Evaluation of Exhaust Emissions from Three Diesel-Hybrid Cars and

Article pubs.acs.org/est

Evaluation of Exhaust Emissions from Three Diesel-Hybrid Cars and Simulation of After-Treatment Systems for Ultralow Real-World NOx Emissions Vicente Franco,†,‡ Theodora Zacharopoulou,§ Jan Hammer,∥ Helge Schmidt,∥ Peter Mock,† Martin Weiss,⊥ and Zissis Samaras*,§ †

International Council on Clean Transportation Europe, Berlin 10178, Germany Laboratory of Applied Thermodynamics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece ∥ TÜ V Nord Mobilität, Essen 45138, Germany ⊥ Sustainable Transport Unit, Directorate C − Energy, Transport, and Climate, Directorate-General Joint Research Centre, European Commission, Ispra 21010, Italy §

S Supporting Information *

ABSTRACT: Hybridization offers great potential for decreasing pollutant and carbon dioxide emissions of diesel cars. However, an assessment of the real-world emissions performance of modern diesel hybrids is missing. Here, we test three diesel-hybrid cars on the road and benchmark our findings with two cars against tests on the chassis dynamometer and model simulations. The pollutant emissions of the two cars tested on the chassis dynamometer were in compliance with the relevant Euro standards over the New European Driving Cycle and Worldwide harmonized Light vehicles Test Procedure. On the road, all three diesel-hybrids exceeded the regulatory NOx limits (average exceedance for all trips: +150% for the Volvo, +510% for the Peugeot, and +550% for the Mercedes-Benz) and also showed elevated on-road CO2 emissions (average exceedance of certification values: +178, +77, and +52%, respectively). These findings point to a wide discrepancy between certified and on-road CO2 and suggest that hybridization alone is insufficient to achieve low-NOx emissions of diesel powertrains. Instead, our simulation suggests that properly calibrated selective catalytic reduction filter and lean-NOx trap after-treatment technologies can reduce the on-road NOx emissions to 0.023 and 0.068 g/km on average, respectively, well below the Euro 6 limit (0.080 g/km).

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INTRODUCTION

and achieve catalyst light-off temperatures more quickly from cold start or shut off the engine during decelerations and idling to reduce air mass flow and avoid engine and catalyst cooling.2−5 This paper evaluates the emissions of CO2 and air pollutants as well as the fuel consumption of three different diesel-hybrid cars certified to the Euro 5 and 6 emission standards. We place special emphasis on emissions of nitrogen oxides (NOx), which are a major cause of urban air quality problems in European cities.6 Since the full phase-in of the Euro 6b standard in the EU in September 2015, all newly registered diesel passenger cars must meet a NOx emissions limit of 0.080 g/km over the European vehicle emissions certification cycle [i.e., the New European Driving Cycle (NEDC)], constituting a reduction of

Diesel hybrids comprise just a small niche of the European passenger car market, accounting for 0.15% of all new registrations of passenger cars in the European Union (EU) in 2015 (with the share being 51.5% for conventional diesel cars).1 However, diesel hybrids could offer significant environmental benefits by combining the low urban fuel consumption of hybrid powertrains with the motorway cruising efficiency of a diesel engine and offering an increasing number of control strategies to achieve very low levels of pollutant emissions. With regard to the latter, electric hybridization of diesel powertrains can offer several advantages over conventional powertrains: (1) hybrid architectures enable shifting the speed/torque operating points of the internal combustion engine (ICE) toward regions of higher efficiency (thus lowering CO2 emissions); (2) the torque boost provided by the electric motor can smooth out the torque demand on the ICE, thus avoiding NOx emission peaks from sudden changes in load demand; and (3) hybrid vehicles can use electric power to heat after-treatment systems © 2016 American Chemical Society

Received: Revised: Accepted: Published: 13151

July 17, 2016 November 1, 2016 November 4, 2016 November 4, 2016 DOI: 10.1021/acs.est.6b03585 Environ. Sci. Technol. 2016, 50, 13151−13159

