N2O Instrument EvaluationOInstrumentEvaluation3/22/121U.S. Environmental Protection AgencyGC-ECD Comparison to FTIREvaluation ResultsU.S. Environmental Protection Agency 2Overview• GC-ECD and FTIR analyzed bags over threephases of the FTP and HWFET for N2O.– Ambient measurement performed.• Blended bag analysis of N2O using NDIR andFTIR.– Testing repeated, once on 5/9/11 and once on5/31/11.– Ambient analysis included.3U.S. Environmental Protection AgencyARB Comparison of GC-ECD to FTIR• ARB analyzed bags over three phases of theFTP and HWFET for N2O.– Bag analysis on GC-ECD and FTIR meeting ARBSOP No. MDL 136.Testing was done on 3 vehicles no repeats–Testingwasdoneon3vehicles,norepeats.– Tests were performed at ATDC under EPAcontract.– FTIR compared very well to GC-ECD, which isconsidered the gold standard.4U.S. Environmental Protection Agency5U.S. Environmental Protection Agency6U.S. Environmental Protection Agency7U.S. Environmental Protection Agency8U.S. Environmental Protection Agency9U.S. Environmental Protection Agency10U.S. Environmental Protection Agency11U.S. Environmental Protection Agency12U.S. Environmental Protection Agency13U.S. Environmental Protection Agency14U.S. Environmental Protection AgencyNDIR Comparison to FTIREvaluation ResultsU.S. Environmental Protection Agency 15Comparison of NDIR and FTIR• Horiba loaned us one of their only AIA-721(LE) N2Oanalyzers for evaluation.•AVL new generation FTIR was also made availableAVLnewgenerationFTIRwasalsomadeavailableto EPA for evaluation.• We just recently evaluated the analyzers on bagsi ti f bl d f CO COt NO dNconsisting ofblends ofCO,CO2, waer,N2, andN2.• The purpose was to validate the analyzers’ ability tocompensate for CO, CO2, and water interference.• Both the NDIR and FTIR analyzers performed well,however some questions regarding performanceremain.16U.S. Environmental Protection Agency17U.S. Environmental Protection Agency18U.S. Environmental Protection Agency19U.S. Environmental Protection Agency20U.S. Environmental Protection Agency21U.S. Environmental Protection Agency22U.S. Environmental Protection Agency23U.S. Environmental Protection Agency24U.S. Environmental Protection Agency25U.S. Environmental Protection AgencyConclusion• Current NDIR and FTIR technologies can have atendency to bias the measurement high due tointerference contributions.interferencecontributions.– Horiba NDIR can minimize interference effects by targetingrepresentative CO2concentration for factor generation.–Precision of NDIR CO correction remains an open issue(other possible contributing factors?).– ARB FTIR data shows no bias, while AVL does (typically0.75 ppm on average).–Overall, interference contributions are well below the 1 ppmlimit in 1065.375.• GC-ECD does not have any measurement issues.26U.S. Environmental Protection AgencyHoriba MEXA-1100QL EvaluationResultsU.S. Environmental Protection Agency 27Evaluation of Horiba MEXA-1100QL• Horiba loan EPA a MEXA-1100QL quantum cascadelaser based N2O measurement instrument forevaluation.• EPA GC-ECD is not yet operational, therefore MEXA1100QL performance was evaluated against bagblends of CO COwater NO and NblendsofCO,CO2,water,N2O,andN2.• The evaluation was identical to pervious evaluationsof NDIR and FTIR N2O analyzers performed by EPA.• The purpose was to validate the analyzers’ ability tocompensate for CO, CO2, and water interference.28U.S. Environmental Protection AgencyEvaluation of Horiba MEXA-1100QL• The MEXA-1100QL performed with effectivelyno span drift over days of operation andminimal zero drift.• The instrument consistently read ambientb k dNO 3121 backgroundN2as±ppb.• Interference check results:–-9 ppb response on 15.19% CO2– 2 ppb response on 485 ppm CO29U.S. Environmental Protection Agency0.6Comparison of N2O Concentrations Across Different Bag Blends of CO2and CO0.51.461%CO2194 8ppmCO1.948%CO2292 2ppmCOTargetN2OConcentration=0.391 ppmH2OConcentration=2.2%0.30.4

