What Energy Will Ships That Can’t Electrify Use?


  • Of all the alternatives, biodiesel is by far the most bunkered today, with millions of tons of it being used in ships globally.
  • Biofuels are also in the 100 million ton range already, although most are currently wasted on ground transportation.
  • Wind as a partial energy source for shipping is considered.

As we electrify everything everywhere all at once, some shipping stands out as an exception to directly using electrons. As we’ve explored the space, it’s become clear that bulk shipping tonnage will plummet as fossil fuel use diminishes, all inland and most short-sea shipping will be powered by batteries and efficiency will increase, but still, roughly 70 million tons of liquid or gaseous fuels will be required annually.

But if not electrons from batteries, what energy carriers will be used? asks Michael Barnard for Forbes.

Bet on green methanol

A.P. Moller Maersk, until recently the largest container shipping firm in the world, has made a bet on green methanol. The ammonia industry is working hard to convince shipping that its carbon-free product should be the fuel of choice. Both have merits and weaknesses and are already manufactured in volumes of 150 to 170 million tons annually, and shipped in tankers through ports today, making them obvious possibilities.

Others, of course, are focusing on liquid hydrogen, although outside of bulk carrier firms hoping to ship the product between countries, few shipping concerns are considering it seriously. However, major transportation think tanks like the International Council on Clean Transportation do take it seriously, more seriously than it merits.

It’s worth noting that green methanol and ammonia are mostly focusing on synthesizing the products from green hydrogen, so it’s fairly easy to argue that Maersk and others are betting on hydrogen as well, just more easily managed derivatives of it.

And, of course, there are biofuels, with that industry hoping that plug-compatible biodiesel or perhaps corn ethanol might become the energy carrier that dominates the industry. Of all the alternatives, biodiesel is by far the most bunkered today, with millions of tons of it being used in ships globally. Further, biofuels are also in the 100 million ton range already, although most are currently wasted on ground transportation, a segment that will fully electrify.

Wind as a partial energy source for shipping

It’s also worth noting that at least some are considering the wind as a partial energy source for shipping again. For more than a decade, a couple of firms have been putting fabric parafoils, somewhat similar to steerable parachutes, on the bows of ships to drag them through the water when the winds are favourable. And this year an America’s Cup spin-off and one of the world’s largest bulk shipping concerns mounted two 37.5 meter, folding rigid sails on a ship to test their theories.

There is a great romance in considering a return to sail-powered ships, one that runs straight into the thickets of expanding containerization and the large, pier-mounted, overhead, ship-to-shore cranes that it requires. The romance of tall ships also runs into the grimy reality of major bridges crossing the mouths of bays in many of the biggest ports in the world as well as crossing the inland shipping routes of China, Europe and North America.

Before we sound the depths of each of the gases and liquids, let’s finish off with the wind in this piece. Does it have merit to go with the romance? Yes, it does, but it’s much smaller than many believe, in my opinion. Romance does tend to inflate expectations.

The reality of container shipping is that containers are stacked high above the decks and container ships must fit under cranes. The Marie Maersk, for example, currently sailing south off of Madagascar in the Indian Ocean, can stack containers 21 high, with 10 or 12 of those tiers above the deck. Any sails would have to, to integrate with these realities, disappear entirely in port and somehow work around the containers while moving.

The bow-mounted parafoils are likely the only solution that would work for container ships. Auto launching, auto furling and self-flying parafoils aren’t a particularly difficult combination, although there are failure conditions on launching and furling that will crop up. They are suitable on some legs of some routes and can reasonably reduce a few percentage points of round-trip journey fuel consumption, although benefits are typically touted just for the legs where they are applicable. The failure conditions mean that occasionally they’ll not be available when expected simply because they fouled in some way that the onboard crew can’t be bothered to sort out.

For rigid sails, the requirement to get under low bridges and to integrate with bulk offloading gantries that also tower over ships means that they must fold flat on a deck out of the way of cargo hatches. This is a difficult requirement to meet, as it does require mostly clear decks. This restricts their potential to two major classes of vessels, bulk carriers and roll-on/roll-off car carriers

The latter are tall, boxy vessels, as they typically have multiple decks inside. The Höegh Target, currently sailing off the coast of Sierra Leone in western Africa, is as tall as it is wide, roughly 37 meters holding its 14 cargo decks. Sails starting at 39 meters above sea level are not particularly helpful, and the stress on the ship would outweigh the value.

That leaves bulk container ships, which tend to be wider compared to their height. The ship that was equipped this year with rigid, folding sails, the Pyxis Ocean, is in that category, its deck roughly 21 meters above the sea. The sails have three rotating wings and can be pivoted and adjusted to catch the wind. They also fold flat against the deck. This is necessary as bridges like the one between Oakland and San Francisco are shorter than the combined height of ships and sails. The complexity and failure conditions of folding, multi-part, rigid sails are high and as noted, bulk shipping is diminishing.

Wind power technology

It’s worth mentioning what is likely an even less prevalent wind power technology, the Magnus effect or Flettner rotors. They are cylinders mounted vertically on the decks or superstructures of ships which are rotated at speeds of up to 250 revolutions per minute. This rotation uses the same physics effect as balls that bend direction in flight, like curve balls in baseball or slices in tennis. Spun up with electric motors, in the right wind conditions they provide forward momentum. However, they are much harder to fold flat, so are even more limited in the types of ships that they can be added to.

Inland shipping, of course, is even less likely to be using wind power due to innumerable bridges and turbulent wind over the banks of rivers.

Sails also have the owner-lease conflict problem, similar to much commercial real estate. One firm builds the ship, but in many cases other firms operate them, and further, ships trade hands over their lifetimes. Sails of any type add capital costs that benefit the operators, not necessarily the people who paid to have them built. This puts further constraints on the likelihood of sails appearing on many ships.

As a vector, sails are only likely to scrape a per cent or two off of global shipping fuel consumption due to their constraints. Barnard expects that parafoils will dominate due to much lower capital costs and complexity.

For context, there are 50,000 to 60,000 cargo ships in operation today, the Flettner rotor was first invented a hundred years ago, the use of parafoils on modern ships was first explored in the late 2000s, and yet today there are only a handful of larger cargo ships globally with sails of any kind on them. They capture the imagination much more than they capture any real volumes of wind.

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Source: Forbes