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New Measurement Techniques & Procedures for Measuring "Real World"

Emissions with PEMS and PAMS Carl Fulper

United States Environmental Protection Agency, OTAQ

PEMS Conference

UC-CERT

April 11, 2013

Outline

New Way to Think About How to Test in the “Real

World” – “The Modeling Way”

Using the right “tools” for the operation to achieve data

goals quickly, effectively and accurately

Data Reports

– Data Validation Report

– QA/QC, time alignment & corrected Emissions Rpt

Vehicle Representativeness

– Improve sample design and recruitment methods

PEMS Installation Techniques

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PEMS Testing in the “Real” World

Measurement is difficult and expensive

– Vehicles and engines are diverse

– Vehicles are difficult to acquire or recruit (reduce burden to owne)

– Techniques are detailed and labor intensive

– Emissions are highly variable

Most test programs install PEMS and owner drives around their

“normal” route for 8 -10 hours and test the vehicle over 3-5 days

or longer.

Represents “real” driving, but in the modeling world, you could be

missing key operating modes or not get enough emission data

Is there a better way?

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What kind of operation? “put the vehicle thru its paces”

On choreographed drive route:

– Start

– Parking lot

– Residential street

– Arterial

– On-ramp

– Freeway

– Off-ramp

– Idle

– Grade (hills)

or loads

– Accelerations

– Decelerations

– Cold/Hot Start 5

This can be used for all mobile

sources (HDVs, MDVs, LDVs and

nonroads) in about 2-3 hours.

For HDVs: load via trailer & hills

For Nonroad: Running set operations

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0

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1000

1500

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2500

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0 1 11 12 13 14 15 16 21 22 23 24 25 27 28 29 30 33 35 37 38 39 40

NO

x (

g/h

r)

opModeID

MOVES Drayage

inc. STP inc. STP inc. STP

1-25 mph 25-50 mph 50+ mph

Draft Data: Houston Drayage (weighted) vs. MOVES: MY 2003-2006

Shifts to higher or lower

VSP bins because of

grade (+ or -) No Grade

With Grade

VSP Bin (kW/ton)

VSP Bin Frequency

Benefits:

Full profile of a vehicle operations/emissions at

moment in time. (no missing data profiles)

More accurate emission data for mode of operation

Reduces time per choreographed drive route/test

Minimize possible failure of PEMS units

Allows for scheduled zeros/spans for drift correction

Allows for more “better” designed tests to be

conducted.

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PAMS: What parameters are needed?

Date/Time Stamp

GPS

OBD Parameters – Normal

– Engine Speed (RPM)

– Vehicle Speed

– Load %

– Air/Fuel Ratio

– Catalyst Temperature

– Short-Term Fuel Trim

– Long Term Fuel Trim

– Ambient Temperature

– MAP or MAF

– Inlet Temperature

– OBD Codes

– Accelerator Position

– Others

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• OBD Parameters – Enhanced

- Fuel Economy

- Battery State of Charge (hybrid)

- Others

Instruments and measurements: In-Use Activity

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Instrument: Logger (by HemData)

Keys features:

• OBD/CAN & GPS (second-by-second)

• “Sleep mode”

• X,Y & Z Accelerometer

LDVs/MDVs HDVs/Nonroad (J1939)

Skid-steer loader: Operation by Day of Week

Measurement Period: Monday June 11, 2007 – Monday, July 2, 2007

Total operation: 16.6 hours

Skid-steer loader: Operation by Hour of Day

PEMS vs PAMS When to use one of them or both?

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PEMS – Great for Measure emissions, activity & vehicle parameters

– Labor intensive to install/uninstall & calibrate

– High cost

PAMS – Small unit & easy to install

– Only records vehicle parameters & GPS

– Much lower costs

– Captures “real world” activity/non-activity for long periods of time

Use Right Data Gathering Tool: PEMS vs PAMS (Statistical Power)

Portable Emission Measurement Systems (PEMS) – Full emissions profile of vehicle at that moment of time

Represents its aging (odometer, maintenance, environmental

factors)

– Recruit, test, give back vehicle to owner in 2-3 days, allows for more

tests per vehicle or more vehicles tested.

– Include simulated loads emission profiles

– Repeat recruitment to document vehicle’s seasonal or longitudinal

deterioration effects

Portable Activity Measurement Systems (PAMS) – Able to rematch “real world” activity profiles by vehicle OBD

parameters back to emissions.

– Able to install more PAMS device on vehicles for 2-4 weeks or longer

including seasonal effects.

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How Good is Your Data?

Do you know how good your data is from your PEMS

unit?

How long does it take to know the data gathered

from the PEMS unit is good?

– 15 minutes? 30 minutes?, 1 hour? or hours?

Quick Data Stream Validation is the key to your first

primary determination on data gathering &what next

test your going to conduct next.

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One Solution: NI Diadem Software

Generates a graph data report on all data streams to confirm or

validate them.

Look to confirm minimum/maximum range values

Advance Features: Perform QA/QC procedures and provides

quick indications that data with “normal” ranges or within

min/max ranges.

Allows for creating set reports that calculated emissions for quick

comparisons between vehicles

Ability to reuse reports for other test programs …… reducing

data validation & QA/QC time and more time on analyzing

emission results.

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17 Gives full report on data parameters

PM Mass (Int. Filter Time)

DIAdem REPORT Layout 18

Cold start : Peak not shown (2,700 μg/m3!)

