DNV classification society: Bulbous bow redesign cuts fuel burn 5pc
REDESIGNING a ship's bulbous bow for slow steaming can produce fuel savings of five per cent, which means the retrofit can pay for itself in less than a year, says classification society Det Norske Veritas (DNV), reports Vancouver's Ship & Bunker.
DNV conducted a study of a series of 8,600-TEU ships operated by Hyundai Merchant Marine (HMM), which were designed to operate at 27 knots. Maersk Line has made retrofits to several of its vessels.
Today, those vessels are slow steaming at 15 to 18 knots, making the ships' original bulbous bow shapes inefficient, said the report.
DNV developed a new bulbous bow shape for the vessels based on expected conditions, and the first conversion, done by Daewood Ship Engineering Company (DSEC), was completed in March at a cost of US$680,000.
Shipboard measurements showed modifications reduced fuel use by almost 1,000 tonnes per year.
"The performance of the new bulbous bow has carefully been evaluated as part of verification over about two months period after delivery and fuel saving in operation so far has been found to be around five per cent or above," said Hyundai vice president Taeg-Gyu Lee.
"The payback period is expected to be much shorter than the one year originally estimated," he said.
Said DNV business director Jost Bergmann: "Existing ships have to compete with a new breed of efficient and flexible designs. One result of the high design speed of many existing containerships is that the bulb is highly tuned to reach the maximum speed. The new reality for much of the existing fleet is that this affects efficiency at lower speeds."