How Syroco Live computes fuel consumption

This post explains through simple steps how Syroco Live computes fuel consumption and carbon emissions for a given vessel, sailing on a specific route with a determined speed profile. Route and voyage optimisation are not discussed here.

Core principles: models and forces

The digital twin can be found at the core of the Syroco platform. It is a virtual representation of a physical vessel, with her detailed characteristics. The twin is built through the assembly of a set of accurate models representing the interactions of the vessel with the environment. 

There is a model for each component of the vessel that is involved in propelling the vessel, slowing her down, or consuming/producing energy. For a typical ship, models include: calm water resistance, added wave resistance, rudder drag, windage, engine and propulsion chain, shaft generator, etc. More complex vessels require additional models: sail propulsion, LNG boil-off, hotel/reefer load, etc. 

Each model describes how the interaction of the vessel component with specific sea and weather conditions creates a force, and provides computation of the intensity and direction of this force. The role of the twin is to assemble the models, and compute the total force that results from each model.

Knowing the route

A key input for fuel computation is the exact route and speed profile followed by the vessel. The route is defined as a sequence of geographical coordinates and timestamps. It can be the route of a past voyage, one that the vessel did indeed sail, or a prospective route that is considered for a future voyage. 

Interestingly enough, even though speed is probably the most important input in the calculation of fuel consumption, speed information is not specifically included in the route, but is rather inferred from the distance and time between two points. This approach greatly reduces the noise inherent to speed measurements. 

There are two essential criteria for a route to be usable for computation of fuel consumption: the first one is density - ensure that points are sufficiently close to account for all gridcells of the weather model; the second one is consistency - points must be evenly spaced, from a temporal point of view for a consistent point to point analysis on time series graphs. 

Getting the weather

Based on the route, the platform gathers weather data for each geographical position at the exact time of the vessel crossing this position. The weather is a set of measurements: wind speed and direction, significant wave height, direction and period, current speed and direction. 

Depending on the type of voyage (future, current or historical) the weather is obtained from forecasts (predictions), nowcasts (current measurements) or hindcasts (measured historical conditions). For simulated voyages further in the future (beyond the useful prediction window), a climate forecast system can also be used. The only difference between these cases is the reliability and accuracy of weather data and therefore of the computation of fuel consumption. 

Computing the power and fuel consumption

Accurate power computation is one of the most significant innovations in Syroco Live. Taking as input the weather conditions and the speed over ground (SOG) of the vessel, the digital twin computes the sum of the forces that apply. In order to achieve that speed, the engine needs to deliver a certain amount of power. The propulsion chain model translates this power into an instantaneous fuel consumption. 

Because the models of the digital twin are very accurate and represent with high fidelity the behaviour of the vessel, the fuel consumption is computed with a high degree of precision. 

Sailing the twin

The route is set, weather data has been acquired. Now comes the time to start the virtual voyage. Syroco Live sails the digital twin of the vessel along the route following the timing set by the timestamps. At each point, the digital twin computes power and fuel consumption. Thanks to the cloud power of the platform, this only takes a fraction of a second. And in no time, the digital twin reaches the destination, carrying along a payload of performance data! 

Summing up the fuel and computing emissions

All that’s left to do is to compute the total fuel consumption and carbon emissions. Of course there can be some caveats, or some post-processing required: 

  • Account for type of fuel used (VLSFO or MGO) on different segments, in ECA zones, etc.
  • Measure carbon emissions depending on the fuel type
  • Assess CII impact of voyage
  • Compute carbon allowances under EU-ETS or other regulations

This is mainly arithmetics... but this is a different story!