Microscale analysis of the introduction of electric vehicles in a real urban hot-spot for several meteorological and traffic conditions

This work presents the impacts on NOx emissions and concentrations of several mitigation strategies considering different meteorological conditions in a real air pollution hot spot. For this purpose, a methodology based on Computational Fluids Dynamics (CFD) has been used. The SUMO microscopic traffic simulator, coupled with an emissions model, is used to obtain road-traffic-related emissions for each selected scenario. These emissions are then used as input data to a set of steady-state CFD simulations which were previously performed for all wind direction sectors. Relevant meteorological variables are obtained from WRF simulations using the urban parameterization BEP-BEM. Finally, background NOx concentrations are obtained from an urban background air quality monitoring station (AQMS) in Madrid. 

 

Using this methodology, we have studied four periods:

 

Year 2016: Base case.

Year 2019: Reorganization of traffic flows by changing traffic directions in some streets.

Year 2022: Implementation of a Low Emissions Zone (ZBE) affecting the most polluting vehicles; with still some reduction of traffic due to the COVID-19 pandemic.

Year 2023: The recovery of traffic after the COVID-19 pandemic.

 

Results were evaluated using the observed concentrations at the AQMS in the study area. The impacts of the traffic variations are investigated for different meteorological conditions. The results show that the meteorological conditions affect both local and background concentrations and its net changes can be comparable to those due to emission reductions. Furthermore, we have considered two additional scenarios for each period considering different future levels of insertion of electric vehicles included in the Spanish National Energy and Climate Plan to assess their potential impact on emissions and air quality. Preliminary results show that the emissions reduction resulting from the replacement of fossil-fuelled vehicles with electric vehicles in the study area is not linear and depends on the composition of the traffic float prior to the replacement.