Performance of the Point Sampling Method and Inter-Comparison with State-of-the-Art Remote Emission Sensing
MARKUS KNOLL, Martin Penz, Tommaso Rossi, Simone Casadei, Alexander Bergmann,
Graz University of Technology Abstract Number: 248
Working Group: Instrumentation and Methods
AbstractEmissions from internal combustion engine vehicles are currently not properly monitored during their entire lifetime. Remote emission sensing (RES) is a promising technique for screening in-use vehicles. State-of-the-art open-path RES systems deliver acceptable emission factors (EF) for gaseous species, but lack accuracy for particulate matter (PM). Extractive point sampling (PS) is an alternative approach that is capable of screening different particle metrics, such as particle number (PN) concentration or black carbon (BC). To date, detailed studies evaluating the PS method as well as performance comparisons with commercial open-path RES are missing.
Validation measurements were performed with test vehicles equipped with portable emission measurement systems (PEMS). Next to the PS system, the commercial open-path RES system EDAR (HEAT) was co-located for 8 days. Further co-located measurements were conducted with the open-path RES system AccuScan
TM (OPUS) during two city measurement campaigns.
For the PEMS test drives, a strong correlation (R²=0.97) was found between PEMS and point sampling PN EFs. Absolute values are in good agreement with a median deviation of 22 %. BC EFs from PS were compared against PM EFs from the EDAR system and the PEMS PN results. For a high PM emitter, a good agreement was found for PS BC (R²=0.66) and EDAR PM (R²=0.47) compared against the PEMS PN results. For a second, lower-emitting diesel vehicle, the PS system delivers a good performance (R²=0.76) in contrast to the EDAR system (R²=0.01). In addition to the test drives, the results from the overall vehicle fleet measurements of several 1,000 vehicles were compared. Average values of PS BC and EDAR PM are in good agreement (115.46 mg/kg fuel, 85.77 mg/kg fuel), but median values differ by a factor of over 30 (16.25 mg/kg fuel, 0.46 mg/kg fuel).