Innovative Sensor System Could Protect Fuel Quality at Hydrogen Filling Stations

Hydrogen is required to run fuel cell vehicles, but that gas should not contain any contaminants as these can possibly damage the fuel cell.

Now, Professor Andreas Schütze, along with his research group at Saarland University, is teaming up with research associates to create a new sensor system that would enable continuous in-situ monitoring of the quality of hydrogen at hydrogen fuelling stations. The novel infrared measuring cell will be fitted within the hydrogen filling station and will need to work under extremely adverse settings. In spite of short refueling times and very high pressures, the new sensor system will need to operate consistently. This autumn, the system will be subjected to operational trials. At the Hannover Messe, which will begin from April 1^st, 2019, the research group from Saarbrücken will demonstrate their high-pressure test rig at the Saarland Research and Innovation Stand in Hall 2, Stand B46.

When cars are forced to operate on low-purity or low-quality fuels , their performance becomes substandard. The same holds true for vehicles that are driven by fuel-cell technology. A fuel cell vehicle driver fills up with hydrogen, instead of a fossil-based fuel; however, even hydrogen may not be free of contaminants. During the production process of hydrogen, impurities like hydrocarbons, ammonia, or sulfur-containing compounds, can contaminate this gas. Such contamination can also occur during the refilling process or during transportation to the hydrogen station. Such aspects can make driving a tedious process.

“Contaminants can actually poison the fuel cell,” explained Andreas Schütze, sensor expert Professor from Saarland University.

The fuel cell membranes can be affected by even low levels of impurities. Consequently, the fuel cell generates less amounts of electricity and power output is decreased, causing the vehicle to move shorter distances. In the worst scenario, the fuel cell will be damaged permanently and the car will merely stop running.

In order to prevent things from reaching this extreme scenarios, Schütze and his research team have been closely working with research associates to come up with a novel technology that makes sure that only high purity hydrogen is fed to the fuel cell, thus prolonging the service life of the fuel cell. Hydac Electronic GmbH and the Fraunhofer Institute for Solar Energy Systems ISE are the project partners.

To date, hydrogen purity was ascertained by examining samples in a lab. At Zema—Center for Mechatronics and Automation Technology in Saarbrücken Saarland University—and at Saarland University, investigators are developing a unique sensor system that constantly tracks the hydrogen quality at the time of the refueling process.

The challenge is twofold: measuring at the required level of precision and coping with the conditions under which the sensor system needs to operate.

Andreas Schütze, Sensor Expert Professor, Saarland University.

Hydrogen pressures of 700 to 900 bar are used by the refueling process, which lasts less than three minutes.

As a result, the team is creating a new infrared measuring cell that would be able to accurately and reliably determine under these adverse conditions. Actually, the extremely high pressures to which the sensors are subjected to are used by the researchers to further develop their process’ sensitivity.

Along with his research team, Andreas Schütze has already developed salable measuring cells for tracking the quality of liquids, including oils. However, the pressures that the investigators currently have to tackle mean that they are in uncharted areas.

Up until now, no one has made measurements of this type at pressures this high. Normally, these sorts of measurements are done at pressures of no more than 40 or 50 bar.

Andreas Schütze, Sensor Expert Professor, Saarland University.

After installing the measuring cell for the odorless gas H₂ within the hydrogen fuelling station, the hydrogen fuel is allowed to flow via a tiny tube.

We illuminate the gas passing through the tube with light from an infrared source and we collect the light passing out on the opposite side of the tube. If there has been a change in the chemical composition of the gas, the infrared spectrum will change accordingly. This allows us to detect the presence of unwanted additives or contaminants.

Andreas Schütze, Sensor Expert Professor, Saarland University.

At present, Schütze’s research team members are performing experiments and are allocating specific infrared absorption signals to the numerous contaminants. In addition, the team is ascertaining which wavelengths of the infrared spectrum would be most appropriate for the measurements and is configuring the system.

Such vital preparatory stages have to be concluded prior to this autumn, when the novel sensor system will be deployed to a hydrogen refueling station for operational trials.

“One of the questions we’re studying at the moment is whether and how the intensity of the infrared spectrum we measure changes with pressure. The sensor system has to be able to reliably detect a range of contaminants at concentration levels significantly below what we find in oils,” explained Marco Schott, a doctoral student focusing on the hydrogen measuring cell.

The German Federal Ministry of Education and Research is supporting the project through a grant worth €2.5 million.