Making progress and promoting health

Intelligent cabin air filter system saves energy and increases filter lifetime

More and more people worldwide are suffering from the effects of air pollution. In the area of automotive engineering the focus is therefore increasingly on cabin air filter systems. Due to the existing potential to save energy, further developments in this area are particularly interesting for electric vehicles.

We have already become accustomed to pictures which clearly show air pollution with people trying to protect themselves using breathing masks. Smoke pouring out of industrial chimneys, traffic jams which last for kilometers and smog alerts in inner cities are more and more becoming the norm. But people are less informed about how dangerous polluted air can also be indoors. According to a study carried out by the Environmental Protection Agency (EPA) in America, the air pollution indoors may be two to five times higher than outdoors. Pollen and coarse, fine and oily dust, bacteria, harmful gases and released allergens are present to a similar extent in rooms as in cars. Therefore, high efficient cabin air filters have already been fitted as standard in modern vehicles for a number of years.

In particular with regard to electric vehicles, MANN+HUMMEL is working intensively on the continuous improvement of the effectiveness and efficiency of cabin air filter systems. Here is on the one hand the extension of the driving range one of the biggest challenges. On the other hand a larger installation space is available which offers the possibility of using a multi-stage system. The FreciousSmart cabin air filter system currently being developed by MANN+HUMMEL is an intelligent concept which sets new standards. Using an intelligent fresh air management, the system is able to save a considerable amount of energy and this in turn has a positive effect on the driving range of electric vehicles. The demand-based control of the fresh-air proportion depends on the level of CO2 concentration inside the vehicle. In comparison to conventional systems this enables a reduction of the total amount of ambient air which has to be directed into the vehicle compartment. This means that a smaller amount of air has to be adjusted to the temperature level inside the vehicle, which saves energy. At the same time the system reliably protects the vehicle occupants against particulates, harmful gases, allergens and other substances harmful to health.

FreciousSmart cabin air filter system

Ambient air filter

HEPA filter

Interior air filter

Three times effective

The three filters of the FreciousSmart cabin air filter system provide the maximum protection for the vehicle occupants. Sensors determine the inside and outside air quality. The system then correspondingly regulates the volume of ambient air to be directed into the vehicle and selectively applies the required filtration stages. The highly effective interior air filter with its biofunctional coating binds allergens, filters almost all fine dust particulates (PM2.5) and prevents the spread of bacteria and mold fungi inside the passenger compartment. If more ambient air is required and/or the pollution level outside is higher, the ambient air filter in form of a newly developed NO2 fine dust combi filter is activated. This separates the fine dust particulates (PM2.5) from the ambient air and also filters out pollen and harmful gases such as nitrogen dioxide. If necessary, in the third filtration stage, a HEPA filter (high efficiency particulate air filter) separates even ultrafine particles (<0.1 μm), e.g. soot and brake dust, a technology which up to now has found application in cleanrooms.

Intelligent control

In the FreciousSmart cabin air filter system, the HEPA filter and the two other filter stages are only in operation when they are required. In cooperation with the École Centrale de Nantes engineering school in France, the experts at MANN+HUMMEL have simulated different traffic scenarios, for example in a traffic jam, through a tunnel or when the vehicle is full of occupants. The target was to determine how the ideal air conditions can be achieved while using the least amount of energy. The sensors monitor the air quality inside and outside the vehicle, whereby in the passenger compartment amongst other things the CO2 concentration, particle concentration and the relative air humidity is measured. After a defined limit is reached, the FreciousSmart cabin air filter system increases the inflow of ambient air. The outside air quality sensors recognize the air pollution level of the air. Given this information, the system decides which of the three filters the air should flow through.

Accordingly, when the outside air pollution level is low, the cabin air filter already offers a very good filtration performance. If the allowed limit of CO2 in the passenger compartment is exceeded, more air from outside is required and if this new air is polluted – for example due to heavy traffic – the ambient air filter is activated as a second filtration stage. The HEPA filter as a third filtration stage is only activated when the outside air is heavily polluted, e.g. in a tunnel or in a prolonged traffic jam. This intelligent, demand-based control strategy lengthens the service life of the HEPA filter and simultaneously lowers the energy consumption of the whole system. As a result, the FreciousSmart cabin air filter system literally allows electric mobility to make progress.