Marine refrigeration plants for passenger ships:Low-GWP refrigerants and strategies to reduce environmental impact

This paper is devoted to the evaluation of the use of low-GWP refrigerants in marine provision plants for cruise ships.We present the state of the art of current refrigeration plants, and we identify ammonia (NH3), carbon dioxide (CO2), and the HFOs R1234yf and R1234ze(E) as the most promising low-GWP refrigerants adequate for the marine refrigeration systems considered in the paper. Single-stage, two-stage and cascade plant configurations are examined, and the performances of the different alternatives are evaluated through simulations. The results are analyzed, and the performances are compared with those of the current systems with R407f: in the comparisons we consider COP, volumetric capacity, safety and environmental impact.We conclude that switching from current technologies to systems using low-GWP refrigerants entails a worsening of the performances in at least one of the areas considered. Moreover, we observe that the reduction of the GWP value of the refrigerants is not an effective strategy to diminish the total environmental impact of the refrigeration systems considered.