Many shipowners and operators are turning to bulbous bow retrofits to increase their vessels’ energy efficiency. DNV GL has developed a new tool as part of the ECO Retrofit service to support the industry in tailoring retrofit projects to the future needs of their fleet. While the service identifies new bow shapes based on computational fluid dynamics (CFD) calculations, the new tool explores the effect of alternative operational options. Overall, this approach can customers help save five to ten per cent on their annual fuel bill.
The biggest issue in many retrofit projects is the definition of the individual operational profile. In the past two years the ECO Retrofit service has already helped to upgrade some 200 vessels. Aside from analysing their fleet’s past performance, shipowners and operators frequently have questions concerning the future, such as: What if I operate at other conditions some day? Can we change the operational profile again? “Even though our new ECO Retrofit tool cannot change the volatility of the market, it quantifies performance for a bandwidth of scenarios from worst-case to best-case scenarios, supporting more informed business decisions,” says Carsten Hahn, Senior Project Engineer ECO Lines at DNV GL – Maritime.
DNV GL’s new ECO Retrofit service creates 5,000 to 10,000 vessel-specific bow designs and assesses them for a broad range of operational conditions using CFD. An interactive excel-based tool allows easy and immediate exploration of “what-if” scenarios for changing operational conditions. The input is drawn from the target operational profile and is typically displayed in a matrix of four speeds and three drafts.
Optional constraints, such as reaching design speed at 85 per cent engine power, are also considered before the best bow shape for the operational profile is chosen. The tool can then assess the performance of this bow for alternative operational profiles. It displays estimated savings (in USD per year and amount of power in per cent) and payback time of the best bulbous bow option for all specified operational profiles. The payback time calculation takes aspects like fleet size, conversion costs and fuel price into account. Should customers want to change any elements of the analysis the tool simply recalibrates the new input to create more what-if-scenarios and to ensure that the final design is future-proof.