Green Scene: Carbon Dioxide Monitoring at the City Level

As the countries of the world emerged from the Paris climate talks, having committed to reducing their carbon emissions, questions remained about how emissions will be monitored. One potential answer was Harris Corp.'s introduction of its GreenLite (video) real-time spatial carbon dioxide monitoring system, which was demonstrated in Paris while the talks were underway.

The laser-based system was co-developed with AER with support from the Department of Energy and National Institute of Standards and Technology (NIST) and is targeted at cities and governments. GreenLite is the latest addition to Harris' arsenal of atmospheric measurement tools, which includes satellite instruments as well as aircraft-based systems.

The system utilizes multiple lasers, reflectors, and detectors that are set up at elevated line-of-sight locations above a city, including towers and high-rise buildings. The lasers, which operate at a wavelength that is absorbed by CO₂, bounce off the reflectors before being collected by the detectors. Software performs tomographic reconstruction of spatial CO₂ concentrations above the city or other site being monitored.

"This system will provide a verifiable and effective method to directly monitor, measure, and validate emissions, particularly at the city level," said Eric Webster, Harris' vice president and director of environmental systems. The fact that information is collected much closer to the source, as opposed to measuring overall atmospheric levels, makes it far more actionable, Harris claims.

The system that was demonstrated in Paris had two lasers and 16 reflectors.

The availability of real-time data not only provides valuable monitoring, allowing a municipality to understand where it stands on emissions, the spatial aspect can pinpoint major sources. This capability can be used to monitor carbon sequestration sites for potential leakage. Or, with the lasers tuned to a different wavelength, users can monitor methane levels from natural gas extraction or transmission facilities. The accompanying graph shows the various types of information that can be extracted from different parts of the electromagnetic spectrum.

"As you watch the monitor screen throughout the day, you can actually see the city 'breathe CO₂' as rush hour comes and goes and power plants respond to peaks in demand," Webster said.

Combined with satellite data and aircraft-based measurements, monitoring and enforcement agencies have detailed looks at emissions. Besides municipalities, businesses can self-monitor to meet their own targets. While the satellite-based systems collect radiation coming from the Earth, and aircraft systems use DIAL (differential absorption lidar), which bounces off the ground, the GreenLite system is based on one or more emitter-detector pairs operating at a specific wavelength for the specific substance being monitored.

The capability was initially demonstrated in a one-square-kilometer sector of Boulder, Colo. NIST took an interest in this capability and worked with Harris to expand it to 25 square kilometers. Webster said increasing the coverage area involved boosting laser power and reflector quality, but added that the lasers are still safe from any vision hazard.

Harris worked with LSCE (Laboratoire des Sciences du Climat et de l'Environnement) on the Paris installation. Installing the system required a good deal of permitting, selection of locations to capture specific areas, and alignment of all optical elements.

A video of the GreenLite's demonstration can be seen here.READ MORE ARTICLES BY RP SIEGEL ON DESIGN NEWS:

RP Siegel, PE, has a master's degree in mechanical engineering and worked for 20 years in R&D at Xerox Corp. An inventor with 50 patents, and now a full-time writer, RP finds his primary interest at the intersection of technology and society. His work has appeared in multiple consumer and industry outlets, and he also co-authored the eco-thriller Vapor Trails.

Like reading Design News? Then have our content delivered to your inbox every day by registering with DesignNews.com and signing up for Design News Daily plus our other e-newsletters. Register here!

Design engineers and professionals, the West Coast's most important design, innovation, and manufacturing event, Pacific Design & Manufacturing, is taking place in Anaheim, Feb. 9-11, 2016. A Design News event, Pacific Design & Manufacturing is your chance to meet qualified suppliers, get hands-on access to the latest technologies, be informed from a world-class conference program, and expand your network. (You might even meet a Design News editor.) Learn more about Pacific Design & Manufacturing here.