Curbing Wave & Wind Resistance
The Yamato, a module carrier, uses air bubbles to decrease friction resistance with seawater. © NYK-Hinode Line, Ltd.
An artist's sketch of the Mitsubishi Air Lubrication system (MALS), showing air bubbles blown at the bottom of a ship.
© Mitsubishi Heavy Industries, Ltd.
Eco-ships are also built to reduce the frictional resistance of waves and wind. In probably the most interesting way of doing so, some Japanese ships have a system for generating air bubbles at the bottom of the bow and sending them by a blower from bow to stern. The bubbles reduce frictional resistance between the ship and seawater, helping to propel the vessel. The bubble effect was known theoretically before, but it was Japan that actually built ships to take advantage of air bubbles for the first time in the world. Three bubble ships entered service since 2010, including the Yamato, a “module carrier” that transports modularized heavy and large loads. The ships have proven to reduce CO2 emissions by about 6%. It is a unique idea that a ship rides on air bubbles, isn't it?
The City of St. Petersburg, an energy-saving car carrier built by Kyokuyo Shipyard Corporation, which has a hemispherical bow to reduce wind resistance.
Also, the City of St. Petersburg, a car carrier commissioned in December 2010, has a hemisphere-shaped bow. The rounded bow of the ship, which travels back and forth across the North Atlantic carrying a Japanese carmaker's vehicles, helps reduce wind resistance by up to 50%, slashing CO2 emissions by about 2,500 tons per year as a result.
An artist's sketch of the next-generation car carrier ISHIN-I featuring both a ship design for reducing air resistance and solar panels. © Mitsui O.S.K. Lines, Inc.
There is an ongoing plan to combine the two technologies – the hemispheric bow and solar panels on board – to build very fuel-efficient ships capable of curbing wind resistance and taking advantage of solar energy.
In addition, Japan is recently experimenting with new methods for painting the ship hull. Inspired by Mother Nature, new sorts of surface painting, such as one likened to the skin of sharks moving swiftly through the water or to lotus leaves repelling water, are being developed with nanotechnology. Alloys such as aluminum as well as carbon fiber used for aircraft are also under consideration to reduce ship weight.
Dream Eco-Ship Planned
There is a plan in Japan to build a "Super Eco-Ship" using both solar and wind power by 2030. The ship, 352 meters long, will have solar panels as well as eight large masts to take advantage of wind propulsion. It looks like a honeybee gliding on the water.
An artist’s sketch of the future container ship NYK Super Eco-Ship 2030. © Nippon Yusen K.K.
In additional to these natural energy sources, the ship is supposed to mainly use fuel-cell power derived from LNG. The ship will have a total of 16 modular fuel cells, each the size of a standard freight container, which can be replaced with new ones during a port call.
In 2030, the dream eco-ship will be partially powered by LNG. Compared with current ships powered by diesel engines which burn heavy oil, the dream ship will cut CO2 emissions by 69%. Eventually, the ship will aim at zero waste emission.
Ships all over the world are said to emit 1.05 billion tons of CO2 per year, accounting for 3.3% of total global CO2 emissions. That is more than the total amount of CO2 emitted by Germany per year. Now that emerging countries are developing rapidly, the world's ocean-going ships in 2050 will be emitting 2.5 times more CO2 than today, according to some experts. There is much hope in the world for Japan's eco-ship technologies to help preserve the global environment.
(November 2012)