Using the forward movement of a container ship navigating in the Arctic to air-cool a marine organic Rankine cycle unit

Ice coverage in the Arctic is declining, opening up new shipping routes which can drastically reduce voyage lengths between Asia and Europe. There is also a drive to improve ships energy efficiency to meet international emissions design regulations such as the mandated Energy Efficiency Design Index. The organic Rankine cycle is one thermodynamic cycle that is being actively examined to improve the design and operational efficiency of ships. Low heat sink temperatures can significantly increase waste heat recovery systems thermal efficiency. In Arctic regions, the ambient air temperature can be much lower than the sea temperature, presenting interesting opportunities. However, using air as the cooling medium requires larger condensers and power compared to a water-cooled system. This paper investigates the exploitation of the forward movement of a container ship navigating in the Arctic and density-change induced flows as means of moving air through the condenser to reduce the fan power required. The organic Rankine cycle unit uses the waste heat available from the scavenge air to produce electric power. A two-step optimisation method is used with the objective of minimising the annual CO2 emissions of the ship. The results suggest that the supportive cooling could reduce the fan power by up to 60%, depending on ambient air temperature