PIGC - A Low Cost Solution for Air Quality Monitoring and Methane detection

Transcription

1 PIGC - A Low Cost Solution for Air Quality Monitoring and Methane detection L. L. Gordley, GATS. Inc. B.T. Marshall, GATS, Inc. D.C. Fritts, GATS, Inc. R.L. LaChance, GPI LLC J. Gubeli, Riverview Enterprises LLC J. Fisher, Brandywine Photonics D. Guerin, Brandywine Photonics

2 ABSTRACT We have demonstrated the ability to accurately measure key greenhouse and pollutant gasses with low cost solar observations using Pupil Imaging Gas Correlation (PIGC ) spectrometry. A methane abundance sensitivity of 0.3% or better of ambient column has been demonstrated with sub second direct solar observations. These under $3k sensors can be deployed in autonomous grids to quasi-continuously monitor the flow of chosen gasses, and infer their source locations. Measureable gases include CH 4, 13 CO 2, N 2 O, NO, NH 3, CO, H 2 S, HCN, HCl, HF, HDO and others. This poster reviews the measurement technique, performance demonstration and grid deployment strategy.

3 As climate warming becomes an ever increasing global concern, the interest in accurately locating and assessing sources of greenhouse gases is growing. Recent studies using satellite data such as Kort et al 2014, and studies using a variety of sources such as Miller et al 2014 are just a few of many that are now sounding alarms at the growing global warming potential of methane. As argued in our 2013 AGU poster (IN41C-1625 see upper right corner) called GHAPS ( a monitoring solution would be a low-cost solar spectrometer deployed in large grids. We previously proposed a microbolometer based sensor, but have now switched to photodetectors.

4 In pursuit of our goal we constructed a roof-top heliostat (figure 1) to reflect a solar image into a new laboratory, and proceeded to test a variety of detectors. A bench top lab set-up used for testing is shown in Figure 2. In the course of those efforts we discovered that 2D photodetector arrays, that bring shot-noise limited performance, are soon to become available in quantity for under $1000 per unit. This opens the door to a new domain of measurements, namely point-to-point (sensor-to-light bulb) column measurements with accuracy potential matching the solar full atmosphere column measurements. The same sensor (figure 3) can now be configured to perform both the solar column and point-to-point column measurements by simply applying different neutral density filtering and frame integration time schemes.

5 The solar measurements, using less than a 2 cm aperture, have 2+ orders of magnitude margin in signal, while a simple 60 watt incandescent spotlight at 50 meters has ample margin for point-to-point measurements. These sensitivity predictions have been verified in our lab. The next step is to construct a beta version of the sensor (figure 3) for testing in the field. That sensor is under development at Brandywine Photonics, with expected first light in weeks. A PIGC Beta CAD model is pictured in figure 4. This instrument will be tested in a scenario depicted in figure 5. With a PIGC instrument mounted on a tower or pole, surrounding bulbs supply light sources for monitoring leaks and flaring 24/7, while total atmospheric column is monitored by using solar observations.

6 The integration time flexibility of modern 2D detector arrays and neutral density filtering strategies, makes this dual measurement possible. With the dual observation capability, this sensor can be deployed in large grids (Figure 6) for monitoring flux throughout the grid area (given auxiliary wind information), simultaneously monitoring ground level concentrations by observing simple light sources. Finally, mounted to mobile platforms with pointing systems for locking on the sun, the high signal-to-noise enables rapid total column measurements and resulting plume cross section quantification, providing source venting rates when combined with wind speed and direction.

7 In Summary 1. The PIGC sensor concept has emerged as a result of low cost photodetector arrays. 2. Performance of an Alpha version has been validated in a new lab with heliostat. Calibration schemes are now being tested. 3. A Beta version is under development. 4. Beta testing is scheduled to begin in 3 months. 5. News of PIGC progress will start to appear soon at

8 References 1. Eric Kort et al, GRL Volume 41, Issue 19, pages , 16 October Miller et al,

9 Heliostat first lights up the PIGC lab in May See the solar reflection in our mascot s eye.

10 Figure 1. A Heliostat consisting of a tracking mirror mounted to a FLIR 2-axis gimbal reflects solar light off a fixed relay mirror down into the laboratory at GATS in Newport News, Virginia.

11 Tracker control computer Detector camera control Solar Beam Cable for roof-top Heliostat control Gas Cells Covered Detector Turbo vacuum pump for detector dewar Figure 2. PIGC optical bench-top model can be illuminated by either sun from Heliostat, light bulb down the hall, or IR source.

12 Calibration Light Figure 3. The core PIGC sensor is small, light, and easily mass produced. The filter wheel in combination with gases in both cells provides a multi-channel system.

13 Figure 4. CAD model of PIGC Beta 1 instrument now being constructed by Brandywine Photonics. First light expected in 12 weeks.

14 Figure 5. Oil & Gas field methane monitoring is our first objective. A dual port version will allow solar observations of total atmospheric column and sensor-to-light column 24/7. Neutral density filter scheme allows illumination of detector with similar intensity for both observations.

15 Jonah fracking field WY, 3000 wells Oil Tanks Gas Plant Natural Gas Refinery Natural Gas Refinery Figure 6. Grids of PIGC sensors, observing sun, combined with wind field data, provide a low cost continuous monitoring of gas emission levels and locations. Light bulb illumination can also provide ground level monitoring. (Lower right example)

16 Figure 7. Mobile Solar PIGC locked to sun can achieve column measurements in milliseconds providing overhead plume cross sections, and leak estimates given wind data.

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