Development of The CO2 Transcritical Heat Pump

In the 1990s, researchers Lorentzen and Pettersen from the Norwegian research institute SINTEF conducted theoretical and experimental studies on the application of CO2 transcritical cycles in heat pump water heaters. The research showed that CO2 transcritical cycles not only have a high heating coefficient, but also have a compact system and produce high water temperatures. In 1996, SINTEF completed the first experimental CO2 heat pump water heater with a power of 50kW. The experimental results showed that at an evaporation temperature of 0℃, the water temperature could be heated from 9℃ to 60℃, with a heat pump coefficient of up to 4.3. Furthermore, compared to electric and gas water heaters, its energy consumption can be reduced by 75%. In addition, a significant advantage of CO2 heat pump water heaters over traditional heat pump water heaters is that they are more capable of providing hot water up to 90℃.