The transition away from the production and consumption of high global warming potential (GWP) hydrofluorocarbons (HFCs) under the 2016 Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer has prompted air conditioning, refrigeration, and heat pump equipment manufacturers to seek alternative refrigerants with lower direct climate impacts. Additional factors affecting alternative refrigerant choice include safety (i.e., flammability and toxicity), environmental, and thermodynamic constraints. At the same time, manufacturers are incentivized to seek refrigerants with higher energy efficiency, which saves on electricity costs and reduces indirect greenhouse gas emissions from electricity generation. The life cycle climate performance (LCCP) metric is commonly used to assess the combined direct and indirect climate impacts of refrigerant-use equipment. Here, we consider an additional impact on climate performance: the degradation of refrigerant in equipment, i.e., the direct climate impacts of high-GWP byproducts that can form as the result of adding trifluoroiodomethane (CF3I) to refrigerant blends to reduce flammability. Such a production of high-GWP gases could change the acceptability of CF3I-containing refrigerants. Further, it highlights the need to understand refrigerant degradation within equipment in calculations of the environmental acceptability of new cooling technology.
Life Cycle Climate Performance (LCCP) is a widely accepted metric to evaluate the carbon footprint of air conditioning (AC) systems “from cradle to grave.” This paper: (1) reviews the invention and evolution of LCCP, including a comprehensive timeline and bibliography; (2) documents the successful application of LCCP in the replacement of HFC-410A with HFC-32 in room air conditioners; (3) compares the conceptual frameworks and the operational approaches; and 4) reflects on the drawbacks of current LCCP research and points out possible future work.
The major policy-relevant findings are: 1. The indirect emissions caused by energy consumption is 70 to 80 percent of the LCCP of AC systems in most countries but will decline in importance as electric power supply shifts rapidly from fossil fuel to renewable energy sources, which have near-zero carbon intensity; 2. The embodied greenhouse gas (GHG) emissions in refrigerant manufacture are, in most cases, negligible but the physical and chemical properties are crucial for system optimization for low carbon footprint; 3. The LCCP metric can be used for multiple purposes such as refrigerant selection and AC system architecture optimization; and 4. Data limitations in material manufacturing and the carbon intensity of electric power are the most significant challenges. Finally, this paper describes a variety of methods to fill in data gaps, including the correction factor method, the data-driven method, and the database searching method. The next-generation LCCP will be an enhanced evaluation process considering local climate, heat islands, and local power supply characteristics.
The comprehensive carbon metric accounts for the fact that AC electricity use and the integrated carbon intensity of that electricity can be up to 48% higher than estimated using national “average” assumptions. Taking real-world operating conditions and the actual carbon intensity of electricity generation, transmission, and distribution at the end-use into consideration provides for a more accurate assessment of the significant climate and economic benefits from energy efficiency and power grid investment.
This article was published in ASHRAE Journal, November 2018. Copyright 2018 ASHRAE. Posted at www.ashrae.org.
The Kigali Amendment to the Montreal Protocol phases down the production and consumption of hydrofluorocarbon greenhouse gases that were once necessary to rapidly phase out ozone-depleting substances but are no longer needed. The Kigali Amendment complements the emission controls of the UNFCCC Kyoto Protocol and contributes to satisfying the “nationally determined contributions” to reduce greenhouse gas emissions pledged under the 2016 Paris Climate Agreement. In 2016, the International Institute of Refrigeration proposed using Life-Cycle Climate Performance metric for air-conditioning systems while summing up carbon-equivalent direct refrigerant emissions, indirect power plant greenhouse gas emissions, and carbon equivalent embodied emissions. This paper describes an Enhanced and Localized Life Cycle Climate Performance metric developed by a team of international experts to reflect real-life air conditioning system operations.
