energy savings and emissions reduction


Retrofi tting for


When it comes to fuel efficiency, people usually think about new designs that should be more fuel efficient. However, potentially there is a huge existing fleet, which could be optimised in respect of fuel consumption as well. Patrick Hooijmans, p.hooijmans@marin.nl


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The EU project RETROFIT demon- strates a methodology about how to evaluate fuel savings and


emissions reduction, while the project GRIP studies the principles of energy saving devices, which could be applied for powering performance improvement. When brought together, the impact of retrofitting an existing ship can then be evaluated.


In order to analyse and judge the economic, energy and emissions performance of a ship design in all its relevant operational conditions, an accurate and comprehensive analysis model and assessment method are required. In the analysis model the perfor- mance is determined and in the assessment model the results from the analysis model are judged in comparison to a benchmark. This benchmark can be the original ship before retrofitting. The analysis model is thus used to assess the ship before and after retro- fitting, thereby establishing the improvement in energy and emissions performance.


Scenario simulation tool A scenario simulation tool has been developed to


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simulate the complete round trip of a ship, including the harbour approach. Simulations have been split into a harbour manoeuvring and transit part. Each round trip will be simulated using available weather data from the area of operations. A typical simu- lation is based on round trips from over a four to five year period. The basic elements in the simulations are the ship’s calm water and seakeeping characteristics and the environment (wind, waves, current). An op- erational scenario representing the captain’s reaction to actual and predicted conditions can also be included. In addition, the impact of the climate on the ship’s earning capacity is specifically taken into account.


Within the transit simulations, MARIN’s tool SHIPMO is used to determine the motion response of the vessel and the added resistance due to waves. For the RETROFIT project, SHIPMO computes the motions with a 2D diffraction method and the added resist- ance with the Gerritsma-Beukelman method.


Wave and wind parameters on open ocean routes are available from various sources and


comprise wind, sea and swell parameters and the wind speed. The complete wave spectrum is reconstructed from these para meters by adding assumptions on the spectral shape and the directional spreading. Waves in the coastal zone can be represented by two-dimensional wave spectra at arbitrary time steps. Ocean and tidal currents are obtained from multi-parameter models. An example of a voyage simulation is given in Figure 1.


Fuel consumption and emissions Based on the calculated wave added resistance for each time step on the route, the total resistance at each time step is determined. When coupling this information to the engine model GES of TNO, the required engine out- put, fuel consumption and emissions can be determined for each voyage.


Similar simulations are performed for the harbour approach and departure using the SCYLLA tool in combination with a dynamic engine tool of Delft University of Technology. In these simulations the vessel will sail a predefined track of waypoints, see Figure 2.


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