Air Conditioning: A Cool Breeze Of Harmful Pollutants?

Air conditioning units are a common feature in many homes and buildings, providing much-needed relief from hot temperatures. However, it is important to consider the potential environmental impact of these cooling systems. Air conditioning units, particularly older models, can contribute to air pollution through the release of fluorinated refrigerants, which have a high global warming potential. These refrigerants, such as CFC-12 and HFC-134a, are major contributors to greenhouse gas emissions, with consequences for climate change. Understanding the pollutants associated with air conditioning is crucial for making informed choices and mitigating any negative impacts on the environment.

Fluorinated refrigerants in air conditioning

Fluorinated refrigerants, such as hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs), have been commonly used in air conditioning systems. These substances are also known as fluorinated greenhouse gases and have a high global warming potential (GWP). Due to their climate-damaging effects, there has been a push to transition to non-fluorinated alternatives.

HFCs, including R-134a and R-125, are widely used in refrigeration and air conditioning equipment. They also have applications as blowing agents, aerosol propellants, and solvents. However, these refrigerants have been found to degrade atmospherically, forming trifluoroacetic acid (TFA) as a persistent degradation product. The increasing levels of TFA globally highlight the urgency to adopt non-fluorinated alternatives and prevent direct emissions from leakage or improper handling of fluorinated refrigerants.

One alternative that has gained attention is 2,3,3,3-Tetrafluoropropene (R1234yf), a fluorinated substance with a lower GWP than commonly used HFCs. However, R1234yf is flammable and produces hydrogen fluoride (HF) upon combustion, which has raised safety concerns. As a result, an EU directive banned the use of fluorinated greenhouse gases with a global warming potential exceeding 150 in mobile air conditioning systems, leading to the phase-out of R134a in new passenger cars and similar commercial vehicles since 2011.

The search for suitable refrigerants considers both environmental impact and efficiency. While non-fluorinated alternatives like hydrocarbons and ammonia have been adopted in some countries, the transition in the EU has faced barriers. CO2 is favoured by the Federal Environment Agency (UBA) for mobile air conditioning systems due to its lower environmental impact and the inability to refill systems with ozone-depleting substances. Additionally, the Montreal Protocol, implemented in 1989, played a crucial role in regulating ozone-depleting substances, leading to the substitution of CFCs with HCFCs and HFCs in refrigeration and air conditioning systems.

CFC-12 in older air conditioning models

CFC-12, also known as Freon or R-12, was the coolant most frequently used in automobile air conditioning (A/C) systems and accounted for 20% of all US CFC consumption in 1992. CFCs have been used for many years in refrigeration and aerosol cans, but they have been linked to ozone depletion and are therefore being phased out of use. CFC molecules are stable and rise into the stratosphere, where they are split by the sun's ultraviolet radiation, releasing chlorine molecules that react with and split ozone molecules. This depletion of the ozone layer, situated 10 to 30 miles above the Earth's surface, is harmful as the ozone layer protects biological life from the sun's ultraviolet radiation, which can cause skin cancer, cataracts, and immune system suppression.

In response to the environmental concerns caused by CFCs, the US Environmental Protection Agency (EPA) has implemented regulations governing their use. The Clean Air Act Amendments of 1990 included regulatory requirements for personnel and facilities servicing automobile A/C units, and it is now illegal to vent CFCs into the atmosphere. Penalties of up to $25,000 per day per violation can be levied, and prison terms can be given to those who knowingly release CFC-12 into the atmosphere. The EPA also requires that CFC-12 be recycled. To become certified, all technicians servicing automobile A/C systems must complete an EPA-approved refrigerant recycling course.

The Montreal Protocol, an international environmental agreement established in 1987, set out the phase-out of CFCs. While Freon is highly restricted and regulated in its use today, older appliances, including air conditioning units and freezers, still use and release this harmful gas. As of January 1, 2015, the US should have been below 90% of its baseline CFC use, and by January 1, 2020, usage needed to be 99.5% below the baseline. This phase-out may increase costs for those using Freon, encouraging the replacement of older AC models with more environmentally friendly alternatives.

To retrofit a CFC-12 (R-12) system to HFC-134a (R-134a), service procedures have been outlined to preserve the performance and integrity of the A/C system while minimizing the release of refrigerant into the atmosphere. This process involves using separate service equipment for CFC-12 and HFC-134a, including refrigerant recovery/recycle (R/R), service manifolds, vacuum pumps, and charging equipment. Hydrochlorofluorocarbons (HCFCs) are also used as substitutes for CFC-12 in A/C systems, although their ozone depletion capability is significantly less. However, under the Montreal Protocol, HCFC production is also scheduled to be banned by 2030.

HFC-134a in newer air conditioning models

HFC-134a, also known as R-134a, is a type of hydrofluorocarbon (HFC) refrigerant used in some newer car air conditioning models. It is considered more environmentally friendly than its predecessor, R-12, which uses chlorofluorocarbons (CFCs) that are damaging to the ozone layer. HFC-134a has a lower environmental impact due to its chlorine-free composition, making it a popular choice for automotive air-conditioning systems.

