China is the largest producer and consumer of hydrochlorofluorocarbons (HCFCs), and the production of HCFC-22 accounts for more than 80% of all HCFCs. This paper concentrates on the residential air-conditioner industry and analyzes the environmental benefits of accelerating the phase-out of HCFC-22 in China. According to the comparison of the baseline and phase-out scenarios of HCFC-22, the findings show that using HC-290 (propane) as a refrigerant alternative will directly reduce the greenhouse effect, and indirectly reduce the emission of greenhouse gases due to a reduction in the electricity consumption. The comparison of two scenarios of HC-290 and HFC-410A refrigerant alternatives shows that the use of HC-290 refrigerant will produce significantly higher environmental benefits than the HFC-410A refrigerant.
HCFC-22 ; HFC-410A ; HC-290 ; residential air-conditioner ; GWP ; ODP
Climate change and ozone layer depletion are extremely serious global environmental problems in the world. Hydrochlorofluorocarbons (HCFCs) are one kind of global greenhouse gases with high global warming potentials (GWP). They are the most important ozonedepleting substances in mass-production and consumption in the world and rank as Class-1 controlled substances in Annex C of the Montreal Protocol on Substances that Deplete the Ozone Layer (hereinafter referred to as Montreal Protocol) [ UNEP , 1992 ]. Since HCFCs have a significant impact on climate change and ozone layer depletion, the international community decided to accelerate HCFCs phase-out at the 19th conference held by Montreal Protocol Parties in September 2007 [ UNEP , 2007 ]. Based on the UNEP report “Production and consumption of ozone-depleting substances under the Montreal Protocol ”, the statistical data on production and consumption of HCFCs and their ozone-depleting potential (ODP) indicate that China is the largest producer and consumer of HCFCs since 2003 [ UNEP , 2005 ]. According to the latest phase-out schedule under the Montreal Protocol , China, as a developing country, is expected to limit the production and consumption of HCFCs in 2013 at the average level of 2009–2010. Further it is expected to reduce HCFCs by 10% in 2015, 35% in 2020, 67.5% in 2025, and finally phase-out all HCFCs in 2030 [ UNEP, 2007 ].
HCFC-22 (CHF2 Cl) is a refrigerant widely used in residential air-conditioner, industrial and commercial refrigeration, refrigerators and freezers. Its ODP is estimated at 0.055 [ UNEP , 1992 ] and its GWP is defined at 1,780 [ IPCC, 2005 ]. In China, the production capacity of HCFC-22 accounts for 80% of all HCFCs production. The residential air-conditioner industry is the largest HCFC-22 consumption sector with an annual consumption of about 60,000 t, which is equivalent to 0.1 Gt CO2 -eq and 3,300 t ODP. In addition, annual energy consumed by residential air-conditioner industry is about 5.5×1011 kW h. International research show that substitutes with lower ODP and GWP are of great significance both in protecting the ozone layer of the earth and reducing greenhouse gas emissions [Minh et al., 2003; Velders et al. , 2007 ]. In addition, substitute refrigerant based residential air-conditioner consumes less power than that of HCFC-22 [ Chen , 2008 ; Atul , 2008 ]. Based on the aforementioned studies, the assessment and prediction of the phase-out of HCFC-22 in residential air-conditioner industry will play a significant role in environmental protection with regard to the reduction of greenhouse gas emissions as well as the implementation of the Montreal Protocol in China.
Residential air-conditioner industry in China emerged in the early 1960s. China has become the world’s largest producer of residential air-conditioners since 2000, and accounts for 75% of the global production with an annual output of 230 billion RMB. According to nearly 10 years’ statistics from the China Household Electrical Appliances Association (Table 1 ), the production of residential air-conditioners in China grew from 8.49 million units in 1997 to 72.50 million units in 2008 with an average annual growth rate of 22%. From 2005 to 2007 the average annual growth rate decreased significantly compared to the previous years. In 2008 the annual growth rate in production is negative. Residential air-conditioners exports increased significantly from 0.84 million units in 1997 to 35.78 million units in 2008 with an average annual growth rate of 41%. The average imports of residential air-conditioners from 1997 to 2003 only account for 0.15% of the total domestic consumption. The imports show a continuous downward trend and were therefore neglected from the calculation of the domestic consumption. The domestic consumption is defined by the difference of production and export. Due to the improvement of living standards, the domestic consumption for residential air-conditioners increased rapidly from 7.65 million units in 1997 up to 36.72 million units in 2008. The growth rates of production and domestic consumption show similar trends, especially with the lowering rates from 2005 to 2007.
