Even though there are currently many indications that battery-powered mobility will win the battle to succeed the internal combustion engine, the final decision has not yet been made. If there is to be "one" solution at all. There are still competing approaches, which, in addition to the criterion of sustainability that hovers above everything else, also involve arguments regarding performance, operating time, infrastructure and, last but not least, costs. While, as mentioned at the beginning, battery-powered electric vehicles currently lead the field in the area of individual mobility, the fuel cell, which has already been written off in many places, is also fighting its way back into the focus of developers. Particularly in the commercial vehicle sector, but also in the maritime sector, there is a lot to be said for its use. This is due not least to developments such as the new air filter sensor technology from MANN+HUMMEL. The Ludwigsburg-based filter specialist expects the ISAAC research project to optimize the performance-lifetime ratio.

Problem: Unwanted substances in the cathode air

To put it precisely, the ISAAC project, which is funded by the German Federal Ministry of Digital Affairs and Transport, is about developing a sensor array for pollutant gas-adsorbing cathode air filter systems as part of a German-Chinese cooperation.

"The service life of a PEM fuel cell depends, among other things, on the cleanliness of the cathode air in the catalyst," explains Dr. Michael Harenbrock, Principal Expert Electric Mobility at MANN+HUMMEL. "Oxygen is reduced at the platinum-coated cathode, but gases containing nitrogen or sulfur also bind to the platinum particles. As a result, they block the catalyst and thus impair the fuel cell's performance."

Lack of experience

Effective protection is offered by activated carbon filters specially adapted to such harmful gases, which selectively absorb them. Unfortunately, however, these have limited storage capacity. "Empirical values for recommended time intervals for filter changes do not yet exist for fuel cells to the same extent as we know from combustion engines, since the technology is still quite new," Harenbrock explains. "Consequently, predicting filter service life remains difficult as long as we don't know the amount of pollutant gas acting in real operation. Field tests in Germany show that this depends very much on the local traffic environment in which driving takes place."

Sensor array to indicate maintenance needs

In order to compensate for the lack of empirical values and thus enable use-oriented maintenance, MANN+HUMMEL is conducting research in a consortium with two other partners on a sensor array for the cathode path that indicates the saturation of the activated carbons used and the incipient breakthrough of harmful gases. For example, the Duisburg Institute for Energy and Environmental Technology e. V. (IUTA) is developing a breakthrough sensor array based on gas-sensitive surfaces for automotive use in changing ambient conditions and an intelligent signal evaluation system adapted to this. The fem research institute Edelmetalle + Metallchemie in Schwäbisch Gmünd, in turn, supplies the sensor layers that react sensitively and selectively to selected harmful gases or harmful mixtures. "Our task at MANN+HUMMEL - in addition to developing cathode air filter media specially adapted to the pollutant gas profiles - is to integrate the array into the cathode air path," says Harenbrock. "The end result is a prototype that then has to be brought to production readiness."

Practicality through cost reduction

The consortium sees the focus for use of the market-ready new development primarily in fuel cell systems for commercial vehicles. "The service life requirements for commercial vehicles are much higher than in the passenger car sector," explains Harenbrock. "In addition, the drive technology competes with the combustion engine, so the overall costs must be economical. The sensor measurement technology required here, which can reliably determine even very low gas concentrations, is used today mainly on test benches. It is too expensive for use in vehicles. The goal of our project is to reduce the cost of the sensors while increasing the fuel cell's service life - in other words, to ensure sustained performance over as long a period as possible, made possible by predictive maintenance, i.e., changing the filter at the required time."

Strengthening the domestic economy

Some of you may still be wondering what purpose the government funding is intended to serve in this context. According to the parties involved, the main aim is to establish hydrogen and fuel cell technology competitively in the transport sector and thus strengthen the domestic economy. Of particular importance, therefore, is the dovetailing with a sister project in China funded by the Chinese Ministry of Science and Technology (MoST). Partners on the Chinese side are Tongji University in Shanghai, MANN+HUMMEL China and an OEM partner for field trials. Harenbrock: "Due to the different air quality, it is necessary to first obtain corresponding measurement data from China for the design of filter elements. In the end, the prototype we have developed is sent to China for testing. China is a highly interesting sales market, as they want to greatly expand the hydrogen strategy there, especially in the commercial vehicle sector."

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