The development of a model for energy consumptions in shipping technology

There are a number of ways to make shipping more energy efficient. In his research Francesco Baldi uses computational models to show how to save energy.

Francesco Baldi, Chalmers, Shipping and Marine Technology

In his research Francesco Baldi has studied two different ships, one chemical tanker which operates international routes, and in collaboration with Fredrik Ahlgren at Linnaeus University, one cruise ship which operates a fixed route. During Lighthouse seminar about the energy efficient shipping sector he addressed several areas where he and colleagues have conducted their research. 

  • Waste heat recovery
  • Heat storage
  • Propulsion system modelling
  • Trim optimization
  • Hybrid propulsion

Using computational models, the research show that by optimizing the waste heat recovery, yearly fuel savings can reach 11% over one year for the cargo ship and generate up to 22% of the electric power demand, over one reference voyage, for the cruise ship.

By using heat storage up to 60% savings of yearly boiler fuel consumption can be reached with a relatively small storage tank in the cargo ship. And for the cruise ship, with short time in port, boiler fuel consumption can be completely avoided during the summer and middle season.

By using models, it is possible to predict engine efficiency starting from limited operational data. In order to analyse how efficiently the company operates its ships, a propulsion system model was created in order to simulate different types of operational modes. The research shows that using these models it is possible to predict the behaviour of the whole propulsion system, and in particular its fuel consumption.

The cargo ships trim optimization was also studied using mathematical models and was, according to the research done efficiently from the crew. The results of this study also showed  that these models work, and particularly that gray box models is very accurate.

When it comes to the cruise ship, the use of a hybrid propulsion was modelled. The cruise ship operates mostly between 8 and 14 knots while the ship is designed to be operated at 21 knots. The aim of the research was to study if fuel efficiency could be gained by installing motors/generators connected to the gear boxes, so the main engine could produce electric power when needed, and the auxiliary engines could produce mechanical power for propulsion.
The results of the simulations show an estimate of 3% in fuel savings which is less than Francesco Baldi expected.

- For me it was a bit deceiving. I expected to be able to save more, especially when you look at the literature in the field. The reason for that is that there are a lot of losses in the conversions, so they have to be taken into account and conversion play a quite big role.

Francesco Baldi concluded his presentation by pointing out that mathematical models are an efficient way to test different technologies for energy efficiency and that gathering operational data opens new possibilities. But you have to know what you need to measure and what you do with what you measure.

Francesco Baldi will defend his doctoral thesis on May 20th.

Text and photo: Andreas Kron