A Low Cost, Absolute Ambient Carbon Dioxide Monitor

Although carbon dioxide is monitored worldwide at hundreds of monitoring stations, existing monitoring methods, which rely on the use of high pressure calibration gas cylinders, are both labor intensive and expensive. Thus, there is a pressing need for an affordable, highly-accurate (1 part in 3000) carbon dioxide monitor for the ambient atmosphere. In addition to being extremely accurate, the required monitor must operate unattended for several months or more. This project will develop an absolute carbon dioxide monitor that compares the integrated absorbance of an isolated temperature-independent line of carbon dioxide (near 2 microns) in a flowing sample cell to that in a permanently-sealed quartz reference cell. The permanently-sealed reference cell provides an absolute column density standard that will allow the instrument to measure mole fraction of carbon dioxide with an accuracy of 0.1 ppm (one part in 3000) during long-term unattended operation without the use of any consumables. In Phase I, a prototype, absolute carbon dioxide monitor will be designed and constructed. The long term stability of the quartz reference cells will be confirmed by comparing the absorbances of two reference cells over long time periods. In addition, the system will be challenged with variations in temperature, laser power, cell pressure, and ambient CO2 concentration. Commercial Applications And Other Benefits as described by the Applicant: The carbon dioxide monitor should be an attractive addition to the hundreds of monitoring stations throughout the world since it will run unattended and will not require frequent calibration. Improved CO2 measurements would help us better understand and mitigate global warming and global climate change.