Greenhouse Gas Emissions for Refrigerant Choices in Window Air Conditioner Units

Refrigerant selection for cooling processes is a topic of controversy in the U.S. and around the world.  Air conditioning systems originally used toxic refrigerants (ammonia), flammable substances (propane), and CFCs that were banned by the Montreal Protocol.  HFC refrigerants are currently undergoing regulatory procedures that may lead to their ban.  Although HFCs have nearly zero ozone-depletion potential, they contribute to global warming. HFC emissions have increased since 1990, mostly due to increases in air conditioner usage in the U.S. Greenhouse gas emissions can be induced directly and indirectly while operating an air conditioner, with direct emissions resulting from the 3% leakage rate of residential air conditioners and emissions incurred during the release of refrigerant at the end of the equipment’s life.  Indirect emissions stem from the burning of fossil fuels to produce electricity for the AC unit.  Prior studies have offered suggestions on the next industrial air conditioning refrigerant choices; however, all have been examined within different scopes which inhibit comparison.  This study seeks to place all recommendations in the same boundaries to determine which refrigerant is the best.  The decision will be based on a gate-to-grave thermodynamic analysis of multiple refrigerants used in the vapor compression refrigeration cycle of a residential air conditioner.  Refrigerants included in this analysis are natural refrigerants, mixtures of current refrigerants, and possible future refrigerants known as HFEs.