CO2 Vending Machines

This paper describes CO₂ compressors and systems for light commercial refrigeration applications such as vending machines. The natural refrigerant CO₂ (R-744) has the potential to replace HFC-based applications, as it has no Ozone Depletion Potential (ODP) and a negligible Global Warming Potential (GWP) of just 1. Furthermore, as CO₂ features better efficiency for heating, Heat Pump Water Heaters (HPWH) using CO₂ refrigerant have been sold in Japan since 2001. The main challenge to apply CO₂ for refrigeration applications was its lower theoretical efficiency and the fact that CO₂ systems operate at 3 to 5 times higher working pressure than the conventional HCFC and HFC-based systems. Sanyo’s rotary 2-stage compressor developed for HPWH was applied to refrigeration applications with suction line heat exchangers and intercoolers to address the lower efficiency. As a result, lower indirect emissions were attained as well as lower direct emissions with no ODP and negligible GWP.