Consultant report

Assessing real-world CO2 emissions using simulation and PEMS data

The Real Driving Emissions (RDE) testing procedure will introduce on-road testing as well as not-to-exceed emission limits for new passenger cars in Europe. However, for the time being, these on-road tests and on-road emission limits will only apply to air pollutant emissions. The fuel consumption and the CO2 emissions level of a vehicle will still be tested in a laboratory only.

The ICCT commissioned researchers at the Laboratory of Applied Thermodynamics (LAT) of Aristotle University, Thessaloniki (Greece), to investigate the possibility of evaluating real-world CO2 emissions with generic simulation models. Such models would be developed on the basis of Portable Emissions Measuring System (PEMS) data and RDE recording, and could therefore potentially extend RDE testing to also cover fuel consumption and CO2 emissions of a vehicle.

In the study, a validated model for a vehicle equipped with start-stop and regenerative braking was used to specify and investigate the difficulties and limitations of such an approach. At a second step, a new vehicle model with generic characteristics, such as the engine map and the power train losses, was created and compared against the same PEMS data, providing satisfactory results. Finally, cold-start and hot-start simulations for NEDC, WLTC, FTP, ERMES and Artemis were conducted, providing CO2 emissions for different driving patterns.

The study offers a sound basis for a rationale to underpin an assessment of real-world CO2 emissions and fuel consumption. Further investigations, covering existing vehicle and engine technologies such as gasoline port and direct injection, are needed in order to support and extend the findings of this work.

ICCT staff contact: Peter Mock