Engineers at China State Shipbuilding Corp, the world's largest shipbuilder, have developed one of the world's largest models of rotor sail, aiming to tap the burgeoning global market of green ships.

The rotor sail system, which is yet to be named, has been designed at the Luoyang Ship Material Research Institute, and has undergone a series of ground-based, full-system tests.

It marks a major breakthrough in China's efforts to ensure a leading position in green ship technology, and will facilitate the global shipping industry's endeavor to reduce carbon emission.

The Luoyang institute is part of CSSC and specializes in shipbuilding materials and techniques. Engineers at the institute used their expertise in green composite materials and wind turbine blades when designing the rotor sail.

With a maximum rotating speed of 180 revolutions per minute, each of the new rotor sails is able to produce a top thrust of more than 355 kilonewtons.

The sail measures 5 meters in diameter and 35 meters in height, placing it among the largest rotor sail systems in the world.

Also known as Flettner rotor, a rotor sail is a large cylinder mounted upright on a ship's deck and mechanically spun. The effect of this spinning area in contact with the wind flowing around it creates a thrust effect that is used to propel the ship.

However, since its inception in the 1920s, the technology had only been deployed on a handful of cargo ships and small test vessels until the 2010s. With the international shipping industry placing growing emphasis on energy conservation and emission reduction, rotor sail technology has gained increasing prominence and gradually been adopted on commercial vessels including bulk carriers and roll-on/roll-off ships.

Feng Wei, a project manager of the new rotor sail, said on Friday that the shipping industry carries more than 80 percent of global trade by volume and is responsible for approximately 3 percent of total global carbon emissions. Given the global consensus on tackling climate change, the green transition of the shipping industry has shifted from a discretionary choice to a mandatory requirement.

"Wind-assisted propulsion represents one of the most promising and practical pathways for the shipping industry to achieve immediate emission reductions.

"Among various wind-assisted propulsion technologies, rotor sails exhibit distinct advantages — they occupy little deck space, do not disrupt cargo loading and unloading operations, feature a high level of automation, and require virtually no modification to a ship's original structure or operating procedures. And such characteristics make them highly suitable for installation on bulk carriers, oil tankers, and other vessel types. They can save an average of 5 to 25 percent of fuel consumption on each vessel," he explained.

The project manager said the use of the rotor sail system will help shipowners hedge against oil price fluctuations and reduce future carbon tax expenses.

He noted that the new product features easy control and maintenance as well as a high level of automation as it has many smart sensors on the exterior.

Feng cited projections by leading research organizations anticipating that around 7,000 ships worldwide will be fitted with various wind-assisted propulsion systems by 2030, with the number rising to approximately 21,000 by 2050.

zhaolei@chinadaily.com.cn