ClassNK - The Naval Architect insert - Feb 2013

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Research & Development

Revolutionary air lubrication aids energy and fuel savings ClassNK’s financial and technical commitment to the development of air lubrication systems to reduce maritime Green House Gas (GHG) emissions is reaping benefits for the entire maritime industry.

The Society’s work, in partnership with Mitsubishi Heavy Industries Ltd (MHI), Nippon Yusen Kaisha (NYK), Monohakobi Technology Institute (MTI) and others, has seen the installation of revolutionary air lubrication systems to module carriers, a coal carrier and most recently to a ferry. This was the first successful application of such technology to a ‘slender’ vessel.

“The successes we are seeing from these projects today are a direct product of the vast technical knowledge that the Japanese maritime industry has developed over the past several decades,” says Noboru Ueda, ClassNK Chairman and President.

“For us at ClassNK and the industry as a whole, the important thing is that we find ways to use this vast knowledge and experience to develop revolutionary new technologies that will benefit the entire maritime industry.”

For air lubrication in particular, two major factors have to be considered with regard to ensuring effective application. In order to maximise the reduction in hull friction, air bubbles need to spread thinly across a wide area of the ship’s bottom. As a result, it is easier to reduce the hull friction of large, low speed vessels with wide flat bottoms than it is to reduce the friction of high speed vessels with narrow bottoms.

As the draft of the vessel increases, a greater amount of energy is needed to supply sufficient air to the system, making it more difficult to reduce a vessel’s total

efficiency. Vessels which are widebodied, slow-moving and have a small draft, such as heavy lift and module carriers, should benefit the most from air lubrication systems and should be among the easiest targets for application of this technology.

The successful application of air lubrication systems to slender, high speed vessels such as container carriers poses a greater challenge, though as container carriers have a small draft, air lubrication systems are still likely to provide benefits in terms of efficiency.

Bulk carriers, tankers, and other large wide-bodied and relatively low speed vessels are fully within the expected range of application for such systems and it is expected that blower systems can be arranged differently, based on the shape and size of these vessels.

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While efforts to make use of air lubrication technology, such as those by Maersk Lines, have failed in the past, new Japanese technology is making air lubrication systems a practical option for commercial vessels.

Backed by a national initiative to support green shipping, testing of new Japanese air lubrication systems began in March 2011 with the installation of an air lubrication system on NYK-Hinode Lines’ 14,538 gross tons Panamanian flag newbuilding Yamatai, a module carrier. A similarly equipped sister ship, the Yamato, was delivered in November that year.

Constructed at MHI’s Nagasaki shipyard & Machinery Works, the Yamatai and Yamato were the world’s first vessels to be equipped with the Mitsubishi Air Lubrication System (MALS), the first air lubrication system to be successfully brought to market by a Japanese shipyard. The MALS system uses an air blower to create bubbles that reduce the frictional resistance of the hull surface against sea water, achieving energy savings of up to 10% including the energy required by the blower.

Energy saving effect of the air lubrication system in sea trials.

Tests on the Yamato and Yamatai concluded in July 2012 and results confirmed an average 6% reduction in CO2 emissions under various weather and sea conditions, compared with the 10% reduction measured during sea trials by NYK and MTI. In October 2012, MHI announced it had installed MALS on a ferry for the first time. The verification experiment was conducted at sea on the 8,072gt Ferry Naminoue, built at MHI’s Shimonoseki Shipyard & Machinery Works and owned by Japan’s A-Line Ferry Co Ltd. With a designed draft of 6.2m the vessel is deployed on the long range KagoshimaAmami-Okinawa route in southern Japan. Sea trials revealed that the improvement in the reduction

of fuel (reduction in propulsion power required) had exceeded 5% even in waves up to 2.5-3m high.

Beyond just ferries and module carriers, MALS are now slated to be installed on a wider variety of ships, including three post-Panamax bulk carriers ordered by American grainmajor ADM, as well as two large cruise ships ordered by AIDA Cruises, the German brand of Carnival Group, and potentially, even container vessels.

“As cruise vessels and container carriers can have very different hull forms, it is hard to give a concrete estimate of the savings possible for these ships in general.

However, we believe that this technology could offer large improvements in fuel efficiency for both container vessels and cruise ships, just as we have seen with the application on a ferry vessel,” says Shuji Mizokami, Engineering Manager, Shipbuilding & Ocean Engineering Department, MHI.

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In response to questions as to whether MALS needs to be optimised for certain design speeds or whether it is effective at any operational speed, Mr Mizokami, says: “MALS can be optimised for use with each vessel by using the vessel’s service speed as the maximum speed for the vessel.

However, the system is designed to provide benefit at any speed by automatic adjustment of the blower power in accordance with vessel speed.”

