High-Global Warming Potential F-gas Emissions in California: Comparison of Ambient-Based versus Inventory-Based Emission Estimates, and Implications of Refined Estimates

Abstract

To provide information for greenhouse gas reduction policies, the California Air Resources Board (CARB) inventories annual emissions of high-global-warming potential (GWP) fluorinated gases, the fastest growing sector of greenhouse gas (GHG) emissions globally. Baseline 2008 F-gas emissions estimates for selected chlorofluorocarbons (CFC-12), hydrochlorofluorocarbons (HCFC-22), and hydrofluorocarbons (HFC-134a) made with an inventory-based methodology were compared to emissions estimates made by ambient-based measurements. Significant discrepancies were found, with the inventory-based emissions methodology resulting in a systematic 42% under-estimation of CFC-12 emissions from older refrigeration equipment and older vehicles, and a systematic 114% overestimation of emissions for HFC-134a, a refrigerant substitute for phased-out CFCs. Initial, inventory-based estimates for all F-gas emissions had assumed that equipment is no longer in service once it reaches its average lifetime of use. Revised emission estimates using improved models for equipment age at end-of-life, inventories, and leak rates specific to California resulted in F-gas emissions estimates in closer agreement to ambient-based measurements. The discrepancies between inventory-based estimates and ambient-based measurements were reduced from -42% to -6% for CFC-12, and from +114% to +9% for HFC-134a.

Benefits of Energy Efficient and Low-Global Warming Potential Refrigerant Cooling Equipment

“…An installation emission factor of 1% and average annual operating emissions of 10% are assumed, based on Gallagher et al (2014), and the Intergovernmental Panel on Climate Change (IPCC 2006). Operating emissions are the loss in refrigerant charge from leakage during equipment operation relative to the charge at the beginning of each year.…”

“…We found that many references (e.g., IIR (2015) and EPA (2014)) refer back to the IPCC (2006) data and the sources described therein for their quoted leakage loss numbers.…”

“…Total charge lost over the lifetime of the unit is estimated to be 296% of the initial charge assuming a 15-year lifetime, 18.6% annual operating loss, charge topping each year, and 20% charge loss at end-of-life (ARB 2018; ICF 2011). Economic and maximum potential energy efficiency savings estimated to be comparable to that for remote condensing units or 40% and 45%, respectively [CLASP (2014); DOE (2018)]. In the case of trans-critical all-CO2 systems, improvements in energy efficiency have been reported in cool and mild climate with some loss in efficiency in hot climates (e.g., NCI 2015).…”

“…As with centralized systems, the baseline refrigerant leakage is high and lifetime charge loss is estimated to be 254% of initial charge (15% annual operating loss and 34% charge loss end-of life (ARB 2018)). Economic and maximum potential energy efficiency savings is estimated to be 40% and 45% respectively [CLASP (2014); DOE (2018)]. Generally, hydrocarbon refrigerants will realize equivalent to improved energy efficiency compared to conventional HFC refrigerants.…”

Benefits of Leapfrogging to Superefficiency and Low Global Warming Potential Refrigerants in Room Air Conditioning

“…An installation emission factor of 1% and average annual operating emissions of 10% are assumed, based on Gallagher et al (2014), and Intergovernmental Panel on Climate Change -IPCC (2006). Operating emissions are the loss in refrigerant charge from leakage during equipment operation relative to the charge at the beginning of each year.…”