n traiton (ppm)194.8ppmCO292.2ppmCO0.2

N 2 O Conce n0.00.1Bag 5 Bag 630U.S. Environmental Protection AgencyCalculated BlendHoriba MEXA-1100QL0.8Comparison of N2O Concentrations Across Different Bag Blends of CO2and COTargetNOConcentration0 587ppm0.60.70.97%CO287.3ppmCO1.457%CO2116.5ppmCO0.777%CO268.0ppmCO0%CO2193.9ppmCO1.457%CO20ppmCO1.457%CO2193.6ppmCO1.457%CO2291.3ppmCO1.942%CO2194.2ppmCO1.942%CO2291.3ppmCOTargetN2OConcentration=0.587ppmH2OConcentration=2.2%0.40.5

e ntraiton (ppm)0.20.3

N 2 O Conc e0.00.1Bag 8Bag 4Bag 1Bag 9Bag 2Bag 7Bag 12Bag 11Bag 1031U.S. Environmental Protection AgencyBag8Bag4Bag1Bag9Bag2Bag7Bag12Bag11Bag10Calculated BlendHoriba MEXA-1100QL350Comparison of CO Concentrations Across Different Bag Blends of N2O, CO2,and CO300350200250

i ton (ppm)100150

CO Concentra050B 1B 2B 3B 4B 5B 6B 7B 8B 9B 10B 11B 1232U.S. Environmental Protection AgencyBag1Bag2Bag3Bag4Bag5Bag6Bag7Bag8Bag9Bag10Bag11Bag12Calculated BlendHoriba AIA-721 NDIR Analyzer2 5Comparison of CO2Concentrations Across Different Bag Blends of N2O, CO2,and CO2.02.51.5

traiton (%)1.0

CO 2 Concen0.00.5B 1B 2B 3B 4B 5B 6B 7B 8B 9B 10B 11B 1233U.S. Environmental Protection AgencyBag1Bag2Bag3Bag4Bag5Bag6Bag7Bag8Bag9Bag10Bag11Bag12Calculated BlendHoriba AIA-722 NDIR AnalyzerMEXA-1100QL Measurement Error vs. GasDivider Generated ConcentrationsTarget Generated Concentration Measured Concentration ErrorDividerGeneratedConcentrations5.056 5.077 0.41%3.0336 3.0415 0.26%1.0112 0.9971 -1.41%0.9101 0.9023 -0.86%0.809 0.8035 -0.68%0.7078 0.7035 -0.61%0.6067 0.6081 0.23%0.5056 0.5093 0.73%0.4045 0.4075 0.74%0.3034 0.3088 1.75%0.2022 0.2054 1.56%0.1011 0.0983 -2.85%0 0.0086 0.17%34U.S. Environmental Protection AgencyConclusion• The MEXA-1100QL performed very well and doesnot appear to show any susceptibility to CO, CO2, orwater interference.• Based on CO and CO2measurement error, webelieve that the bulk of the associated N2Omeasurement error is due to bag blending error( i f 5% f ll i )(maximum error of5%for allspecies).• MEXA-1100QL out performs FTIR and NDIRpreviously tested by EPA.All i di ti th t th MEXA1100QL i i bl•Allindications arethattheMEXA-1100QLis a viable,accurate instrument for measurement of N2O at theconcentrations expected during light-duty chassistesting35U.S. Environmental Protection Agency.MAHA QCL Evaluation ResultsU.S. Environmental Protection Agency 36Evaluation of MAHA QCL Analyzer• Maschinenbau Haldenwang (MAHA) loaned EPA aMAHA QCL quantum cascade laser based N2Omeasurement instrument for evaluation.measurementinstrumentforevaluation.• EPA GC-ECD is not yet operational, therefore MAHAQCL performance was evaluated against bag blendsof CO COwater NO and NofCO,CO2,water,N2O,andN2.• The evaluation was identical to previous evaluationsof QCL, NDIR, and FTIR N2O analyzers performed byEPA.• The purpose was to validate the analyzers’ ability tocompensate for CO, CO2, and water interference.37U.S. Environmental Protection AgencyEvaluation of MAHA QCL• The instrument had issues with the computer thatcontrolled the zero and span functions (a complication ofconverting the instrument from 220 VAC to 110 VAC).S h d t b t d ll–Spanhadtobe enteredmanually.– During the evaluation we lost the ability to rezero theinstrument.–Zero/span drift issues and the inabilityto calibrate out this driftycould be the cause of the negative bias seen throughout thetesting.• The instrument read ambient background N2O as 320ppb drifting down to 305 ppb over the course of the dayppb,driftingdownto305ppboverthecourseoftheday.• Interference check results:– 4 ppb response on 15.19% CO2–-2ppb response on 485ppm CO38U.S. Environmental Protection Agencypp p pp0.9Comparison of N2O Concentrations Across Different Bag Blends of CO2and COT tNOC t ti0 5870.70.80.976%CO287 8ppmCO1.457%CO2116 5ppmCO0%CO2195 4ppmCO1.467%CO20ppmCO1.467%CO2293 4ppmCO1.956%CO2195 6ppmCO1.956%CO2293 4ppmCOTargetN2OConcentration=0.587ppmH2OConcentration=2.2%0.50.6

