Delft sensor enables safe and reliable use of hydrogen

TU Delft scientists team up

To tackle the need for hydrogen sensors for aviation applications, scientists from the Faculties of Aerospace Engineering and Applied Sciences teamed up. Supported by funding from EU projects Overleaf and HYDEA, an interdisciplinary team is now working on developing both the materials making detection of hydrogen possible, as well as the optical components and integration of the hydrogen sensors with other sensor technology. Focussing on hydrogen-powered aircraft, sensors to detect hydrogen leakages are required at various locations to ensure safe operations of the airplane. Think about near hydrogen storage tanks, propulsion systems, but also along hydrogen pipes. At these locations, temperatures can get down to as low as -60 °C during flight.

Fun fact: freezer finetuned

The challenge of hydrogen detection a low temperatures is that processes such as molecular hydrogen dissociation and diffusion slow down significantly, extending the sensor’s response time. Creating a set-up in which we can test the materials for a sensor is difficult: we need to introduce a well-defined leak of a specific hydrogen concentration in an environment at –60 °C. For this, we had to design an experimental set-up from scratch. This turned out to be quite challenging, especially since supply chains were disrupted due to the global pandemic. For example, since all laboratory freezers were sold out and used for the storage of vaccine, we had to be creative in finding solutions. We used components from all kinds of suppliers, including DIY stores and a freezer originally designed for storing tuna. This freezer was completely converted and served as the backbone of this study.

First results and follow up

The novelty of the work published in Advanced Functional Material Optical Hydrogen Sensing Materials for Applications at Sub-Zero Temperatures is that it is the first time that these optical hydrogen sensors were seen to work at temperatures as low as -60°C. This was especially one of the challenges Ziqing Yuan is facing in her PhD project: finding the right materials. The TU Delft patented tantalum-based hydrogen sensing materials provide large enough changes of the optical properties to be used as sensing materials even at low temperatures. On top of that, she demonstrated response times below the 10 s limit. Surprisingly, her rigorous analysis shows that this response was not limited by diffusion of the hydrogen atoms within the material, but by the dissociation of the hydrogen molecule on the top of the sensor. This knowledge provides fundamental insights into these materials and clear directions on how to enhance the properties even more. 

Lars Bannenberg: “The journey to the perfect hydrogen sensor does not end here. TU Delft scientists are working on developing advanced optical methods to implement the sensors. This would enable obtaining information on the hydrogen concentration at multiple positions inside the aircraft with just one system. On top of that, we will be testing the sensor under more realistic conditions. Including environments where also gaseous pollutants such as CO are present, in high-humidity conditions that can be encountered in the tropics, and in a range of other conditions provided by the test set-ups of the partners in our European projects.”