Article

Environmental Science & Technology Table 1. Technical Characteristics of the Test Vehicles and Overview of Emission Tests and Simulationsa Volvo V60 plug-in hybrid

Mercedes-Benz S300 Bluetec hybrid

emissions standard ICE fuel hybrid concept type-approval CO2 emissions (NEDC procedure) (g/km) exhaust after-treatment approximate mileage (km) year of manufacturing battery capacity (useable) (kWh) curb weight (kg) nominal battery voltage (V) battery technology nominal electric motor power (kW)

Euro 5 diesel parallel plug-in hybrid 48 DOC + DPF + EGR 1000 2014 8.0 2052 385 lithium ion 52

Euro 6 diesel parallel hybrid 115 DOC + DPF + EGR + SCR 10000 2014 0.8 2015 126 lithium ion 20

ICE power (peak) (kW) transmission

158 150 six-speed automatic seven-speed automatic Emission Tests and Simulation yes (NEDC and WLTP) yes (NEDC and WLTP) yes (16 trips) yes (12 trips) yes (LNT and SCRF) no

chassis dynamometer testing on-road testing with PEMS NOx after-treatment simulation

Peugeot 3008 HYbrid4 Euro 5 diesel parallel hybrid (two electric motors) 99 DOC + DPF + EGR 10000 2012 1.1 1735 202 nickel−metal hydride 8 (front axle) 27 (rear axle) 120 six-speed automatic no yes (5 trips) no

DOC, diesel oxidation catalyst; DPF, diesel particulate filter; EGR, exhaust gas recirculation; WLTP, Worldwide harmonized Light vehicles Test Procedure. a

Table 2. Design Characteristics of PEMS Routes around Milan (Italy; Route 0) and Essen (Germany; Routes 1−4) route ID

urban distance share

rural distance share

motorway distance share

distance (km)

target duration (s)

0 1 2 3 4

1/4 1/3 1/3 1/6 2/3

1/4 1/3 1/3 1/6 1/6

1/2 1/3 1/3 2/3 1/6

61.7 76.1 88.6 110.6 50.6

3500 5700 6700 5700 4700

about 55% from the 0.180 g/km limit of the Euro 5 standard.7 However, several studies have shown that NOx emissions of diesel cars can be substantially higher during “real-world” driving than during laboratory measurements at type approval.8−13 This is especially the case for the on-road NOx emissions from modern (Euro 5 and Euro 6 or equivalent) diesel passenger cars, which can exceed the applicable limits by several factors.14−17 Whereas a minority of diesel Euro 6 cars have demonstrated acceptable on-road emission performance, others have alarmingly high NOx emissions, even during moderate driving conditions outside the certification cycle.18 Our analysis can provide insights into the strengths and limitations of diesel hybrids toward reducing pollutant and CO2 emissions and highlight areas for future technological and regulatory interventions.

topography hilly hilly hilly hilly hilly

flat flat flat flat

(THC), NOx, and CO2 were measured at the exhaust point using MAHA emission analysers. Particulate mass (PM) and particle number (PN) emissions were measured using a MAHA PM sampler and a TSI particle counter. Electric power flows in the hybrid powertrains were monitored with a Hioki electric power meter connected to the high-voltage terminals of the hybrid powertrain. We tested the vehicles over two different test cycles: (1) The NEDC, as defined in the EU type-approval regulations,7 is a synthetic cycle and associated test procedure, designed in the 1990s to measure exhaust emissions of air pollutants from passenger cars and light-duty vehicles in Europe. (2) The WLTC is a transient cycle, designed to provide a better representation of “real-world” driving than the NEDC.12 WLTC and its associated test procedure (WLTP) are expected to replace the NEDC in 2017 for the type approval of passenger cars in the EU, leading also to a more realistic certification of CO2 emissions and fuel consumption.20 We determined the vehicle inertia and road load coefficients (i.e., the necessary parameters for the chassis dynamometer to simulate the driving resistances) separately for the NEDC and WLTP according to the respective procedures (see Table S1 of the Supporting Information). Vehicle pre-conditioning and calculation of results also differed between NEDC and WLTP (see Annex I of the Supporting Information). On-Road Emission Measurements with PEMS. Measurement Equipment. On-road emission measurements were carried out for all three test vehicles (Table 1). The three test vehicles were equipped with the measurement equipment described in Table S2 of the Supporting Information. The

