Life-Cycle Nitrogen Trifluoride Emissions from Photovoltaics

Amorphous- and nanocrystalline-silicon thin-film photovoltaic modules are made in high-throughput manufacturing lines that necessitate quickly cleaning the reactor. Using NF{sub 3}, a potent greenhouse gas, as the cleaning agent triggered concerns as recent reports reveal that the atmospheric concentrations of this gas have increased significantly. We quantified the life-cycle emissions of NF{sub 3} in photovoltaic (PV) manufacturing, on the basis of actual measurements at the facilities of a major producer of NF{sub 3} and of a manufacturer of PV end-use equipment. From these, we defined the best practices and technologies that are the most likely to keep worldwide atmospheric concentrations of NF{sub 3} at very low radiative forcing levels. For the average U.S. insolation and electricity-grid conditions, the greenhouse gas (GHG) emissions from manufacturing and using NF{sub 3} in current PV a-Si and tandem a-Si/nc-Si facilities add 2 and 7 g CO{sub 2eq}/kWh, which can be displaced within the first 1-4 months of the PV system life.