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Air-conditioner Refrigerants and Their Environmental Impact
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Refrigerant Environmental Impact |
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Fluorocarbons refrigerants impact the environment in two main ways: ozone layer depletion and global warming. |
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Causes of Ozone Layer Depletion |
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Ozone layer destruction occurs in the following way. |
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CFCs and HCFCs, chlorine-containing organic compounds that are used as refrigerants, are released into the atmosphere and reach the stratosphere by diffusion and convection. |
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When exposed to ultraviolet rays from the sun, CFCs and HCFCs are decomposed to release chlorine. |
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This chlorine acts as a catalyst, decomposing ozone in the stratosphere to produce oxygen and reducing the amount of ozone in the stratosphere. |
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| (Because the same phenomenon occurs with bromine, halons, used mainly as fire extinguishing agents, are regulated.) |
With ozone layer depletion, more harmful ultraviolet rays reach the Earth’s surface, may cause an increase in skin cancer and other problems. |
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Ozone Depletion Potential |
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The ozone depletion potential (ODP) is the ratio of the potential impact on ozone of a chemical compared to the impact of the same mass of CFC-12, with the latter having an impact of 1. |
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| CFCs |
Since CFCs contain no hydrogen in molecules, they are stable in the atmosphere. This means they cannot be easily broken down until they reach the stratosphere and thus have a high ODP. |
| HCFCs |
Since they contain hydrogen in molecules, HCFCs can be broken down relatively easily in the atmosphere and thus have a low ODP. |
| HFCs |
Since they contain no chlorine or bromine, HFCs have an ODP of zero. |
Global warming refers to a phenomenon in which infrared rays are absorbed by molecules in CO2 and methane, as well as air-conditioner refrigerants like CFCs, HCFCs, and HFCs, thus preventing heat from escaping the Earth’s surface. |
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The Earth radiates infrared rays from being warmed by the sun’s rays in the daytime. |
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These infrared rays should be absorbed in outer space, but before they get there they are instead absorbed within the Earth’s atmosphere. |
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The Earth’s surface gets warmer. |
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Major Global Warming Substances and GWP (Global Warming Potential) |
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The potential impact that substances have on global warming is generally shown by their GWP (global warming potential). GWP is calculated as the integrated value of the potential warming impact of a substance compared to the impact of the same amount of CO2 over a period of time. Usually 100 year values are used. |
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:Substances covered by the Kyoto Protocol |
| Global warming substances |
Atmospheric life |
GWP
CO2=1
Atmospheric life:120years
IPCC2001 |
| 20"N'l |
100"N'l |
500"N'l |
| PFC14 |
50000 |
3900 |
5700 |
8900 |
| SF6 |
3200 |
15100 |
22200 |
32400 |
| NF3 |
740 |
770 |
10800 |
13100 |
| HFC23 |
260 |
9400 |
12000 |
10000 |
| HFE125 |
150 |
12900 |
14900 |
9200 |
| CFC12 |
100 |
10200 |
10600 |
5200 |
| HFC125 |
29 |
5900 |
3400 |
1100 |
| HFC134a |
13.8 |
3300 |
1300 |
400 |
| CH4(Methane) |
12.0 |
62 |
23 |
7 |
| HCFC22 |
11.9 |
4800 |
1700 |
540 |
| HFC32 |
5.0 |
1800 |
550 |
170 |
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In addition to the six substances covered by the Kyoto Protocol, there are other global warming substances.
Global warming impact differs from substance to substance. The atmospheric life of substances has a great affect on their global warming impact.
PFCs (perfluorocarbons) and SF6 (sulfur hexafluoride), which contain no hydrogen molecules, have an atmospheric life ranging from several thousand years to several tens of thousands of years, therefore, the longer the integration period, the higher their GWP.
As for the atmospheric life of HFCs, which contain hydrogen in molecules, HFC25, the major component of HFC blend refrigerants, lasts for 29 years, while HFC32 lasts for only 5 years. For example, comparing HFC125 and PFC14, their GWPs over 100 years are 3400 and 5700, respectively, not that big a difference. However, over 500 years, HFC125 has a GWP just one-eighth of PFC14. This shows the strong effect of atmospheric life on GWP.
HFC134a is a CFC12 substitute refrigerant used in car air-conditioners and refrigerators. The use of this substitute results in global warming potential dropping from 10,600 to 1,300 (over 100 years), a huge difference.
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