March 25, 2008
EDITORS: Watch and link to a video about
ballast-free-ship testing program at: www.umich.edu/news/index.html?Vid/ballast/ballast
At least 185 non-native aquatic species
have been identified
This week, the U.S. Saint Lawrence Seaway
will implement new rules designed to reduce
Meanwhile, Congress is considering legislation that would force freighters to install costly onboard sterilization systems to kill foreign organisms in ballast water. The systems use filters, ultraviolet irradiation, chemical biocides and other technologies, and can cost more than $500,000.
The U-M ballast-free ship concept offers a promising alternative that could block hitchhiking organisms while eliminating the need for expensive sterilization equipment, said Michael Parsons, professor of naval architecture and marine engineering and co-leader of the project.
"There is no silver bullet. But the ballast-free ship has the potential to be an economic winner while addressing the ballast problem in a serious way," Parsons said.
Ships take on ballast water for stability when they're not carrying cargo. They discharge ballast when they load freight, expelling tons of water and anything else – from pathogenic microbes to mollusks and fish – that's in it.
Instead of hauling potentially contaminated water
ocean, then dumping it in a
"In some ways, it's more like a submarine than a surface ship," Parsons said. "We're opening part of the hull to the sea, creating a very slow flow through the trunks from bow to stern.
"You're continuously sweeping water through the ship and out," he said. "So you're always filled with local sea water, not hauling water from one part of the world to the other."
The U-M ballast-free ship concept was conceived in 2001 and patented in 2004. It is intended for new-vessel construction only.
With funding from the Great Lakes Maritime Research Institute, Parsons and his colleagues recently built a 16-foot, $25,000 wooden scale model of an oceangoing bulk carrier to test the concept.
The work is underway at the U-M Marine
towing tank, the oldest facility of its kind that is owned by a
In addition to helping fine tune the design, results from the latest round of tank tests and computer simulations suggest the ballast-free ship will deliver an unforeseen benefit. The design appears to provide a significant savings – possibly as much as 7.3 percent -- in the power needed to propel the ship.
For a 650-foot bulk carrier hauling 32,000 metric
cargo from the Great Lakes to
In upcoming towing tests, tentatively set for late June, the naval engineers will try to confirm and explain the unexpected power savings. Most of the improvement is likely due to the fact that water expelled from the stern-end of the trunks "smoothes out the flow" into the propeller, allowing it to operate more efficiently, Parsons said.
"It's a huge power reduction, a hard-to-believe improvement in power, and we have to convince ourselves that all of it is real," he said.
Building an oceangoing bulk carrier can cost $70 million. The added construction costs of the ballast-free design – for extra hull steel, trunk-isolation valves, piping and welding – would be more than offset by eliminating the filtration system and the ballast tanks.
The researchers conclude that the new design would result in a net capital-cost savings of about $540,000 per ship. Combined with the expected fuel savings, total cargo transport costs would be cut by $2.55 per metric ton.
"It seems that, compared to other ballast
systems, it's a viable alternative,"
"We have proven that the technical part is feasible and that it can be applied to new vessel construction," said Kotinis, a collaborator on the project and a U-M alumnus. "And we have also shown that, regarding the economics, it can reduce the operating cost and reduce or even eliminate the introduction of non-indigenous aquatic species."
For more information on the U-M Marine
-- Jim Erickson News Service University of Michigan 412 Maynard Ann Arbor, MI 48109-1399 Direct: 734-647-1842 Main: 734-764-7260 Fax: 734-764-7084 Office web: http://www.umich.edu/news