Explain global warming caused by refrigerants.
What is global warming potential(GWP)?
What is ozone depletion potential(ODP)?
Ans: Most of the sun's energy reaches the Earth as visible light(0.40-0.76 microns wavelength). Part of the energy is absorbed by the surface of the Earth and converted into heat. Now the heated surface of the earth radiates this heat energy back into the atmosphere and back towards the space as infrared radiation (higher wavelength than visible light), but greenhouse gases like CO2, CFCs(chlorofluorocarbons), HCFCs(hydrochlorofluorocarbons), water vapor, etc absorb this infrared radiation which causes the heat to get trapped near the surface of the earth. This warming process caused due to atmosphere's absorption of heat energy radiated from Earth's surface is called the 'greenhouse effect' or 'global warming'.
What is global warming potential(GWP)?
If leaked into the atmosphere some chemicals directly affect the atmosphere and cause global warming. These effects are measured by an index called Global Warming Potential (GWP). The higher the global warming potential the more it can hold the heat into the atmosphere for a longer amount of time.
The GWP of CO2 is 1. The GWP of other chemicals is compared with CO2.
Some of the new generation refrigerants such as HFCs, HCs, and HFOs, have lower to a moderate value of GWP.
For example,
R134A has a GWP of 1430 which is considered a moderate GWP.
R290 has a GWP of 3.0 which is considered a very low GWP compared to other old generation refrigerants like R22, R12, etc.
What is ozone depletion potential(ODP)?
The ozone(O3) is found in both the stratosphere and troposphere. Ozone in the stratosphere stops harmful ultraviolet rays (UV-B) from reaching Earth.
Most of the CFC and HCFC-based refrigerants cause ozone to deplete. One chlorine molecule can destroy up to 100,000 ozone molecules. The depleted ozone molecules in the stratosphere allow more and more ultraviolet (UV-B) rays to reach Earth which can cause skin cancer and cataracts in humans and animals, decrease the life of plants, weakening of the human immune system.
Hence, United Nations Environment Programme (UNEP) Montreal Protocol created an Index known as Ozone Depletion Protocol (ODP). The higher the ODP the more damage it can cause to the ozone layer.
Old refrigerants like R12, R22, R502, etc which had high ODP have been banned and their manufacturing is stopped.
Some new generation refrigerants which are HFO, HC, and HFC-based have zero ozone depletion potential.
For example,
R1234yf, R1234ze, R290, R600A, R314A, R404A, and R410A have zero ODPvalue and low to medium Global warming potential (GWP).