A dynamic energy modelling approach to low energy ship design

  • Dimitrios Sfakianakis

Student thesis: Doctoral Thesis


Despite remarkable advances in naval architecture in the past few years, limited effort has been expended to improve the energy efficiency of ships due to the relatively low price of fuel oil and lack of stringent environmental regulations. However, the ever-growing intercontinental trade has resulted in an increase of greenhouse gas emissions from ships that triggered the introduction of mandatory environmental measures and shifted the focus of the shipping industry towards more energy efficient designs and operations. This thesis focus is on improving the energy efficiency of ships during design and operation by adopting a direct approach to estimating the requisite thermal energy on board ships over their life cycle. This is achieved by dynamically modelling the thermal energy flows on board, drawing from the considerable developments in Building Energy Simulation (BES), which precedes developments in the maritime industry by five decades. To this end, and in broad terms, the thesis focus is on and embodies the technology transfer from the Buildings Industry to the Marine Industry ("marinisation of BES") whilst accounting for the differences and complexities implicit in some of the ship types as well as the marine environment and operations. This, in turn, necessitates focus on applicability, functionality and limitations of BES in ships with the view to enable developments to fill pertinent gaps and to demonstrate such developments with purposely selected case studies. During the investigation of the applicability of BES in ships, the main differences between ships and buildings were identified, and their effect on energy simulation was pointed out. The results of this comparison served as the basis for the marinisation of the selected building energy simulation software 'ESP-r', which was enhanced to also cater for energy flows present in the marine environment, leading to the development of 'ESP-r marine'. Despite the ability of the tool to model the majority of thermal energy flows on board ships, several modelling and computational problems were presented during the development of large accommodation models that triggered necessary simplification considerations. In an attempt to allow energy modelling of smaller groups of spaces and drop the requirements for explicit and topologically correct model representation, the geometrical decoupling of major space types was examined. A verification process based on energy simulation was used to construct guidelines, indicating acceptable assumptions for the boundary conditions of individually modelled or groups of accommodation spaces. This methodology was then used to facilitate further simplification of thermal modelling, which was achieved through the concept of space grouping that encompassed the process of the consecutive merging of adjacent spaces, until groups of spaces were represented by a single thermal zone. Throughout this process the loss of accuracy in the results was quantified, and results were used to develop design guidelines for the group representation of major types of on board spaces. All findings were used to form a methodology for the design of the most common ship accommodation spaces and relevant HVAC systems which outer performs current practices, since it provides detailed information about state variables in accommodation spaces and energy systems components, and allows for the calculation of the power consumption of the energy systems serving the accommodation over the ship's life-cycle at a low computational cost. Implementation of the methodology was exhibited with two case studies, one for a cargo and one for a passenger ship. The work undertaken and the derived results clearly demonstrate the applicability of BES to ships and the extent to which it can be simplified during the design process, thus introducing the concept of Dynamic Energy Modelling as a platform in shipping to support life-cycle energy management. This constitutes a significant development in shipping.
Date of Award4 Sept 2015
Original languageEnglish
Awarding Institution
  • University Of Strathclyde

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