The CoFlow Jet cylindrical sail boasts numerous advantages, such as being environmentally friendly, having no moving parts, and the ability to retract when the vessel is entering or leaving port.
American startup CoFlow Jet has developed a cylindrical sail system without moving parts, promising to reduce fuel costs for cargo ships by up to 90%, as reported by New Atlas on July 31.
Simulation of a ship equipped with a cylindrical mast. (Photo: CoFlow Jet).
Rising fuel costs, coupled with the goal of achieving carbon neutrality by 2050, make enhancing efficiency and reducing emissions for cargo ships increasingly essential. One way to achieve this is by using sails to harness the power of the wind. However, two significant issues have made traditional sails less popular than in the past.
First, traditional sails require a large crew. A ship weighing 921 tons, like the Cutty Sark, requires around 30 people to manage the sails and complex rigging. In contrast, a modern container ship weighing 196,000 tons only needs 13 crew members, most of whom simply push buttons instead of pulling ropes.
Second, traditional sails are entirely dependent on the wind. A journey will be smooth if the wind is strong enough and in the right direction, but it can become challenging if the wind is too light, too strong, or in the wrong direction. Without wind, the ship cannot move at all.
Professor of Aerospace Engineering GeCheng Zha, the founder of CoFlow Jet, has designed a new type of sail based on the Flettner rotor developed in the 1920s. Zha is also the director of the Computational Fluid Dynamics and Aerodynamics Laboratory at the University of Miami’s College of Engineering.
The Flettner rotor consists of large rotating cylinders that generate aerodynamic lift at appropriate angles with the airflow. Zha’s cylinders do not rotate. Instead, they draw a portion of the air from the incoming wind and expel it from another part of the cylinder. The process of drawing a small amount of air from the intake, compressing it with a fan, and then expelling it creates a pressure imbalance and significant thrust along the length of the cylinder.
According to Zha, this creates a highly efficient propulsion system that relies on wind, providing 100% of the necessary thrust for the ship to operate thanks to enhanced lift coefficients and reduced drag. Unlike the Flettner system, Zha’s cylinders do not rotate, helping to reduce fuel consumption by up to 50% for large cargo vessels and 90% for smaller ships. In fact, sailing ships can achieve a 100% reduction in fuel use by raising their sails and shutting down their engines completely, although this depends on the wind’s strength and direction. Another advantage is that the system can be retrofitted to existing ships, and the cylinders can be retracted when the vessel is in port.
“With today’s technological advancements, wind propulsion systems represent an effective alternative to diesel engines. A significant advantage is that it is environmentally friendly, effectively reducing carbon emissions in maritime transport, which contributes approximately 3% of global greenhouse gas emissions,” Zha stated.
