I have presented several examples of Sankey diagrams in the field of maritime technology before (see here).

This recent article (Baldi, F., Ahlgren, F., Nguyen, T., Gabrielii, C., Andersson, K. (2015): Energy and exergy analysis of a cruise ship. In: Proceedings of ECOS 2015 – the 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems) confirms that “the complexity of the energy system of a [cruise] ship where the energy required by propulsion is no longer the trivial main contributor to the whole energy use thus makes this kind of ship of particular interest for the analysis of how energy is converted from its original form to its final use on board.”

The authors conduct a thorough energy and exergy analysis for a cruise ship in the Baltic Sea. The ship has different operation modes (sea-going, manoeuvring, port stay). The energy analysis “allows identifying propulsion as the main energy user (41% of the total) followed by heat (34%) and electric power (25%) generation”. Nevertheless, “it can be seen that the energy demand for auxiliary power is comparable in size to that for propulsion.”

The data for this Sankey diagrams in the annex of the paper and shows that flows are in TJ for an operation period of 11 months. Blue, yellow and green arrows depict energy use, while the orange arrows reveal heat losses to the environment.

The study continues with an exergy analysis of the ship, since it reveals more on the system inefficiencies. The exergy analysis is shown as a Grassmann diagram in the paper. This is structured similarly to the Sankey diagram above, but has dark orange arrows representing the exergy destruction. This is mainly from the Diesel engines and the oil-fired boilers.

I recommend this paper not only to naval engineers, but to everyone who wishes to get a better understanding of exergy and Grassmann diagrams. Can we consider Grassman diagrams a subset of Sankey diagrams? What do you reckon?

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