A new wind drive from startup CoFlow Jet looks like a set of bridge pylons accidentally installed on a cargo ship. The drive provides fuel savings of up to 90%.
Improve efficiency
With rising fuel prices and increasing government regulation, there is a strong drive to increase the efficiency of cargo ships and reduce their emissions. This can be done, for example, by taking inspiration from history and using sails to harness the wind. This sounds logical at first glance because sailing ships have sailed the world's oceans for thousands of years. However, there are two main barriers.
First, traditional sailing ships require a large crew. For example, the 921-tonne tea clipper Cutty Sark needed a crew of around 30 to operate the sails and the complex sheets and lines. Compare that to a modern 196,000-tonne container ship that needs only 13 officers and sailors. Moreover, most of them push buttons instead of pulling lines.
The second problem is that sails are completely dependent on the wind. If it blows hard enough AND in the right direction, it's great. If it blows too little or too hard, or from the wrong angle, it is less so.
Yet the idea of sails is experiencing a renaissance. But instead of acres of canvas strung on a forest of wooden masts, the new systems use kites, windvanes made of composites or inflatable, while some even use the hull of the ship itself as a sail. GeCheng Zha, a professor of aerospace engineering and director of the Aerodynamics and Computational Fluid Dynamics Lab at the University of Miami College of Engineering, uses a variant of the Flettner rotors developed in the 1920s.
Renaissance
Flettner rotors are large rotating cylinders that produce aerodynamic thrust at right angles to the air passing over them. The CoFlow Jet cylinders developed by Zha do not rotate. Some air is drawn in from the wind passing over the cylinders, which is then pressurised and released through an exhaust. This creates a pressure imbalance that provides a significant amount of thrust along the length of the cylinders.
According to Zha, this creates a highly effective wind propulsion system that can provide 100% of the thrust needed to propel the ship. Unlike the Flettner system, there are no rotating parts and it can provide fuel savings of up to 50% for large cargo ships and 90% for small ships. An additional advantage is that the system can be retrofitted to existing ships and the cylinders can be retracted to enter and exit the port.
Wind-assisted propulsion is thus becoming another efficient and environmentally friendly alternative to diesel engines. The shipping industry is responsible for about 3% of global greenhouse gas emissions. This can be significantly reduced in this way.
