Progress towards Collaborative NGEM Methods

Disclaimer: The views expressed in this presentation are those of the author(s) and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

NGEM: Next Generation Emissions Monitoring FMD: Fixed Methane Detector

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  • Fixed Methane Detector (FMD) Tunable Diode Laser Spectroscopy (TDLAS) system tested at U.S. EPA Test Range

  • Deployed 6 units at Colorado State University (CSU) Methane Emissions Technology Evaluation Center (METEC)

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  • Acquired dataset from 6 FMD units along with information regarding calibrated releases

  • Approached U.S. EPA to help explore METEC data
    Joint collaborative activity with open-source publishing goals. No compensation provided by U.S. EPA ORD

  • Others are welcomed!
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  • SENSOR CLASS DEVELOPMENT
    Understand the core capabilities and limitations of the technology

Application Purpose Sensor/INSTRUMENT Needs
In-Process-Unit Detect and characterize emissions
  • Fast sensor response is important, however concentrations can be very high
  • Application-specific accuracy/ precision
In-Community Quantify ambient levels
  • Fast sensor response not as important
  • Precise and accurate measurements required
Fenceline Detect and characterize emissions
  • Between in process unit and in-community
  • Fast response can be important to capture “dilute plume” – probe overlap

In Process Unit

High concentration faster source signal
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In community

Lower concentration slower source signal

  • OPEN-SOURCE DEVELOPMENT OF METROLOGY AND ALGORITHMS
    Provide model for data sharing and transparency

U.S. EPA TEST RANGE

TDLAS Operating Principal
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Methane Detector Specification
Technology Near Infrared (IR) TDLAS with Multi-Pass Cell
Wavelength 1650 nm
Range 0-100 vol.%
Noise Floor 0.3 Part Per Million (PPM)
T90 10 seconds
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  • SENSIT FMD TDLAS system co-located with other methane detectors and reference instruments

Minimum Detection Limit (MDL = 3X 𝝈 (St.Dev.)

Co-located with reference instruments
Calculations are 0.1 Hz Noise Based MDL (Excluding Drift Term). No baseline corrections applied

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Preliminary data - MDL measurements and calculations are ongoing and contain the noise term only.

10-s FMD Pre-Test [PPM]

Day x̅ 𝝈 MDL
1 2.96 0.021 0.063
2 3.02 0.030 0.089
3 3.43 0.014 0.044
4 3.14 0.028 0.833
Avg. 3.14 0.234 0.070

10-s Reference Grade [PPM]

Inst. x̅ 𝝈 MDL
Ref 1 2.20 0.003 0.010
Ref 2 2.17 0.010 0.030

10-s FMD Between Tests

Day x̅ 𝝈 MDL
1 2.49 0.041 0.122
2 2.97 0.029 0.086
3 3.25 0.081 0.243
4 - - -
Avg. 2.90 0.050 0.150

Deployed FMD

Measuring wind speed, wind direction, CH4 concentration

CSU METEC DEPLOYMENT

6 FMDs Deployed at a simulated oil gas site. Controlled emissions introduced.
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Advanced Methane Detection System Capable of identifying and locating introduced emissions.
Deployment Start 2/8/2023 End 4/28/2024
TEMPERATURE Minimum -25.5°C Maximum 29°C
Events Experiments 279 Releases 565
Avg. Release Size 1566 g/hr Avg. Duration 3.11 hr
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METEC RESULTS – Provider P

  • Accomplished via manual visual inspection of the data*
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  • As wind direction changes, the source is observed by different sensor nodes
  • Some detections at very low wind speeds are off-axis and are not good for quantification
  • Let's look at four sub-events
    (marked by colored squares)
    • FMD1012 (North) - Event 1
    • FMD1000 (West) - Events 2 and 4
    • FMD 1008 (East) - Event 3
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Measured Concentrations for Quantification Trials

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Quantification by:
OTM 33A1 simple emission estimate

Q =2π*u*c*σyσz

Where:
u=mean wind speed (max bin)
c=mean max bin concentration (kg/m3)

Open-source WindTrax™ backwards Lagrangian stochastic (bLs) model with inputs from OTM 33A binning.

Known source location (4T-1)

1https://www.epa.gov/emc/emc-other-test-methods – draft, results, nonstandard wind data, night observations (10°max bin mean for a1 and wind speed) 2http://www.thunderbeachscientific.com/ - inputs for bLs determined by OTM 33A max fit. Used Pasquil-Giiford (PG) Class D OTM33A PGI index 6
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Conclusions

  • Open collaboration leads to better understanding of the data and greater transparency

  • SENSIT FMD is for capturing plume-probe overlap within process units and at the fence line.

  • Deployment at METEC was able to identify and localize leaks.

  • Freeware modeling packages capable of providing approximate estimates of leak rates.

  • Be careful of model assumptions - know when they aren't applicable

  • Work on this data set continues!

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