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Optimization of Coupled Ship Energy Systems

The global shipping industry is one of the largest producers of climate-impacting emissions and is committed to consistent decarbonization due to the IMO's increasingly stringent emission targets. In particular, comprehensive measures to increase efficiency must be taken in the design of new ships that go beyond incremental improvements to combustion engines and flow-optimized hulls or propellers. There is great potential in improving energy systems, from architecture and supply structures to operations. At the same time, the complexity of possible energy system configurations is increasing due to measures such as hybrid-electric propulsion concepts, sector coupling, or the integration of energy storage systems or fuel cells. This increasing design freedom is addressed in conventional ship design with a conventional, iterative process, so that primarily intuitive concepts based on previous designs are pursued.


The Maritime Energy System Optimizer (MESO), developed at the TUHH's Institute of Mechatronics in Mechanical Engineering, is a methodology and tool for the holistic configuration and operational optimization of a ship's coupled energy systems. This optimization also unbiasedly suggests architectures and supply structures that would not be considered in conventional design.

MESO - Methodology

In abstract terms, MESO offers the possibility of optimizing operation, system structure, and component dimensioning on the basis of representative load profiles. MESO is fundamentally based on a genetic algorithm whose genes map the optimization variables of configuration optimization—for example, the type, number, and performance of generators, batteries, or steam boilers, as well as their connections. An individual in the genetic algorithm therefore represents exactly one configuration of the energy system. The quality of a configuration—the fitness of an individual—is composed of up to three cost factors:

  1. Operating cost, based on fuel consumption and greenhouse gas emissions over the duration of the load profiles. To determine this, the energy systems are modeled in the Open Energy Modeling Framework at the power flow detail level. An energy balance-based optimization problem for the operation of the generation and storage components is then set up and solved using suitable mixed-integer linear solvers. The goal of this operational optimization is to minimize fuel consumption.
  2. Fixed cost, which consist of acquisition/installation costs (CAPEX) and fixed operating and maintenance (O&M) costs, each for the period of the load profiles.
  3. Topology cost (optional), based on the volume occupied by the energy system. For this purpose, the ship is mapped in a three-dimensional graph and the length of connections between the components is determined using a Dijkstra pathfinding algorithm. Together with power-specific cable diameters and component volumes, the volume is determined and converted into costs using a volume-specific factor for opportunity costs.

 

The aim of the work at the institute is to further develop, generalize, and validate the methodology so that it can be applied quickly and reliably to various problems and configurations.

 

Application of MESO

Research activities related to MESO are largely shaped by collaboration with industry partners, as this is the only way to ensure usability in the ship development process. Previous application studies have primarily been in the field of cruise and cargo shipping:

Cruise ship – overall system: MESO's development is based on comprehensive operating data from a 300-meter-class diesel-electric cruise ship, some of which was collected as part of the SuSy project. In configuration optimization, diesel gensets and high-temperature fuel cells compete primarily, supplemented by battery and thermal storage systems. One electrical and four different thermal energy systems with a total of over 100 consumers are taken into account.

Container cargo ship – hotel loads: The application in the cargo shipping sector is based on profiles of the secondary electrical system of a 15,000 TEU container ship recorded during regular operation. Based on this data, MESO was expanded to include generators with non-linear efficiencies, and the potential of optimized operating strategies was estimated at ~1.5% fuel savings. Depending on the parameterization, additional savings of 5-30% can be achieved by optimizing the configuration, in particular by dimensioning the generators to match the load and adding battery storage systems to cushion peak loads.

Cruise ship – Thermal systems: An application study focused on the configuration optimization of several coupled thermal systems on a cruise ship, with particular attention to emission-free port operations, is currently being conducted.

MESO – Outlook

The basic functionality of MESO has been verified using various application examples, at the same time it is being continuously developed in three main areas:

 

Expansion of Functionality

Various functions in and around MESO are currently under development. At present, MESO relies on the provision of representative load profiles, which means that rapid concept studies for ship classes that have not yet been investigated, for example, cannot be carried out without further ado. To this end, a methodology for generating load profiles based on rudimentary information about a ship and typical route data is being developed.

Within MESO, the operation of the system is being optimized, but such operation cannot be applied in real ships, as knowledge of the entire load profile is always required. For this reason, a methodology is to be developed with which control strategies can be derived from the optimized operation.

Generalization

MESO is implemented in a modular fashion, but changes to the basic boundary conditions, such as the permitted components or options for the energy system, such as specified components, always require manual changes. Current efforts are therefore being made to generalize the method. The aim of this generalization is to enable MESO to be applied to new problems with minimal effort. To this end, it should be possible to freely parameterize energy systems, connections, components (fixed and to be optimized), and consumers via clearly defined interfaces. Application to a wide variety of systems will result in a collection of components and parameterizations, which in turn will accelerate and facilitate future investigations.

Validation

In addition to verification, which in the case of MESO is carried out using various application examples, the development of a methodology also includes validation. Both relevant partners in industry and more specific physical simulation models will play a role in verifying the results. The aim of validation is to confirm the applicability and accuracy of MESO.

Contact

Mattis Molinski
M-4 Mechatronik im Maschinenbau
  • Mechatronik im Maschinenbau
Office Hours
nach Vereinbarung
Eißendorfer Straße 38 (O),
21073 Hamburg
Building O, Room 0.013
Phone: +49 40 42878 3245
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