Sea trials confirmed a near-4% reduction in CO2.

“The challenge this time with the Soyo was in finding a way to use scavenging air from the main engine exhaust for the air lubrication system in order to minimise the energy required to blow air to the ship’s bottom,”

says Tomoki Inoue, Researcher in MTI’s Technical Strategy Group.

“Thanks to the technical solutions developed as part of this project, the range of applicable merchant vessels benefiting from this system can be widely expanded.”

The CO2 reduction reported for the Soyo during sea trials was 4%

While MHI has emerged as an early leader in air lubrication technology, MALS is not the only lubrication system to have entered the market. NYK took delivery of the 91,443 dwt coal carrier Soyo in July 2012, and the vessel has become the first traditional commercial vessel engaged in international trade to have an air lubrication system installed permanently.

The Soyo was constructed at Oshima Shipbuilding Co Ltd in Nagasaki and features a main engine scavenging air bypass that uses waste exhaust from the engine to produce the air bubbles and reduce the frictional resistance between the ship’s bottom and seawater. This system was developed by Oshima and a consortium of shipyards, manufacturers and other bodies.

Alongside MHI, Oshima has become another Japanese yard to successfully make use of air lubrication technology.

For a coal carrier, installation of an air lubrication system posed different challenges to those encountered with the shallow draft vessels Yamato and Yamatai.

Unlike the tests with the Yamato and Yamatai, the intention was to verify the effectiveness of the system on a coal carrier having a conventional deepdraft hull so that the range of applicable merchant vessels benefiting from this system could be expanded.

Top: module carrier Yamatai, the world’s first vessel to be equipped with MALS; middle: coal carrier Soyo; bottom: Ferry Naminoue.

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MALS airflow simulation against 8% for shallow drafts, a result which the owner and MTI verified along with the yard and other project partners. “To verify the effectiveness of the systems, we conducted the sea trial and the reverse speed trial with the air lubrication system both ON and OFF,” says Mr Inoue. “We then evaluated the effectiveness comparing speed power curves obtained with the air lubrication system ON and OFF. As the air lubrication system is controlled automatically, it does not cause any additional work for the crew.

We think the potential for this technology is huge, and we are currently planning on expanding the use of air lubrication technology to other types of ships in our fleet.”

True to its word, NYK has already placed new orders for two PCCs using MALS to be built to at Japan’s Imabari Shipbuilding, which looks to become the next yard to successfully make use of this revolutionary new technology.

Backing the development of these projects is the world’s largest classification society ClassNK, which has not only provided research support and funding for these projects, but also addressed key questions over possible implications of this technology in terms of safety and regulation and

whether the use of these systems has any effect on Energy Efficiency Design Index (EEDI) or other new environmental regulations.

Mr Ueda says: “Our research has verified that this technology can greatly reduce GHG emissions without affecting the vessel’s safety or cargo capabilities. We expect that this will be a key technology that owners and yards around the world use to meet new EEDI requirements and other emission reduction initiatives.

“Since releasing the first results from these projects, we have seen a tremendous surge in interest from shipowners around the world, and have had inquiries from owners of all types about the potential for using air lubrication systems on their vessels. We think this will become a key technology going forward, and are proud to help support its success,” says Mr Ueda.

ClassNK’s participation in these projects was carried out as part of its Joint R&D for Industry programme to support joint maritime research begun in 2009. The programme has become the cornerstone of ClassNK’s R&D activities, which saw the society invest nearly $60 million in R&D in 2012.

“We have received a tremendous amount of support from the

industry not only here in Japan, but from around the world for our part in advancing this kind of forward looking and practical research.” says Mr Ueda.

ClassNK’s first major investment as part of Joint R&D for Industry programme was a near-$30 million commitment to a national project to develop technology to reduce GHG emissions from ships beginning in 2009 and ending in 2013. Air lubrication systems are just some of the innovative technologies being developed by the programme.

“Full results of the projects will be released upon completion; however the beauty of this programme is that we are supporting the development of actual new technologies,” says Mr Ueda. “This means that more than just data, ship owners will be able to make use of these technologies to reduce GHG emissions from their own vessels.

“With this programme in particular, our goal was to create technologies that could collectively reduce GHG emissions by 30% compared to existing vessels, but I think this is only the first step. Progress demands that we to set an ever higher target and carry out the practical research and development needed to make that technology a reality,” Mr Ueda adds.

For further information, please contact: ClassNK Practical R&D Promotion Division 4-7 Kioi-cho, Chiyoda-ku, Tokyo 102-8567, Japan Tel: +81-3-5226-2025 Fax: +81-3-5226-2019 E-mail: rx-sec@classnk.or.jp