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MATERIALS AND METHODS Test Vehicles. Two diesel-hybrid cars with different powertrain concepts and emission controls were sourced independently from their manufacturer for testing on the chassis dynamometer and on the road with a portable emissions measurement system (PEMS). The European Commission’s Joint Research Centre contributed on-road test results from a third diesel-hybrid car (Table 1).19 Emission Measurements on the Chassis Dynamometer. The exhaust emissions of the Volvo and Mercedes-Benz were tested on the chassis dynamometer (Table 1). The emissions of carbon monoxide (CO), total hydrocarbons 13152

DOI: 10.1021/acs.est.6b03585 Environ. Sci. Technol. 2016, 50, 13151−13159

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Environmental Science & Technology

emissions are equal to or lower than the regulatory limit; a CF above 1 indicates that the emissions are above the regulatory limit. Although the term CF is borrowed from the European RDE regulation to be used in the analysis of our results, it is not strictly applicable in the regulatory sense because the testing conditions (e.g., route characteristics) may deviate from those of the RDE test. Similarly, we define the on-road CO2 ratio as the ratio of measured on-road CO2 emissions to the corresponding type-approval CO2 emissions value for the vehicle. Dynamic Driving Indicators. The driving dynamics of the PEMS trips were evaluated against the boundary conditions described in the RDE regulation,24 consisting of an upper limit curve for the 95th percentile of the product of instantaneous positive acceleration and vehicle speed for urban, rural, and motorway driving and a lower limit curve based on relative positive acceleration (RPA) over these three driving bins (see Figures S1 and S2 and Table S2 of the Supporting Information). Simulation of NOx After-Treatment Systems. For the Volvo V60 plug-in hybrid, we complemented the emissions testing by a dedicated simulation of two different after-treatment systems: a selective catalytic reduction filter (SCRF) and lean-NOx trap (LNT). The simulation was conducted using axisuite,25 a software for the simulation of flow-through, honeycomb catalytic converters and wall-flow particulate filters (Figure 1).

complete PEMS setup adds about 200 kg of payload to the vehicle under test. Test Routes. We chose four different routes around Essen (Germany) to analyze the influence of different route designs on the emissions of the Mercedes-Benz and Volvo (routes 1−4 in Table 2). Routes 1 and 2 have balanced distributions of urban/rural/motorway driving, with the latter having a hillier profile. Route 3 contains a high share of motorway driving and was designed to highlight the efficiency potential of diesel cars during high-speed cruising. Route 4 contains a high share of urban driving and should highlight the efficiency potential of hybrid powertrains. Each route was driven at least twice. Testing started each day with a cold engine. For the plug-in hybrid car (i.e., the Volvo V60), the tests started with a fully loaded battery and continued with driving in charge-sustaining mode. The Peugeot 3008 was driven 5 times on the same route (route 0 in Table 2) in the greater Milan area (Italy). A combined total of 33 PEMS trips were driven for all three cars (Table S3 of the Supporting Information). Data Analysis. We calculated the average distance-specific pollutant and CO2 emissions over the NEDC and WLTC following the provisions of the European type-approval regulations. The on-road emissions measured with PEMS were analyzed with a focus on the impact of driving dynamics and the operation of the hybrid powertrain. Moving Averaging Windows. The PEMS emission data were grouped using two moving averaging window concepts: For the evaluation of the operation of the hybrid systems, the window size was set at 500 m. For the simulation of the improved NOx after-treatment systems, the window size was defined by the amount of CO2 emitted over each window and set equal to the total CO2 emitted during the type-approval test. Moving averaging windows based on the cumulative amount of CO2 emitted during type approval in the laboratory are used in the European heavy-duty vehicle regulations21,22 and constitute also the basis for one of the data evaluation methods used in the European light-duty Real-Driving Emissions (RDE) regulation.23 The use of moving data windows (whether based on driving distance, emitted CO2 mass, or any other parameter) makes it possible to derive thousands of windows from a single trip, which can then be used to approximate the statistical distribution of distancespecific pollutant and CO2 emissions. Hybrid Operation. We evaluated the operation of the hybrid-electric systems by calculating the net hybrid energy as the cumulative value of the power signal measured by the Hioki meter at 1 Hz (scaled by 1/3600 to convert to kWh) for each distance window. By convention, energy flows from the battery to the electric motor (corresponding to charge-depleting operation) were assigned a positive sign and red hues in the analysis plots. Conversely, energy flows from the electric motor to the battery (corresponding to battery-recharging operation) were assigned a negative sign and green hues in the analysis plots. Conformity Factor (CF). The concept of the CF is used for a simple and easily understandable assessment of the emissions performance of the test vehicles relative to the applicable certification limit. We calculated the CF as the ratio of the measured distance-specific emissions (over the driving cycles in the laboratory, each PEMS trip, or individual moving averaging windows) to the applicable emissions limit (e.g., 0.18 and 0.08 g/km of NOx for Euro 5 and 6 diesel passenger cars, respectively). A CF of 1 or below therefore means that the

