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Informational Update Diamond Bar, CA October 22, 2015
Advanced Clean Cars PM Measurement Feasibility
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2
Background LEV III PM Standards
Current 2017 2025
10
3
1
GHG
ZEV
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PM E
mis
sion
s (m
g/m
i)
• In 2012, the Board approved more stringent PM standards for light duty vehicles
• And directed staff to follow-up on two questions: – Can we measure emissions at
1 mg/mi levels? – Can we move the 1mg/mi
standard to earlier than 2025 with new GHG technologies?
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How Do We Determine Vehicle PM Mass Emissions?
Sampling System
Mass Analysis PM Sampler
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PM Emission Testing at ARB
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Driver follows speed trace for the emission test
Filter holder & PM sampler
Vehicle on chassis dynamometer
Exhaust transferred to the sampling system
Mass Analysis
Key Industry Concerns
Is current mass-based method capable of quantifying PM mass at 1 mg/mile level?
What are the sources and magnitude of variability in laboratory measurements?
Can PM be measured reproducibly among different laboratories?
Are sampling options allowed by regulation equivalent?
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ARB Study Objectives
• Address industry concerns
• Investigate use of alternatives to mass-based measurement: – Particle number – Particle size – Black carbon
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Summary of Testing Assessing Measurement Feasibility
• 8 testing programs focused on individual measurement issues
• 67 unique vehicles tested • Collected and analyzed PM from
over 350 emission tests • Over 2000 individual filters
analyzed • Utilized over 10 different
measurement devices • 5 peer-reviewed scientific
publications from ARB’s findings
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Vehicles
Veh 1
Veh 2
Veh 3
Veh 4
Veh 5
Veh 6
Veh 7
Veh 8
Veh 9
Veh 1
0Ve
h AVe
h BVe
h CVe
h DVe
h EVe
h FVe
h GVe
h H Veh I
Veh J
Veh K
Veh L
Veh M
PM E
miss
ions
, mg/
mile
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
COV,
%
0
10
20
30
40
50
60Pre-2004 MY 2005-2009
ARB Study U.S. EPA Study
PC LDT
MY 2005-2009MY 2006-2009
PC PC
w/o background corrections w/ background corrections
Technical Support Document
• Detailed report summarizing ARB staff’s findings on PM measurement
• Posted: http://www.arb.ca.gov/msprog/levprog/leviii/leviii.htm
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Sources of Total Variability
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3. Emissions Source
2. Sampling System
1. Mass Analysis
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How Much Is the Result Influenced by Sampling and
Mass Analysis?
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0.02 0.1 0.11 0
0.2
0.4
0.6
0.8
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1.2
Mass Analysis Sampling System (ARB) Sampling System (Industry)
1 mg/mi Standard
PM E
miss
ion,
mg/
mi
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Allowable subtraction for sampling system contamination
How Well do Repeated Measurements Show the Same
Results?
• Collected PM samples using up to five simultaneous samplers during a single test
• Compared results across many vehicles emitting at or below 1 mg/mi
• Precision found to be ±11% (~0.1 mg/mi) 11
Multiple PM Samplers
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Do We Get the Same Results for a Vehicle in Different Test Cells?
• Approximation of lab-to-lab variability – Different equipment, vehicle drivers, and equipment
operators – Same low PM vehicle tested 9+ times per cell across
three test cells at ARB
• No statistically significant difference in average emissions across the test cells
• Test-to-test variability is consistent across all test cells, which means this method is robust
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New Sampling Option
Evaluated
• Compared conventional 3-samples per emission test to a new 1-sample per emission test method
– Confirmed results to be equivalent – Potential cost/resource savings from streamlined mass analysis
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+ + vs.
Staff Conclusion -- Regulatory PM Mass Method
• Current mass-based method is suitable and adequate
• Contamination in sampling process can easily be corrected by background subtraction already allowed by regulation
• Good precision (<0.1 mg/mi) confirms measurement capability is sufficient.
• Test-to-test variability is consistent among ARB’s test cells. Measurement is not a concern.
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Courtesy of Dr. Markus Kasper/Matter Engineering, Switzerland
What about other sampling methods?
• Counting particles • Sizing them • Europe’s particle
number standard • Measuring black
carbon
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“As One Goes So Do All Others”
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• Alternative methods generally in good correlation with PM mass – Reducing PM mass also reduces black carbon and
number of particles – But exact relationships with PM mass vary significantly
across vehicle types and test cycles • Similar measurement repeatability • Real-time data provides useful insight
– Potential saving in test resources • These metrics do not measure all parts of PM • Instrumentation lacks robust calibration procedures
Next Steps -- Vehicle Feasibility
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• Reassess vehicle feasibility to meet 1 mg/mi standard – Evaluate newer vehicle
technologies for PM control – Evaluate vehicle variability
• Consider 1 mg/mi standard implementation timing – Earlier phase-in than 2025
model year possible?
Conclusion
• Mass-based method is adequate and will remain the approved test method for ARB’s LEV III PM emission standards
• PM mass control technology will also likely reduce number of particles and black carbon emissions
• ARB will continue research on improvements in sampling and measurement approaches for their potential to improve data quality and reduce testing costs
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