Previously, we discussed why most ideas to decarbonize shipping don’t have a clear path to practicality or affordability.

Wind energy does! In this post, I’ll explain how the Outsail team knows that wind energy is the best way to decarbonize maritime shipping.

A quick history primer:

Battle of Scheveningen (Slag bij Ter Heijde)(Jan Abrahamsz. Beerstraten)We know that wind energy can move ships across the sea, because there’s historical precedent! During the Age of Sail (circa 1550-1850), sailing ships were the dominant force in global trade and warfare. These sophisticated vessels were the container ships and aircraft carriers of their time, allowing for purely wind-powered voyages all over the world.

Though they traversed the globe, the sailing vessels of two centuries ago were limited in a few ways:

  • Speed: Ancient sailing ships were relatively slow, with normal sailing speeds of between five and eight knots in favorable winds.
  • Intermittency: If the wind was in the wrong direction, or too light, ancient ships weren’t able to maintain their desired speed.
  • Unpredictability: Forecasting was limited to rudimentary guesses based on wind, clouds, and barometric pressure

We’ll need to solve these problems, so let’s set some goals.

How capable must wind-powered ships be?

Recently, we set the following three goals for the future of maritime shipping:

  • Move a ship with zero emissions
  • Do so cost-effectively
  • Do so while matching fossil-fuel performance.

chris-leboutillier-TUJud0AWAPI-unsplashFor the solutions we evaluated, it was easy to directly compute the energy requirements of a contemporary fossil-fuel powered ship and do some napkin math comparisons.

Analyzing wind energy is a little more complex than napkin math. This is for two reasons:

  1. The amount of wind energy that a ship can collect depends on the specific route and speed of the ship, and the exact weather at that time
  2. The amount of wind energy that a ship can collect is very dependent on the design of the vessel and type of sails used.  

To see if maritime wind energy can meet our above goals, we’ll get a little more specific about what ‘matching fossil fuel performance’ means.

  • We must match the speed of modern vessels. We’ll pick container ships as our reference point. These vessels move slower every year as fuel gets more expensive.  Current averages are around ~13.8 knots, with a predicted drop to roughly 12 knots by 2025. We’ll set an average speed of 12 knots as our goal.
  • We must match the schedule reliability of modern vessels. COVID aside, the overall schedule reliability of container carriers hovers around 70%. Since the comparative schedule reliability of fossil fuels is what drove commercial sailing ships extinct, we decided to blow this metric out of the water, setting an ambitious goal of 99% schedule reliability.

For our modern wind-ships to hit the above performance goals, we’ll have to improve on historical ships. There are three key parts to our solution:

Aerodynamic Advances: Improved Sailing Performance

In the 1550s, a three-masted, ship-rigged vessel was the pinnacle of sailing technology. In the intervening five hundred years, aerodynamic advances have closed the gap, allowing sailing vessels to sail far faster and with far less dependence on fair winds.

The key to this is wingsails. We’ll dive into the underlying physics in a future post, but for now let’s focus on the advantages wingsails offer:

  • Wingsails can provide useful thrust while sailing nearly directly into the wind
  • Wingsails provide useful propulsion at vessel speeds that turn other sails into parachutes
  • Wingsails can work hand-in-hand with an engine, enabling new forms of hybrid propulsion

Wingsails alone will solve our speed issue, providing far more propulsive force than ancient sails with far less drag.  By allowing us to sail almost directly upwind, they also solve part of the intermittency issue. ‘The wrong wind direction’ barely exists for a wingsail-equipped vessel! By working hand-in-hand with an engine, wingsails offer a novel solution to light winds. Let’s examine how:

Propulsion Breakthroughs: Saving wind for a calm day

How Wind Can Beat Fossil Fuels 1It’s a counterintuitive leap that a new age of sail will depend on auxiliary power from engines. 

When the wind was too light to move an ancient sailing ship at the desired speed, ancient sailors were forced to sail slower. In the worst case, no wind at all, the ship could be ‘becalmed’ for days or weeks.

Modern ships need not suffer in this way. Our sailing vessels can be equipped with batteries and electric turbines capable of storing electricity on windy days, and powering the ship when the wind is too light. In this way, our modern, hybrid vessels can compensate for the intermittency of the wind.

Conventional sails wouldn’t allow this, as conventional sails add much more drag than useful propulsion when an engine is on! Wingsails, fortunately, are low-drag enough that they can provide useful propulsion, even on a day when the winds are light and the electric motor is providing 90% of the ship’s propulsion. 

The new issue: Knowing when to store energy, and when to use it! Software is the key.

Modern Forecasting & Artificial intelligence: Predictable Wind Energy

The last, most important pillar of our modern vessel’s performance is planning software. When the Outsail team began in June of 2022, we didn’t start by building hardware. We started by building a software suite which would allow us to simulate the performance of various sailing ships in historical weather conditions.

This software tool allowed us to determine how fast any given vessel design would be, on any route, given any start date in recent history. We quickly discovered that the hardest problem wasn’t simulating the vessel performance (which was easy to test by comparing the model with a real vessel). It was planning the optimal route! 

For example: Leaving Hawaii for California, it is often better to sail north first, skirting the North Pacific High before catching the Easterlies in the mid-latitudes. The North Pacific High is an area of little wind which can becalm a vessel for days, and it moves. Mistime the turn to the east, and the vessel will get stuck!

We found that by using clever software, our wind-powered vessels can plan routes which keep them powered for their entire journey. They could decide, for example, when it made sense to power through a high-pressure zone using their electric motors, and when to skirt around and save energy for later.

With these three advances together, our simulated, zero-carbon vessels achieved speeds over 12 knots with the required 99% schedule reliability. We knew that wind was the clear path to maritime decarbonization.

Until next time,
Arpan