Figure 1. Layout of the SCRF and LNT systems modeled in the simulation study.

axisuite includes catalyst models that simulate the behavior of three-way catalysts, diesel oxidation catalysts, selective catalytic reduction (SCR) catalysts, and LNTs. The diesel particulate filter (DPF) model simulates the filtration and pressure drop behavior as well as the thermal and catalytic regeneration of the filter. The model has been presented and validated in numerous previous publications.26−31 It solves the transient mass, momentum, species, and energy balances in the channels of after-treatment devices, accounting for the catalytic surface reactions. axisuite uses differential and algebraic equations for the heat and mass transfer in the converter and is equipped with intralayer washcoat discretization to account for the coupling between reaction and diffusion phenomena. The software is able to deal with any reaction scheme and rate expressions (“elementary” and “global” reactions) and supports several ammonia adsorption submodels. For the accurate prediction of the critical thermal behavior of the catalyst bricks at near-zero flow conditions, frequently faced in HEV applications, the simulation was enhanced with a submodel to take into account the heat losses from the monolith periphery 13153


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Environmental Science & Technology and faces.32 As mentioned above, the raw emission data gathered during the on-road measurement campaign were divided into CO2 windows and used as inlet data for the simulations. Both NOx and NH3 emissions were predicted. Using the axitrap module of axisuite, the SCRF modeled was a 2.5 L cordierite monolith, with 180 cells per square inch (cpsi) cell density and 150 g/L Pt-zeolite washcoat. The simulations were performed assuming gaseous NH3 injection instead of AdBlue to simplify mixing and vaporization calculations. An active NH3 level control was implemented on the basis of the accurate calculation and control of ammonia storage levels in the catalyst. No ammonia injection was allowed when the ICE was not operating and when the inlet temperature of the device was lower than 180 °C. The LNT device modeled using axicat was a 1.5 L cordierite monolith, with 400 cpsi cell density and 370 g/L washcoat. Several enrichment strategies were tested over test route 1 (Table 2), and the most efficient closed-loop control system for the extra fuel injection was implemented in MATLAB/ Simulink, enabling the coupling with axicat. Quantities of high hydrocarbon (HC) concentration were injected for a specific period of time at the LNT inlet for the accumulated NOx in the device to remain in pre-specified ranges, different for LNT inlet temperatures above 400 °C and below 400 °C (but >120 °C). During the extra fuel injection periods, the exhaust gas λ was set to the value of 0.95.

