A team of researchers have developed an infrared imaging system that could at some point in time offer cost-effective, real-time detection of methane gas leaks at oil and gas facilities and also in pipelines. Leaks of methane, the key component of natural gas, can be dangerous and expensive in addition to contributing to climate change as a greenhouse gas.
Despite methane gas being invisible to the eye, we have developed a method of color-coding this gas information and overlaying it onto a conventional camera image. This allows the user operating the camera to look around, identify things and see an overlay of where the gas is present.
Graham M. Gibson, University of Glasgow
Gibson, with other members of the research team, developed the real-time infrared imaging system by working with M Squared Lasers. The Optical Society journal Optics Express presents a report in which the researchers demonstrate that the system can obtain videos of methane gas leaking from a tube at about 0.2 liters per minute.
It is possible to expand the technology to other ranges of wavelengths or wavelengths, thus permitting the detection of a host of chemicals and gases.
One of the challenges from a commercial point of view has been translating infrared technology to bigger markets where price points are sensitive. This new technology could allow infrared imaging and sensing to become more readily available and help improve the environment by reducing gas losses in the oil and gas industry.
Graeme Malcolm, M Squared Lasers
Despite the availability of commercial systems that use imaging to detect methane gas, these systems still fail to work well under all environmental conditions and are extremely expensive. The newly developed imaging system is capable of offering a sensitive and less inexpensive method for detecting methane gas in a wide variety of conditions. The new system employs a single-pixel camera developed by the Glasgow research team and an active hyperspectral imaging technology developed by M Squared Lasers Ltd.
This new system carries out hyperspectral imaging by projecting a series of infrared light patterns onto the scene with the help of a laser wavelength that is absorbed by methane. These patterns are formed with a laser and tiny device together with hundreds of thousands of moving mirrors, called a digital micromirror device.
The system further reconstructs an image displaying areas where the light has been absorbed by methane by detecting the light that scatters off the scene and then computationally comparing it to the original projected patterns.
The new methane gas imaging system uses active illumination - it provides its own light source. This fact has a number of advantages compared to the passive illumination systems used in the existing gas detectors, also including systems that detect gas through the usage of differences in temperature.
For systems using passive illumination, darkness or rain will cause the signal reaching the imaging system to vary or be non-existent. An active illumination source is independent of environmental changes, including changes in temperature or light, and provides enhanced contrast and higher sensitivities.
Nils Hempler, M Squared Lasers
Since conventional cameras containing millions of pixels are either prohibitively inexpensive or unavailable in the infrared wavelengths, a single-pixel camera was used by the team to measure the light scattered from the scene.
The single-pixel camera plays a significant role in developing a commercial methane gas imaging system that could cost just a few thousand dollars, considerably less than the existing gas detection imagers that are commercially available. The system can be effortlessly turned into a portable instrument as it does not use any scanners or various other moving parts.
In the paper, the team demonstrated that their system was capable of imaging methane gas leaking from a tube almost 1 meter from the camera with a video-rate imaging speed of about 25 frames per second. The researchers further showed that their new method was sensitive to methane even in situations when other gases were present between methane and the camera.
One of the things that we found is that we don't necessarily need high-resolution images when detecting gas leaks. A relatively fast frame rate on your camera provides more information about where the gas is leaking from than having very high-resolution images.
Graham M. Gibson, University of Glasgow
Moving out of the Lab
Next, the researchers plan to demonstrate their imaging setup outside the monitored laboratory setting to examine how it functions in real-world scenarios. They also aim to try the approach with increasingly powerful lasers, which could permit imaging from a greater distance and then enhance the sensitivity of the gas detection.
“Using broadly tunable laser sources rather than the fixed wavelength source used in this paper can extend this method to detection of other hydrocarbons, threat materials such as chemical warfare agents and explosives, and other biologically important substances used in healthcare and diagnostics,” said Hempler.