Trim guidance in perspective
The energy-saving strategy is dependent on the vessel type and size, and it must be considered which measures will provide the best return on investment.
So far, slow steaming has become the favorite choice of many shipowners in order to reduce the required power and thereby fuel consumption. Energy-efficient technologies Various means of improving the ship energy efficiency are available, and selecting which technology to invest in can be a difficult task. Energy-efficient solutions can both be physically implemented in the ship design such as pre-swirl or counter rotation propeller etc. which normally have a large cost impact.
As an alternative to physical implemented solutions, the shipowner can improve the way the ship is operated, for example through trim optimisation, route planning or ship performance optimisation. The latter are initiatives which FORCE Technology support in the package of onboard systems called ‘SeaSuite’, and in the following, we will focus on trim guidance of ships which is one of the methods offered in SeaSuite. Trim guidance Trim optimisation is a way of optimising the ship’s energy efficiency in the operation of the vessel.
Choosing the optimum trim has a significant impact on the fuel consumption for ship types like container vessels due to the effect of the ship’s bulbous bow and relatively high operating speed. However, trim optimisation can also be adopted to other vessel types like tankers and bulk carriers. FORCE Technology can supply trim guidance data to be used either in the vessel loading computer software or in our self-developed software tool, SeaTrim, to select the optimum trim. We have so far supported more than 280 vessels with trim guidance data for use in the daily task of selecting optimum trim for the given speed and displacement of the ship.
SeaTrimSeaTrim is a decision support tool used for displaying the trim guidance data provided by FORCE Technology. The software itself is provided for free in connection with delivery of trim guidance data, but the data can also be used for implementation in the vessel loading computer if this is supported by the manufacturer.
In order to use SeaTrim, only three parameters are typed into the programme: draught forward, draught aft and planned vessel speed. The program will display the power consumption for the given vessel condition and guides the user by simple colour codes to a condition with less power consumption. Alternatively, the programme can show the relative increase or decrease in required power compared with the initial trim condition and speed of the vessel. Moreover, a report can be generated to display the initial trim and power as well as selected and optimum trim conditions and power for the given displacement and ship speed. In the latest edition of SeaTrim, version 2.0, a side view of the vessel in the selected trim condition is displayed at the top of the user interface as well as the propeller clearance.
Potential gainsThe potential gain of using trim optimization depends not only on vessel type and size, but also on the way the vessel is operated. In a recent study completed under the Danish joint industry project Green Ship of the Future, the operational data for six 10,000 DWT tankers of 118 meters, operated by Nordic Tanker, was analysed with respect to trim optimisation. The operational data used in the study came from the noon reports submitted by the six ship crews from October 2009 to January 2012 logged with our onboard tool SeaTrend.
From the dataset, the distance sailed, speed, draught and actual trim were used to compute the potential saving by using trim optimisation. The results of the study showed an average fuel saving per day of 2.9% when using optimum trim compared to the way the vessel was actually operated. For tankers, the major gain from trim optimisation was achieved in ballast condition in which there was better opportunity to use the ballast water to achieve optimum trim. The study showed that the average potential saving was 2.6% for loaded conditions and 3.7% for ballast condition. When operating at a fuel price of $615 per ton, the ROI was in all 274 days at sea, or for the six vessels 46 days at sea per vessel.
The conclusion was that there is considerable fuel savings to gain from using trim optimization for vessel types such as tankers and bulk carriers. Moreover, the payback time even for smaller vessels with small absolute fuel consumptions is also reasonable.