|Year||Production (growth rate: %)||Exports (growth rate: %)||Domestic consumption (growth rate: %)|
CFC-12 (CCl2 F2 ) was originally used as refrigerant in residential air-conditioner. Since HCFC-22 shows more excellent thermal performances, its application in refrigeration products exceeds that of CFC-12 [ Wang , 2007 ]. HCFCs are chemicals which should be phased-out according to the Montreal Protocol . As a consequence, many countries have begun to develop and use substitute refrigerants.
Currently, HFC-410A and HC-290 (propane) are main HCFC-22 substitute refrigerants for residential air-conditioner. HFC-410A is a mixture comprising 50% HFC-32 (difluoromethane) and 50% HFC-125 (pentafluoroethane). HFC-410A has a low toxicity, is non-flammable, and has chemical and thermal stability [Zeng , 2001]. HC-290 as a natural substance is cheap, abundant, and has good thermal and chemical stability, and is good oil-soluble and non-toxic [ Wang and Liu , 2003 ]. It has no significant hazard to the environment, and has been used as refrigerant for decades. However, due to its inflammable and explosive character, its application as refrigerant was greatly reduced after the emergence of chlorofluorocarbons. Due to the demand for ozone protection, research on hydrocarbon substitute HCFC-22 has increased in recent years. The theoretical cycle of hydrocarbons or its mixture has been analyzed in many studies [ Wang et al., 2001 , Wang et al., 2002 and Wang, 2005 ].
Compared with HCFC-22, HFC-410A has zero ODP. But its GWP is up to 2,060, which makes it a greenhouse gas controlled in the Kyoto Protocol [ UN , 1998 ]. The physical properties of HFC-410A are different from HCFC-22. HFC-410A has a higher heat transfer coefficient and its refrigerating capacity per unit volume is 40% higher than HCFC-22. Although the price of HFC-410A is higher, and so is the cost of the machine maintenance, HFC-410A needs less raw material, so the producing costs of HFC-410A based air-conditioner and HCFC-22 based air-conditioner will be similar with the expansion in production capacity [ Chen , 2008 ]. HC-290 has zero ODP and negligible GWP. HC-290 shows the similar thermodynamic properties with HCFC-22 [ Wang , 2005 ]. When HC-290 was directly filled into the HCFC-22 based residential airconditioner the operation conditions were not ideal, but better results were obtained after adjustments on the capillary system took place [ Wang , 2005 ]. Therefore, air-conditioners need to be adjusted to achieve better operation conditions with HC-290. The volume of cooling capacity of HC-290 is slightly less than that of HCFC-22, about 97% to 99% of HCFC-22 [ Wang , 2005 ]. As HC-290 is flammable and explosive, the infill amount should be strictly controlled and the explosion-proof device needs to be installed on electrical equipment of production lines for the purpose of safety issues. The costs to substitute HC-290 will be higher due to the installation and maintenance costs on explosive devices. In general, HC-290, with good environmental compliance and better energy efficiency, becomes a popular substitute for HCFC-22.
HFC-410A is being used mainly in the USA, European Union (EU) and Japan. HC-290 is being used in some European countries. In China, the price of HFC-410A is 2–3 times higher than HCFC-22 due to patent protection. Also, the safety technology is not mature enough for HC-290 to be used in residential air-conditioner; therefore all domestic residential air-conditioners still use HCFC-22 as refrigerant. Japan and the EU had refused to import HCFC-22 based residential air-conditioner since July 1, 2004, and the USA refuses to import HCFC-22 residential air-conditioner from July 1, 2010. Therefore, in order to meet the foreign standards of air-conditioners, China has chosen HFC-410A as refrigerant in residential air-conditioner for the export to developed countries. As a signing party of the Montreal Protocol , China will phase-out HCFC-22 refrigerant in domestic residential air-conditioner.
