Modelling and simulation of organic rankine cycle for waste heat recovery on an offshore service vessel

Organic Rankine cycle (ORC) have been used widely in the geothermal and solar industry to generate electrical power from thermal heat sources. Recently, there had been more research on applying this thermodynamic cycle for waste heat recovery from internal combustion engine. Most simulation studies forecast ORC efficiencies between 15-20% while realistic expectations lie between 7-10% which make fuel savings of around 10% feasible [1]. In choosing the optimum ORC system to recover waste heat from a thermal plant, there will be various options to examine, for example, selecting the working organic fluid from among the hundreds available, identifying the waste heat source temperature and quantity which will in turn affect the choice of the cycle components such as evaporator, expander, condenser and feed pump. To overcome this challenge and provide flexibility in detailed thermal analyses, a commercial multi-disciplinary 1D software called Siemens LMS Imagine.Lab Amesim which is based on model-based systems engineering is used to derive the optimised system design for the ORC system. Using this software and base on operational data from a seagoing offshore service vessel, it is found that annual fuel savings of 9% is possible through the use of ORC to recover waste heat from diesel engine exhaust and high temperature cooling water. When the cost of installing such system is estimated, payback period is about 8 years and can be interesting to shipowners with investment horizons of 10 years. © 2017: The Royal Institution of Naval Architects.