Figure 2. Overview of pollutant and CO2 emissions determined over the NEDC and WLTP on the chassis dynamometer. Error bars indicate the standard deviation of values. Particulate mass and particle number emissions are not shown.

emissions averaged 175 g/km for the Mercedes-Benz and Peugeot and 133 g/km for the Volvo (average deviations between type approval and on-road driving of +52, +77, and +178%, respectively). These deviations are higher than the expected value for conventional European diesel passenger cars, which is about +40% for new models.34 Over several trips, the CO2 emissions of the Volvo exceeded the type approval value by more than 300% (Figure 3). This observation can be attributed to the fact that the plug-in powertrain affords this vehicle a great advantage in fuel consumption and CO2 emissions during the relatively short type-approval test with the NEDC (i.e., over a distance of 11 km) that does not easily translate into low on-road CO2 during the longer PEMS trips. Analyzing the average on-road NOx emissions separately for the urban, rural, and motorway velocity bins (comprising all data points with velocities of 0−60, >60−90, and >90 km/h, respectively), we find that the bin-average NOx emissions of the Volvo (Euro 5) and Mercedes-Benz (Euro 6) were similar in average terms (with more scatter for the Volvo) (Figure 4). The scatter in urban and rural emissions was largest for the plug-in hybrid Volvo, while the Peugeot (Euro 5) showed the highest overall emissions in each bin. NOx emissions for the Volvo were highly dependent upon the initial state of charge of the hybrid battery (four of the five trips with lowest urban and rural NOx emissions were started with a full battery). The operation of the hybrid systems under different driving conditions and their effect upon the on-road emissions of NOx and CO2 during the PEMS tests is visualized in Figure 5 (Mercedes-Benz) and Figure 6 (Volvo). These figures show different scatterplots of the on-road emissions (on-road CO2 ratio and NOx CF), the 95th percentile of acceleration × velocity, and the net hybrid energy over moving averaging windows. All of these scatterplots use distance-based data windows, and they cover all data windows derived from all trips recorded for the corresponding vehicle. To improve interpretability, scatterplot a highlights the windows with the highest net hybrid energy (windows with the most intense hybrid operation have larger markers and are plotted in the foreground), whereas scatterplot b highlights windows with the lowest net hybrid energy (where the engine charges the battery). Scatterplot c highlights windows with both high and

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RESULTS AND DISCUSSION Emission Measurements on the Chassis Dynamometer. The pollutant emissions of the two vehicles tested on the chassis dynamometer were below the applicable limits for both the NEDC and WLTP. CO2 emissions over WLTP were higher than over NEDC (+19% for the Volvo and +26% for the Mercedes-Benz). This increase is higher than the increase of 14% previously modeled for conventional Euro 6 diesel passenger cars,33 which points to a (possibly legitimate) optimization of the energy management of the hybrid systems to achieve optimum results over the current certification procedure. NOx emissions of the Euro 5 compliant Volvo were higher than those of the Euro 6 Mercedes-Benz that controls NOx emissions with a SCR after-treatment system. Because both vehicles are equipped with a DPF, particulate mass and particle number emissions remained well below the applicable limits and are not further discussed here. Moreover, both cars showed good compliance with the type-approved values reported for the NEDC (compare to Table 1). We also determined the electric range of the plug-in hybrid Volvo to be 54.5 km, a value that is 5% below the type-approval value of 57.3 km. On-Road Emission Measurements with PEMS. All three vehicles significantly exceeded their applicable NOx emissions limit when driven on the road. Considering all trips, the average NOx emission factors for the Mercedes-Benz, Volvo, and Peugeot were 0.52 g/km (Euro 6 CF of 6.5), 0.45 g/km (Euro 5 CF of 2.5), and 1.10 g/km (Euro 5 CF of 6.1; Figure 2), respectively. The on-road CO emissions of the three vehicles generally remained below the limit of 0.5 g/km for all trips (with the only exception of trip xPH4-1 for the Volvo). We note that trip xPH4-1 included a DPF regeneration event, leading to increased NOx, CO, and THC emissions and elevated fuel consumption. More details about the distancespecific on-road emissions of the three vehicles can be found in Table S5 of the Supporting Information. The on-road CO2 13154


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Figure 3. Average NOx and CO2 emission results by vehicle and trip.

