Carbon emissions comparison of the vapor compression refrigeration unit and phase change cold change unit for refrigerated vehicles

Refrigeration transportation requires energy to maintain the cold chain activities, which leads to a large amount of greenhouse gas (GHG) emissions (A. Rai et al, 2017). The vast majority of refrigerated vehicles employ vapor compression refrigeration systems (VCRS) driven by a diesel engine. Such technology is recognized as relatively expensive, noisy and its efficiency is only 35 – 40% (Liu M. et al, 2012). Ongoing research is currently developing new technologies based on phase-change refrigeration systems (PCCSS) that use electric energy for refrigeration. This new solution is promising and is considered to become a good alternative to traditional VCRS systems in the future (Liu G. et al, 2019). The goal of the study is to assess and compare the GHG emissions of VCRS and PCCSS Life Cycle Assessment (LCA) according to ISO 14040-44 was used as a reference methodology with a focus on GHG emissions. The functional units are defined as a volume of 16,8 m3 refrigerated at the temperature of 0° over ten years lifetime when the outside temperature is + 30°C. This is the operating condition that can be found in Guangzhou (China) where the research was carried out. The model considered a life cycle cradle to grave perspective including production, installation, transport, use, repair, and recycling on greenhouse gas emissions expressed as the CO2 equivalent emissions in total. Inventory data on the two different refrigeration systems were collected adopting the same data quality parameters. Primary data on energy use and refrigerant use of the two systems were collected. Results showed that the PCCSS understudy due to its high energy use resulted to have slightly higher GHG emission (228.030 kgCO2 eq) if compared to VCRS (219.640 kgCO2 eq) in a life cycle perspective. The reason for these results depended on the storage capacity design of the PCCSS understudy that resulted to have an unreasonable cold storage capacity. The study proved that, in order to reduce GHG emissions of PCCSS, the coldstorage capacity should be reduced from the original 443 kg to 150 kg. As a consequence, the carbon footprint efficiency of the PCCSS can be increased by 31.2%. Another issue that was identified is the electricity use profile of PCCSS. This aspect should be more investigated especially at night when energy use is not productive. Further research is needed. PCCSS has better potential performancesrelated to climate change regarding the trough electricity of the entire region or city.