n traiton (ppm)87.8ppmCON2ODiff‐0.035116.5ppmCON2ODiff‐0.010195.4ppmCON2ODiff‐0.0240ppmCON2ODiff‐0.032293.4ppmCON2ODiff‐0.038195.6ppmCON2ODiff‐0.017293.4ppmCON2ODiff‐0.0360 20.30.4

N 2 O Conce n0.00.10.2B 8B 1B 9B 7B 12B 11B 1039U.S. Environmental Protection AgencyBag8Bag1Bag9Bag7Bag12Bag11Bag10Calculated BlendMAHA QCL350Comparison of CO Concentrations Across Different Bag Blends of N2O, CO2,and CO300200250

i ton (ppm)100150

CO Concentra05040U.S. Environmental Protection AgencyBag 1 Bag 7 Bag 8 Bag 9 Bag 10 Bag 11 Bag 12Calculated BlendHoriba AIA-721 NDIR Analyzer2.5Comparison of CO2Concentrations Across Different Bag Blends of N2O, CO2,and CO2.01.5

n traiton (%)1.0

CO 2 Conce n0.00.5Bag 1Bag 7Bag 8Bag 9Bag 10Bag 11Bag 1241U.S. Environmental Protection AgencyBag1Bag7Bag8Bag9Bag10Bag11Bag12Calculated BlendHoriba AIA-722 NDIR AnalyzerConclusionTh MAHA QCL f d ll d d•TheMAHAQCLperformedwellanddoes not appear toshow any susceptibility to CO, CO2, or water interference.• Based on CO and CO2measurement error (maximum3%) we believe that some of the associated NO3%),webelievethatsomeoftheassociatedN2measurement error is due to bag blending error.• It should also be noted that the average 5% negative biason N2O measurement is influenced bythe inabilityto2y yproperly zero/span the instrument after the initialzero/span at the start of the testing.– The negative drift is evident when looking at the increase innegative bias in the order the bags were read:7 8 9 10 11negativebiasintheorderthebagswereread:7,8,9,10,11,12, and 1.– It is also noted in the decreasein ambient concentration overthe course of the testing: 320, 310, 305 ppb.42U.S. Environmental Protection AgencyConclusion cont.Th MAHA QCL f FTIR d NDIR•TheMAHAQCLout performsFTIRandNDIRpreviously tested by EPA.• All indications are that if the instrument zero/spanf ti ki l th MAHA QCLfunctions are working properly,theMAHAQCLshould be a viable, accurate instrument formeasurement of N2O at the concentrations expectedduring light-duty chassis testingduringlightdutychassistesting.• EPA intends to re-evaluate this instrument after themanufacturer has resolved issues regarding thepower configuration for use in North AmericapowerconfigurationforuseinNorthAmerica.• We will update our results with this instrument afterour re-evaluation.43U.S. Environmental Protection AgencySensors LASAR Evaluation ResultsU.S. Environmental Protection Agency 44Evaluation of Sensors LASAR• Sensors loaned EPA a LASAR scanning laser basedN2O measurement instrument for evaluation.• EPA GC-ECD is notyet operational,therefore thep ,LASAR’s performance was evaluated against bagblends of CO, CO2, water, N2O, CH4, and N2.