observed for windows with a moderately negative net energy flow that occurs when the combustion engine recharges the battery (see top of Figure 6b). For this car, the overall net electric energy flows are less balanced than those of the Mercedes-Benz (as evidenced by the positive net energy flow windows inside the trapezoidal area delimited by dashed lines in Figure 6d). The windows in the left half of the triangular dashed area are driven with an energy flow to the battery and show a substantial concentration of windows with elevated NOx emissions. Some of the highest NOx emissions tend to happen during windows with negative net electric energy flow, even when the driving dynamics are not particularly aggressive (note the orange markers around the bottom section of the left dashed triangular area in Figure 6d). Simulation of NOx After-Treatment Systems. The simulations of the selective catalytic reduction system mounted on a diesel particulate filter (SCRF) resulted in average NOx emissions of about 0.023 g/km per window for all routes, which is well below the RDE CFs of 2.1 and 1.5 (applicable for new passenger car type approvals in the EU from 2017 and 2020, respectively) and even the Euro 6 limit of 0.08 g/km (Figure 7). By comparison, the Euro 6, SCR-equipped Mercedes-Benz vehicle had an average CF of 6.5. This indicates that the SCR system in this car was not performing to the full extent of its capabilities during the PEMS tests, likely as a result of a urea dosing strategy that is ill-adapted to real-world driving. We attribute the improved performance of the simulated SCRF to a more adequate urea dosing strategy. On the other hand, the simulated average tailpipe NOx emissions for the LNT were consistently above the SCRF results (except, by a small margin, for trip xPH4-1, for which a DPF regeneration event was identified). The simulated NOx emission factors for complete trips and for the urban/rural/motorway velocity bins can be found in Table S7 of the Supporting Information.

Figure 4. Average on-road NOx emission results by vehicle and trip (urban, rural, and motorway speed bins).

low net hybrid energy, and scatterplot d highlights windows with the highest and the lowest NOx CF). In the case of the Mercedes-Benz, the windows with both a low on-road CO2 ratio and a low NOx CF also tend to have high electric energy consumption (dark red and yellow markers in Figure 5a and dark green and blue markers in Figure 5b). High NOx emissions are associated with high CO2 emissions and also with high values of the 95th percentile of the product of positive acceleration and speed (i.e., with aggressive driving; Figure 5b). As expected from a non-plug-in hybrid, the overall net electric energy flow is balanced (see the evenly distributed window markers among the two triangular areas delimited by the dashed lines in Figure 5d). The plug-in hybrid Volvo shows a similar relationship between net electric energy flow and the average NOx and CO2 emissions of windows. Specifically, high NOx emissions can be 13155


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Figure 5. Visualization of the interaction between on-road emissions (CO2 and NOx), driving dynamics, and hybrid system operation of the Mercedes-Benz S300 (scatterplots a, b, c, and d as explained in the text).

diesel passenger cars could be decreased in the first few years of application of the RDE regulation. All three vehicles showed on the road higher CO2 emission levels than those certified during type approval (especially in the case of the plug-in hybrid Volvo, which was only fully charged at the beginning of selected trips). This observation has two implications. First, it suggests that the efficiency advantages of hybridization do not fully translate from the chassis dynamometer laboratory to real-world conditions. The discrepancy between certified and actual, on-road CO 2 emissions appears to increase with an increasing degree of powertrain hybridization, which could erode consumer trust in both declared CO2 emission values and the efficiency potential of novel hybrid vehicles. The deficiencies of the EU vehicle type approval regarding the representativeness of CO2 emission values are currently addressed through the introduction of the WLTP. Second, it shows that using the distance-specific CO2 emissions at type approval as an indicator for driving severity during on-road tests may lead to distortions in the RDE evaluation procedure because (i) hybrid vehicles can be propelled in part by electric energy that does not lead to tailpipe CO2 emissions and (ii) the management of the hybrid powertrain may differ between type approval and on road driving, thus leading to the previously described deviations in CO2 emissions. On the basis of our technical insights, we would argue that both implications are likely to apply to gasoline− electric hybrids as well.

