Ballast-Free Cargo Ship Design

Researchers at the University of Michigan are developing a new design for cargo ships which could eliminate the need for ballast tanks. Ballast tanks are cited as environmental hazards as they often carry sealife in conjunction with water which is dumped in foreign ports. 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 many invasive species such as the infamous zebra musscle.While Congress is considering costly legislation for tankers, the new design would eliminate the threat altogether.

The ballast-free ships have a constant flow of local seawater through a network of large pipes, called trunks, that runs from the bow to the stern, below the waterline, much like a submarine.

Not only would the newer design protect against invasive species, but researchers found it had an unexpected bonus; it requires 7.3 percent less power to propel the ship. The improvement is due mostly from water being expelled from the stern-end of the trunks into the propeller, allowing the ship to operate more efficiently.

Researchers concluded 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.

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