• The evaluation was identical toprevious evaluationsof NDIR, FTIR, and QCL N2O analyzers performed byEPA.• The purpose was to validate the analyzers’ ability tot f CHCO COd tcompensaeforCH4,CO,CO2, andwaterinterference.• The LASAR is advertized as not being susceptible toit f f h t i45U.S. Environmental Protection Agencyanyinterferencefrom exhaustgas species.Evaluation of Sensors LASAR• The analyzer was set up for the followingranges:– N2O calibrated for 0 – 50 ppm– CH4calibrated for 0 – 100 ppmNHlib t d f 0100–3calibratedfor0–ppm– CO2calibrated for 0 – 30 %HO calibrated for 030 %–2Ocalibratedfor0–46U.S. Environmental Protection AgencyEvaluation of Sensors LASAR• CO and CO2bag concentrations were measuredwith Horiba MEXA 700 series NDIR analyzers.• CH4measurement was performed using theLASAR system.The LASAR performed ith effecti el no span•TheLASARperformedwitheffectivelynospandrift over days of operation and minimal zerodrift.• The instrument consistently read ambientbackground N2O as 338±1 ppb.47U.S. Environmental Protection AgencyEvaluation of Sensors LASAR• Interference check results:– 21 ppb response on 15.42% CO225 ppb response on 475 ppm CO–25ppbresponseon475ppmCO– 37 ppb response on 24 ppm CH4– 25 ppb response on pure N2• Instrument was not zero calibrated at EPA.– Response from CO2and CO is the same as N2.•Indicates no interferenceIndicatesnointerference.• Response could be zero offset or N2O contamination ofbalance gas.•CH4response 12 ppb higher than N248U.S. Environmental Protection AgencyCH4response12ppbhigherthanN2.0.6Comparison of N2O Concentrations Across Different Bag Blends of CO2and COTargetN2OConcentration=0.391ppm0.51.465%CO2195.3ppmCON2ODiff0.011ppm1.952%CO2292.9ppmCON2ODiff0.008ppmg2ppH2OConcentration=2.3%0.30.4

e ntraiton (ppm)2pp0 10.2

N 2 O Conc e0.00.1Bag 5 Bag 649U.S. Environmental Protection AgencyCalculated BlendLASAR0.9Comparison of N2O Concentrations Across Different Bag Blends of CO2, CO,and CH4TargetN2OConcentration=0.586 ppmHOC t ti2 3%0.70.80.977%CO287.9ppmCON2ODiff0.0271.466%CO2117.3ppmCONODiff0 0110.782%CO268.5ppmCONODiff0 00119.9ppmCH4N2ODiff0.020H2OConcentration=2.3%0 40.50.6

centraiton (ppm)N2ODiff0.011N2ODiff‐0.0010.20.30.4

N 2 O Con0.00.1Bag 4 Bag 1 Bag 2 Bag 750U.S. Environmental Protection AgencyCalculated BlendLASAR350Comparison of CO Concentrations Across Different Bag Blends of N2O, CO2,and CO250300200

r aiton (ppm)100150

CO Concent050Bag 1 Bag 2 Bag 3 Bag 4 Bag 5 Bag 651U.S. Environmental Protection AgencyCalculated BlendMEXA2 5Comparison of CO2Concentrations Across Different Bag Blends of N2O, CO2,and CO2.02.51.5

