The acceleration of electrification

Though their engines are among the most efficient on the planet, ships waste 50-70% of their energy as heat, although waste heat recovery devices can save a small percentage of the energy loss.

Electrical systems, on the other hand, are far more efficient. Electric cars may have had their problems storing energy, but once they come to use it, 90% goes to the wheels; the same is true of heat pumps and electric stoves.

There may be scant prospect of building enough wind turbines and solar panels to replace all of the fossil fuels on Earth; but it will not be necessary to do so, because running all of the same processes on electrical energy would more than halve the energy required.

Shipping could be part of the solution. Along with their cargoes, COSCO Shipping’s Green Water 01 & 02, two riverine container vessels of 700TEU, load and offload containerised batteries to power their propulsion. Though each is fitted with a 50,000kWh battery pack, the 20ft containerised batteries, which contain 1,600kWh each, can be loaded to support longer voyages.

Meanwhile, Eitzen Electric has received a US$19 million grant from Norway’s Enova for the development of two similarly sized 850TEU feeder containerships, with some 100MWh of energy storage each, double that of Green Water 01 & 02. Preliminary renderings show a house-forward design similar to the COSCO vessels – but instead of river trade, the two vessels would operate on open sea, carrying cargoes between Norway, Sweden and Germany.

The project was granted funding from Enova, a research fund operated by the Norwegian Government, in June last year.

“The Eitzen Group sees great potential in the electrification of regional shipping,” said Fridtjof C. Eitzen, CEO of the Eitzen Group, at the time. “Battery prices have decreased by over 80% in the last decade and will continue to fall as demand increases worldwide. Like a train that cannot be stopped, the use of electric ships will force itself forward as the most cost-effective way to transport goods at sea over time."

Powering shortsea trade requires a lot less electricity than might be expected: recently, the Captain of Yara Birkeland told The Naval Architect that the vessel, with 6.7MWh of capacity, reliably has around a third of its energy left after a round-trip voyage between Herøya and Brevik.

In the five years since that vessel was delivered in 2021, batteries have improved by around 35% in energy-by-volume and energy-by-weight. At the higher end, at the Columbia University School of Engineering and Applied Science, researchers believe they have identified a new gel electrolyte, which could be a solution to the problem of dendrites holding back anode-free batteries. If it works, it could double the volumetric energy capacity of batteries.

But the business case could improve yet further if shipping implements a suggestion by researchers at the Mærsk Mc-Kinney Møller Centre for Zero Carbon Shipping, in a 2024 research paper. Instead of displacing cargoes, the size and weight of battery systems are used as an asset.

Located at the bottom of the vessel, heavier than cargoes, batteries could act as ballast. Unlike bunker fuel, the weight of batteries does not change as they discharge, meaning that there is no need to alter ballast to account for it. While there would still need to be some ballast water, therefore, it could lead to much less ballast being transported around in tanks.

The study expects a theoretical 1,100TEU battery-hybrid feeder vessel to be on par with a methanol-fuelled ship in terms of cost, with the increased capital costs of the former offsetting the operating costs of the latter.

“We could note that, for very heavy cargo and a stratified loading scenario (i.e., heavier containers at the bottom, lighter at the top), the amount of ballast water required is reduced and, at some point, the loss of cargo intake will approach the deadweight loss in the fully loaded condition,” the Centre determined.

A great deal of effort is going into reducing the size, weight and cost of batteries, which are already being containerised; meanwhile, large amounts of renewable electricity are being produced that is, in effect, unsellable. Perhaps it is not a huge stretch of the imagination that short sea vessels might someday carry around cargoes of electricity, rather than oil and gas.