HFC-134a has become a widely adopted refrigerant in the automotive industry, particularly in family cars. Its use has expanded due to its recognition and recommendation by many countries worldwide. This refrigerant is known for its relatively low toxicity, although it can be toxic in large volumes. HFC-134a has also been utilised in rescue Albuterol inhalers for this reason.

One key advantage of HFC-134a is its ability to meet the requirements of automotive air-conditioning systems. When used in these systems, the compression ratio increases due to changes in evaporation and condensation pressures. However, the decrease in compressor displacement results in a lower system flow rate compared to R-12. To address this issue, technical improvements are made to rubber hoses and sealing materials, and high-efficiency condensers are employed to enhance heat exchange performance.

While HFC-134a is considered a more environmentally friendly option, it has come under scrutiny for its high global warming potential (GWP). As a result, the Environmental Protection Agency (EPA) has been phasing out its use in new vehicle air conditioning systems and chillers since 2021. Industries are now shifting towards more eco-friendly alternatives with lower GWP, such as R1234yf and R744.

HFC-134a is not without its challenges, as it has been associated with refrigerant leakage. The molecular volume of HFC-134a is smaller than that of R-12, and its permeability is stronger, contributing to this issue. Additionally, the lubricating oil used in the R-12 system is not compatible with HFC-134a, requiring the development of new synthetic lubricating oils like PAG (Polyalkylene Glycols) and POE (PolyolEsters).

Air conditioning as a contributor to greenhouse gases

Air conditioning is a major contributor to global warming, accounting for about 3% of global greenhouse gas emissions. This figure is expected to increase as the demand for air conditioning rises due to climate change and increasing incomes.

Air conditioning units use a lot of electricity, and they can also leak potent greenhouse gases, such as hydrofluorocarbons, into the atmosphere. These refrigerants are powerful greenhouse gases, and their use contributes significantly to the overall carbon footprint of air conditioning. In 2022, greenhouse gas emissions from air conditioning totalled 1,750 tCO2eq, or 3.2% of all greenhouse gas emissions. If the current trend continues, emissions from air conditioning are expected to double by 2030 and triple by 2050, rising from 7% of global GHG emissions today.

The impact of air conditioning on global warming creates a vicious cycle. As the planet warms due to greenhouse gas emissions, the demand for air conditioning increases, leading to even more emissions. This cycle has significant implications for the future, as it could leave a large portion of the global population exposed to life-threatening heat and humidity.

To address this issue, it is important to improve the energy efficiency of air conditioning units. Some companies are working to incentivize and finance the adoption of green technologies, such as electric heat pumps and energy-efficient retrofits. Additionally, cities can play a crucial role in reducing the environmental impact of cooling by enforcing planning rules, integrating nature into urban areas, providing social housing, and promoting district cooling approaches.

Nature-based solutions, such as planting and preserving trees and forests within cities, can significantly cool the urban environment and reduce the demand for air conditioning. Investing in street trees can provide a cooling effect equivalent to running multiple air conditioners for extended periods. Similarly, creating water bodies, such as lakes, canals, ponds, and wetlands, in urban areas can have a substantial cooling impact.

Air conditioning and the Clean Air Act

The Clean Air Act (CAA) is a federal law that regulates air emissions from stationary and mobile sources. The Act authorises the Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) to protect public health and welfare and to regulate emissions of hazardous air pollutants.

One of the goals of the CAA was to set and achieve NAAQS in every state by 1975 to address the health and welfare risks posed by widespread air pollutants. The Act required states to develop State Implementation Plans (SIPs) to outline how they would achieve these standards. The CAA has been amended several times to add further protections for the environment and public health, including the 1990 Amendments, which introduced new regulations to phase out the use of chemicals that harm the ozone layer.

Ozone-depleting chemicals (ODCs) regulated under the CAA include chlorofluorocarbons (CFCs), which were commonly used in refrigeration and air conditioning. Section 608 of the CAA includes specific provisions regarding ozone protection, requiring technicians to pass an exam to handle and purchase refrigerants that affect the ozone layer. The Act also sets standards for recovering and reclaiming refrigerants, including removing them from systems and storing or reprocessing them.

Air conditioning can produce several pollutants, including ozone-depleting chemicals such as CFCs, as well as indoor air pollutants like carbon monoxide, nitrogen dioxide, and particulate matter. The CAA aims to reduce these pollutants by setting standards for air quality and regulating emissions from various sources, including air conditioning equipment.

While the CAA has been generally effective in improving air quality, there are still areas that do not meet all NAAQS, and tens of thousands of premature deaths are caused by fine-particle pollution and ground-level ozone pollution each year. Climate change and local factors, such as geography, industrial activity, and transportation, also pose challenges to managing air pollution effectively.

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