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Saturday, January 26, 2019  (Comments: 1)

The University of Bonn has competed a study into how new high-tech superhydrophobic surfaces and coatings could greatly reduce ship drag and CO2 emissions. If ship hulls were coated with special high-tech air trapping materials, up to one percent of global CO2 emissions could be avoided. This is the conclusion reached by scientists from the University of Bonn together with colleagues from St. Augustin and Rostock in a recent study.

According to the study, ships could save up to 20 percent of fuel as a result of reduced drag. If so-called antifouling effects are also considered, such as the reduced growth of organisms on the hull, the reduction can even be doubled. The study has now been published in the journal Philosophical Transactions A.

Depending on the type of ship, drag accounts for up to 90 percent of energy consumption. But novel high-tech coatings promise a solution.

“Around ten years ago, we were already able to demonstrate on a prototype that in principle it is possible to reduce drag by up to ten per cent,” explained Dr. Matthias Mail from the Nees Institute for Biodiversity of Plants at the University of Bonn, one of the authors of the study.

“Our partners at Rostock University later achieved a 30 per cent reduction with another material developed by us.” Since then, various working groups have taken up the principle and developed it further. The technology is not yet mature enough for practical use. Nevertheless, the authors forecast a fuel-saving potential of at least five per cent in the medium term, but more likely even 20 percent.

In their article in  the Royal Society’s Philosophical Transactions, they calculate the economic and ecological advantages this would bring. For example, a commercial containership on its way from Baltimore (USA) to Bremerhaven could reduce fuel costs by up to US$160,000. Worldwide, emissions of the greenhouse gas carbon dioxide would be reduced by a maximum of 130 million tonnes.

Taking into account the reduced growth of barnacles and other aquatic organisms, which causes enormous additional drag loss, this quantity even rises to almost 300 million tonnes. This corresponds to almost one percent of global CO2 emissions. “Of course, these figures are optimistic,” says Mail. “But they show how much potential this technology has.”

The high-tech layers are based on models from nature, such as the floating fern Salvinia molesta. This is extremely hydrophobic: When submerged and pulled out again, the liquid rolls off it immediately. After that, the plant is completely dry. Or to be more accurate: It was never really wet in the first place. Because underwater the fern wraps itself in an extremely thin dress of air. This prevents the plant from coming into contact with liquid - even during a many weeks-long dive. Scientists call this behaviour “superhydrophobic”.

These are water-repellent at their base, but hydrophilic at their tip. With these hair-tips, the aquatic fern firmly “pins” a water layer around itself.

Reader Comments (1)

1. Most ships operate in salt water, not fresh water. Maintaining artificial superhydrophic surfaces in fresh water for long periods, such as quoted for the floating fern, is one achievement. It requires another leap in technology to achieve the same in saline conditions. 2. Current fouling control coatings already save considerable CO2 emissions, so the figures quoted above for future savings need to improve on these, not start from scratch.

By Colin Anderson on Monday, January 28, 2019

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