Wind-assisted propulsion with the potential to cut large ships’ fuel consumption by up to 30% has until now existed only on the computer screens of a few idealistic naval architects.

This is about to change with projects in the running to take wind propulsion to commercial scale in the near future — and potentially even, in tandem with other technologies, create truly low-carbon tankers and bulkers.

Leading the way in terms of confirmed installations is trader and charterer Cargill, which plans to fit two of BAR Technologies’ WindWings rigid sails to a kamsarmax bulker that will be in operation by early 2022.

Cargill Ocean Transportation started its green journey fairly early and even tried wind energy 10 to 15 years ago with a kite-based technology.

Those early kite tests were not a success. Nevertheless, “We really like wind because it’s kind of agnostic with whatever fuels or technology you get going forward,” says president Jan Dieleman.

To get a full 30% saving on a kamsarmax would require four of the 37-metre WindWings. With two fitted to the chosen ship (already chartered from a progressive but as yet unnamed owner) Cargill and BAR are looking for fuel use reduction percentages in the high teens.

Cargill Ocean’s sustainability projects leader, Keith Dawe, says modelling suggests that the larger a vessel, the easier it is to implement wind propulsion, but the company wanted to start at a manageable scale. It expects just a few voyages can confirm how well the sails operate.

BAR Technologies chief executive John Cooper tells TW+: “After this retrofit we are talking to them [Cargill] about a run of MR2 tankers and other vessels, and it’s likely there will be a run of new bulk carriers after the MR2s.”

BAR Technologies WindWings sails to be installed on a Cargill kamsarmax. Photo: BAR Technologies

Dawe confirms that Cargill is running several projects in parallel, with the Singapore-flag kamsarmax in the lead. Others “will snap into place” once it is happy with the WindWings’ performance.

“Even with the first voyage we will learn a lot, and very quickly after that make progress with those other projects that have been started but paused at the appropriate milestones until we spend big money on them,” Dawe says.

“Dry bulk is what we are all about. We will be putting wind-assistance propulsion on our tankers, but where we can really scale up is on the dry.”

Cargill has built a business model for adding energy-saving technologies to ships it does not own, to help finance their installation.

“I think we will see much more of that happening where entities such as ourselves take a bit of control over the technology on the vessels, do our bit to finance them, help the owners get over some of the hurdles and then split the risks and rewards in an appropriate way,” Dawe says.

Dieleman adds: “It’s about partnership and having some skin in the game. You can’t just say to an owner: ‘You need to finance this and take all the risk’.”

He says Cargill is sometimes prepared to entirely finance an energy-saving device, getting its payback from savings over the period of a charter, while the owner ends up with a more valuable ship.

Plus Point

There are three main wind technologies: kites, rotors and sails. The physics of kites are good, but the practicalities are not, says Cargill’s Keith Dawe, although he hopes they can be made to work. “It’s not as crazy as it might first seem,” but Cargill’s early experiments ended with the kites in the water.

Flettner rotors work well and are easier to fit, but have a natural limit to fuel savings of around 10%. “But with wind-assisted propulsion you are really changing the way a ship works. If you are going to go to the lengths of creating a new sub-class of vessel, you should go all out for the highest level of savings” — and that means big sails.

The trader expects average savings from WindWings to be in the region of a high 20% to 30%, and is targeting payback periods of around five years when operating globally across high- and low-wind trades.

Dawe says early wind-assisted ships will be operated in windier latitudes where Cargill can get the most from them, probably North Atlantic routes or round the capes. But he adds: “We have a fleet that tramps, and ultimately we have to be able to sail our vessels anywhere and everywhere.

“Other energy-saving devices will pay back sooner, but no energy-saving device can get you to this order of magnitude of saving and still have a positive business case within the lifetime of a long period charter.”

Dieleman says Cargill has a lot of potential partners for further wind-assisted ships that are watching the kamsarmax project. Proof of the concept will not just be how the ship sails, but how well it works in ports and with cargo discharge.

“The purpose is to take a lead. Once it has been demonstrated, I think you will see some owners doing this speculatively,” adds Dawe.

Cooper says BAR will develop a family of three WindWings. Initially it thought the 37-metre model, also to be used on the MR2s, would be the medium size, but now it believes that may be the smallest. Four 50-metre tall units would be needed for VLOCs, and a midsize wing will probably come in at 44-45 metres.

It chimes with Dawe’s assertion that wind is better for bigger ships: “If you go too small, you end up with vessels that are geared, and it is quite difficult to mix wind-assisted propulsion with cranes. At some point we will crack that nut.”

Jan Dieleman. Photo: Wilson Santinelli/Global Maritime Forum

Installation challenges are also greater for retrofits than newbuilds, says Cooper. “You need to ensure the vessel is reinforced in the right place, because WindWings are not light — they are 100 tonnes — and that they are on a bulkhead, and the load is spread across the bulkhead and the deck.”

BAR signed a deal in April with Yara Marine Technologies for the Norwegian scrubber supplier, which is branching out into greener shipping markets, to take charge of the sails’ construction, maintenance and support services. They will be marketed as BAR Tech WindWings by Yara Marine Technologies.

The WindWings have gone through hazard workshops with class society DNV to demonstrate their safety and effectiveness, which included green-water loadings and ice build-up scenarios, and are making progress towards approval in principle.

“Our clear intention is that they need to last as long as the vessel and that they must be absolutely robust for all sea conditions, routes and times of year,” Cooper says.

DNV is also working with flag states on proposals for camera systems that can pass field-of-vision regulations.

“When the wings are up, there is no doubt that line of sight will be compromised if we want these savings,” says Cooper, who believes in the long run new vessels are likely to have extended bridges and possibly front accommodation and augmented-reality systems.

“We are very much looking beyond this first retrofit to having a much more expanded market in the newbuild sector, but we won’t discount retrofitting the current legacy fleet, because there is a lot of CO2 to save and good economics to satisfy.”

Dieleman says one of Cargill’s learning experiences from its early kite tests was the need for a lot more work in modelling before installing them. It develops the confidence that the equipment can be scaled up to commercial levels.

It was something that attracted Cargill to BAR: its experience in simulation of wind technologies that arose from the company’s birth from racing yacht designs developed for British sailor Sir Ben Ainslie Racing’s America’s Cup campaigns.

Foil systems used in the America’s Cup lift yachts out of the water, necessitating aerodynamics as much as hydrodynamics skills. A ban on tank testing for the races a decade ago pushed teams deep into computational fluid dynamics simulation and analysis.

Dawe says Cargill’s early work led it to conclude it wanted something different from most conventional wind sail designs, and it liked BAR’s solution. “They had the capabilities to really analyse in depth before starting.”

Dieleman comes back to the theme that full decarbonisation will require deploying numerous technologies and various alternative fuels.

Shorter payback times for wind sails are likely to be possible with more expensive green fuels, but it won’t just be cost savings. They will also help reduce the volume of less energy-dense fuels that will need to be taken on board, he says.

“If you can save 20%-30%, or whatever number you want to use, it’s always a win.”