S R C C Alternatives to H F s in the efrigeration and Air Conditioning Sector ection 01 29 refrigerant charges and leak risk significantly and is preferred in several applications on some markets. Indirect systems also give more flexibility in the selection of refrigerants as the risks and costs of using flammable (HCs) and toxic (NH3) refrigerants decrease. CO2 is also a leading candidate as an alternative to R-134a in automotive air conditioning as the latter will be phased out in new car models in the EU from 2011. Europe where these heat pumps are used for combined hot water and space heating. CO2 is also used as a secondary fluid in low temperature applications as it can reduce the energy consumptions for pumps and tube dimensions in indirect cooling systems. The use of indirect systems is increasing as it reduces the Sub critical CO2Refrigerant inside: NH3 or HFCAir or liquidcondenserCO2 Pump“Standard” chillerRefrigerant inside: NH3 or HFCAir or liquidcondenser Fig. 1.9 CO2 in sub-critical operation in cascade with hydrocarbon, ammonia, or HFC refrigerant. Fig. 1.10 CO2 as secondary fluid in an indirect system. 1.4.4 HFC alternatives used in new and retrofitted systems with new oil Su mmary HFCs HFCs are by far the most common replacement of HCFCs in new equipment and a wide range of such equipment has been available on the market for the past 15 years. The relatively high GWGWP of HFCs have increased the pressure on finding alternatives with lower impact on climate and the development efforts have increased as climate change has become the number one environmental challenge. The arguments used in favour of HFCs are that they can be used safely and cost effectively in all applications where CFCs and HCFCs have been used with minimal technical changes. As the focus on climate change increased, this also resulted in an increased focus on energy efficiency. In many applications the energy efficiency of today’s HFCs