Comparative environmental assessment of nanofluid application in refrigeration of Power Electronic Traction systems

In Power Electronic Traction (PET) applications one of the central problems is the effective temperature management, since power demand and reliability requirement grow and devices become increasingly miniaturized. This paper presents a comparative Life Cycle Assessment (LCA) study among three systems: 1. Baseline Cooling System (BCS) that uses as refrigerant a mixture 50wt% of water and glycol; 2. Nanofluid Cooling System single stage (NCSsingle) that uses alumina nanofluid as refrigerant produced with the single stage process; 3. Nanofluid Cooling System two stage (NCStwo) that uses alumina nanofluid produced with the two stage process. The functional unit is a liquid cooling system for Insulated Gate Bipolar Transistor (IGBT) in PET system for train with a lifetime of 30 years. The system boundary is from cradle to grave. Both NCSsingle and NCStwo show lower potential environmental impacts than the BCS for all impact categories, due to better energy efficiency and increased lifetime of the IGBT. The latter is possible thanks to the lower service temperature. NCStwo has lowest potential impacts for all categories, due to the less energy consumption in the alumina nanofluids two stage production. A sensitivity analysis using several IGBT lifetime shows that the longer is the lifetime the more potential environmental advantages arise for all impact categories, due to a more efficient use of materials. Anyway, nanofluid application requires further development in terms of improvements of nanofluid stability and a new design of the cooling system.