Sandia researchers Ken S. Chen (1514) and Mike Hickner (6245) are working hand in hand to understand key phenomena that control hydrogen-fueled PEM (proton exchange membrane or polymer electrolyte membrane) fuel cells. Ken is developing computational models to describe the phenomena while Mike is performing physical experimentation.

Their work is internally funded through a three-year Laboratory Directed Research and Development (LDRD) grant to tackle several key technical challenges. Proper water management and performance degradation or durability must be addressed before PEM fuel cells can be used to routinely power automobiles and homes.

“A natural byproduct of using hydrogen and oxygen to produce electricity in a PEM fuel cell is water [with waste heat being the other],” Ken, project principal investigator, says. “One challenge is maintaining the proper amount of water in a PEM fuel cell. Sufficient water in the membrane is needed to maintain its conductivity, whereas too much liquid water can result in flooding the cathode gas diffusion layer, which prevents reactant oxygen from reaching catalytic sites and causes performance deterioration.”

The work being done by Ken and Mike is leading to a better understanding of a couple of important areas, including how liquid water is produced, transported, and removed efficiently in PEM fuel cells and how PEM fuel cell performance degrades. A better understanding is key in finding ways to maintain the cells’ long-term performance during normal and harsh (e.g., freezing) conditions and improve their durability.

The close teaming between Ken’s modeling and Mike’s experimental efforts has been quite helpful in meeting project objectives.

“Our approach in combining computational modeling with experiments is unique,” Ken says. “Typically, Mike would perform discovery experiments to gain physical insights. I would then develop a model to describe the observation or data that Mike has obtained. Mike would perform further experiments so I can validate the model I have developed.”

Mike says they’ve obtained some “nice feedback” between the experiments and analyses. The intent is to build a computational tool that can be used in designing fuel cells, eliminating the need to do experiments on every single part of them.

“We want to have all the small pieces worked out in the modeling process so we can concentrate on the larger issues with experiments,” he says.

Ken has been using GOMA, a Sandia-developed multidimensional and multi-physics finite-element computer code, as the basic platform to develop 2-D performance models for PEM fuel cells. With the assistance of Nathan Siegel (6218), he is also exploring the development of quasi-3D PEM fuel cell models using FLUENT, a commercial computational fluid dynamic computer code. Ken emphasizes that the focus of this LDRD project is on understanding the key phenomena using experimental means and computational models, both simplified and multidimensional.

Joel Lash, manager of Multiphase Transport Processes Dept. 1514, concurs. “Sandia’s state-of-the-art multi-physics codes, like GOMA, form the backbone from which simplified phenomena- centric models can be developed to explore complex behavior, such as occurs in operating PEM fuel cells,” he says.

For the past couple of years Ken and Mike have focused mainly on liquid water transport, developing a PEM fuel cell model that can be employed to simulate a fuel cell’s performance, and performing diagnostic tests on fuel cells for phenomena discovery and model validation. Next, Ken says, they will tackle the key technical issues of performance degradation or durability, including performance degradation under normal operating conditions and under freezing operating conditions.

To date, the team — with contributions from Chris Cornelius (6245), David Ingersoll (2521), David Noble (1512), and Nathan Siegel (6218), as well as collaborations with Professor Chao-Yang Wang of Penn State University and researchers at the National Institute of Standards and Technology — has reported portions of its work in three refereed publications, four proceedings papers, and half a dozen technical presentations.

“People are taking notice of our work, and we are at the leading edge of understanding liquid water transport and removal in PEM fuel cells and becoming an important player in the PEM fuel cell research community,” Mike says. “Our validation method is new and exciting and leading us to learn some things not well known previously.”

Bruce Kelley, project manager for the PEM Fuel Cell LDRD and manager of Chemical Biological Systems Dept. 6245, says the project was developed specifically to leverage Sandia’s capabilities in multiphysics modeling and membrane materials to develop broader capabilities with applicability to fuel cells and other related technology areas. In doing so, Bruce says, “We have attracted significant industrial interest in the work, which is key to attracting DOE and other programmatic funding.”