Moisture management

Humidifier membranes for water management in fuel cells

One approach to a sustainable energy economy is the use of hydrogen as an energy carrier. This can be produced by electrolysis, e.g. by fluctuating renewable energy, and used for mobile and stationary applications by generating electricity from it with fuel cells. The management of the resulting water plays an important role for the performance and lifetime of the fuel cell.

Commercial membrane humidifiers for moisture management in automotive fuel cells insufficient

Membrane humidifiers can be used as an external component to protect the ionomer membrane in the fuel cell from drying out at any time.

However, commercial membrane humidifiers do not adequately meet the very demanding requirements for automotive applications in terms of water transfer, long-term stability, harmful gas tolerance and cost.

Test rigs for automated testing of humidifier membranes

In the AMBITION project, the innovation field Membranes at Fraunhofer IGB has built up an extensive infrastructure and the corresponding know-how to comprehensively characterize humidifying membranes.

Automated testing of hollow fiber and flat membranes on behalf of customers

A total of four test rigs for hollow fiber and flat membranes are now available to determine the water transfer of humidifying membranes in relevant parameter spaces automatically (24/7).

Gas leakage tests and long-term stability investigations are also carried out. With the help of these data, membranes can be rationally evaluated and also different geometries can be compared with each other. This know-how is offered as a service to customers.

Test rig for parallel characterization of three humidifier membranes
© Fraunhofer IGB
Test rig for parallel characterization of three humidifier membranes
Glass module for hollow fiber membranes
© Fraunhofer IGB
Glass module for hollow fiber membranes
Flat membrane module
© Fraunhofer IGB
Flat membrane module

Development of humidifier membranes

However, the existing infrastructure for testing and our membrane expertise are also used to develop humidifying membranes in a targeted manner in the HIKS project.

Roll-to-roll coating of hollow fiber and flat membranes

Based on the preliminary work on coated hollow fiber membranes [1, 2], flat membranes can now also be coated with suitable fluorine-free polymers on a Coatema smartcoater roll-to-roll. One material approach here is the use of hydrophilic, uncharged polymers that are crosslinked via suitable reactions [3].

The membranes developed in this way offer a good alternative to commercially available membranes in terms of their humidification performance.

Typical measurement curve for water transfer with a variation of overflow and temperature
© Fraunhofer IGB
Typical measurement curve for water transfer with a variation of overflow and temperature
SEM image of an IGB flat membrane for humidification
© Fraunhofer IGB
SEM image of an IGB flat membrane for humidification

Publications

  1. Jesswein, I., Hirth, T., & Schiestel, T. (2017). Continuous dip coating of PVDF hollow fiber membranes with PVA for humidification. Journal of Membrane Science, 541, 281-290. doi:https://doi.org/10.1016/j.memsci.2017.07.010.
  2. Jesswein, I.; Uebele, S.; Dieterich, A.; Keller, S.; Hirth, T.; Schiestel, T. (2018) Influence of surface properties on the dip coating behaviour of hollow fiber membranes, J. App. Pol. Sci. DOI: 10.1002/APP.46163.
  3. Michele, A., Paschkowski, P., Hänel, C., Tovar, G. E. M., Schiestel, T., & Southan, A. (2021). Acid catalyzed cross-linking of polyvinyl alcohol for humidifier membranes. Journal of Applied Polymer Science, 51606. doi:https://doi.org/10.1002/app.51606.