Marine transport produces about three percent of the world's CO2 emissions. Tightened emission limit values along with rising energy prices make efficiency-raising measures in this field more attractive. Some large 2-cycle marine diesel engines now already use power turbines combined with steam power processes.

The power turbine utilises the excess hot exhaust gas which is not needed to power the exhaust turbo charger. The steam for the steam power process is generated from the residual heat downstream from the power turbine and the turbo charger.

Future measures on the engine and charging system will considerably lower the temperature relevant in the steam process. This is where ORC is an interesting option for the low temperature waste heat recovery technology.

Various configurations of a 2-cycle marine diesel engine were simulated and the potential of ORC systems combined with a power turbine was assessed.

An ORC system and a power turbine can produce a total of ten to fourteen percent of the installed engine power. This can either be utilised as additional mechanical power for main propulsion or alternatively as the power supply for the on-board power.

Heat from the exhaust gas is delivered to the pressurised water intermediate loop and then transferred to the ORC loop through the heat exchanger.