The latest developments on the use of CO2 as refrigerant
CO2 heat pump water heaters have been studied extensively in the last decade in universities and research labs. Although much research has been conducted, few systems have been commercialized outside of Japan. This situation is likely to change in the next few years, as compressor manufacturers release reliable CO2 compressors and other CO2 system components become commonly available. Inside Japan, CO2 heat pump development continues at a furious pace, with effi ciency improvements common.