Life-Cycle Nitrogen Trifluoride Emissions from Photovoltaics

Abstract

Amorphous- and nanocrystalline-silicon thin-film photovoltaic modules are made in high-throughput manufacturing lines that necessitate quickly cleaning the reactor. Using NF₃, 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 NF₃ in photovoltaic (PV) manufacturing, on the basis of actual measurements at the facilities of a major producer of NF₃ 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 NF₃ 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 NF₃ in current PV a-Si and tandem a-Si/nc-Si facilities add 2 and 7 g CO₂(eq)/kWh, which can be displaced within the first 1-4 months of the PV system life.

Nitrogen trifluoride global emissions estimated from updated atmospheric measurements

“…2B). The largest increase in the growth rate occurred between 2000 and 2006, when there was a significant relative rise in NF 3 production and use (2,23). Using a radiative efficiency of 0.211 W·m (7), an average instantaneous radiative forcing in 2011 is calculated at 1.8 × 10 −4 W·m −2 .…”

“…As well as considering the pace at which NF 3 replaces other fluorinated gases, the rise in future NF 3 emissions depends on the SC+ market (likely to grow significantly) and on progress in reducing the amount released. The global NF 3 production rates are not well documented, and estimates have been revised over successive years (3,7,23). The latest production estimate from industry is ∼12 Gg in 2011 (2); however, an independent report suggests sales are closer to ∼10.5 Gg (24).…”

“…The latest production estimate from industry is ∼12 Gg in 2011 (2); however, an independent report suggests sales are closer to ∼10.5 Gg (24). Using a 2011 production estimate of 12 Gg, and scaling emissions in previous years using the relative year-to-year changes documented in more detailed sources (23,24), we calculate an emissions/production ratio of over 0.20 for the early 2000s, decreasing to 0.10 ± 0.03 in 2011 (Fig. 3B).…”

“…The a priori emissions used to calculate the emissions growth rates for the inversion were estimated using data from independent sources (2,14,23,24). The EDGAR v4.2 emission estimates are also shown (25).…”

Photovoltaic Conversion: Outlook at the Crossroads Between Technological Challenges and Eco-Strategic Issues

“…The data concerning PV systems varies according to the technologies used, the energy performances of the solar cells, the capacities of the systems, the impact assessment methods used and, therefore, the databases used. The PV industry also produces ammonia emissions (NH 3 ) and volatile organic compounds (VOCs) (Pehnt, 2006;Fthenakis et al, 2010), but the existing data cannot be used to provide a rigorous comparative assessment. If there is a stage that could be crucial for the PV industry, it would be the end of the systems' lifecycle.…”