Energy and environmental comparison of two-stage solutions for commercial refrigeration at low temperature: Fluids and systems

International agreements will restrict in the near future the use of high-GWP refrigerants in Europe. These restrictions will favour the implantation of refrigeration systems with low-GWP fluids, especially in applications with high leakage rate. To clarify possible solutions that accomplish the forthcoming F-Gas Regulation, we present simplified models of five two-stage vapour compression refrigeration systems and evaluate them with low-GWP refrigerants (HFC, HFO and naturals). We analyse the energy performance over a wide range of evaporating and environment temperatures and present the TEWI analysis under a same scenario, typical of a centralized commercial refrigeration application. We conclude that, for high-GWP refrigerants, direct emissions have greater weight in TEWI than the indirect ones, so future solutions might be based on low-GWP fluids, in some cases with risk of toxicity or flammability. We observe the indirect two-stage systems (cascades) with CO2 as low temperature fluid are promising solutions, especially for warm regions.