Researchers from the Swiss Center for Electronics and Microtechnology (CSEM) have developed a new gas sensor that is compact and lightweight enough to monitor emissions in ship exhaust from an airborne vehicle.
The device uses mid-infrared supercontinuum gas spectrometry to simultaneously monitor the methane -a potent greenhouse gas- and water vapor concentration in the exhaust of moving ships in real-time. This can help governments and industry understand the scope of methane pollution from ships and potentially inform new approaches to reduce these emissions.
The sensor developed by the center relies on a novel spatially coherent mid-IR light source, in a region of the electromagnetic spectrum where several of these pollutants can be detected by absorption spectroscopy. Our system can measure several gases simultaneously, but for this demonstration, we particularly looked at methane emission from different sources,
…said S. Chin from the CSEM.
[smlsubform prepend=”GET THE SAFETY4SEA IN YOUR INBOX!” showname=false emailtxt=”” emailholder=”Enter your email address” showsubmit=true submittxt=”Submit” jsthanks=false thankyou=”Thank you for subscribing to our mailing list”]
As explained, spectrometers measure the chemical composition of gases or objects by applying a light source and measuring how the light interacts with what is being measured. For this new work, researchers took advantage of recent advances in broadband high-brightness light sources to develop a spectrometer that can efficiently measure the chemical fingerprint of methane and other gases in air.
This efficiency gives the new spectrometer a high level of sensitivity, allowing it to reliably differentiate between methane and other components and to measure methane at concentrations below the normal background level of less than 2 parts per million (ppm).
The most exciting part about this technology is the broadband supercontinuum light source. Due to its spatial coherence properties, it is possible to have a very long interaction length with the sample gas mixture and thus lower the limit of detection to trace amounts,
…added Chin.
Meanwhile, its large spectral coverage allows researchers to simultaneously detect several gas species in a single device, and to avoid measurement artifacts by checking the measured absorbance spectrum, he said.
The refresh rate, on the order of 1 second, makes it a fast detector compatible with airborne applications. It is like having a Swiss army knife: it replaces a series of single component gas detectors in one device.”
To test the use of the spectrometer in an airborne vehicle, the researchers first mounted the device aboard a Zeppelin airship and flew it in the vicinity of a simulated methane leak from a pole-mounted bottle 4 meters off the ground. The spectrometer detected a rise in methane when the Zeppelin flew near the methane source and recorded a drop to background levels when it flew away from the leak.
Then, the researchers mounted the spectrometer aboard a helicopter which was flown behind ships cruising along the Kattegat channel between Denmark and Sweden. In this test, the device successfully and reproducibly measured emission levels of methane at approximately 20 ppm from several vessels, all of which were powered by LNG. The measurements from the sensor aligned well with those from a commercial methane sensor used as a reference.
The center is now working towards increasing the spectral coverage of the supercontinuum up to 10 µm in order to expand the list of gases that can be measured by the system. One of the challenges there is to ruggedize the light source.