Our results indicate that diesel hybrids offer interesting technological potential to reduce fuel consumption and pollutant emissions. However, the realization of these reductions depends heavily upon usage patterns, the management of the hybrid powertrain, and the calibration of the aftertreatment systems. The diesel hybrid cars tested showed onroad NOx emission levels comparable to those of conventional Euro 5 and 6 diesel cars (which have come under public scrutiny for the potential use of illegal defeat devices). This observation raises questions regarding real-world performance of the NOx control strategy of the test vehicles. In any case, we expect a substantial reduction in the NOx emissions of hybrid diesels with the introduction of the complementary RDE test procedure.24,25 This expectation is supported by the results of our simulations that suggest advanced calibrations of existing Euro 6 NOx control technologies, which RDE will necessitate, are able to reduce NOx emissions on the road to below the Euro 6 limit. Our simulations also suggest that advanced calibration of after-treatment technologies is more effective for NOx control than heavy hybridization (e.g., through plug-in hybrid powertrains) coupled with an exhaust gas recirculation (EGR)-only NOx control. Moreover, the simulated calibrations can be realized while achieving reasonable trade-offs with AdBlue tank refill intervals (for the SCRF) and fuel economy (for the LNT). To the extent that such calibrations are widely adopted for RDE-compliant vehicles, the gap between certified and on-road emissions of NOx for newly registered Euro 6 13156


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Figure 6. Visualization of the interaction between on-road emissions (CO2 and NOx), driving dynamics, and hybrid system operation of the Volvo V60 (scatterplots a, b, c, and d as explained in the text).

Inertia masses and road load parameters used for the chassis dynamometer tests (Table S1), overview of the on-road emission test setups with PEMS (Table S2), overview of PEMS trips (with indication of conditions at the test start; Table S3), evaluation of driving dynamics of the urban/rural/motorway velocity bins by trip (Figures S1 and S2), driving dynamic indicators by trip (Table S4), overview of PEMS testing results (Table S5), detailed NOx emission factors by trip and urban/rural/ motorway velocity bins (Table S6), detailed simulated NOx emission factors by trip and urban/rural/motorway velocity bins (Table S7), simulated AdBlue consumption and projected tank autonomies for simulated PEMS trips (SCRF after treatment; Table S8), simulated LNT fuel penalty (increase over baseline fuel consumption) for simulated PEMS trips of the Volvo V60 (LNT after treatment; table S9) and further details on vehicle preconditioning and results of calculation procedures for NEDC and WLTP tests (PDF)

Figure 7. Average NOx emissions by trip as measured on road with PEMS and as simulated for SCRF and LNT after-treatment systems.

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AUTHOR INFORMATION

Corresponding Author

ASSOCIATED CONTENT

*Telephone: +30-23-10-996014. E-mail: [email protected].

S Supporting Information *

ORCID

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.6b03585.

Zissis Samaras: 0000-0002-5823-3814 13157


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Environmental Science & Technology Present Address

