The cylindrical CoFlow Jet sail boasts numerous advantages, including environmental friendliness, absence of moving parts, and the ability to be retracted when ships enter and exit ports.
On July 31, New Atlas reported that the American startup CoFlow Jet has developed a cylindrical sail system without moving parts, promising to cut fuel costs for cargo ships by up to 90%.
With rising fuel costs and the goal of achieving carbon neutrality by 2050, increasing efficiency and reducing emissions for cargo ships have become imperative. One solution is harnessing wind power through sails. However, two main issues have made traditional sails less popular in modern times.
First, traditional sails require a large crew. A ship like the 921-ton Cutty Sark needed around 30 people to manage the sails and complex rigging. In contrast, a modern 196,000-ton container ship requires only 13 crew members, who primarily press buttons rather than haul ropes.
Second, traditional sails are entirely dependent on wind conditions. While voyages are smooth with favorable winds, challenges arise when winds are too light, too strong, or in the wrong direction. Without wind, the ship can be rendered immobile.
Aerospace engineering professor GeCheng Zha, founder of CoFlow Jet and director of the Computational Fluid Dynamics and Aerodynamics Laboratory at the University of Miami, has developed a new type of sail based on the Flettner rotor from the 1920s. Unlike traditional Flettner rotors that rotate to generate aerodynamic thrust, Zha’s cylindrical sails remain stationary. Instead, they draw in air from one side and expel it from another, creating a pressure imbalance and significant thrust along the cylinder’s length.
Zha explains that this process results in a highly efficient wind-based propulsion system, providing 100% of the necessary thrust for the ship thanks to its high lift coefficient and low drag. Unlike Flettner rotors, Zha’s cylinders do not rotate, reducing fuel consumption by up to 50% for large cargo ships and 90% for smaller vessels. Remarkably, sailing ships can eliminate fuel use entirely by deploying these sails and turning off engines, though this depends on wind strength and direction. Additionally, the system can be retrofitted to existing ships, with the cylinders retractable for port maneuvers.
With today’s technological advancements, wind propulsion systems offer a viable alternative to diesel engines. A major benefit is their environmental friendliness, significantly reducing carbon emissions in the shipping industry, which accounts for about 3% of global greenhouse gas emissions,” Zha stated.
