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Sleuthing fugitive natural gas emissions from 1500 feet above the ground with two lasers and NI’s FPGA-based FlexRIO module

by Xilinx Employee on ‎06-05-2017 04:27 PM (87,637 Views)


Ball Aerospace Methane Monitor Aircraft.jpg According to pipeline101.org, there are 2.1 million miles of natural gas distribution pipelines in the US alone. With that much pipe, you can bet that there are leaks. In fact, a very recent, massive, and famous leak occurred at the Aliso Canyon underground gas storage facility near Los Angeles in 2015 that released an estimated 97,100 tonnes of methane and 7,300 tonnes of ethane into the atmosphere. Although PHMSA (the Pipeline and Hazardous Materials Safety Administration) programs have reduced serious pipeline incidents by 39% since 2009, more than 250 serious leaks have occurred in the past eight years.


Manual inspection of millions of miles worth of pipeline is problematic and expensive so a fast way to conduct such inspections from low-cost aircraft could cut costs significantly, increase inspection coverage, and make inspections more timely. Using its 50 years of remote-sensing expertise, Ball Aerospace in Boulder, CO has developed just such a method using a pair of airborne lasers with fast processing supplied by an FPGA-based FlexRIO PXIe module from National Instruments (NI).


Natural gas consists primarily of methane (CH4) and methane absorbs light between 1.6455nm and 1.6456nm. It does not absorb light at 1.6454nm. Firing two laser pulses into air at those wavelengths and measuring the reflected energy, again at those wavelengths, produces a differential absorption lidar (DIAL) measurement. In other words, the result is a remote-sensing tool for long-range detection of airborne methane. Ball engineers used these methane characteristics to develop Methane Monitor, which can measure methane concentrations in the air. Better yet, this system can visualize methane plumes, positively identifying and pinpointing leaks.


Proper location and tracking of targets, attitude correction, and geo-location of methane measurements requires some pretty tight synchronization among all of the Methane Monitor’s components. Ball used an NI PXIe chassis as a measurement platform and populated it with:





The Methane Monitor uses three or four transducers with the NI 5761 FlexRIO digitizer adapter module and the resulting throughput (between 11.2Gbps and 15.2Gbps) dictates the FPGA processing. After calibrating each ADC for the transducer chain, the FPGA performs variable offset correction and serializes the high-throughput data between laser firings. The Virtex-5 FPGA captures the DIAL signals, measures range, and calculates methane concentration at 1000 to 10,000 measurements per second. Naturally, all of this is programmed using NI’s LabVIEW system engineering software.


To date, this system has logged more than 100 hours of flight time and can detect methane flow rates as low as 50 standard cubic feet/hour with sensing swaths as wide as 200m. The system produces strikingly vivid results like this:




Ball Aerospace Methane Monitor.jpg 


Real-world methane plumes discovered by Methane Monitor. On the left is real-time data overlaid on Google Maps. On the right is postprocessed data overlaid on Google Maps. The straight green lines are overlays of buried oil and gas infrastructure. The legend ranges from 0 ppm-m (blue) to 1,000 ppm-m (red) CH4 above background. For reference, the current background level of methane globally is approximately 1.9 ppm.




Ball Aerospace plans to double the operating altitude of this system to 3000 feet, double the spatial resolution, and quintuple the width of the survey swath by upgrading the digitizer to an NI PXIe-5172 Reconfigurable PXI Oscilloscope, which is based on a Xilinx Kintex-7 FPGA.


This impressive project won a 2017 NI Engineering Impact Award in the Energy category last month at NI Week and is documented in this NI case study.