Insights from on-road tests with Portable Emissions Measurement Systems (PEMS). Atmos. Environ. 2012, 62 (C), 657−665. (15) Ligterink, N.; Kadijk, G.; van Mensch, P.; Hausberger, S.; Rexeis, M. Investigations and Real World Emission Performance of Euro 6 Light-Duty Vehicles; TNO Earth, Life & Social Sciences: Delft, Netherlands, 2013; TNO 2013 R11891. (16) Franco, V.; Posada Sánchez, F.; German, J.; Mock, P. Real-World Exhaust Emissions from Modern Diesel Cars. A Meta-analysis of PEMS Emissions Data from EU (Euro 6) and US (Tier 2 Bin 5/ULEV II) Diesel Passenger Cars. Part 1: Aggregated Results; International Council on Clean Transportation (ICCT): Washington, D.C., 2014. (17) Kadijk, G.; van Mensch, P.; Spreen, J. Detailed Investigations and Real-World Emission Performance of Euro 6 Diesel Passenger Cars; TNO Earth, Life & Social Sciences: Delft, Netherlands, 2015; TNO 2015 R10702. (18) Yang, L.; Franco, V.; Mock, P.; Kolke, R.; Zhang, S.; Wu, Y.; German, J. Experimental Assessment of NOx Emissions from 73 Euro 6 Diesel Passenger Cars. Environ. Sci. Technol. 2015, 49 (24), 14409− 14415. (19) Hammer, J.; Schmidt, H.; Franco, V.; Posada Sánchez, F.; Zacharopoulou, T.; Samaras, Z. Development of a Method for Assessing Real-World Emissions of Hybrid Diesel Light Duty Vehicles; DirectorateGeneral for Environment, European Commission: Brussels, Belgium, 2013; 2013/S 250-438115. (20) Mock, P.; Kühlwein, J.; Franco, V.; German, J.; Tietge, U.; Bandivadekar, A. The WLTP: How a New Test Procedure for Cars Will Affect Fuel Consumption Values in the EU; International Council on Clean Transportation (ICCT): Washington, D.C., 2014; ICCT Working Paper 2014-9. (21) European Commission (EC). Commission Regulation (EU) No 582/2011 of 25 May 2011 Implementing and Amending Regulation (EC) No 595/2009 of the European Parliament and of the Council with Respect to Emissions from Heavy Duty Vehicles (Euro VI) and Amending Annexes I and III to Directive 2007/46/EC of the European Parliament and of the Council; EC: Brussels, Belgium, 2011. (22) European Commission (EC). Commission Regulation (EU) No 64/2012 of 23 January 2012 Amending Regulation (EU) No 582/2011 Implementing and Amending Regulation (EC) No 595/2009 of the European Parliament and of the Council with Respect to Emissions from Heavy Duty Vehicles (Euro VI); EC: Brussels, Belgium, 2012. (23) European Commission (EC). Commission Regulation (EU) 2016/427 of 10 March 2016 Amending Regulation (EC) No 692/2008 as Regards Emissions from Light Passenger and Commercial Vehicles (Euro 6); EC: Brussels, Belgium, 2016. (24) European Commission (EC). Commission Regulation (EU) 2016/646 of 20 April 2016 Amending Regulation (EC) No 692/2008 as Regards Emissions from Light Passenger and Commercial Vehicles (Euro 6); EC: Brussels, Belgium, 2016. (25) Exothermia SA. axisuite: Vehicle Emissions Aftertreatment System Modelling Platform; Exothermia SA: Thessaloniki, Greece, 2016; http://www.exothermia.com. (26) Tsinoglou, D.; Haralampous, O.; Koltsakis, G.; Samaras, Z. Model-based optimization methods of combined DPF + SCR systems. SAE Tech. Pap. Ser. 2007, DOI: 10.4271/2007-24-0098. (27) Koltsakis, G.; Fragkiadoulakis, P.; Samaras, Z.; Georgiadis, E.; Bizet, C.; Calendini, P.-O.; Hayat, O.; Dubois, V.; Manetas, C. SCR System Optimization and Control Supported by Simulation Tools. SAE Tech. Pap. Ser. 2013, sdf DOI: 10.4271/2013-01-1075. (28) Tronconi, E.; Nova, I.; Marchitti, F.; Koltsakis, G.; Karamitros, D.; Maletic, B.; Markert, N.; Chatterjee, D.; Hehle, M. Interaction of NOx Reduction and Soot Oxidation in a DPF with Cu-Zeolite SCR Coating. Emission Control Sci. Technol. 2015, 1 (2), 134−151. (29) Karamitros, D.; Koltsakis, G. SCR Reactor Models for FlowThrough and Wall-Flow Converters. In Urea-SCR Technology for deNOx After Treatment of Diesel Exhausts; Nova, I., Tronconi, E., Eds.; Springer Science + Business Media: New York, 2014; Chapter 13, pp 385−424, DOI: 10.1007/978-1-4899-8071-7_13. (30) Koltsakis, G. C.; Margaritis, N.; Haralampous, O.; Samaras, Z. Development and Experimental Validation of a NOx Trap Model for

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Vicente Franco: Directorate-General for Environment, European Commission, 1049 Brussels, Belgium. Notes

Disclaimer: The views expressed here are those of the authors and may not represent the position of the European Commission. The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was funded by the Directorate-General for Environment of the European Commission (Service Request ENV.C.3/SER/2013/0034).

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