Salvage, SMIT Engineering and IJmuiden- based Offshore Ship Designers (OSD) has developed from the vision that environ- mental gain can be achieved by fine-tuning the selection of available power sources, against the power that is actually required during the various operational conditions.


The Green Tug project focuses on the development of an azimuthing stern-drive harbour tug that can provide 65 tonnes bollard pull, both ahead and astern. MARIN was tasked with making a thorough review of the hull lines by CFD and to carry out model testing to reduce resistance, while maintaining excellent manoeuvring charac- teristics, both sailing ahead, astern and during escort duties.


Green Tug artist impression T


he Port of Rotterdam aims to reduce the amount of air pollution by 10% by the year 2020 and operators in


the port are being encouraged to reduce emissions to help achieve this ambitious goal. As the main tug operator in the port, SMIT initiated the E3


tug project in close


cooperation with shipbuilder Damen, Alewijnse Marine Technology, Delft Techni- cal University, MARIN, IMARES and the Port of Rotterdam. The triple E stand for Environ- mentally friendly, Efficient in operation and Economically viable. The project aims to make a more environmentally-friendly tug and to develop a realistic analysis of the environmental impact a tug has on its direct environment. The E3


project is divided into three main


stages. The first stage will result in an op- erational profile of a Damen ASD Tug 2810 operated by SMIT, the SMIT Elbe. This operational profile consists of speed and power settings, together with engine per- formance and emissions. The emission measurements focus on CO2


, SO2 , NOx , CO,


particulate matter and hydrocarbons. These measurements show interesting results about power usage in normal service conditions. Currently, the measurements are being analysed to form the benchmark for the remainder of the project. Under the second phase, a new propulsion installation will be designed and built. After building the tug, similar emission measure- ments will be done to check the improve- ment against the benchmark provided by the Smit Elbe. The third phase will look into emerging technology, which at present, is not available for practical application. LNG for instance, is such an emerging technology, where the


technology is available but the infrastruc- ture is not. The design’s emission perform- ance will be computer-simulated using tools that have been validated in the earlier stages.


Green Tug project The low-emission, green harbour tug under development by a Dutch partnership lead by Iskes Towage and


An efficient power supply was designed for each mode of operation, together with a power management system to ensure smooth transitions between the various power sources. A hybrid system was select- ed, which offers a combination of electricity generation and storage. Inherently, a hybrid system facilitates optimisation of the components for the expected load profiles, with respect to system efficiency (e.g. peak shaving), dimensions and cost.


Considering the environmental objective, the design was based on the implementation of hydrogen and fuel cell technology. Hydrogen was selected because it is a non-carbon fuel, the disadvantage being the large storage volume (low density). The modular power of fuel cell technology was selected because it offered better system efficiency, reduced maintenance costs, a highly automated operation and inherent near-zero emissions. Where maritime emissions’ regulations (IMO tier III) only restrict NOx emissions, this project also focuses on CO2


, SO(x) and par- ticulate matter.


Only when the tugs assists sea-going ves- sels will they require a selection of diesel- driven generator sets to be switched on for more power on the two azimuthing stern drives. At first glance, just a conventional harbour tug, although with remarkably small exhaust pipes. But in reality the Green Tug project offers a major step forwards in the improvement of fuel economy and in emission reduction.


report 21


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