EMISSION FACTORS FROM EMISSION MEASUREMENTS VERSIT+ methodology Norbert Ligterink Symposium Vehicle Emissions November 3, 2016
GETTING THE COMPLETE PICTURE fuels SCR DPF hybrid technology downsizing dynamometer settings aging Vehicle technology What is the average local emission? Driving and usage driving cycles GPS cruise control weight gear shifting short trips air conditioning idling trip advice speed limits lane widths intersections road layout 2 Emission factors from emission measurements Road type Congestion traffic lights road capacity signalling travel times mean velocity
DUTCH AIR-QUALITY MODEL EMISSION MEASUREMENTS FOR EMISSION FACTORS For both emission totals (National Emission Ceilings) and local air quality modelling there are three requirements: 1. match vehicle emissions with the local traffic situations (speed limit, congestion). 2. use the local fleet composition to determine the average vehicles. 3. match traffic situations with the intensities and distance travelled. and have an appropriate air chemistry and dispersion model, local information, NO 2 concentrations calibrated 2014 prediction 2015 prediction 2020 prediction 2030 3 Emission factors from emission measurements
NECESSARY DILUTION PER VEHICLE WITH CLEAN AIR TO REACH 40 μg/m 3 AIR-QUALITY STANDARD 4 Emission factors from emission measurements
10+ POLLUTANTS (CO, HC, NO X, CH 4, CO 2, NH 3, ), BUT ONLY A FEW IMPORTANT ONES NO x emissions for European NO 2 air-quality limits particulates emissions from the diesel exhaust linked to health issues PM: particulate mass (filter measurements since 1980 s) PN: Particulates Number (since ~2011) EC: Elemental Carbon (NEW!) 350+ VEHICLE CATEGORIES CONTRIBUTING TO THE TOTAL EMISSIONS, BUT ONLY A FEW IMPORTANT ONES. diesel vehicles in general for NO x emissions limited decrease in emissions for passenger cars large contribution of vans Euro-V trucks, but no longer Euro-VI trucks and buses older diesel vehicles for PM, PN, and EC emissions 5 Emission factors from emission measurements
KEEPING TRACK OF THE FACTORS IN THE EMISSION MODEL the complex picture: each line: an operation, a method or a model 6 Emission factors from emission measurements
ON-ROAD TESTING FOR EMISSION FACTORS WITH A FOCUS ON DIESEL From 2009 for heavy-duty vehicles emissions factors are determined from on-road (PEMS) testing: stable results and high reproducibility a shift to PEMS was essential: Euro-V urban NO x emission 3 times higher than previously estimated From 2014 for light-duty diesel vehicles the emission factors are determined from on-road testing (SEMS/PEMS): high variability, limited reproducibility, unexplained effects. Euro-5 vans all have similar high NO x emissions Euro-6 passenger cars show large variation and deviations: From 2015 enough confidence for NO x emission factors SEMS PEMS 7 Emission factors from emission measurements
BUT NOT THE ONLY ON ROAD. ADDITIONAL TESTING IS STILL NEEDED Field tests: emissions during idling on a parking place (e.g. DPF- check) Light-Duty and heavy-duty chassis dynamometer: controlled and type-approval tests particulates emission chemical analyses (e.g. EC and NO 2 ) Heavy-duty engine tests: particulates emission exposure tests 8 Emission factors from emission measurements
REPORTING AFTER DIESEL GATE Transparency is needed (e.g. make and model information) but the results are always a combination of: vehicle technology + maintenance state + test + conditions reporting complete information and disclaimers 9 Emission factors from emission measurements
VEHICLE EMISSION TESTING FOR RDE LEGISLATION AND EMISSION FACTORS Covering the relevant traffic situations for the Netherlands (~600 km): stop-and-go traffic in Amsterdam ~ 15-20 km/h different speed limits on the motorway (80, 100, 120, 130 km/h) congestion on the motorway busy rural routes cold starts RDE Amsterdam 80 km/h motorway rural RDE 80 km/h motorway Amsterdam rural Rotterdam VW Passat Rotterdam Renault Megane 10 Emission factors from emission measurements
acceleration [m/s 2 ] NO x emission rates [mg/s] acceleration [m/s 2 ] NO x emission rates [mg/s] PRECISE DRIVING DYNAMICS IS IMPORTANT FOR THE SPECIFIC EMISSIONS standardized plots of NO x emission rates for (more) fair comparisons high NO x Euro-6 low NO x Euro-6 effect of dynamics NEDC region WLTP region velocity [km/h] velocity [km/h] 11 Emission factors from emission measurements logarithm scale, 100-fold increase!
MAINTAINING ACCURACY WHEN: 5% OF THE TIME ~ 50% OF THE EMISSIONS High acceleration and incidences are important for the majority of the emissions (depends on technology/euro class) Emission models have a second-by-second prediction accuracy of 40% of the average emissions (at best) Non-deterministic, hence enough representative emission measurements are needed (close to the relevant traffic situations) occasional NO x, HC and CO emissions for petrol vehicles, especially during hard accelerations Example from GDI report 12 Emission factors from emission measurements
fraction of the time DYNAMIC DRIVING HAS A LARGE SHARE IN THE TOTAL EMISSIONS typical Euro-5 emissions: never low NO x CO 2 and NO x emission rates emissions = rate x time CO 2 and NO x emission totals 13 Emission factors from emission measurements
VERSIT+: TNO EMISSION MODEL TO GENERATE NATIONAL EMISSION FACTORS General philosophy: representative measurements for the different traffic situations collecting enough data for statistical significance (> 600 km) limited modelling, only based of velocity and acceleration data fitting map with data representativeness check EFs fixed traffic situations 14 Emission factors from emission measurements
start here TNO, PBL, CBS AND ROAD AUTHORITIES MERGING AND DISPERSING BY RIVM fleet composition information vehicle selection for testing emission measurements per vehicle check variation over the tests and vehicles 15 Emission factors from emission measurements emission model interpolate to standard traffic situations representativeness traffic intensity, congestion level per road local emission from traffic intensities total emission from annual mileages average over the fleet based on mileages air quality emission totals consistency
ONGOING IMPROVEMENTS KEEPING AHEAD OF THE DEVELOPMENTS emissions decoupled from driving behaviour: hybrid vehicles (charging, electric driving, electric boost or not, ) LNT (failed) regenerations (too) low temperatures for SCR driving behaviour: dynamic speeds limits and spitsstroken normal behaviour outside the RDE strict enforcement and congestion risk of high emissions: tampering, DPF removal, etc. deterioration of after-treatment technology malfunctioning retention of older vehicles 16 Emission factors from emission measurements
CONCLUSIONS Reliable emission factors for air quality depend on many aspects which need separate investigation. Large variations in emissions with vehicle technology and driving behaviour require special attention to capture the effects. The measurement program focusses on the most relevant polluters in their natural habitat. The complexity increases with modern vehicle technology in combination with the different local traffic situations. 17 Emission factors from emission measurements
www.tno.nl/voertuigemissies www.tno.nl/vehicle-emissions