NPL is developing a range of in situ techniques for measuring critical parameters such as temperature, humidity, potential, current density and gas composition during operation of PEMFCs and SOFCs. The primary function of these measurements is to provide input data and validation for the NPL fuel cell model. In addition, more detailed information on the spatial distribution of these parameters will allow designers to optimise material properties and stack design to prolong fuel cell life without compromising performance. Novel techniques for in-situ temperature mapping offer a potentially viable method for detecting hotspots, which are often a significant limiting factor in fuel cell lifetime.

As part of this work, a paper by NPL scientists detailing the first ever in situ measurements of temperature and humidity along both gas channels of an operational PEMFC was published in the Journal of Power Sources, the premier international fuel cell journal. Miniaturised probes were incorporated into specially designed recesses in the graphite flowplates to carry out the measurements, shedding new light on the distribution of water in a fuel cell during operation. The key observation was the appearance of a significant amount of water at the anode due to back diffusion from the cathode.

Thermal imaging has also been demonstrated as a powerful tool for the characterisation of SOFC materials and cells. Ongoing work is extending the range of in situ measurement techniques to reference electrodes for PEMFCs and DMFCs, local mapping of current density in PEMFCs and sensing of gas composition. The development of these techniques is essential for validation of the NPL fuel cell model.

Objectives

• Establishment of measurement techniques for in-situ characterisation of fuel cells
• Use of experimental data to support model validation

Outputs

• Journal of Power Sources paper on humidity measurement in a PEMFC
• Journal of Power Sources paper on thermal imaging of SOFCs
• NPL Report on reference electrodes in solid polymer fuel cells

For more information, please contact Gareth Hinds.