On optimal integration of PEMFC and low temperature waste heat recovery in a cruise ship energy system

Hydrogen fuelled Polymer Electrolyte Membrane Fuel Cells (PEMFC) systems could play a key role in the decarbonization of shipping, as they would guarantee the zero-emission navigation. However, the low temperature of PEMFC waste heat (<70°C) could hamper future installation of PEMFC power systems for larger vessels as cruise ships, where Waste Heat Recovery (WHR) is essential for supplying heating power onboard. Recent studies address PEMFC WHR for stationary systems, but it appears to be a lack of studies on PEMFC WHR for ship applications. To fill this literature gap, this study proposes a Mixed-Integer Linear Programming approach to minimize operating and investment costs of a cruise ship energy system. It is assumed that PEMFC supply the auxiliary electrical power onboard, WHR solutions as high temperature heat pumps and absorption chillers recover PEMFC heat, and internal combustion engines supply mechanical power. The design and operation of the energy system components is optimized to match the mechanical, electrical, thermal, and cooling power demand over three operating seasons of a 177 m long cruise ship, taken as case study. Three temperature levels are distinguished for the thermal power demand. The results show that the optimal plant configuration encompasses 4 MW of PEMFC and about 1.8 MWh of Lithium-ion battery. 58% of the PEMFC waste heat can be recovered, supplying 41% of the ship low temperature thermal demand. The proposed plant allows to cut marine diesel oil consumptions by 23% with respect to the current ship energy system.