02 April 2023 |

Smooth(er) sailing


There are many things I don’t understand fully about our world. How planes get off the ground. How wireless communication works. Why people bring their phones and AirPods into the sauna. Here’s one more, relevant to climate tech funding this week, to add to the list—the Magnus effect. 

When a spinning object moves through a fluid (e.g., air or water), it creates a region of high pressure on one side and low pressure on the other. This pressure difference generates a force perpendicular to the direction of motion, deflecting the object’s path.

This physical phenomenon is the Magnus effect, observable in the rotation of many spinning objects. If you’re a baseball fan (happy opening week!), you’ve seen the Magnus effect when a baseball’s spin can cause it to curve in flight. 

If you’re a fan of decarbonizing shipping, you’re also in luck. This week, Norsepower, based out of Finland, announced a €28M Series C fundraise for its mechanical rotor sails for large ships, which harness the Magnus effect, too.

Norsepower’s 30-meter mechanical rotor sails (via Maersk and Norsepower)

Making use of the Magnus effect

Norsepower’s sails don’t look like conventional sails. While other firms are going the old-school route, aiming to equip freighters with inflatable wing sails, Norsepower’s big, cylindrical, mechanical rotor sails spin to create a pressure differential & propulsion. When added to ships, the sails can help save fuel. In a deployment with Maersk in 2019, the sails cut fuel use by ~8%. That helps shipping operators save money and reduce emissions.

The concept has been around for a century. The underlying technology, the Flettner Rotor, was invented by an engineer (also Finnish) and used in an Atlantic crossing for the first time in 1926.

Flettner rotors are smooth cylinders that spin. Like other sails, they generate the most thrust when winds are strong. When wind meets a spinning rotor, the air flow accelerates on one side of the sail and decelerates on the other. This change in airflow speed creates the pressure difference and force which the rotor sails translate into forward propulsion. You can watch a handy video from Norsepower here (complete with a majestic, sanguine soundtrack).

Few firms have tried to use the Magnus effect in shipping over the past hundred years. For a while, there was no catalyst; global warming wasn’t on folks’ minds, and the energy density of heavy fuel oils for maritime shipping makes them ideal for powering ever-bigger container ships.

Further, Fletter rotors alone can’t power a ship, especially large commercial-scale freighters with places to be and timetables to stick to. The faster the wind, the better. But absent wind, tech like Norsepower’s has little to offer in the way of propulsion for ships. 

And the direction of the wind is also crucial. Ideal conditions for tech like Norsepower’s feature wind hitting the hull from the side. Remember, the Magnus effect generates a force perpendicular to the direction of motion; if wind hits a ship head-on or from behind, the thrust generated by Flettner rotors is askew to the ship’s desired heading. Finally, the rotors themselves need to be motorized to spin in the first place.

Other firms have tried to commercialize similar concepts to Norsepower’s. Enecron built a ship, the E-Ship-1, in 2008 that leverages Flettner rotors and has claimed fuel consumption savings of up to 25%. It’s still in operation, currently sailing from Bremen, Germany to Mejillones, Chile. 

Enecron’s EShip 1 (current latitude & longitude = -22.43 / -70.87)

Norsepower, as evidenced by its most recent fundraise, has more ambitious commercialization plans. It also partners with shipbuilders and operators to put its sails on their boats rather than building boats itself. Its sails are used on ships owned by Bore, Sea-Cargo, Scandlines, Vale, Nippon Marine, and Socatra.

The net-net

Succinctly, this is a fuel-saving technology. We love a good fuel-saving technology!

If you had to decarbonize international freight shipping by 10% in 10 years, which path would you choose:

  • Commercialize a zero-carbon fuel source and convince shipping operators globally to use it to move 10% of all oversea freight
  • Ask shipping owners to invest in mechanical sails that cut fuel use by 10%

Tough one, I know. The easy answer is some combination of both, coupled with software for things like route efficiency. But if I had to choose just one, especially with speed-to-deploy in mind, I’d pick the one that doesn’t involve a comprehensive fuel-source overhaul.

And while ~10% fuel savings via mechanical sails might not sound that sexy, and while Norsepower’s mechanical sails require an upfront capital investment, they save both fuel and emissions. Saving fuels means you start paying back upfront capital costs immediately. Contrast that to alternative fuel sources, which will almost certainly cost more than oil for maritime shipping for a long time.

The big open questions concerning Norsepower and its sails are, well, the perennial ones.

  1. How much appetite is there from the global shipping industry?
  2. How serious are shipping giants about cutting emissions now, as that’s probably still the primary catalyst for adoption here? Is that a concern they’re OK mortgaging five to ten more years?
  3. Can Norsepower keep its costs in check, scale manufacturing, and navigate supply chain constraints, which are hammering manufacturing for other renewable energy technologies?

To all of which I say: “Add it to the watch list.”