PARTICULATE MEASUREMENT: CONTINUOUS AND AGGREGATE

Second by second

Particulate!

Summing the

second-by-second

gives a back-up to

mass on the filters

Exhaust Flow

Accumulating mass on

three filters

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Why Worry about Vehicle Selection & Representativeness?

In modeling world ….. Is it critical to know

the selection criteria for the vehicle(s) tested

and how it fits within its like total population

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Total State LDV

population:

N = 10,000

Tested LDV #1

Tested LDV #2

One Company’s LDV Fleet: N=300

Vehicle Selection: Is there a better way?

Is there a way to screen large numbers of vehicles? – Before selecting sample for laboratory measurement?

– By getting a quick inexpensive measure of emissions?

That correlates with lab measurements

– Best candidate: remote sensing

Has been demonstrated for LDV evaporative emissions

Has been demonstrated for Heavy-duty vehicles

Presently being conducted on Tier 2 RSD/PEMS correlation

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Instruments & measurements: secondary screening (@ NVFEL)

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Instrument: ESP 4000

HC/CO/NO (remote sensing):

Tier 2 LDVs RSD/PEMS corelation

RSD

Equipment

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• Conducted by University of Denver (two weeks in July 2009)

• Gaseous pollutants (CO2, CO, THC & NOx)

• Measured at entry gate of Barbour’s Cut port

• Matched license plates to TX DOT database

• RSD readings: 4,032

• Unique vehicles: 1,877

Sampling methodology: HDVs

Classification – “Stratified sampling”

– Population divided into separate ‘classes’ based on RSD NOx

emissions and model year groups

– Each class sampled as an independent sub-population

Quota sampling within each class based on – Probability that a vehicle is actually in the assigned NOx Bin

– Frequency that the vehicle will drive in the Port of Houston during

PEMS & PAMS instrumentation

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Sampling ‘classes’ based on RSD scores1

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-4.5-4.1-3.7-3.3-2.9-2.5-2.1-1.7-1.3-0.9-0.5-0.1 0.3 0.7 1.1 1.5 1.9 2.3 2.7 3.1 3.5 3.9 4.3

Pe

rce

nt

(%)

RSD NOx z-Value

NOx Bin -2 (2.5%)

NOx Bin -1 (20%)

NOx Bin 0 (55%)

NOx Bin 1 (20%)

NOx Bin 2 (2.5%)

1 Data Collection of Drayage Trucks in Houston-Galveston Port Area Draft Report. EP-C-06-080. May 27, 2011

Emissions Analysis

Assign second-by-second measurements from

PEMS into MOVES operating mode bins

– Function of vehicle speed and Scaled Tractive Power

(STP)

– Consist of idle, braking, coast, and cruise modes

– Additional detail provided in the Appendix

Calculate average emission rates by model year

groups

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Emissions Analysis (cont’d)

Apply population weights based on RSD sampling methodology – Why apply the weights?

In order to capture ‘high-emitting’ trucks in the sample, trucks were recruited with unequal probabilities of selection

Thus, it is necessary to adjust the sample distribution to conform to the known distribution in the RSD population

– Trucks without RSD measurements excluded from the analysis

Compare “in the wild” emissions data to MOVES emission rates for heavy-duty short-haul combination trucks

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PEMS NOx vs. STP by RSD NOx Bin

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PE

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STP

MYG 1991-1997

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MYG 1998

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MYG 2003-2006

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Cleaner

Bottom line: correlation between RSD readings and PEMS

measurements work but can be improved.

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500

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0 1 11 12 13 14 15 16 21 22 23 24 25 27 28 29 30 33 35 37 38 39 40

NO

x (

g/h

r)

opModeID

MOVES Drayage

inc. STP inc. STP inc. STP

1-25 mph 25-50 mph 50+ mph

Draft Data: Houston Drayage (weighted) vs. MOVES: MY 2003-2006

Conclusions

The Tools (PEMS/PAMS) are there to measure

mobile sources

By improving are sampling techniques, selection

criteria, data gathering techniques, analyses and use

of PEMS/PAMS:

– Good data becomes better data

– Able to gathering more data (Statistical power)

More Cooperative Research/Discussions are

needed to support each other in Gathering Data

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Gallery

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PEMS Vehicle Example MY 1994 Freightliner

Exhaust

System

PM

Proportional

Sampler

System Semtech_DS

PM Filters

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Portable Emissions - SEMTECH DS

• Gaseous pollutants (CO2, CO, THC, NO & NO2), with exhaust flow

• Teflon membrane filters (PM) @ 47 C

Portable Activity

• Isaac data loggers

• GPS and RPM (older vehicles)

• GPS & engine parameters (J1708 & J1939)

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PEMS

partially

inside with

Filters/MPS

outside cab

PEMS filters

and DS

inside cab

with MPS

flowmeter

outside

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Typical PAMS installation to gather

activity:

• GPS & RPM (older vehicles)

• GPS & engine parameters

(J1708/J1939)

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Questions?

Appendix

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Time Alignment?

How are you determining time alignment of

data from all data streams?

– Each analyzer has a different , OBD/CAN;

flowmeter, GPS, environmental probe,

proportional sampling & sampling lines lengths

PEMS manufacturers or yourself need to

establish procedures to document this

properly for each equipment setup

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Time Series: Engine Parameters

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Elapsed Time (Sec)

Exhaust Flow Temperature (°C)

Exhaust Mass Flow (SCFM)

Engine Speed (RPM × 0.1)