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

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3

1

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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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