Chlorofluorocarbons & Hydrofluorocarbons (HL) (DP IB Environmental Systems & Societies (ESS))

Chlorofluorocarbons & Hydrofluorocarbons

Overview of HCFCs

• What are CFCs?

  • Chlorofluorocarbons (CFCs) are chemical compounds containing chlorine, fluorine, and carbon

  • They were commonly used in the 20th century in products like aerosols, refrigerators, and air conditioning systems

• Impact of CFCs:

  • CFCs release chlorine radicals in the stratosphere, which deplete the ozone layer

  • Ozone depletion increases harmful ultraviolet (UV) radiation reaching the Earth's surface

• Regulation:

  • The Montreal Protocol (1987) banned CFCs globally due to their harmful environmental effects

  • Alternative chemicals, including HFCs, have largely phased out ODSs like CFCs

Overview of HFCs

• What are HFCs?

  • Hydrofluorocarbons (HFCs) are chemical compounds containing hydrogen, fluorine, and carbon

  • They were introduced as replacements for CFCs because they do not deplete ozone significantly

• Impact of HFCs:

  • Although less harmful to the ozone, HFCs are potent greenhouse gases (GHGs)

  • They have a high global warming potential (GWP)

  • HFC emissions contribute to climate change by trapping heat in the atmosphere

• Regulation:

  • The Kigali Amendment (2016) to the Montreal Protocol set targets to reduce the production and consumption of HFCs globally

  • Developed and developing countries have agreed to phase down HFCs gradually

Air Conditioning

• Air conditioning regulates indoor temperature and humidity to improve comfort

• It is widely used in homes, workplaces, vehicles, and public buildings

• Environmental impacts:

  • Air conditioning is energy-intensive, increasing electricity consumption

  • It contributes to greenhouse gas (GHG) emissions through:

    • Fossil fuels used in electricity generation

    • Leakage of refrigerants, some of which are potent GHGs

  • Traditional air conditioning units used ozone-depleting substances (ODSs) like CFCs

Refrigerants in air conditioning

• ODSs:

  • CFCs and HCFCs:

    • CFCs and HCFCs caused ozone depletion

  • HFCs:

    • Introduced as alternatives with low ozone depletion potential but high global warming potential (GWP)

    • Their use is now being phased down under the Kigali Amendment

• New refrigerants:

  • Hydrofluoroolefins (HFOs) have lower GWP and are being increasingly adopted in air conditioning systems

  • Natural refrigerants, like ammonia and carbon dioxide, are also being explored

Alternatives to air conditioning

Improved building design

• Incorporating natural ventilation, insulation, and reflective materials into buildings can stop them getting too hot

• Cool roofs reflect sunlight, reducing indoor heat absorption

  • Materials used:

    • Cool roofs can be made using reflective paint, tiles, or shingles designed to reflect sunlight

  • How they work:

    • They are usually lighter in colour or use materials that reflect solar radiation effectively

  • Benefits:

    • Reduces urban heat island effect

    • Improves indoor comfort in warm climates

    • Reduces need for air conditioning, lowering energy consumption and related emissions

• Window shading or double glazing can be used to minimise solar heat gain

Urban greening

• Urban greening refers to the process of incorporating vegetation, trees, parks, and green spaces into urban environments

• It is a sustainable approach to improving city landscapes and mitigating the effects of urbanisation and climate change

• How it works:

  • Trees, shrubs, and green spaces cool the air through shade and evapotranspiration (release of water from plants)

  • Vegetation absorbs carbon dioxide and reduces air pollution, improving air quality

  • Green roofs and walls add greenery to buildings, improving insulation and reducing heat absorption

• Benefits:

  • Lowers urban temperatures and combats the urban heat island effect

  • Reduces need for air conditioning in densely urbanised areas

Passive cooling

• Passive cooling involves architectural and design strategies that naturally reduce indoor temperatures without using energy-intensive cooling systems like air conditioning

• It is a sustainable way to create comfortable indoor climates

• How it works:

  • Utilises shading, ventilation, and thermal insulation to minimise heat gain and maximise heat loss

  • Structures are designed to capture natural breezes or block direct sunlight

• Key techniques:

  • Shading: overhangs, awnings, and trees block direct sunlight from entering buildings

  • Ventilation: windows, vents, or courtyards are designed to enhance airflow

  • Reflective materials: roofs and walls use reflective coatings to reduce heat absorption

  • Thermal mass: materials like concrete or stone store and release heat slowly, moderating temperature fluctuations

  • Green roofs: plant-covered roofs provide natural cooling by insulating buildings and reducing heat absorption

• Benefits:

  • Reduces reliance on artificial cooling systems, cutting energy consumption and costs

  • Minimises greenhouse gas emissions associated with air conditioning