In this paper, we use a scenario analysis (by setting the baseline scenario and phase-out scenario) to predict the refrigerant consumption and emissions for different scenarios. Because the emissions of refrigerants from exported residential air-conditioners do not occur in China, only the emissions of domestic residential air-conditioner are considered. Therefore, only the consumption of domestic residential air-conditioner refrigerants is predicted. Its consumption mainly includes the filling of new air-conditioner and the refrigerant refilling in the process of maintenance. The average service life of air-conditioner is 10 years with some servicing and scrapping in each year. The used formula of calculation is as follows.
Where C1t means the refrigerant consumption for new products in year t ; C2t is the refrigerant consumption for servicing in year t ; Ct means the total refrigerant consumption in year t ; m1 is the filling amount per unit in the production; m2 means the filling amount per unit during servicing; Si is the consumption of domestic residential air-conditioners in year i ; ki means the total scrapping rate of years i ; xi means the servicing rate in year i .
In the presumed baseline situation for this paper, HCFC-22 refrigerant will be used for all domestic residential air-conditioner in China in the future. According to predicted residential air-conditioner data from the China Household Electrical Appliances Association, we suppose that the average HCFC-22 filling amount for each set of new products is 1.35 kg, and 0.9 kg refrigerant will be needed for refilling in maintenance. Applying the formula of refrigerant consumption to the data, the consumption of HCFC-22 in residential air-conditioner under the baseline scenario is shown in Table 2 .
|Year||Residential air-conditioner consumption* (million)||HCFC-22 consumption in new products (t)||HCFC-22 consumption in maintenance (t)||Total consumption of HCFC-22 (t)|
It is assumed that HCFC-22 consumption of residential air-conditioner industry (excluding the export consumption) in 2013 and 2014 will be the average of the 2009 and 2010 levels. The phase-out schedule was set as follows: No increase in consumption in 2013, 10% reduction by 2015, 35% reduction by 2020, 67.5% reduction by 2025, and a complete phase-out (zero consumption) by 1 January 2030. The consumption of HCFC-22 residential air-conditioner and HCFC-22 under the phase-out scenario is shown in Table 3 . The consumption of HCFC-22 residential air-conditioner will be reduced gradually from 38.16 million units in 2013 to 0 in 2030. HCFC-22 consumption will decrease from 65,875 t in 2013 to 5,082 t in 2030 (for servicing purposes only).
|Year||HCFC-22 residential air-conditioner consumption (million)||HCFC-22 consumption in new products (t)||HCFC-22 consumption in maintenance (t)||Total consumption of HCFC-22 (t)|
In order to compare the maximum environmental benefit of different substitute refrigerants, two different phase-out scenarios have been established. Scenario 1: HFC-410A is used as substitute refrigerant. Scenario 2: HC-290 is used as substitute refrigerant. Following the phase-out scenarios, the reduced domestic consumption of HCFC-22 residential air-conditioner is equal to that of residential airconditioner using substitute refrigerants. Since HC-290 has zero ODP and negligible GWP, it is not necessary to calculate the consumption of HC-290 when estimating the environmental effect of HC-290 refrigerant. The average filling amount of HFC-410A based on residential air-conditioners is 1.1 kg, and the refilling amount for each set of HFC-410A air-conditioner during servicing is 1.1 kg under the assumption that the original filled refrigerant needs to be discharged completely. The calculated HFC-410A consumption based on the formula is shown in Table 4 .
