Opt. Eng. 52, 010502 (2013)
Reducing CO2 emissions is an essential step in the fight against global warming. This need has driven the development of CO2 sequestration schemes that involve pumping CO2 underground for long-term storage. It is thus necessary to monitor CO2 levels on the ground and underground in real time to estimate CO2 movement and leakage. Conventional electrochemical or semiconductors CO2 sensors are cross-sensitive to other chemical species, and often cannot operate at high temperatures and humidities. Dian Fan and co-workers from Wuhan University of Technology, China, and Virginia Tech, USA, have now proposed a CO2 detection system based on near-infrared laser spectroscopy. Instead of probing the strong absorption of CO2 gas in the mid-infrared region, they used a weak absorption line near 1,572 nm. During tests, the researchers tuned the laser wavelength in the range of 1,571.0–1,572.5 nm and filled CO2 samples with concentrations of 0–90% in a 20-cm-long gas cell. After obtaining absorption spectra, they uncovered a linear relation between the absorption intensity and the CO2 concentration. The experimental data was reproducible to within an accuracy of 1%. As ambient air has a CO2 concentration of around 0.03%, this detection accuracy is sufficient for CO2 sequestration monitoring.
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