The white sailboat outside of Michelin Group’s Swiss office doesn’t have a sail at all. Instead, it has a wing. The puffy, inflatable structure towers over the vessel, resembling an enormous meringue with a spine of stiff peaks. At sea, it cuts through the wind like an airplane wing, sending the sailboat flying across the water. Now Michelin wants to fit the technology onto cargo ships. The goal is to harness wind energy to reduce the use of diesel fuel—and thus curb greenhouse gas emissions.
The French tire maker unveiled its Wing Sail Mobility, or WISAMO, project earlier this month. The set-up operates with the push of a button. First, the telescopic mast rises from its base, reaching up to 17 meters high. The wing, which starts as a pile of fabric, slowly unfurls as a small air compressor inflates the double-sided material. As wind flows over the 93-square-meter wing, the variations in air pressure create lift, helping propel the vessel forward. When the ship approaches a bridge or encounters rough weather, the system automatically retracts.
Michelin estimates the wing can improve a ship’s fuel efficiency by up to 20 percent, based on measurements from technical tests and simulations, said Benoit Baisle-Dailliez, who leads Michelin’s WISAMO initiative. For a large container ship, that could mean avoiding burning tens of thousands of liters of fuel on a given day. The company plans to test the technology on a commercial freighter in 2022.
“WISAMO is a significant step towards Michelin's ambition to completely decarbonize its supply chain,” Baisle-Dailliez said in an email.
The project joins a growing fleet of “wind-assisted propulsion” initiatives around the world. On the bulk carrier MV Afros, four Flettner rotors (or rotor sails) spin at a dizzying pace, creating thrust that pulls the ship forward. The cargo vessel Lysbris Seaways is outfitted with two suction wings. The non-rotating structures have vents and internal fans that suck in the thin layer of air lying over the surface of the wing. Airseas, an Airbus spin-off, said it will install a high-flying towing kite on a bulk carrier by the end of 2021.
After years in development, these wind-blown technologies are taking off as the global maritime industry faces pressure to address climate change. Cargo shipping is responsible for nearly 3 percent of the world’s annual greenhouse gas emissions, and ships are a significant source of toxic air pollution in ports and coastal communities. For shipping companies, these next-generation sails are a potentially immediate way to reduce emissions, since most systems can be retrofitted to existing vessels. And curbing fuel use can reduce ships’ operating costs—saving money while avoiding CO2.
“More shipowners are starting to wake up to that fact,” said Gavin Allwright, secretary of the International Windship Association.
By Allwright’s count, 15 vessels are currently sailing with wind-assisted propulsion devices, and five more are expected by the end of this year. By late 2022, the total number could double, to about 40 vessels. That’s a tiny fraction of the world’s roughly 60,000 cargo ships. But it’s an important start for an industry that’s relied almost exclusively on diesel power over the past century.
Among the current crop of initiatives, WISAMO is the only one to use inflatable wings. Two Swiss inventors, Edouard Kessi and Laurent de-Kalbermatten, first patented the concept. In 2015, they launched a prototype on a small dinghy and, two years later, they sailed around Lake Geneva with a 42-square-meter inflatable wing.
Michelin has since enhanced the original design with new patents, one of which is related to wing inflation, Baisle-Dailliez said. The company now runs simulations and real-world tests on the sailboat in Switzerland, which was provided by French navigator and technical expert Michel Desjoyeaux.
The WISAMO system is designed to operate autonomously, so as not to burden crew with extra tasks or training requirements. It can also work when the vessel is facing into the wind, allowing the vessel to cover more routes. Baisle-Dailliez said Michelin plans to start testing the wing in the Atlantic Ocean, off the coast of France, starting in September. As for next year’s cargo ship trial, he said contracts with potential customers are being signed but remain confidential.
Demonstrations like these are key to help wind-assisted propulsion catch on more widely across the global shipping industry. Companies wary of investing in novel technologies will be looking to see if trial runs can deliver the fuel reductions and cost savings that developers promise. And regulations that encourage decarbonization—such as by taxing CO2 emissions—would likewise bolster this niche sector, especially if the tax dollars became loans or grants to help companies pay for wings, kites, or sails, Allwright said.
“That would have a double impact on the industry,” he said, noting that international maritime regulators are set to debate such a policy later this year.
Maria Gallucci is an IEEE Spectrum contributing editor based in New York City. She was the 2017-2018 Energy Journalism Fellow at the University of Texas at Austin. Previously, Maria has worked as a staff writer for publications in New York and Mexico City, covering a wide range of energy and environment issues in the United States and Latin America.