Replacing SF6 in electrical gas-insulated switchgear: technological alternatives and potential life cycle greenhouse gas savings in an EU-28 perspective

To date, global atmospheric concentrations of F-gases with alleged high global warming potential are still on the rise. The most potent among the greenhouse gases identified as such by IPCC is sulfur hexafluoride (SF6), which has been used in various applications because of its chemical stability and inertness, next to its high dielectric strength. In the European Union, its use has to date been banned from several applications, for which technological alternatives exist. An important exception is gas-insulated electrical switchgear (GIS), both for medium voltage and high voltage applications, to which cost-effective and environmentally sound alternatives were unavailable when the F-gas regulation was last revised in 2014. Yet, to date, interest in technological alternatives has grown, and we argue that a next step in the phasing out of SF6 may spur the accelerated development of alternatives with lower carbon footprint. The installed SF6 amount in switchgear in the EU-28 is unclear, estimated between 10 800 and 24 700 t (with a mode at 12 700 t) in 2017, resulting in 68 to 140 t of annual emissions from operational leakage only, corresponding to 1.6 to 3.3 Mt of CO2-eq. The higher emissions value seems more likely, as its underlying model (EDGAR) was earlier corroborated by measurements. In our study, we estimate the potential greenhouse gas savings over the lifecycle of one exemplary 145 kV gas-insulated switchgear bay upon replacing SF6 by decafluoro-2-methylbutan-3-one (C5-FK) and heptafluoro-2-methylpropanenitrile (C4-FN) mixtures. These single-bay results were projected over estimated future installed high-voltage GIS in the EU-28 consequentially. A phase-out scenario starting from 2020 onwards could reduce the carbon footprint by 4 to 31 Mt, with median at 14 Mt, of CO2-eq., over a period of 50 years. A phase-out starting in 2025, allowing more time for further technology development, results in 12.5 Mt of CO2-eq. (median) savings by 2070. Extrapolation to medium voltage is uncertain, given the decentralization of electricity distribution, yet one can assume savings of similar magnitude.