Looking like a bridge support set that accidentally got stuck on a cargo ship, a new wind-powered system from startup CoFlow Jet promises to reduce ship fuel costs by up to 90% by using fixed cylinders with no moving parts.
Between rising fuel costs and increasing government mandates requiring shipping companies to be carbon neutral by 2050, there is strong pressure to reduce emissions while improving the efficiency of cargo ships. One way to do this is to take a page from the history books and re-embrace sails to harness the wind.
On the surface, this makes sense. Sails have propelled ships around the world for thousands of years and were still used for commercial shipping after World War II. But there are two problems with sails that have kept them out of the cargo market, except in the most localized niches.
Co Flow
First, traditional sailing requires a huge crew. Something the size of the 921-ton tea ship Cutty Sark would need a crew of around 30 to man the sails and the complex sheets and ropes that control them. Compare that to a modern 196,000-ton container ship, which would need just 13 officers and sailors—and most of them are pushing buttons rather than pulling ropes.
The second problem is that sails are completely dependent on the wind. If the wind is strong enough and blowing in the right direction, great. If it's too little or too hard, or blowing in the wrong direction, not so great. If it's not blowing at all, you're not going to go anywhere.
As a result, steam and diesel power became useful because of their low labor costs and ability to provide energy on demand, sails soon came into use for recreational and exploratory purposes.
Today, the idea of sailing is experiencing a similar renaissance as it did during the energy crisis of the 1970s, with shipping companies looking to updated versions of old technology to reduce fuel costs. But instead of acres of canvas stretched from a forest of timber poles, new systems use kites, windmills made of composites or inflatables, and some even use the ship’s hull as a sail.
GeCheng Zha, professor of aerospace engineering and director of the Aerodynamics and Computational Fluid Dynamics Laboratory in the University of Miami College of Engineering, is using an approach that is a variation of the Flettner rotors developed in the 1920s, but with a key difference.
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. They draw in some of the air as the wind passes through them and through them, and then dispose of it elsewhere in the cylinder. By drawing in a small amount of air from the intake, pressurizing it using a propeller, and spraying it out the outlet, this creates a pressure imbalance and a significant amount of thrust spread over the entire length of the cylinders.
According to Zha, this creates a very effective wind propulsion system that can provide 100% of the thrust needed to propel the ship due to the system’s very high lift coefficient and reduced drag. Unlike the Flettner system, there are no rotating parts and it can provide fuel reductions of up to 50% on large cargo ships and 90% on small cargo ships.
This may seem sensational, but remember that any sailing vessel can achieve 100% reduction by simply adjusting the sails and completely shutting down the engines. Of course, this all depends on the strength and direction of the wind. However, another advantage is that the system can be retrofitted to existing vessels and the cylinders can be retracted to enter and leave port.
“What’s old is new again,” Zha said. “With today’s technological advances, wind-assisted propulsion is an effective alternative to diesel engines. And its biggest advantage is that it’s environmentally friendly — it’s an effective way to decarbonize the shipping industry, which accounts for about 3% of global greenhouse gas emissions. The shipping industry has tended to resist change because diesel engines are so powerful, but now, willingly or unwillingly, under increasing pressure, it will have to change.”
Source: University of Miami