The government aims to make Norway a world leader in environmentally friendly sea transport. The objective of InnoCurrent project has been to contribute to achieve this goal.
Environmentally forces from wind, waves, and sea surface current are important variables that will influence the speed, propulsion and hence also emissions from a vessel. In areas sheltered from ocean waves, the local current is normally the most important unknown of these external forces that affect the speed loss and energy consumption.
The InnoCurrent project studies the isolated effect of sea surface current on propulsion and fuel consumption of the vessel. The goal is to utilize the potential of the energy in the sea currents in a voyage optimization method to reduce fuel and emissions.
An important objective of the project is to monitor and understand the relationship between speed and fuel consumption. The following calculation example demonstrate the potential in utilizing the energy in the surface current to reduce fuel and emission from a vessel. The cargo ship sails initial with vessel speed 15 knots. If the vessel is operating in a tail current of one knot, the propulsion power can be reduced with 400 kW. This reduction is comparable with the emission from 100 personal cars, calculated in gram per kilometer.
We have analysed on-board measurements from the cargo-ship Kvitbjørn to study and identify areas along the Norwegian coast where the ship operates in tail and counter current, and how the different patterns of these surface currents influence on the power and fuel consumption. Choice of route for the vessel at different current and weather conditions is also analysed. As an example, we see that for the northern sailing lane at the Helgelandskysten the vessel can choose the outer lane though this area is more exposed to wind and waves, but tail current is prevailing most of the time on northbound course. The other option is to sail through the longer inner lane that is less exposed to ocean waves. The results show that the choice of route is important for the time spent and fuel consumption for the specific voyage.
Since information about local currents are important for the fuel consumption, reliable oceanographic data are crucial for voyage planning, hence for selecting the most energy efficient speed. The Norwegian Meteorological Institute has a forecast model (NorKyst800) that provide daily predictions of the sea surface current.
Daily variations of the mean current along actual routes for Kvitbjørn has been studied using surface current from the forecast model. The results of the analyses shows large daily variations related to the currents along the route. For a sailing route between Trondheim and Bodø, specified to last 19 hours, calculations estimate a difference of about 7 percent in propulsion power depending on time of departure during a day. Daily variations can mainly be related to tidal variations, but also weather conditions can influence the current conditions. Time of departure can hence be decisive for the current conditions the vessel will experience during the voyage, and hence also for the fuel consumption and emissions from the vessel.
An advanced instrument (Acoustic Doppler Current Profiler) was installed in the hull of the cargo-ship Kvitbjørn early in the project. This vessel operates along the entire Norwegian coast and the goal was to compare the current data recorded to the predicted sea surface current from the NorKyst800 model along then sailing routs. The instrument was prior the project tested with good result at several vessels, but unfortunately, we have not been able to provide a significant amount of data from the instrument at Kvitbjørn with sufficient quality for the purpose. This is mainly due to disturbances from noise and air bobbles from the vessel influenced flow field.
When using current prognoses from an oceanographic forecast model in energy optimizing a sailing route, knowledge about the accuracy of the prognoses is important. We have performed a qualitative comparison of a current estimated based on on-board measurements to current data from Norkyst800 along the Kvitbjørn sailing rout with good correlation. A comparison of measured data and forecast data is valuable to be able to correct systematic deviations in the forecast model and improve the estimated current from the model. The current estimates from Norkyst800 have aslo been compared to current recorded from stationary measurement buoys at Sunnmøre, financed by the Norwegian Public Road Administation, with good results.
Studies of on-board data and predicted current data have contributed to increase our knowledge about the currents where the ship operates. Knowledge gained through InnoCurrent will provide a basis for further development of on-board decision support tools for rout planning and speed adjustments to reach the most energy efficient operation and thereby save fuel and reduce emissions.
InnoCurrent have explored the impact of sea currents on the speed and energy consumption of a ship. The basic idea and a main research question has been to investigate whether operational current forecast can be utilized to optimize and run at the most energy efficient ship speed at a given time and route for the ocean area where the ship sails. An approximation of the current speed based on ship-board measurements recorded on a cargo vessel has been analysed and compared to sea current extracted from an operational ocean circulation model with a generally good correlation. In addition, the quality of the model is assessed with good correlation against current measurements from moored oceanographic data-buoys located on a near-coast fjord area. The outcome and experience from InnoCurrent intends to further improve voyage planning and route optimization, and expected to improve accordingly as the reliability of oceanographic forecast models are likely to improve in the years to come.
InnoCurrent will combine current from ship-board measurements with operational oceanographic forecast models for current to develop voyage optimizing methods for ships in coastal service.
Monitoring the condition and performance of ships is important for safety and profitability of ship operation. New and better monitoring on ships in operation in combination with computational intelligence may be utilized to obtain reductions in fuel consumption and emissions. A key aspect to monitor is the relationship between speed and power consumption of a ship. The influence of wind, waves, and current are important parameters to understand this relationship and in coastal operation and in the Norwegian fjords and fairways the local currents are the most important unknown parameter. Therefore, reliable detection of the actual speed-through-water is crucial.
Reliable oceanographic data input is crucial for voyage planning and optimizing of the energy efficient speed at any time. The operational model NorKyst800 (Meteorologisk Institutt) will be used to provide current forecast to the improvement of the ship operational efficiency.
In order to enable high quality speed-through-water measurements, an advanced Acoustic Doppler Current Profiler (ADCP) from Nortek AS will be installed at the cargo-ship M/S Kvitbjørn. This makes it possible to obtain high-temporal sampling in the North Sea and along the entire Norwegian coast, where M/S Kvitbjørn operates. The current data recorded by the Nortek instrument fitted to M/S Kvitbjørn will provide a good basis for validation of the NorKyst800 model. In addition, validation data will be obtained from the Breisundet area where an extensive met-ocean data survey (financed by the Norwegian Public Roads Administration) is ongoing. M/S Kvitbjørn will pass this area from time to time which enables correlation studies to be made from the ship-board current measurements and the stationary current monitoring devices in Breisundet.