t raiton (%)1.0

CO 2 Concen t0.00.5B 1B 2B 3B 4BB 652U.S. Environmental Protection AgencyBag1Bag2Bag3Bag4Bag 5Bag6Calculated BlendMEXAConclusion – Part 1• The Sensors LASAR performed very well and does notappear to show any susceptibility to CO, CO2, CH4, orwater interference.B d CO d COt b li•BasedonCOandCO2measurementerror, webelievethat the bulk of the associated N2O measurement error isdue to bag blending error (maximum error of 6% for allspecies).)• LASAR out performs FTIR and NDIR previously tested byEPA.• Results are comparable to Horiba MEXA-1100 QLpreviously tested by EPA.• All indications are that the LASAR is a viable, accurateinstrument for measurement of N2O at the concentrationsexpected during lightduty chassis testing53U.S. Environmental Protection Agencyexpectedduringlight-dutychassistesting.Exhaust Emissions Analysis - Overview• EPA used their RepTruck repeatable vehicle to perform several 505 cycles toevaluate analyzer performance• Three “stabilized” tests were performedin addition to a “cold” and “hot” start505’s.Th CVSFl ti ll 550f•eowrae was nominally550scm• The Sensors analyzer evaluated was able to measure N2O, CH4, CO2, NH3&H2O.• Horiba bench results were also recorded.•The Sensors analyzer was mounted on a portable cart with a twoway valveTheSensorsanalyzerwasmountedonaportablecartwithatwo-wayvalveinstalled on the sample port to allow switching between ambient and the samplebag.• The unit was a 19” rack-mount (3U or 4U form) with a depth of approximately24”• The sample bag line was installed with a quick disconnect to allow the operatorto remove the line from the Horiba benchto connect to the Sensors sample port.• 10 Hz data was collected from the Sensors instrument54U.S. Environmental Protection AgencyExhaust Emissions Analysis – Purpose• N2O measurement evaluation– Measure actual exhaust data– Repeatability of stabilized cycles– Capture “Cold” & “Hot” start emissions–Evaluate response time and stabilization– Overall Analyzer Performance55U.S. Environmental Protection AgencyExhaust Emissions Analysis – Results• The instrument experienced instability issues when itwas moved to the test cell. Unfortunately we hadalready performed the first two stabilized tests andd t ti t i t ld t t thduetotime constraints couldnotrepeatthem• Data from the first two stabilized tests were evaluatedbut upon further investigation by the instrumentf t th i t bilit d th d t it blmanufacturertheinstability madethedata unsuitablefor any meaningful analysis. This instability didprovide insight into the functioning of the instrumentand would be useful as a diagnostic toolandwouldbeusefulasadiagnostictool.• The “Cold” and “Hot” start tests provided usadditional information on response time andstabilization56U.S. Environmental Protection AgencyInstrument InstabilityTh f t fi d th t th f th i t bilit th•The manufacturer confirmedthatthe source oftheinstability wasthespectrometer temperature not being stabilized after the instrument wasfirst moved to the test cell. The instrument had been off for approximatelytwo hoursprior to its installation in the test cell.• This instability is evident from theTauparameter (dynamic measurementof the path-length and resonance quality at 10Hz) and theValMaxparameter (dynamic measurement of the variation of light source intensityt 10H ) Th t t bi d i t i l di tiRDat10Hz).Thesetwo parameters are combinedinto a singlediagnosticNormalizedwhich is plotted on the following graph.5/24/2012 U.S. Environmental Protection Agency 575/24/2012 U.S. Environmental Protection AgencyGraph supplied by Sensors Inc.58Determining Signal StabilityTh f t i d d t f th thi d t bili d t t d th “C ld”•The manufacturer revieweddataforthethirdstabilizedtestandthe“Cold”and “Hot” start 505’s and re-plotted the graphs. The instability thatoccurred in the first two tests rendered that data unusable.