In a recent press release, “GE Opening a Door to a Future of Cleaner Home Refrigeration,” GE Appliances announced a petition to the Environmental Protection Agency (EPA) requesting approval to use the hydrocarbon isobutane (R-600a) as the refrigerant in GE’s new Monogram® brand refrigerator, which is slated for introduction in the U.S. in early 2010. According to the press release, the new refrigerant not only reduces appliance greenhouse emissions caused by off-gassing, but it also improves efficiency, making the technology a double bonus for U.S. consumers.
Until the 1990’s chlorofluorocarbons (CFC) were the dominant working fluid type in US refrigeration and air-conditioning systems. However, the Montreal Protocol led to a ban on these working fluids due to their ozone depletion potential (ODP). A painful conversion to hydrofluorocarbon (HFCs) refrigerants ensued, which often necessitated hardware modifications because the thermo-physical properties of HFC’s are mismatched to CFCs. While HFC’s are more benign toward the ozone layer, they have high global warming potential (GWP). Thus HFCs are undesirable, especially in countries that have ratified the Kyoto Protocol, but also in the U.S. where preventing global warming has become a national obsession.
So-called natural refrigerants such as carbon dioxide (R-744), isobutane (R-600a), and propane (R-290a) represent another alternative to CFCs. However, fear of flammability and other health risks caused natural refrigerants to be resisted by U.S. regulators. Nonetheless, if the EPA approves GE’s petition, this trend may see swift reversal.
According to a recent article by Larry Adams of ApplianceDesign.com entitled, “Cooling Technologies: Alternative Refrigerants Attract Attention,” isobutane and propane are the most widely used alternative refrigerants in the world; they have zero ODP and negligible GWP and can be found operating safely today in European appliances. Most importantly, the feature setting hydrocarbons apart from other natural refrigerants is that they are a near drop-in replacement for current refrigerants. Thus, painful system modifications required for the CFC to HCF switch will be less prevalent if hydrocarbon refrigerants are widely adopted in the U.S.
Despite the benefits of isobutene refrigerant, this working fluid is still flammable and exposure to gas at high concentrations can be toxic. GE and other hydrocarbon refrigerator designers must ensure that no ignition sources are present. However, the extra required system robustness should be worth the benefits.