Bridger Photonics is one company leading the way in aerial LiDAR applications for methane gas mapping. By offering LiDAR devices optimized for methane detection in combination with advanced image and data analysis methods, Bridger Photonics has been able to develop a cost-effective approach that can identify the site of the leak and quantify the leakage rate.
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LiDAR technology – Light Detection and Ranging – is the basis for most machine vision applications. LiDAR works by sending light from a source and timing the interval between the light transmission and detection of the reflected light. The time of flight information can be converted to depth information and the scene information can be reconstructed.
Common applications include autonomous vehicles, manufacturing automation, and agriculture. By combining the reconstructed scene information with advanced image processing and analysis algorithms, it is possible to accurately determine shapes and any possible deformations in almost real time.
Another application of LiDAR technology is gas mapping. Many conventional gas sensors use infrared detection to quantitatively assess local gas concentrations, which works well for gases such as methane and carbon dioxide that are strong infrared absorbers.
With LiDAR technology for gas mapping, it is possible to assess not just the various concentration maps of the gaseous species but also generate geo-registered gas plume images. The gas plume data is particularly valuable for assessing gas leaks as analysis of the plume can provide information on the site and the magnitude of the leak so identification and rectification of any issues can happen more quickly.
Greenhouse gases are called as such because they trap heat within the Earth’s atmosphere. The reason certain gases are particularly efficient as greenhouse gases is because they have stronger infrared absorption and so absorb a greater proportion of solar radiation.
Other factors that mean certain gases can have an even more problematic effect on the atmosphere include how long-lived the atmospheric species is. Molecules like SF6 and chlorofluorocarbons are especially long-lived, as there are few reactions that remove from the atmosphere or break them down into other chemical products.
Often, the warming potential of greenhouse gases is evaluated relative to that of carbon dioxide. Another highly abundant greenhouse gas with over 80 times the warming potential of carbon dioxide is methane.
Methane emissions are highly problematic because of their environmental impact and how many potential sources of methane there are. Agriculture, fossil fuel consumption, and industrial activity are all significant sources of anthropogenic methane.
A substantial amount of methane emissions come from methane leaks in the oil and gas industry. One of the challenges with preventing methane leaks is many of these occur from remote pipes or gas fields that are in very remote or challenging locations, making an inspection of equipment a costly and challenging endeavor.
Reducing methane emissions is integral to meeting climate change targets as well as avoiding unnecessary financial losses. Reducing losses means identifying and understanding leaks in a more efficient and effective way, which can be achieved through the use of remote sensing or LiDAR applications.
Modern LiDAR devices can be sufficiently small and lightweight, can be mounted on aerial devices, and can be used for remote sensing.
With the use of GPS information in combination with highly sensitive methane detection, Bridger Photonics has provided a way of monitoring remote equipment and meaning remote inspection teams need only be sent in the event of a problem.
There are a number of different LiDAR schemes that can be used. LiDAR technology can make use of either pulsed or continuous wave laser sources. Continuous wave LiDAR methods such as frequency-modulated continuous wave LiDAR tend to excel in their distance resolution.
With continuous sources, distance information is continually measured as the laser is scanned over the object of interest. One issue can be that, if the velocity of the measured light is changing due to the relative motion of the laser source and object, it is possible to measure this as surface roughness rather than motion.
In frequency-modulated continuous wave measurements, the frequency modulation of the transmitted signal is used to encode the timing information for the transmitted light so the recorded time of flight information is meaningful.
Alternative methods that still make use of continuous sources include continuous-wave laser absorption. For this method, the transmitted light must be of a wavelength that is absorbed by the target of interest, not just scattered. This is an ideal approach for compact, lightweight devices that will be mounted on unmanned aerial vehicles.
Measuring the amount of absorption in the frequency-modulated light is a way to calculate the concentrations of the gases measured and so a good option for gas monitoring applications.
Bridger Photonics also offers pulsed light LiDAR solutions including direct detect LiDAR and pulsed differential absorption LiDAR. Pulsed laser sources typically have higher peak powers than continuous wave sources which increase the risk of target damage by the measurement.
Bridger Photonics Solutions
By opting for the right LiDAR solution for gas mapping, Bridger Photonics can help provide real-time data for methane losses to help teams mitigate the damage caused by leaks.
Reducing emissions and operating losses is not the only motivation for employing gas mapping solutions. Methane is highly flammable and an explosion risk, and every year there are still a number of deaths of workers, particularly in mines, due to methane explosions. Gas mapping can help improve worker safety and will become an increasingly important part of environmental regulatory compliance n the future.
More from AZoOptics: How Do FTIR Gas Analyzers Work?
References and Further Reading
Royo, S., & Ballesta-Garcia, M. (2019). An Overview of Lidar Imaging Systems for Autonomous Vehicles. Applied Sciences, 9, 4093. https://doi.org/10.3390/app9194093
Shuk, P., McGuire, C., & Brosha, E. (2019). Methane gas sensing technologies in combustion: Comprehensive review. Sensors & Transducers, 229(LA-UR-18-31101). http://permalink.lanl.gov/object/view?what=info:lanl-repo/lareport/LA-UR-18-31101
Khalil, M. A. K. (1999). Non-CO2 Greenhouse Gases in the Atmosphere. Ann. Rev. Energy Environ., 24, 645–661. https://www.proquest.com/scholarly-journals/non-co2-greenhouse-gases-atmosphere/docview/219876033/se-2?accountid=14511
Karakurt, I., Aydin, G., & Aydiner, K. (2012). Sources and mitigation of methane emissions by sectors : A critical review. Renewable Energy, 39(1), 40–48. https://doi.org/10.1016/j.renene.2011.09.006
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