|Year||HFC-410A residential air-conditioner consumption (million)||HFC-410A consumption in new products (t)||HFC-410A consumption in maintenance (t)||Total consumption of HFC-410A (t)|
The environmental benefits gained from the phase-out of HCFC-22 refrigerant in China include the direct environmental benefits of ozone-depleting and global warming caused by reduced emissions and indirect environmental benefits of energy consumption. The recovery rate of refrigerants in China is zero, i.e., all the refrigerants are released to the atmosphere. The direct environmental benefits are calculated based on the refrigerant consumption. Annual electricity consumption of a single unit of HCFC-22 based residential air-conditioner is 2,032 kW h, HFC-410A based residential air-conditioner is 55 kW h less than that of HCFC-22 [ Chen , 2008 ]. The electricity consumption of HC-290 based residential air-conditioner is 371 W h–1 lower than that of HCFC-22 [ Atul , 2008 ]. According to statistics of the China Residential Electrical Appliances Association, the number of average running hours of residential air-conditioner for China is 784 hours. Annual electricity consumption of each HC-290 residential air-conditioner is 291 kW h lower than that of HCFC-22. In China, the generation of 1 kW h electricity will result in the emission of 0.88 kg CO2 -eq [ Wang and Liu , 2003 ]. The reduced emissions of greenhouse gases, ODP, and electricity (the energy-saving amount can be convertible to the emission-reduction volume) from phase-out of HCFC-22 residential air-conditioner industry in China is shown in Table 5 .
|Year||Phase-out scenario||Greenhouse gas emission reduction (Mt CO2 -eq)||ODP reduction (t)||Electricity-saving (kW h)||Reduction from saving electricity (Mt CO2 -eq)|
|in that year||accumulative total||in that year||accumulative total||in that year||accumulative total||in that year||accumulative total|
Compared with the baseline scenario, the greenhouse gas emission under scenario 1 will reduce at first and then increase, due to the higher GWP of HFC-410A. Following scenario 1, the accumulative increase of greenhouse gas emissions will be 34.4 Mt CO2 -eq from 2013 to 2030. The reduction of greenhouse gas emissions under scenario 2 will become more and more significant. Here, the accumulative reduction of greenhouse gas emission will be 3,784.8 Mt CO2 -eq from 2013 to 2030. Because both HC-290 and HFC-410A have zero ODP, the ODP emission-reduction under the two scenarios is the same. The ODP reduction will be more and more significant along with the phase-out schedule. The accumulative ODP reduction will be 116,946.5 t. The energy-savings under the two phase-out scenarios will increase rapidly along with the phase-out schedule. The energy-saving under scenario 2 will be higher than that of scenario 1. Energy-saving amounts under scenario 1 and 2 for the 2013–2030 period are 3.8×1011 kW h and 2.0×1012 kW h, respectively. This is equivalent to an emission reduction by 337.9 Mt CO2 -eq and 1,787.5 Mt CO2 -eq, respectively. Therefore, residential air-conditioner using HFC-410A and HC-290 will both reduce the ODP, which is beneficial to the protection of the ozone layer, and also reduce electricity consumption. Benefit to the ozone layer protection and energy-saving will increase rapidly along with the phase-out of HCFC-22. Residential air-conditioner with HC-290 will produce more environmental benefits compared with HFC-410A, due to a high reduction of greenhouse gas emissions which slows down global warming.
China has not chosen a distinct substitute refrigerant in domestic residential air-conditioner, but is actively carrying out studies on this issue and is promoting the phase-out of HCFC-22. HFC-410A and HC-290 as the possible future substitute refrigerants both have advantages and disadvantages. The phase-out of HCFC-22 in the residential air conditioner industry with HFC-410A and HC-290 substitutes in China will produce significant environmental benefits: 1) It reduces the emission of ozone-depleting substances, which will protect the ozone layer; 2) it will save energy and reduce greenhouse gas emissions indirectly as a result of the improvement in efficiency of refrigeration equipment. The efficiency of energy-saving and the ozone layer protection will increase rapidly along with the advancing phase-out amounts of HCFC-22 conditioner, whereas HC-290 will save more energy than HFC-410A. In addition, the substitution of HC-290 will bring direct environmental benefits due to greenhouse gas emissions reduction. In contrary, the substitution of HFC-410A will cause an increase of greenhouse gas emissions due to its higher GWP value. However, because hydrocarbons are inflammable, it is necessary to take precautions in the production, product installation and consumption processes. HC-290 will become an important substitute for the residential air conditioner industry if its security issues are solved.