A simulation based approach for quantifying CO2 emissions of light duty vehicle fleets. A case study on WLTP introduction

摘要

This paper presents a new technology-oriented modelling approach for assessing the effect of different technologies and fleet composition on energy consumption/CO2 emissions. The methodology follows a hybrid approach between a statistically founded instantaneous emission model and a complete vehicle-simulation model. It makes use of as limited information as possible referring mainly to already available data sources. It is split into two modules, the sampling module where individual vehicles are defined, each one corresponding to a real vehicle present in the fleet, and the simulation module where each vehicle is run in a predefined mission profile. The vehicle simulation model is based on simple longitudinal dynamics featuring an extended-Willans powertrain simulation module. The fleet “generator” module that selects and assigns vehicle characteristics per vehicle is based on existing databases and the annual CO2 emissions monitoring database new vehicle registrations in the European market. The implementation code is built so that several thousands of simulations are possible in limited time. In this example, the methodology is applied for assessing the introduction of the new Worldwide Harmonized Test (WLTP) protocol in the European light duty vehicle type approval procedure. A representative fleet of approx. 4,000 vehicles, model year 2013-2014, was defined and run over the existing and forth-coming type approval cycles. Results showed good correlation of fleet-wide predicted CO2 emissions against preliminary certification data for year 2014 that were used for validation. Following, the WLTP provisions were introduced and calculations were made with regard to the expected increases in average CO2 emissions of the new registrations with the new protocol.