•In addition to the raw 10 Hz data a 10-second moving average is alsoInadditiontotheraw10Hzdataa10secondmovingaverageisalsoplotted on the graph. This averaged signal is constructed from a dynamicboxcar average filter where the dynamic portion consists of testing 5consecutive observations (1 second of data) against a +/- 2 sigma limit,ith i b i 1 t d d d i ti i f th NO i l (1 iwithsigmabeing1standarddeviation noise oftheN2Osignal(1sigma =7.5ppb). If 5 consecutive observations deviate from the boxcar averagecalculated for N2O by more than +/- 2 sigma the boxcar average is reset tozero.o• Once the 10-second signal is stabilized the 30-second average of the 10-second signal is calculated along with the 1 sigma standard deviation ofthe averaged signal. These results are presented at the bottom of thegraph.5/24/2012 U.S. Environmental Protection Agency 595/24/2012 U.S. Environmental Protection AgencyGraph supplied by Sensors Inc.605/24/2012 U.S. Environmental Protection AgencyGraph supplied by Sensors Inc.615/24/2012 U.S. Environmental Protection AgencyGraph supplied by Sensors Inc.62Exhaust Emissions Analysis Summary TableTest#1* Test#2* Test#3 Test#4 Test#5AnalyzerN2O(ppm)CH4(ppm)CO2(%)CO(ppm)N2O(ppm)CH4(ppm)CO2(%)CO(ppm)N2O(ppm)CH4(ppm)CO2(%)CO(ppm)N2O(ppm)CH4(ppm)CO2(%)CO(ppm)N2O(ppm)CH4(ppm)CO2(%)CO(ppm)LASAR 0.024 0.210 0.737 NA 0.021 0.197 0.684 NA 0.014 0.183 0.741 NA 0.583 1.476 0.801 NA 0.203 0.763 0.766 NAMEXA NA 0.3730.7257.498 NA 0.3280.7279.004 NA 0.2760.7224.355 NA 1.579 0.776 125.603 NA 0.882 0.746 17.72CH4Intfrn(ppb)CH4Intfrn (%ofMeas)Test#1 0.2 0.94%Test#2 0.2 0.83%Test#3 0.1 0.69%Test#4 0.8 0.14%Test#50 40 22%• The calculated interference from CH4for all cycles was less than 1% of measurementTest#50.40.22%*LASARAnalyzerUnstable63U.S. Environmental Protection AgencyAnalyzer Performance• The analyzer was able to discriminate nearly a 10 ppb differencebetween the bag and ambient measurements for Test #3• Standard deviations were approximately 1ppb for processed readings(not including Test #4 second measurement cycle)(notincludingTest#4secondmeasurementcycle)• Test #4 & #5 response times (t10– t90) were within 4 seconds onsecond and third measurement cycles• Test #4 & #5 signal response was within +/- 2% of final reading within 9seconds on second and third measurement cyclessecondsonsecondandthirdmeasurementcycles• Cycle times for sample and ambient measurements averaged around 4minutes• The calculated interference from CH4for all cycles was less than 1% ofmeasurement• Bag sample valve opening contamination is being investigated furtherby manufacturer64U.S. Environmental Protection AgencyConclusion – Part 2• Temperature stability is criticalto the proper functioning of theLASAR• The RD diagnostic is an effective tool of determining analyzerstability• Averaged readings eliminate noise from the signal withoutseriously degrading analyzer performance for response time.• Once stabilized the Sensors LASAR analyzer performedexceptionally well.• Response time and reading stabilization period were well withinwhat is generally required in a light-duty test environment.•Calculated interference from CHwas less than 1% ofCalculatedinterferencefromCH4waslessthan1%ofmeasurement for all cycles.• The physical dimensions of the LASAR would facilitateinstallation into most if not all analytical benches used in our lab.65U.S. Environmental Protection AgencyAddendum – FFT of LASAR N2O Data at Ambient0.40 250.30.35ADominant frequency occurs at f = 0HzAmplitude = 338.9 ppb0.150.20.25mplituN2O Signal00.050.10123456de• FFT performed on 10 Hz data• RMS of Signal = 338.3 ppb-0.050123456Frequency (Hz)66U.S. Environmental Protection Agency• Mean of Signal = 338.2 ppb