Energy Efficient Air Quality Solutions for Vehicle Cabins

Doctoral thesis, 2023

Maintaining a good air quality level is essential for reducing potential health risks for human beings. Vehicle cabin is one common environment where people spend increasing amount of time in modern societies. It’s an environment challenged by elevated pollutants from surrounding traffics, especially small particles like PM2.5 and UFP (Ultrafine particles). To efficiently reduce or remove the pollutants from incoming air is one essential focus for development of future vehicles. To achieve that goal with energy efficient solutions would be even more important in the trend of emerging electric vehicles.

The objective of this thesis is to evaluate and propose solutions for improved cabin air quality and energy efficiency, which could be used in the development of vehicle climate system. The work has been conducted through vehicle measurements on road in two different locations, development of an air quality model, modelling of increased recirculation in the climate ventilation strategy, as well as measurements on new prototypes in both rig and road conditions. The purpose of the road measurements is to set the baseline of current air quality levels and evaluate the important influencing factors such as filter age and ventilation settings. The purpose of the model development is to enable a repeatable and comprehensive evaluation environment, which is later used to evaluate the strategy of increased air recirculation under common driving conditions. The purpose of the measurements on prototypes is to evaluate one solution of using EPA (Efficient Particulate Air) or HEPA (high-efficiency particulate air) filters as pre-filters, to prove the concept and the limitations.

The results are showing that cabin particles are highly influenced by the outside particle concentrations, the filter design and status, and to some extent the ventilation settings. Besides the application of pre-ionization assisted filtration was proved valuable. The air quality model, implemented in an existing climate system model, is validated with road measurements. Modelling of increased recirculation results in significant reduction of energy use and particles. In warm climate it’s more applicable to avoid fog risks and in all climates the use of high recirculation (for example 70%) should be evaluated based on the number of passengers. One way to achieve that is adding a control based on cabin CO2 concentration in the climate system.  It is also shown feasible to improve air quality using an EPA/HEPA pre-filter. The main limitations come from space and acceptable pressure-drop in the relatively compact environment.