO Green River 01 result can scale to other scenarios. For example, with only 36 TEU containers used for energy, and with a total of 700 TEU capacity, it is possible to consider double the number of energy containers, with 36 fewer cargo shipping containers for approximately twice the range.

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Shorter Distance Routes, Lower Energy Storage

Let’s examine the possibilities for Atlantic and Pacific maritime routes to see if the route lengths can be shortened. Ocean-going trips can be broken into more segments, requiring a smaller pack than a full route would require. Swapping containers would not require excessive time compared to full trip times. Major Pacific routes travel past Japan and South Korea. Many ships stop in Prince Rupert, Canada. Ships can stop in Alaska as well. The distance from Kushiro, Hokkaido in Japan to Dutch Harbor, Alaska is 3,730 km or 2,320 miles. This is the shortest cross-Pacific segment. Kushiro has existing container ship capacity. Dutch Harbor Unalaska Marine Center also handles container ships.

There are shorter routes across the Atlantic. Cork, Ireland to St Johns, Newfoundland in Canada is 3,166 km or 1,967 miles. This is the shortest North Atlantic route.

For the 7,000 TEU container ship example considered, required energy and weight percentages would scale downwards with shorter distances. The example case used 12,500 km trip distance. The reduced longest trip distance is in the range of 4,000 km, less than 33% of that distance.

An Atlantic-route 7,000 TEU container ship could traverse 3,166 km, using 2,600 MWh (3,166/12,500 × 10,280 MWh). At 3 MW per TEU, it would require 867 TEU out of 7,000, or 12.4% of cargo. The longest leg of the Pacific route would entail roughly 3,070 MWh (3,730/12,500 × 10,280 MWh), or 1,020 TEU, 14.5% of the total TEU.

Cost

NMC battery pack costs have already fallen below $139/kWh, and LFP packs have lower costs, in the range of $60–80/kWh, with sodium-based battery packs going even lower and predicted by some as low as $10/kWh by 2028.

With those values, it is possible to figure out that pack DC energy storage costs for such a 7,000 TEU vessel are in the range of $70/kWh, yielding costs for a 3 MWh unit of  $210,000 ($70,000/MWh × 3 MWh). For the 7,000 TEU ship, on the Atlantic route requiring 3,166 km range, the energy container costs would be $182M at today’s costs (867 TEU × $0.210M/energy TEU), falling to $26M at future sodium battery costs.

New-build 7,000 TEU ships cost in the neighborhood of $100M.

Given this, it appears that electric long-distance ocean container shipping vs. FF propulsion parity is affected by battery cost. Technical limitations of range and cargo capacity, by comparison, can be remedied if changes in operational methods using battery swap at shorter intervals are utilized. A calculation of today’s electricity costs versus fuel costs does not reveal significant differences. At $0.10/kWh, or $100/MWh, the 12,500 km trip would cost $1.028M (10,280 MWh × $100/MWh). Average industrial electricity rates in the US are around 9.47¢/kWh. If lower rates may be obtained at nearer wholesale levels, or by sourcing from low-cost renewables, results will vary accordingly. Grid-fed renewables, such as solar and wind, are now comfortably below $ 0.50/kWh, and battery storage will bring that cost up somewhat. Lazard’s 2024 study shows LCOE in the range of $0.01 to $0.10 per kWh for solar plus storage or wind plus storage.

The fuel for 14.66 days at 112.5 tons per day is 1,650 tons. Bunker oil has been about $700/MT (MT=metric ton), but the price varies considerably by location and the average price now is about $600/MT. At 1,650 tons, the approximate cost of fuel is $1.15M. Traveling the Pacific routes could mean as many as 20 transits a year, adding up to annual fuel costs of $23M, a significant percentage compared to initial capital cost.

Pollution from bunker fuel is high — in particular, sulfur emissions. Most notably, MGO, low sulfur fuel, is not that much more expensive, about $700–800/MT. MGO has been required for port operation in many areas, but at sea, operations revert to bunker fuel. In addition to sulfur emissions, fossil fuel creates NOx emissions.

For the Future

Today, there is a push to provide lower carbon and other emission in the next round of ship builds. It is likely that future requirements for lower-emission fuel would affect cost comparisons between electric and FF ship propulsion, tipping the scales toward electric propulsion.

Ship designers are exploring a number of options, and already dual fuel ships and other low carbon efforts are raising the price of new-build ships compared to legacy FF ships. While today’s battery technology is now used for inland waterways and coastal shipping, future battery improvements may provide a path to longer range electric ship propulsion.

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