Tuesday, 23 September 2014

Fuel efficiency and floating on air

Fuel efficiency and floating on air

By Tom Stieghorst
*InsightIt’s funny how visions of the future can be both wrong and right.

I had that thought after viewing a museum exhibit of designs by modernist Norman Bel Geddes, including one for a cruise ship.

Bel Geddes’ big idea was streamlining and in the 1930s, he turned out everything from vacuum cleaners to passenger buses with that teardrop profile meant to increase speed. His cruise liner — with room for 2,600 passengers — is a thing of beauty, although it looks as much like a submarine as a surface ship. The exhibit included side views showing how wind eddies swirled around the superstructure of the conventional ships of the time.

Today, however, it isn’t wind resistance that is the focus of cruise industry streamlining, but water resistance. And the object is no longer to be the fastest across the Atlantic, but to cut fuel costs.

That accounts for the bulbous projection at the bow of every cruise ship, an innovation that pushes water quietly aside and improves efficiency. Cruise ships in recent years have been slathered in silicon compounds or other coatings to make them shed marine slime and slip through the water more easily.

The newest streamlining idea is set to debut on the Quantum of the Seas, the first full test of an air lubrication system that uses microbubbles to provide a cushion for the ship to ride on.

Royal Caribbean Cruises Ltd. (RCCL) has tested the system in a small way on the Celebrity Reflection, but installed a full system on the Quantum as part of the ship’s technology emphasis.

The idea is to form and inject tiny air bubbles below the hull that reduce drag as the ship plows forward. Ironically for Bel Geddes, air is the instrument to provide extra cruise ship streamlining.

Other firms have tried this before, but Royal Caribbean has developed its own method of making the bubbles so that they’re small enough to be effective. It involves first heating the bubbles to shrink them, and then cooling them to prevent them from turning to steam as they hit seawater.

“We’re not only riding on air, we’re riding on air-conditioned air,” quipped RCCL Chairman Richard Fain, on a recent tour of Quantum in Germany.

The system — which only works when a ship is traveling at speed — could knock 7% to 9% off of propulsion costs, even taking into account the energy needed for heating and cooling, Fain said.