September 21, 2021

I, Science

The science magazine of Imperial College

Big ships are using a brand new means of propulsion – the wind. This isn’t a hark back to romantic days of white sails and stripy jumpers. This time it’s kites. Huge ones. Hundreds of metres in the air. And now scientists can predict exactly how much power the shipping companies will save.

Big ships run on bunker oil. Thick, gloopy and full of impurities, it’s nasty stuff to burn and releases vast amounts of greenhouse gases. It’s also expensive when ships travel thousands of miles across oceans.

So, to do their bit for the planet and save cash in the process, shipping companies are now flying giant, computer-controlled kites from their vessels. The wind pulls the ship along, reducing the need for fuel.

But the technology is young and currently inefficient, so a team from the University of Southampton, led by George Dadd, has devised a model that allows the kite designers, computer programmers and ship owners to devise the best kite system possible.

Kites are better than sails – they can be winched high into the air where the wind is stronger. But you can’t fly a kite directly overhead because the kite’s face will be pointing down, not into the wind – all power will be lost. Also, height is limited because of the danger of snagging aeroplanes. Add the fact that different kite flying styles – figures of eight, sine waves, loops – and kite shape both have a huge impact on power, and the calculations for the perfect kite become extremely complicated.

The Southampton team used a 300m2 kite in tests. By playing with the variables of their model, pending publication in Renewable Energy journal, they were able to generate 16.7 tonnes of forward force in only a moderate breeze.

The model can be applied to kites and ships of all shapes and sizes and the team are now working with the Ministry of Defence to understand whether kites could save the cash-strapped armed forces some money on their energy bills.