Lessons Learned From the First Year of the Super Emitter ......41% Grade 3 33% BG: 134 AG 35 . Thank...
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Lessons learned from the first year of the Super Emitter Program François Rongere Natural Gas STAR & Methane Challenge Workshop November 5 th , 2019
Transcript of Lessons Learned From the First Year of the Super Emitter ......41% Grade 3 33% BG: 134 AG 35 . Thank...
Lessons learned from the first year of
the Super Emitter Program
François Rongere
Natural Gas STAR & Methane Challenge Workshop
November 5th, 2019
PG&E System
• Key Statistics – 6,600 miles of gas
transmission pipeline
– 42,800 miles of gas distribution main
– 4.3 million natural gas customer accounts.
– Throughput of 839 BCF in 2018
PG&E has been a member of the EPA Natural Gas Star program since 1994 and became a founding member of the EPA’s Methane Challenge Program in 2016
The Distribution System at PG&E
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Material Main (Miles) Services (Miles)
Plastic 22,926 22,543
Steel 18,077 10,881
Copper - 6
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
Mile
s o
f M
ain
Date of Installation
Example of a plat map
The concept of Super Emitters
• Methane emissions in distribution systems are driven by a small number of larger leaks named Super Emitters.
• Opportunity for substantially reducing methane emissions by accelerating detection and repair of the larger leaks.
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Average: 1.7 scfh
Median: 0.2 scfh
Washington State University study : Only 2% of leaks were > 10 scfh but accounted for 56% of total emissions
Super Emitters beyond Distribution Systems
• A. Brandt et al. have observed that for a broad range of assets and devices, the contribution of top 5% of emitters account for more than 50% of emissions.
Source: A. Brandt et al. “Methane leaks from natural gas systems follow extreme distributions” Environ. Sci. Technol., 2016,
50 (22), pp 12512–12520
Compliance surveys
• For compliance, gas distribution systems must be surveyed every five years. In that case more than 2/3 of emissions are due to non-surveyed areas.
• Detecting and repairing large leaks faster is very effective to reduce emissions
Area surveyed in Y-3 Area surveyed in Y-2 Area surveyed in Y-1
Year
of i
nter
est
(Y)
Y-1
Y-2
Y-3
Y-4
Area surveyed in Y-4
4/5 3/5 2/5 1/5 5/5
Un-surveyed area Surveyed area Ti
me
– Li
nea
r G
row
th o
f le
ak n
um
ber
Mobile Leak Detection System
• PG&E introduced Picarro’s mobile detection system for its compliance survey in 2014
• Mobile only surveys are typically 10 times faster than walking surveys
0.1
1
10
100
1000
0.1 1 10 100
Mea
sure
d (
scfh
)
Actual (scfh)
NYSEARCH Tests Unity Plot
The opportunity
• Large leaks are easy to detect with mobile surveys (Picarro).
• Leak flow rate quantification is still challenging with mobile devices but:
– Solid data coming from a NYSEARCH study is now available
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1:1 line
10𝑔𝑟𝑒𝑎𝑡𝑒𝑟
10𝑠𝑚𝑎𝑙𝑙𝑒𝑟
78% of data points within doted lines
Accounting for uncertainties
• By binning validation data and merging them with leak size distribution using Bayesian conditional probability, we adjusted emission factors to include uncertainties in Super Emitter quantification using NYSEARCH results
Actual Predicted
A: The leak is a Super Emitter B: The leak is predicted as a Super Emitter
Validation
• Tested the approach in the field by directly measuring flow rate of 58 large leaks related to large detection by Picarro system (>10 scfh)
NYSEARCH Validation
𝑃 𝐵|𝐴 76% 77%
𝑃 𝐴|𝐵 42% 56%
Within order of magnitude 78% 80%
Procedure
1. Drive Picarro car in the areas not surveyed through
Compliance Survey
2. Filter out any indications <10 scfh (Picarro’s algorithm)
3. Investigate and repair leaks associated with large
indications (>10 scfh)
4. Savings from two sources:
a) Accelerated detection and repair of “Super Emitters”
b) Reduction of Emission Factors for other leaks
5. Add the Super Emitters detected through the Compliance
Survey
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Results
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Super Emitters through Compliance Survey
Super Emitter Survey
Coverage: 23,862 miles of mains and services Findings: 130 Super Emitters 19 No leak found 27 indications with multiple leaks Material: Grade:
Plastic 72%
Steel 28%
Grade 1 47%
Grade 2 23%
Grade 3 30%
BG: 86
AG 44
Coverage: 41,533 miles of mains and services Findings: 169 Super Emitters 57 No leak found 20 indications with multiple leaks Material: Grade:
Plastic, 66%
Steel, 34%
Grade 1 26%
Grade 2 41%
Grade 3 33%
BG: 134
AG 35
