A general-purpose process modelling framework for marine energy systems George G. Dimopoulos, Chariklia A. Georgopoulou, Iason C. Stefanatos, Alexandros S. Zymaris, Nikolaos M.P. Kakalis ⇑ Det Norske Veritas Research & Innovation, 5 Aitolikou Str., Piraeus 18545, Greece article info Article history: Received 24 July 2013 Accepted 13 April 2014 Keywords: Marine energy systems Systems engineering Process modelling Simulation Optimisation abstract High fuel prices, environmental regulations and current shipping market conditions impose ships to operate in a more efficient and greener way. These drivers lead to the introduction of new technologies, fuels, and operations, increasing the complexity of modern ship energy systems. As a means to manage this complexity, in this paper we present the introduction of systems engineering methodologies in mar- ine engineering via the development of a general-purpose process modelling framework for ships named as DNV COSSMOS. Shifting the focus from components – the standard approach in shipping- to systems, widens the space for optimal design and operation solutions. The associated computer implementation of COSSMOS is a platform that models, simulates and optimises integrated marine energy systems with respect to energy efficiency, emissions, safety/reliability and costs, under both steady-state and dynamic conditions. DNV COSSMOS can be used in assessment and optimisation of design and operation problems in existing vessels, new builds as well as new technologies. The main features and our modelling approach are presented and key capabilities are illustrated via two studies on the thermo-economic design and operation optimisation of a combined cycle system for large bulk carriers, and the transient operation simulation of an electric marine propulsion system. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Shipping transports over 85% of world’s merchandise with a fleet of more than 50,000 merchant ships. Rising fuel costs, shipping market volatility, existing and upcoming environmental regulations impose a pressure on marine vessels to be designed and operated in a more efficient, cost-effective, and environmen- tally friendly way. The propulsion power and energy conversion on-board installation is the main contributor to the overall efficiency and emissions footprint of the vessel. To meet those stringent and often contradicting requirements, the sophistication and complexity of modern marine energy systems increase, while often operating close to the design limit. However, any complexity increase in shipping is, in principle, undesirable for safety consid- erations. Therefore, global assessment of performance, safety, and reliability of marine systems under real service conditions and transient operation modes becomes increasingly important for the shipping industry. To date, however, there is no formal methodological framework and consistent practical approaches to effectively manage this complexity in a holistic way. Traditional approaches focus on improving efficiency via the optimisation of individual machinery components. With today’s maturity of equipment technology, in order to achieve step-change improvements in both existing and new marine energy systems, new approaches need to be adopted for systems configuration, design, operation and control that consider machinery and energy conversion from the integrated systems’ perspective. In that respect, the introduction of systems-level modelling, simulation and optimisation methods to the marine industry appears to be the next step to manage the increasing complexity of marine machinery systems. Although this is novel for the marine industry, significant experience can be drawn from process systems engineering, where these approaches have proven to be a game changer in the chemical/process industry with applications spanning from the nano- and micro-scales to enterprise-wide supply chain management. In this work, we present a general purpose modelling frame- work for marine systems engineering. First, its main specifications are given, followed by the mathematical formulation pertinent to the generic process modelling of the physical phenomena within http://dx.doi.org/10.1016/j.enconman.2014.04.046 0196-8904/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: Nikolaos.Kakalis@dnv.com (N.M.P. Kakalis). Energy Conversion and Management 86 (2014) 325–339 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman