LUDWIGSBURG – Differing propulsion systems are currently competing to replace the combustion engine, with the key criteria being performance, operating time, sustainability and not least, cost.

While the focus has mainly been on battery-powered electric systems for individual mobility, there is an increasing focus on the use of fuel cells for commercial vehicles and in this area, Mann+Hummel has developed new air filter sensor technology which promises to improve the performance/lifetime ratio of fuel cells

“The lifetime of a PEM fuel cell is affected by conditions such as the cleanliness of the cathode air in the catalyst,” explains Dr Michael Harenbrock, principal expert in electric mobility at Mann+Hummel. “Oxygen is reduced in the platinum-coated cathode but gases containing nitrogen or sulphur bond to the platinum particles. This causes them to block the catalyst, which impairs the performance of the fuel cell.”

Filter changing

Activated carbon filters specifically adapted to these types of harmful gases offer effective protection by selectively absorbing them, but they only have limited storage capacity.

“We don’t yet have empirical values for the recommended time intervals for filter changes in fuel cells to the same extent as we are used to with combustion engines because the technology is still extremely new,” says Harenbrock. “It therefore remains difficult to predict the lifetime of a filter because we still do not know the quantity of harmful gases the filter will have to contend with in real-life operation. Field trials in Germany have shown that this is heavily dependent on the traffic environment in which the vehicle is being driven.”

In order to facilitate usage-based maintenance, Mann+Hummel is currently working with two other partners in the ISAAC project to develop a sensor array for the cathode path. This will indicate when the activated carbon used has become saturated and harmful gases are beginning to penetrate the filter.

The project has received €840,412 in funding from the German Federal Ministry for Digital and Transport.

The Duisburg-based Institute for Energy and Environmental Technology (IUTA) is developing a penetration sensor array based on gas-sensitive surfaces for use in vehicles in changing environmental conditions and a smart signal processing system. The sensor layers, which will react sensitively and selectively to selected harmful gases and mixtures of them, are being supplied by the Research Institute for Precious Metals and Metal Chemistry in Schwäbisch Gmünd.

 Prototype

“In addition to developing cathode air cleaner media specifically adapted to the profiles of harmful gases, at Mann+Hummel we are focusing on integrating the array into the cathode air path,” says Harenbrock. “At the end of this process, we will have a prototype, which will need to be made ready for series production.”

It is envisaged that this new development will mainly be used in fuel cell systems for commercial vehicles.

“The lifetime requirements are much higher for commercial vehicles than in the passenger car sector,” Harenbrock explains. “Because this type of drive technology has to compete with combustion engines, the overall costs need to be financially viable. The sensor measuring technology required here, which is already capable of reliably identifying very low concentrations of gases, is currently mainly used in test benches. It is too expensive to use in vehicles. The aim of our project is to reduce the costs for the sensors while simultaneously increasing the fuel cell lifetime in order to enable consistent performance for as long as possible through predictive maintenance, i.e. by changing the filter at the right point.”

The intention is that the state funding will help to make hydrogen and fuel cell technology competitive within the transport sector. The work is therefore closely linked with a sister project in China that is being supported 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.

“The differences in air quality mean that in order to design the filter elements, we first need the relevant data from China,” Harenbrock says. “The prototype we have developed will be tested locally in China. The Chinese sales market is extremely interesting as there is currently a lot of support there for expanding the hydrogen strategy in the commercial vehicles sector.”