This work is part of a study aiming to achieve high efficiency and low emissions in a marine
propulsion system. In order to significantly enhance the efficiency of a propulsion plant, it is possible to
recover the exhaust gas heat normally rejected to the atmosphere and the heat of the cooling water
usually rejected to the sea. The study examines the possibility of energy recovery applying ORC
(Organic Rankine Cycle) technology; this technology is very effective for recovering waste heat from
low temperature sources, both from the thermodynamic and the economic standpoint. When a
"combined cycle" ORC-diesel engines set up is considered for this size of engines, an increase in
power output of about 10% can be expect. In addition, a significant amount of heat is released at low
temperature and could be used by other ship services, or by other thermal users, in case of land based
applications. In the present study several possible thermodynamic cycles are simulated using the
AspenĀ® code, considering also different working fluids. The results are evaluated in both
thermodynamics and economics terms.
