Evaluation of the prospects for waste heat recovery on liquefied natural gas-fuelled ships

The project “Evaluation of the prospects for waste heat recovery on liquefied natural gas-fuelled ships” aimed at deriving guidelines with respect to the optimal integration of organic Rankine cycle-based waste heat recovery units on board ships powered by liquefied natural gas. The project included the development of numerical models and methods to evaluate the performance of organic Rankine cycles. The project is part of the larger project, “Waste heat recovery on liquefied natural gas-fuelled ships”, which included also the realization of an experimental setup at DTU Mechanical Engineering
In the first part of the project the various heat sources available on board were screened in order to identify the most suitable solution to integrate the recovery unit on board. The possibility to recover the low temperature heat released by the liquefied natural gas during its preheating phase was included among the considered options. The evaluations indicated that the highest savings could be attained by harvesting the heat of the exhaust gases and that fuel saving up to 10 % could be achieved.
In the second part of the project, guidelines with respect to the optimal integration of the organic Rankine cycle on board were derived. The guidelines were derived based on considerations regarding the energy savings, the economic performance and the space requirement of the unit. With respect to the optimal design of organic Rankine cycle for maritime applications, it emerged that units operating for larger amount of time and of larger nominal size lead to reduced payback times. In particular, it was estimated that payback times in the range from 5 to 10 years can be expected when installing organic Rankine cycle units on board vessels. For retrofit installations the availability of space on board is an essential parameter that needs to be evaluated.