"Each WindWing® saves approximately 1.5t of fuel and 4.7t of CO2 per day" (L. Eatwell, Bar Technologies)

What is BarTechnologies' background and how did you end up creating the WindWing?

The company is a spinoff from an America's Cup team — a yacht racing and design competition. The British team developed simulation and analysis tools for racing yachts, including wing sails and foiling technology. They wanted to apply that toolset to commercial applications for green purposes: if it makes a race yacht efficient, it can make commercial vessels — crew transfer, big shipping, leisure — more efficient, burning less fuel and therefore greener. I joined the company at its inception in 2017 as a structural engineer with a background in composite structures and yacht masts.

We were approached to assess wind-assisted propulsion technologies coming onto the market, using our velocity prediction programmes and routing software to analyse how those technologies would perform on different routes, at different times of the year, accounting for all interaction effects through the entire drivetrain — all the way down to actual fuel burn. The result was that we found none of them were very good. The customer then asked: Could you design something better?

So rather than starting with an idea for a wing, we used our tools in reverse — to define the performance profile of the ideal technology, looking at the percentage of time a vessel spends at different wind angles and speeds across real global routes and weather conditions. That led us to this three-element rigid wing called WindWing.

How long did it take to go from concept to commercialisation?

We started building out our tools specifically for wind propulsion around 2018. The concept design and development phase ran roughly from 2019 to 2021. One major challenge was that classification societies — the bodies that certify the safety of equipment on ships — had no rule for wind propulsion yet. We worked closely with them to develop that rule, which was a collaborative but demanding process with constant design revisions.

We partnered with our first manufacturing partner in 2021. The first vessels launched in 2023 — six wings in total, two on one vessel, four on another. We then changed manufacturing partners to scale up, moving to a larger Chinese company experienced in cranes and offshore structures, with its own supply network. Their first wings went out in summer 2024. We are now on our fourth vessel with them, with five more rolling out in the next six months and more on order to follow.

Do European manufacturers lack competitiveness when you want to scale up?

It is well known that China is hard to beat in terms of production cost, but we are delighted to have established a supply agreement with WindWaves (Spain), who are preparing to start manufacturing soon. For those customers who want to install WindWings in Europe, for example, as a retrofit of a vessel operating transatlantic routes, this will be a good option. Additionally, we are launching a smaller wing this year — all-composite construction, less steel — and at that scale and with those materials, Europe becomes more competitive again.

Can you describe the competitive landscape of wind propulsion?

Wind-assisted propulsion breaks down into four main categories: kites, rotor sails (which use the Magnus effect, like spin on a golf ball), suction sails (aerofoil sections using fans), and rigid wings like ours. Kites have largely been abandoned because they can't go upwind.

We hold a patent on the three-element wing design. All rigid-wing competitors are limited to two elements, and you simply can't achieve the same control, lift, or power with two as you can with three. The 37.5m WindWings is the largest and most powerful device on the market, but that also means they are the heaviest and can't be fitted to smaller vessels. Our main competition comes from rotor sails and suction sails, which fit better at the smaller end of the market. That's why we are bringing out the 24m WindWing.

Are shipowners ready to adopt this technology?

Initially, there was a lot of conservatism and scepticism, with questions like "does it really work, is it safe, is it worth the investment?" Our first partners, MC Shipping and Cargill on the first vessel, and Berge Bulk on the second, were real front-runners. Part of the value they brought was helping open doors with ports and maritime authorities who had concerns about cranes hitting the wings, for example.

Now we are seeing a wave of fast followers. The technology is being proven mechanically, in terms of port acceptance, and in terms of actual fuel savings matching our promises. Uptake is increasing, though attitudes vary across companies. The Greek market, for instance, is traditionally conservative — they'll wait and see which technology wins out, but when they move, they will likely all move at once.

Can you give us some numbers about the fuel savings and the CO2 emissions reductions?

We modelled thousands of routes using ten years of historical weather data and different start dates throughout the year. The figure we arrive at is 1.5 tonnes of fuel saved per wing per day on average across real-world global voyage conditions. That equates to roughly 4.7 tonnes of CO2 avoided per wing per day. What percentage that represents of a ship's total fuel burn depends on the vessel's speed and efficiency.

We offer a performance guarantee with our wings — we have strain gauge measurements in the base that allow us to live-measure the load being produced. That's how confident we are in our numbers.

If the savings are that significant, what bottlenecks remain?

It depends heavily on the routes operated. A ship running exclusively through the Suez Canal north-south won't see much benefit, as there is very little wind. On transatlantic or transpacific routes, you could get an average of four tonnes per wing per day in savings. But many owners charter their ships out and can't guarantee which routes they will operate on, making the payback period hard to predict.

Payback period is central. On the best routes, it can be three to four years; on others, it can be significantly more. That's where mechanisms like FuelEU and a global carbon tax become transformative: if fuel goes from $500 to $700 (€433 to €606) per tonne, the business case changes dramatically and it becomes a straightforward decision.

What policy developments would most accelerate the deployment?

A global framework from the IMO would be transformative. Right now, there are so many scattered regulations and taxes across different jurisdictions that a ship operating globally might need to satisfy eight different criteria simultaneously. That complexity discourages action. A single, standardised global policy would give owners the confidence to invest. The more fragmented and patchwork it remains, the harder it is for anyone to know what to do.

Beyond policy, what other challenges are slowing scale-up?

Geopolitics is one — the US influenced the IMO negotiations in a way that blocked progress on a global framework agreement to reduce GHG emissions from shipping. Trade policy also affects our supply chains: we had components sourced from the US, and when tariffs came in, China stopped buying those components and we had to find replacements.

But the deeper issue is belief. Once people genuinely believe the carbon tax is coming and is real, they will invest. Anyone building a ship today without wind propulsion is, in my view, making a mistake. Alternative fuels like ammonia and hydrogen are promising, but not ready: the infrastructure isn't there. Wind propulsion is ready now, and it works alongside every other decarbonisation lever. We are already fitting wings on dual-fuel LNG vessels, and the more expensive those new fuels are, the stronger the case for wind becomes.

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