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FUEL CELL STACK ASSEMBLY AND DIAGNOSTICS

Final Report Summary - ELECTROCHEM (FUEL CELL STACK ASSEMBLY AND DIAGNOSTICS)

Proton Exchange Membrane (PEM) fuel cells are disruptive technology in the power generation market that can provide the energy for numerous portable, transportation, and stationary power applications. Commercial success mostly relies on improvements in system lifetime, higher power density and cold start-up. In spite of their enormous potential, the cost for PEM fuel cell systems remains too high for mass-market appeal. Bipolar plates constitute 80% volume of a fuel cell system. Fuel cell bipolar plates that are lighter weight, thinner and more robust can reach cost and lifetime targets set by the industry. This includes finding ways of lowering costs with existing materials, as well as developing new manufacturing technologies that will improve yields and quality in short durations.
ELECTROCHEM project worked towards expanded graphite fuel cell bipolar plate development that has commercially acceptable properties, manufacturability and cost structure. Flexible graphite has shown to have properties that favour commercially and technically acceptable properties such as low corrosion, processing flexibility, and favourable mechanical and electrical properties. Electrochemical performance has been tested several different types of membrane electrode assemblies (MEAs) prepared using the coupled screen printing - decal transfer process. Cells are assembled with custom made expanded graphite-epoxy-silica composite material and tested under different fuel cell operating conditions and compared with commercially available molded graphite. Expanded graphite plates developed in this study gives better performance over commercial materials. Expanded graphite has shown to be easily processable form as production with less thickness, light weight and cost advantages.
Project has accomplished the following tasks in parallel:
1. Developing fuel cell research and development (R&D) capabilities with the potential to become best scientific institution in Turkey on fuel cell research.
Integration of Dr. Suha Yazici into research community in Turkey has been achieved through various interactions in the scientific and academic community. Dr. Yazici has started to offer graduate level semester course titled "Electrochemical Energy Conversion and Engineering" during 2010 winter semester with participation of 14 students. In 2011, a graduate level class was offered with 12 students participating. In 2012, two undergraduate level courses (Hydrogen Energy Systems and Fuel Cell Technologies” were offered in English with more than 40 students registering. Dr. Yazici has influenced many students to continue their research in other countries including Europe.
This project allowed us to look at the problem from various interdisciplinary perspectives to educate students and researchers for them to better understand electrochemical fundamentals. Outcome of this research was expected to result several highly educated and trained engineers and researchers with state of the art knowledge of fuel cell systems with hands on experience. Electrochemistry is used for understanding critical issues such as corrosion and lifetime. Material science played critical role on material development such as right types of polymers, processing conditions etc. Mechanical engineering discipline is used to design and characterize plates for their mechanical, electrical properties and flow parameters. Finally, joint effort is to put things together and diagnose product with multidisciplinary knowledge and approach. At the end of the project, researchers with knowledge and hands-on experience on the expanded graphite technology were able to develop new solutions for problems associated with fuel cells and other electrochemical systems.

2. Laboratory capabilities of Gebze Institute of Technology has been expanded to test, characterize not only bipolar plates but also other materials to continue fuel cell and material research into the future. Gebze Institute of Technology (GYTE) were enhanced with several new equipment. Development of new capabilities and new infrastructure allowed group to initiate new projects. In past two years, GYTE has made significant achievements towards this objective. The following capabilities are utilized in this research: Three-point flexural strength (Instron Model 5569 universal testing machine); In-plane electrical conductivity (Jandel RM3-AR four point probe electrical conductivity measurement tool); Through-plane electrical conductivity (custom designed equipment with probes); Hydrostatic press; Keithley Model 2000 digit digital multimeter; Corrosion testing ( in-house 3 compartment electrochemical cell); Potentiodynamic experiments (Volga PGZ4 potentiostat); Contact angle measurements (KSV CAM 200 Optical Contact Angle and Surface Tension Meter); ATMA AT-45PA semi-automatic screen printer and CNC machine for plate manufacturing.

3. Silica impregnated expanded graphite – epoxy composites have shown similar or better characteristics and performance compare to commercial materials. Expanded graphite material with and without resin were acquired from the leading manufacturer and evaluated for various properties. These composite plates are prepared by solution, followed by compression molding and curing. Mechanical properties, electrical conductivities, corrosion resistance and contact angles are determined as a function of impregnation content. Light weight, flexible and thin single layer epoxy impregnated expanded graphite bipolar plates with mechanical strength values up to 17.41 MPa, in-plane electrical conductivity values up to 136.6 S/cm, through-plane electrical resistance of 0.027 Ohm-cm and flexibility (deflection at mid-span) values up to % 4.38 were obtained. The low thickness (~0.5 mm) and density (~1.2 g/cm3) values of the prepared composite plates put them one step ahead of competition.

4. Manufactured plates were characterized at fuel cell setting for performance under developed fuel cell testing protocols. At the end measurements with fuel cell assembly was carried out to compare performance with commercially available materials. Performance up to 1 W/cm2 was obtained with these plates. Approximately 4W was obtained from 1 rectangular MEA of 4cm2 with double serpentine design with 1mm channel thickness, 1mm distance between channels and 0.3mm anode and 0.5 mm cathode channel depth. The thickness of the custom made plate was around 1.5mm. At least 25 of these MEAs were needed to obtain 100W net power.

Note: The full report is attached.